From a33b2d0359a0aae25d5ac7a26b85a5682485ebbb Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Mon, 8 Aug 2016 17:46:23 -0700 Subject: selftests/seccomp: Add tests for basic ptrace actions This adds tests for using only ptrace to perform syscall changes, just to validate matching behavior between seccomp events and ptrace events. Signed-off-by: Kees Cook --- tools/testing/selftests/seccomp/seccomp_bpf.c | 41 ++++++++++++++++++++++----- 1 file changed, 34 insertions(+), 7 deletions(-) diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c index 73f5ea6778ce..e61b963f011b 100644 --- a/tools/testing/selftests/seccomp/seccomp_bpf.c +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c @@ -1262,6 +1262,13 @@ TEST_F(TRACE_poke, getpid_runs_normally) # error "Do not know how to find your architecture's registers and syscalls" #endif +/* When the syscall return can't be changed, stub out the tests for it. */ +#ifdef SYSCALL_NUM_RET_SHARE_REG +# define EXPECT_SYSCALL_RETURN(val, action) EXPECT_EQ(-1, action) +#else +# define EXPECT_SYSCALL_RETURN(val, action) EXPECT_EQ(val, action) +#endif + /* Use PTRACE_GETREGS and PTRACE_SETREGS when available. This is useful for * architectures without HAVE_ARCH_TRACEHOOK (e.g. User-mode Linux). */ @@ -1357,7 +1364,7 @@ void change_syscall(struct __test_metadata *_metadata, #ifdef SYSCALL_NUM_RET_SHARE_REG TH_LOG("Can't modify syscall return on this architecture"); #else - regs.SYSCALL_RET = 1; + regs.SYSCALL_RET = EPERM; #endif #ifdef HAVE_GETREGS @@ -1426,6 +1433,8 @@ void tracer_ptrace(struct __test_metadata *_metadata, pid_t tracee, if (nr == __NR_getpid) change_syscall(_metadata, tracee, __NR_getppid); + if (nr == __NR_open) + change_syscall(_metadata, tracee, -1); } FIXTURE_DATA(TRACE_syscall) { @@ -1480,6 +1489,28 @@ FIXTURE_TEARDOWN(TRACE_syscall) free(self->prog.filter); } +TEST_F(TRACE_syscall, ptrace_syscall_redirected) +{ + /* Swap SECCOMP_RET_TRACE tracer for PTRACE_SYSCALL tracer. */ + teardown_trace_fixture(_metadata, self->tracer); + self->tracer = setup_trace_fixture(_metadata, tracer_ptrace, NULL, + true); + + /* Tracer will redirect getpid to getppid. */ + EXPECT_NE(self->mypid, syscall(__NR_getpid)); +} + +TEST_F(TRACE_syscall, ptrace_syscall_dropped) +{ + /* Swap SECCOMP_RET_TRACE tracer for PTRACE_SYSCALL tracer. */ + teardown_trace_fixture(_metadata, self->tracer); + self->tracer = setup_trace_fixture(_metadata, tracer_ptrace, NULL, + true); + + /* Tracer should skip the open syscall, resulting in EPERM. */ + EXPECT_SYSCALL_RETURN(EPERM, syscall(__NR_open)); +} + TEST_F(TRACE_syscall, syscall_allowed) { long ret; @@ -1520,13 +1551,8 @@ TEST_F(TRACE_syscall, syscall_dropped) ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->prog, 0, 0); ASSERT_EQ(0, ret); -#ifdef SYSCALL_NUM_RET_SHARE_REG - /* gettid has been skipped */ - EXPECT_EQ(-1, syscall(__NR_gettid)); -#else /* gettid has been skipped and an altered return value stored. */ - EXPECT_EQ(1, syscall(__NR_gettid)); -#endif + EXPECT_SYSCALL_RETURN(EPERM, syscall(__NR_gettid)); EXPECT_NE(self->mytid, syscall(__NR_gettid)); } @@ -1557,6 +1583,7 @@ TEST_F(TRACE_syscall, skip_after_RET_TRACE) ASSERT_EQ(0, ret); /* Tracer will redirect getpid to getppid, and we should see EPERM. */ + errno = 0; EXPECT_EQ(-1, syscall(__NR_getpid)); EXPECT_EQ(EPERM, errno); } -- cgit v1.2.3-59-g8ed1b From 967d7ba8415139107033770a40c7ec7dd17fbcb1 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Wed, 2 Dec 2015 11:39:36 -0800 Subject: selftests/seccomp: Add simple seccomp overhead benchmark This attempts to produce a comparison between native getpid() and a RET_ALLOW-filtered getpid(), to measure the overhead cost of using seccomp(). Signed-off-by: Kees Cook --- tools/testing/selftests/seccomp/Makefile | 18 ++-- .../testing/selftests/seccomp/seccomp_benchmark.c | 99 ++++++++++++++++++++++ 2 files changed, 112 insertions(+), 5 deletions(-) create mode 100644 tools/testing/selftests/seccomp/seccomp_benchmark.c diff --git a/tools/testing/selftests/seccomp/Makefile b/tools/testing/selftests/seccomp/Makefile index aeb0c805f3ca..553d870b4ca9 100644 --- a/tools/testing/selftests/seccomp/Makefile +++ b/tools/testing/selftests/seccomp/Makefile @@ -1,8 +1,16 @@ -TEST_GEN_PROGS := seccomp_bpf -CFLAGS += -Wl,-no-as-needed -Wall -LDFLAGS += -lpthread +all: include ../lib.mk -$(TEST_GEN_PROGS): seccomp_bpf.c ../kselftest_harness.h - $(CC) $(CFLAGS) $(LDFLAGS) $< -o $@ +.PHONY: all clean + +BINARIES := seccomp_bpf seccomp_benchmark +CFLAGS += -Wl,-no-as-needed -Wall + +seccomp_bpf: seccomp_bpf.c ../kselftest_harness.h + $(CC) $(CFLAGS) $(LDFLAGS) -lpthread $< -o $@ + +TEST_PROGS += $(BINARIES) +EXTRA_CLEAN := $(BINARIES) + +all: $(BINARIES) diff --git a/tools/testing/selftests/seccomp/seccomp_benchmark.c b/tools/testing/selftests/seccomp/seccomp_benchmark.c new file mode 100644 index 000000000000..5838c8697ec3 --- /dev/null +++ b/tools/testing/selftests/seccomp/seccomp_benchmark.c @@ -0,0 +1,99 @@ +/* + * Strictly speaking, this is not a test. But it can report during test + * runs so relative performace can be measured. + */ +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#define ARRAY_SIZE(a) (sizeof(a) / sizeof(a[0])) + +unsigned long long timing(clockid_t clk_id, unsigned long long samples) +{ + pid_t pid, ret; + unsigned long long i; + struct timespec start, finish; + + pid = getpid(); + assert(clock_gettime(clk_id, &start) == 0); + for (i = 0; i < samples; i++) { + ret = syscall(__NR_getpid); + assert(pid == ret); + } + assert(clock_gettime(clk_id, &finish) == 0); + + i = finish.tv_sec - start.tv_sec; + i *= 1000000000; + i += finish.tv_nsec - start.tv_nsec; + + printf("%lu.%09lu - %lu.%09lu = %llu\n", + finish.tv_sec, finish.tv_nsec, + start.tv_sec, start.tv_nsec, + i); + + return i; +} + +unsigned long long calibrate(void) +{ + unsigned long long i; + + printf("Calibrating reasonable sample size...\n"); + + for (i = 5; ; i++) { + unsigned long long samples = 1 << i; + + /* Find something that takes more than 5 seconds to run. */ + if (timing(CLOCK_REALTIME, samples) / 1000000000ULL > 5) + return samples; + } +} + +int main(int argc, char *argv[]) +{ + struct sock_filter filter[] = { + BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW), + }; + struct sock_fprog prog = { + .len = (unsigned short)ARRAY_SIZE(filter), + .filter = filter, + }; + long ret; + unsigned long long samples; + unsigned long long native, filtered; + + if (argc > 1) + samples = strtoull(argv[1], NULL, 0); + else + samples = calibrate(); + + printf("Benchmarking %llu samples...\n", samples); + + native = timing(CLOCK_PROCESS_CPUTIME_ID, samples) / samples; + printf("getpid native: %llu ns\n", native); + + ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); + assert(ret == 0); + + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog); + assert(ret == 0); + + filtered = timing(CLOCK_PROCESS_CPUTIME_ID, samples) / samples; + printf("getpid RET_ALLOW: %llu ns\n", filtered); + + printf("Estimated seccomp overhead per syscall: %llu ns\n", + filtered - native); + + if (filtered == native) + printf("Trying running again with more samples.\n"); + + return 0; +} -- cgit v1.2.3-59-g8ed1b From f3f6e30669c048f47d51ea59df9946a91f551c4c Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Wed, 2 Aug 2017 14:08:39 -0700 Subject: selftests/seccomp: Refactor RET_ERRNO tests This refactors the errno tests (since they all use the same pattern for their filter) and adds a RET_DATA field ordering test. Signed-off-by: Kees Cook Reviewed-by: Tyler Hicks --- tools/testing/selftests/seccomp/seccomp_bpf.c | 95 ++++++++++++++++----------- 1 file changed, 58 insertions(+), 37 deletions(-) diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c index e61b963f011b..2fb49d99588d 100644 --- a/tools/testing/selftests/seccomp/seccomp_bpf.c +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c @@ -136,7 +136,7 @@ TEST(no_new_privs_support) } } -/* Tests kernel support by checking for a copy_from_user() fault on * NULL. */ +/* Tests kernel support by checking for a copy_from_user() fault on NULL. */ TEST(mode_filter_support) { long ret; @@ -541,26 +541,30 @@ TEST(arg_out_of_range) EXPECT_EQ(EINVAL, errno); } +#define ERRNO_FILTER(name, errno) \ + struct sock_filter _read_filter_##name[] = { \ + BPF_STMT(BPF_LD|BPF_W|BPF_ABS, \ + offsetof(struct seccomp_data, nr)), \ + BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_read, 0, 1), \ + BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ERRNO | errno), \ + BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW), \ + }; \ + struct sock_fprog prog_##name = { \ + .len = (unsigned short)ARRAY_SIZE(_read_filter_##name), \ + .filter = _read_filter_##name, \ + } + +/* Make sure basic errno values are correctly passed through a filter. */ TEST(ERRNO_valid) { - struct sock_filter filter[] = { - BPF_STMT(BPF_LD|BPF_W|BPF_ABS, - offsetof(struct seccomp_data, nr)), - BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_read, 0, 1), - BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ERRNO | E2BIG), - BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW), - }; - struct sock_fprog prog = { - .len = (unsigned short)ARRAY_SIZE(filter), - .filter = filter, - }; + ERRNO_FILTER(valid, E2BIG); long ret; pid_t parent = getppid(); ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); ASSERT_EQ(0, ret); - ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog); + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog_valid); ASSERT_EQ(0, ret); EXPECT_EQ(parent, syscall(__NR_getppid)); @@ -568,26 +572,17 @@ TEST(ERRNO_valid) EXPECT_EQ(E2BIG, errno); } +/* Make sure an errno of zero is correctly handled by the arch code. */ TEST(ERRNO_zero) { - struct sock_filter filter[] = { - BPF_STMT(BPF_LD|BPF_W|BPF_ABS, - offsetof(struct seccomp_data, nr)), - BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_read, 0, 1), - BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ERRNO | 0), - BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW), - }; - struct sock_fprog prog = { - .len = (unsigned short)ARRAY_SIZE(filter), - .filter = filter, - }; + ERRNO_FILTER(zero, 0); long ret; pid_t parent = getppid(); ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); ASSERT_EQ(0, ret); - ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog); + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog_zero); ASSERT_EQ(0, ret); EXPECT_EQ(parent, syscall(__NR_getppid)); @@ -595,26 +590,21 @@ TEST(ERRNO_zero) EXPECT_EQ(0, read(0, NULL, 0)); } +/* + * The SECCOMP_RET_DATA mask is 16 bits wide, but errno is smaller. + * This tests that the errno value gets capped correctly, fixed by + * 580c57f10768 ("seccomp: cap SECCOMP_RET_ERRNO data to MAX_ERRNO"). + */ TEST(ERRNO_capped) { - struct sock_filter filter[] = { - BPF_STMT(BPF_LD|BPF_W|BPF_ABS, - offsetof(struct seccomp_data, nr)), - BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_read, 0, 1), - BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ERRNO | 4096), - BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW), - }; - struct sock_fprog prog = { - .len = (unsigned short)ARRAY_SIZE(filter), - .filter = filter, - }; + ERRNO_FILTER(capped, 4096); long ret; pid_t parent = getppid(); ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); ASSERT_EQ(0, ret); - ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog); + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog_capped); ASSERT_EQ(0, ret); EXPECT_EQ(parent, syscall(__NR_getppid)); @@ -622,6 +612,37 @@ TEST(ERRNO_capped) EXPECT_EQ(4095, errno); } +/* + * Filters are processed in reverse order: last applied is executed first. + * Since only the SECCOMP_RET_ACTION mask is tested for return values, the + * SECCOMP_RET_DATA mask results will follow the most recently applied + * matching filter return (and not the lowest or highest value). + */ +TEST(ERRNO_order) +{ + ERRNO_FILTER(first, 11); + ERRNO_FILTER(second, 13); + ERRNO_FILTER(third, 12); + long ret; + pid_t parent = getppid(); + + ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); + ASSERT_EQ(0, ret); + + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog_first); + ASSERT_EQ(0, ret); + + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog_second); + ASSERT_EQ(0, ret); + + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog_third); + ASSERT_EQ(0, ret); + + EXPECT_EQ(parent, syscall(__NR_getppid)); + EXPECT_EQ(-1, read(0, NULL, 0)); + EXPECT_EQ(12, errno); +} + FIXTURE_DATA(TRAP) { struct sock_fprog prog; }; -- cgit v1.2.3-59-g8ed1b From deb4de8b31bc5bf21efb6ac31150a01a631cd647 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Wed, 2 Aug 2017 15:00:40 -0700 Subject: seccomp: Provide matching filter for introspection Both the upcoming logging improvements and changes to RET_KILL will need to know which filter a given seccomp return value originated from. In order to delay logic processing of result until after the seccomp loop, this adds a single pointer assignment on matches. This will allow both log and RET_KILL logic to work off the filter rather than doing more expensive tests inside the time-critical run_filters loop. Running tight cycles of getpid() with filters attached shows no measurable difference in speed. Suggested-by: Tyler Hicks Signed-off-by: Kees Cook Reviewed-by: Tyler Hicks --- kernel/seccomp.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 98b59b5db90b..1f3347fc2605 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -171,10 +171,14 @@ static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen) /** * seccomp_run_filters - evaluates all seccomp filters against @sd * @sd: optional seccomp data to be passed to filters + * @match: stores struct seccomp_filter that resulted in the return value, + * unless filter returned SECCOMP_RET_ALLOW, in which case it will + * be unchanged. * * Returns valid seccomp BPF response codes. */ -static u32 seccomp_run_filters(const struct seccomp_data *sd) +static u32 seccomp_run_filters(const struct seccomp_data *sd, + struct seccomp_filter **match) { struct seccomp_data sd_local; u32 ret = SECCOMP_RET_ALLOW; @@ -198,8 +202,10 @@ static u32 seccomp_run_filters(const struct seccomp_data *sd) for (; f; f = f->prev) { u32 cur_ret = BPF_PROG_RUN(f->prog, sd); - if ((cur_ret & SECCOMP_RET_ACTION) < (ret & SECCOMP_RET_ACTION)) + if ((cur_ret & SECCOMP_RET_ACTION) < (ret & SECCOMP_RET_ACTION)) { ret = cur_ret; + *match = f; + } } return ret; } @@ -566,6 +572,7 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, const bool recheck_after_trace) { u32 filter_ret, action; + struct seccomp_filter *match = NULL; int data; /* @@ -574,7 +581,7 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, */ rmb(); - filter_ret = seccomp_run_filters(sd); + filter_ret = seccomp_run_filters(sd, &match); data = filter_ret & SECCOMP_RET_DATA; action = filter_ret & SECCOMP_RET_ACTION; @@ -638,6 +645,11 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, return 0; case SECCOMP_RET_ALLOW: + /* + * Note that the "match" filter will always be NULL for + * this action since SECCOMP_RET_ALLOW is the starting + * state in seccomp_run_filters(). + */ return 0; case SECCOMP_RET_KILL: -- cgit v1.2.3-59-g8ed1b From 8e5f1ad116df6b0de65eac458d5e7c318d1c05af Mon Sep 17 00:00:00 2001 From: Tyler Hicks Date: Fri, 11 Aug 2017 04:33:52 +0000 Subject: seccomp: Sysctl to display available actions This patch creates a read-only sysctl containing an ordered list of seccomp actions that the kernel supports. The ordering, from left to right, is the lowest action value (kill) to the highest action value (allow). Currently, a read of the sysctl file would return "kill trap errno trace allow". The contents of this sysctl file can be useful for userspace code as well as the system administrator. The path to the sysctl is: /proc/sys/kernel/seccomp/actions_avail libseccomp and other userspace code can easily determine which actions the current kernel supports. The set of actions supported by the current kernel may be different than the set of action macros found in kernel headers that were installed where the userspace code was built. In addition, this sysctl will allow system administrators to know which actions are supported by the kernel and make it easier to configure exactly what seccomp logs through the audit subsystem. Support for this level of logging configuration will come in a future patch. Signed-off-by: Tyler Hicks Signed-off-by: Kees Cook --- Documentation/sysctl/kernel.txt | 1 + Documentation/userspace-api/seccomp_filter.rst | 16 ++++++++ kernel/seccomp.c | 51 ++++++++++++++++++++++++++ 3 files changed, 68 insertions(+) diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt index bac23c198360..995c42cf86ba 100644 --- a/Documentation/sysctl/kernel.txt +++ b/Documentation/sysctl/kernel.txt @@ -74,6 +74,7 @@ show up in /proc/sys/kernel: - reboot-cmd [ SPARC only ] - rtsig-max - rtsig-nr +- seccomp/ ==> Documentation/userspace-api/seccomp_filter.rst - sem - sem_next_id [ sysv ipc ] - sg-big-buff [ generic SCSI device (sg) ] diff --git a/Documentation/userspace-api/seccomp_filter.rst b/Documentation/userspace-api/seccomp_filter.rst index f71eb5ef1f2d..35fc7cbf1d95 100644 --- a/Documentation/userspace-api/seccomp_filter.rst +++ b/Documentation/userspace-api/seccomp_filter.rst @@ -169,7 +169,23 @@ The ``samples/seccomp/`` directory contains both an x86-specific example and a more generic example of a higher level macro interface for BPF program generation. +Sysctls +======= + +Seccomp's sysctl files can be found in the ``/proc/sys/kernel/seccomp/`` +directory. Here's a description of each file in that directory: + +``actions_avail``: + A read-only ordered list of seccomp return values (refer to the + ``SECCOMP_RET_*`` macros above) in string form. The ordering, from + left-to-right, is the least permissive return value to the most + permissive return value. + The list represents the set of seccomp return values supported + by the kernel. A userspace program may use this list to + determine if the actions found in the ``seccomp.h``, when the + program was built, differs from the set of actions actually + supported in the current running kernel. Adding architecture support =========================== diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 1f3347fc2605..5f19f41e4e50 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -17,11 +17,13 @@ #include #include #include +#include #include #include #include #include #include +#include #ifdef CONFIG_HAVE_ARCH_SECCOMP_FILTER #include @@ -934,3 +936,52 @@ out: return ret; } #endif + +#ifdef CONFIG_SYSCTL + +/* Human readable action names for friendly sysctl interaction */ +#define SECCOMP_RET_KILL_NAME "kill" +#define SECCOMP_RET_TRAP_NAME "trap" +#define SECCOMP_RET_ERRNO_NAME "errno" +#define SECCOMP_RET_TRACE_NAME "trace" +#define SECCOMP_RET_ALLOW_NAME "allow" + +static const char seccomp_actions_avail[] = SECCOMP_RET_KILL_NAME " " + SECCOMP_RET_TRAP_NAME " " + SECCOMP_RET_ERRNO_NAME " " + SECCOMP_RET_TRACE_NAME " " + SECCOMP_RET_ALLOW_NAME; + +static struct ctl_path seccomp_sysctl_path[] = { + { .procname = "kernel", }, + { .procname = "seccomp", }, + { } +}; + +static struct ctl_table seccomp_sysctl_table[] = { + { + .procname = "actions_avail", + .data = (void *) &seccomp_actions_avail, + .maxlen = sizeof(seccomp_actions_avail), + .mode = 0444, + .proc_handler = proc_dostring, + }, + { } +}; + +static int __init seccomp_sysctl_init(void) +{ + struct ctl_table_header *hdr; + + hdr = register_sysctl_paths(seccomp_sysctl_path, seccomp_sysctl_table); + if (!hdr) + pr_warn("seccomp: sysctl registration failed\n"); + else + kmemleak_not_leak(hdr); + + return 0; +} + +device_initcall(seccomp_sysctl_init) + +#endif /* CONFIG_SYSCTL */ -- cgit v1.2.3-59-g8ed1b From d612b1fd8010d0d67b5287fe146b8b55bcbb8655 Mon Sep 17 00:00:00 2001 From: Tyler Hicks Date: Fri, 11 Aug 2017 04:33:53 +0000 Subject: seccomp: Operation for checking if an action is available Userspace code that needs to check if the kernel supports a given action may not be able to use the /proc/sys/kernel/seccomp/actions_avail sysctl. The process may be running in a sandbox and, therefore, sufficient filesystem access may not be available. This patch adds an operation to the seccomp(2) syscall that allows userspace code to ask the kernel if a given action is available. If the action is supported by the kernel, 0 is returned. If the action is not supported by the kernel, -1 is returned with errno set to -EOPNOTSUPP. If this check is attempted on a kernel that doesn't support this new operation, -1 is returned with errno set to -EINVAL meaning that userspace code will have the ability to differentiate between the two error cases. Signed-off-by: Tyler Hicks Suggested-by: Andy Lutomirski Signed-off-by: Kees Cook --- include/uapi/linux/seccomp.h | 5 ++-- kernel/seccomp.c | 26 +++++++++++++++++++ tools/testing/selftests/seccomp/seccomp_bpf.c | 36 +++++++++++++++++++++++++++ 3 files changed, 65 insertions(+), 2 deletions(-) diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h index 0f238a43ff1e..aaad61cc46bc 100644 --- a/include/uapi/linux/seccomp.h +++ b/include/uapi/linux/seccomp.h @@ -11,8 +11,9 @@ #define SECCOMP_MODE_FILTER 2 /* uses user-supplied filter. */ /* Valid operations for seccomp syscall. */ -#define SECCOMP_SET_MODE_STRICT 0 -#define SECCOMP_SET_MODE_FILTER 1 +#define SECCOMP_SET_MODE_STRICT 0 +#define SECCOMP_SET_MODE_FILTER 1 +#define SECCOMP_GET_ACTION_AVAIL 2 /* Valid flags for SECCOMP_SET_MODE_FILTER */ #define SECCOMP_FILTER_FLAG_TSYNC 1 diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 5f19f41e4e50..7a6089f66fed 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -808,6 +808,27 @@ static inline long seccomp_set_mode_filter(unsigned int flags, } #endif +static long seccomp_get_action_avail(const char __user *uaction) +{ + u32 action; + + if (copy_from_user(&action, uaction, sizeof(action))) + return -EFAULT; + + switch (action) { + case SECCOMP_RET_KILL: + case SECCOMP_RET_TRAP: + case SECCOMP_RET_ERRNO: + case SECCOMP_RET_TRACE: + case SECCOMP_RET_ALLOW: + break; + default: + return -EOPNOTSUPP; + } + + return 0; +} + /* Common entry point for both prctl and syscall. */ static long do_seccomp(unsigned int op, unsigned int flags, const char __user *uargs) @@ -819,6 +840,11 @@ static long do_seccomp(unsigned int op, unsigned int flags, return seccomp_set_mode_strict(); case SECCOMP_SET_MODE_FILTER: return seccomp_set_mode_filter(flags, uargs); + case SECCOMP_GET_ACTION_AVAIL: + if (flags != 0) + return -EINVAL; + + return seccomp_get_action_avail(uargs); default: return -EINVAL; } diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c index 2fb49d99588d..1f2888f6678b 100644 --- a/tools/testing/selftests/seccomp/seccomp_bpf.c +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c @@ -1731,6 +1731,10 @@ TEST_F_SIGNAL(TRACE_syscall, kill_after_ptrace, SIGSYS) #define SECCOMP_SET_MODE_FILTER 1 #endif +#ifndef SECCOMP_GET_ACTION_AVAIL +#define SECCOMP_GET_ACTION_AVAIL 2 +#endif + #ifndef SECCOMP_FILTER_FLAG_TSYNC #define SECCOMP_FILTER_FLAG_TSYNC 1 #endif @@ -2469,6 +2473,38 @@ TEST(syscall_restart) _metadata->passed = 0; } +TEST(get_action_avail) +{ + __u32 actions[] = { SECCOMP_RET_KILL, SECCOMP_RET_TRAP, + SECCOMP_RET_ERRNO, SECCOMP_RET_TRACE, + SECCOMP_RET_ALLOW }; + __u32 unknown_action = 0x10000000U; + int i; + long ret; + + ret = seccomp(SECCOMP_GET_ACTION_AVAIL, 0, &actions[0]); + ASSERT_NE(ENOSYS, errno) { + TH_LOG("Kernel does not support seccomp syscall!"); + } + ASSERT_NE(EINVAL, errno) { + TH_LOG("Kernel does not support SECCOMP_GET_ACTION_AVAIL operation!"); + } + EXPECT_EQ(ret, 0); + + for (i = 0; i < ARRAY_SIZE(actions); i++) { + ret = seccomp(SECCOMP_GET_ACTION_AVAIL, 0, &actions[i]); + EXPECT_EQ(ret, 0) { + TH_LOG("Expected action (0x%X) not available!", + actions[i]); + } + } + + /* Check that an unknown action is handled properly (EOPNOTSUPP) */ + ret = seccomp(SECCOMP_GET_ACTION_AVAIL, 0, &unknown_action); + EXPECT_EQ(ret, -1); + EXPECT_EQ(errno, EOPNOTSUPP); +} + /* * TODO: * - add microbenchmarks -- cgit v1.2.3-59-g8ed1b From 0ddec0fc8900201c0897b87b762b7c420436662f Mon Sep 17 00:00:00 2001 From: Tyler Hicks Date: Fri, 11 Aug 2017 04:33:54 +0000 Subject: seccomp: Sysctl to configure actions that are allowed to be logged Adminstrators can write to this sysctl to set the seccomp actions that are allowed to be logged. Any actions not found in this sysctl will not be logged. For example, all SECCOMP_RET_KILL, SECCOMP_RET_TRAP, and SECCOMP_RET_ERRNO actions would be loggable if "kill trap errno" were written to the sysctl. SECCOMP_RET_TRACE actions would not be logged since its string representation ("trace") wasn't present in the sysctl value. The path to the sysctl is: /proc/sys/kernel/seccomp/actions_logged The actions_avail sysctl can be read to discover the valid action names that can be written to the actions_logged sysctl with the exception of "allow". SECCOMP_RET_ALLOW actions cannot be configured for logging. The default setting for the sysctl is to allow all actions to be logged except SECCOMP_RET_ALLOW. While only SECCOMP_RET_KILL actions are currently logged, an upcoming patch will allow applications to request additional actions to be logged. There's one important exception to this sysctl. If a task is specifically being audited, meaning that an audit context has been allocated for the task, seccomp will log all actions other than SECCOMP_RET_ALLOW despite the value of actions_logged. This exception preserves the existing auditing behavior of tasks with an allocated audit context. With this patch, the logic for deciding if an action will be logged is: if action == RET_ALLOW: do not log else if action == RET_KILL && RET_KILL in actions_logged: log else if audit_enabled && task-is-being-audited: log else: do not log Signed-off-by: Tyler Hicks Signed-off-by: Kees Cook --- Documentation/userspace-api/seccomp_filter.rst | 18 +++ include/linux/audit.h | 6 +- kernel/seccomp.c | 171 ++++++++++++++++++++++++- 3 files changed, 187 insertions(+), 8 deletions(-) diff --git a/Documentation/userspace-api/seccomp_filter.rst b/Documentation/userspace-api/seccomp_filter.rst index 35fc7cbf1d95..2d1d8ab04ac5 100644 --- a/Documentation/userspace-api/seccomp_filter.rst +++ b/Documentation/userspace-api/seccomp_filter.rst @@ -187,6 +187,24 @@ directory. Here's a description of each file in that directory: program was built, differs from the set of actions actually supported in the current running kernel. +``actions_logged``: + A read-write ordered list of seccomp return values (refer to the + ``SECCOMP_RET_*`` macros above) that are allowed to be logged. Writes + to the file do not need to be in ordered form but reads from the file + will be ordered in the same way as the actions_avail sysctl. + + It is important to note that the value of ``actions_logged`` does not + prevent certain actions from being logged when the audit subsystem is + configured to audit a task. If the action is not found in + ``actions_logged`` list, the final decision on whether to audit the + action for that task is ultimately left up to the audit subsystem to + decide for all seccomp return values other than ``SECCOMP_RET_ALLOW``. + + The ``allow`` string is not accepted in the ``actions_logged`` sysctl + as it is not possible to log ``SECCOMP_RET_ALLOW`` actions. Attempting + to write ``allow`` to the sysctl will result in an EINVAL being + returned. + Adding architecture support =========================== diff --git a/include/linux/audit.h b/include/linux/audit.h index 2150bdccfbab..8c30f06d639d 100644 --- a/include/linux/audit.h +++ b/include/linux/audit.h @@ -314,11 +314,7 @@ void audit_core_dumps(long signr); static inline void audit_seccomp(unsigned long syscall, long signr, int code) { - if (!audit_enabled) - return; - - /* Force a record to be reported if a signal was delivered. */ - if (signr || unlikely(!audit_dummy_context())) + if (audit_enabled && unlikely(!audit_dummy_context())) __audit_seccomp(syscall, signr, code); } diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 7a6089f66fed..54357e361aea 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -522,6 +522,45 @@ static void seccomp_send_sigsys(int syscall, int reason) } #endif /* CONFIG_SECCOMP_FILTER */ +/* For use with seccomp_actions_logged */ +#define SECCOMP_LOG_KILL (1 << 0) +#define SECCOMP_LOG_TRAP (1 << 2) +#define SECCOMP_LOG_ERRNO (1 << 3) +#define SECCOMP_LOG_TRACE (1 << 4) +#define SECCOMP_LOG_ALLOW (1 << 5) + +static u32 seccomp_actions_logged = SECCOMP_LOG_KILL | SECCOMP_LOG_TRAP | + SECCOMP_LOG_ERRNO | SECCOMP_LOG_TRACE; + +static inline void seccomp_log(unsigned long syscall, long signr, u32 action) +{ + bool log = false; + + switch (action) { + case SECCOMP_RET_ALLOW: + case SECCOMP_RET_TRAP: + case SECCOMP_RET_ERRNO: + case SECCOMP_RET_TRACE: + break; + case SECCOMP_RET_KILL: + default: + log = seccomp_actions_logged & SECCOMP_LOG_KILL; + } + + /* + * Force an audit message to be emitted when the action is RET_KILL and + * the action is allowed to be logged by the admin. + */ + if (log) + return __audit_seccomp(syscall, signr, action); + + /* + * Let the audit subsystem decide if the action should be audited based + * on whether the current task itself is being audited. + */ + return audit_seccomp(syscall, signr, action); +} + /* * Secure computing mode 1 allows only read/write/exit/sigreturn. * To be fully secure this must be combined with rlimit @@ -547,7 +586,7 @@ static void __secure_computing_strict(int this_syscall) #ifdef SECCOMP_DEBUG dump_stack(); #endif - audit_seccomp(this_syscall, SIGKILL, SECCOMP_RET_KILL); + seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL); do_exit(SIGKILL); } @@ -656,7 +695,7 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, case SECCOMP_RET_KILL: default: - audit_seccomp(this_syscall, SIGSYS, action); + seccomp_log(this_syscall, SIGSYS, action); /* Dump core only if this is the last remaining thread. */ if (get_nr_threads(current) == 1) { siginfo_t info; @@ -673,7 +712,7 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, unreachable(); skip: - audit_seccomp(this_syscall, 0, action); + seccomp_log(this_syscall, 0, action); return -1; } #else @@ -978,6 +1017,127 @@ static const char seccomp_actions_avail[] = SECCOMP_RET_KILL_NAME " " SECCOMP_RET_TRACE_NAME " " SECCOMP_RET_ALLOW_NAME; +struct seccomp_log_name { + u32 log; + const char *name; +}; + +static const struct seccomp_log_name seccomp_log_names[] = { + { SECCOMP_LOG_KILL, SECCOMP_RET_KILL_NAME }, + { SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME }, + { SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME }, + { SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME }, + { SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME }, + { } +}; + +static bool seccomp_names_from_actions_logged(char *names, size_t size, + u32 actions_logged) +{ + const struct seccomp_log_name *cur; + bool append_space = false; + + for (cur = seccomp_log_names; cur->name && size; cur++) { + ssize_t ret; + + if (!(actions_logged & cur->log)) + continue; + + if (append_space) { + ret = strscpy(names, " ", size); + if (ret < 0) + return false; + + names += ret; + size -= ret; + } else + append_space = true; + + ret = strscpy(names, cur->name, size); + if (ret < 0) + return false; + + names += ret; + size -= ret; + } + + return true; +} + +static bool seccomp_action_logged_from_name(u32 *action_logged, + const char *name) +{ + const struct seccomp_log_name *cur; + + for (cur = seccomp_log_names; cur->name; cur++) { + if (!strcmp(cur->name, name)) { + *action_logged = cur->log; + return true; + } + } + + return false; +} + +static bool seccomp_actions_logged_from_names(u32 *actions_logged, char *names) +{ + char *name; + + *actions_logged = 0; + while ((name = strsep(&names, " ")) && *name) { + u32 action_logged = 0; + + if (!seccomp_action_logged_from_name(&action_logged, name)) + return false; + + *actions_logged |= action_logged; + } + + return true; +} + +static int seccomp_actions_logged_handler(struct ctl_table *ro_table, int write, + void __user *buffer, size_t *lenp, + loff_t *ppos) +{ + char names[sizeof(seccomp_actions_avail)]; + struct ctl_table table; + int ret; + + if (write && !capable(CAP_SYS_ADMIN)) + return -EPERM; + + memset(names, 0, sizeof(names)); + + if (!write) { + if (!seccomp_names_from_actions_logged(names, sizeof(names), + seccomp_actions_logged)) + return -EINVAL; + } + + table = *ro_table; + table.data = names; + table.maxlen = sizeof(names); + ret = proc_dostring(&table, write, buffer, lenp, ppos); + if (ret) + return ret; + + if (write) { + u32 actions_logged; + + if (!seccomp_actions_logged_from_names(&actions_logged, + table.data)) + return -EINVAL; + + if (actions_logged & SECCOMP_LOG_ALLOW) + return -EINVAL; + + seccomp_actions_logged = actions_logged; + } + + return 0; +} + static struct ctl_path seccomp_sysctl_path[] = { { .procname = "kernel", }, { .procname = "seccomp", }, @@ -992,6 +1152,11 @@ static struct ctl_table seccomp_sysctl_table[] = { .mode = 0444, .proc_handler = proc_dostring, }, + { + .procname = "actions_logged", + .mode = 0644, + .proc_handler = seccomp_actions_logged_handler, + }, { } }; -- cgit v1.2.3-59-g8ed1b From 2b7ea5b5b5799f2878ed454bb48032bed6d101d3 Mon Sep 17 00:00:00 2001 From: Tyler Hicks Date: Fri, 11 Aug 2017 04:33:55 +0000 Subject: seccomp: Selftest for detection of filter flag support Userspace needs to be able to reliably detect the support of a filter flag. A good way of doing that is by attempting to enter filter mode, with the flag bit(s) in question set, and a NULL pointer for the args parameter of seccomp(2). EFAULT indicates that the flag is valid and EINVAL indicates that the flag is invalid. This patch adds a selftest that can be used to test this method of detection in userspace. Signed-off-by: Tyler Hicks Signed-off-by: Kees Cook --- tools/testing/selftests/seccomp/seccomp_bpf.c | 60 +++++++++++++++++++++++++++ 1 file changed, 60 insertions(+) diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c index 1f2888f6678b..abf708e09892 100644 --- a/tools/testing/selftests/seccomp/seccomp_bpf.c +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c @@ -1835,6 +1835,66 @@ TEST(seccomp_syscall_mode_lock) } } +/* + * Test detection of known and unknown filter flags. Userspace needs to be able + * to check if a filter flag is supported by the current kernel and a good way + * of doing that is by attempting to enter filter mode, with the flag bit in + * question set, and a NULL pointer for the _args_ parameter. EFAULT indicates + * that the flag is valid and EINVAL indicates that the flag is invalid. + */ +TEST(detect_seccomp_filter_flags) +{ + unsigned int flags[] = { SECCOMP_FILTER_FLAG_TSYNC }; + unsigned int flag, all_flags; + int i; + long ret; + + /* Test detection of known-good filter flags */ + for (i = 0, all_flags = 0; i < ARRAY_SIZE(flags); i++) { + flag = flags[i]; + ret = seccomp(SECCOMP_SET_MODE_FILTER, flag, NULL); + ASSERT_NE(ENOSYS, errno) { + TH_LOG("Kernel does not support seccomp syscall!"); + } + EXPECT_EQ(-1, ret); + EXPECT_EQ(EFAULT, errno) { + TH_LOG("Failed to detect that a known-good filter flag (0x%X) is supported!", + flag); + } + + all_flags |= flag; + } + + /* Test detection of all known-good filter flags */ + ret = seccomp(SECCOMP_SET_MODE_FILTER, all_flags, NULL); + EXPECT_EQ(-1, ret); + EXPECT_EQ(EFAULT, errno) { + TH_LOG("Failed to detect that all known-good filter flags (0x%X) are supported!", + all_flags); + } + + /* Test detection of an unknown filter flag */ + flag = -1; + ret = seccomp(SECCOMP_SET_MODE_FILTER, flag, NULL); + EXPECT_EQ(-1, ret); + EXPECT_EQ(EINVAL, errno) { + TH_LOG("Failed to detect that an unknown filter flag (0x%X) is unsupported!", + flag); + } + + /* + * Test detection of an unknown filter flag that may simply need to be + * added to this test + */ + flag = flags[ARRAY_SIZE(flags) - 1] << 1; + ret = seccomp(SECCOMP_SET_MODE_FILTER, flag, NULL); + EXPECT_EQ(-1, ret); + EXPECT_EQ(EINVAL, errno) { + TH_LOG("Failed to detect that an unknown filter flag (0x%X) is unsupported! Does a new flag need to be added to this test?", + flag); + } +} + TEST(TSYNC_first) { struct sock_filter filter[] = { -- cgit v1.2.3-59-g8ed1b From e66a39977985b1e69e17c4042cb290768eca9b02 Mon Sep 17 00:00:00 2001 From: Tyler Hicks Date: Fri, 11 Aug 2017 04:33:56 +0000 Subject: seccomp: Filter flag to log all actions except SECCOMP_RET_ALLOW Add a new filter flag, SECCOMP_FILTER_FLAG_LOG, that enables logging for all actions except for SECCOMP_RET_ALLOW for the given filter. SECCOMP_RET_KILL actions are always logged, when "kill" is in the actions_logged sysctl, and SECCOMP_RET_ALLOW actions are never logged, regardless of this flag. This flag can be used to create noisy filters that result in all non-allowed actions to be logged. A process may have one noisy filter, which is loaded with this flag, as well as a quiet filter that's not loaded with this flag. This allows for the actions in a set of filters to be selectively conveyed to the admin. Since a system could have a large number of allocated seccomp_filter structs, struct packing was taken in consideration. On 64 bit x86, the new log member takes up one byte of an existing four byte hole in the struct. On 32 bit x86, the new log member creates a new four byte hole (unavoidable) and consumes one of those bytes. Unfortunately, the tests added for SECCOMP_FILTER_FLAG_LOG are not capable of inspecting the audit log to verify that the actions taken in the filter were logged. With this patch, the logic for deciding if an action will be logged is: if action == RET_ALLOW: do not log else if action == RET_KILL && RET_KILL in actions_logged: log else if filter-requests-logging && action in actions_logged: log else if audit_enabled && process-is-being-audited: log else: do not log Signed-off-by: Tyler Hicks Signed-off-by: Kees Cook --- include/linux/seccomp.h | 3 +- include/uapi/linux/seccomp.h | 1 + kernel/seccomp.c | 26 +++++++--- tools/testing/selftests/seccomp/seccomp_bpf.c | 69 ++++++++++++++++++++++++++- 4 files changed, 91 insertions(+), 8 deletions(-) diff --git a/include/linux/seccomp.h b/include/linux/seccomp.h index ecc296c137cd..c8bef436b61d 100644 --- a/include/linux/seccomp.h +++ b/include/linux/seccomp.h @@ -3,7 +3,8 @@ #include -#define SECCOMP_FILTER_FLAG_MASK (SECCOMP_FILTER_FLAG_TSYNC) +#define SECCOMP_FILTER_FLAG_MASK (SECCOMP_FILTER_FLAG_TSYNC | \ + SECCOMP_FILTER_FLAG_LOG) #ifdef CONFIG_SECCOMP diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h index aaad61cc46bc..19a611d0712e 100644 --- a/include/uapi/linux/seccomp.h +++ b/include/uapi/linux/seccomp.h @@ -17,6 +17,7 @@ /* Valid flags for SECCOMP_SET_MODE_FILTER */ #define SECCOMP_FILTER_FLAG_TSYNC 1 +#define SECCOMP_FILTER_FLAG_LOG 2 /* * All BPF programs must return a 32-bit value. diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 54357e361aea..ed9fde418fc4 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -44,6 +44,7 @@ * get/put helpers should be used when accessing an instance * outside of a lifetime-guarded section. In general, this * is only needed for handling filters shared across tasks. + * @log: true if all actions except for SECCOMP_RET_ALLOW should be logged * @prev: points to a previously installed, or inherited, filter * @prog: the BPF program to evaluate * @@ -59,6 +60,7 @@ */ struct seccomp_filter { refcount_t usage; + bool log; struct seccomp_filter *prev; struct bpf_prog *prog; }; @@ -452,6 +454,10 @@ static long seccomp_attach_filter(unsigned int flags, return ret; } + /* Set log flag, if present. */ + if (flags & SECCOMP_FILTER_FLAG_LOG) + filter->log = true; + /* * If there is an existing filter, make it the prev and don't drop its * task reference. @@ -532,15 +538,22 @@ static void seccomp_send_sigsys(int syscall, int reason) static u32 seccomp_actions_logged = SECCOMP_LOG_KILL | SECCOMP_LOG_TRAP | SECCOMP_LOG_ERRNO | SECCOMP_LOG_TRACE; -static inline void seccomp_log(unsigned long syscall, long signr, u32 action) +static inline void seccomp_log(unsigned long syscall, long signr, u32 action, + bool requested) { bool log = false; switch (action) { case SECCOMP_RET_ALLOW: + break; case SECCOMP_RET_TRAP: + log = requested && seccomp_actions_logged & SECCOMP_LOG_TRAP; + break; case SECCOMP_RET_ERRNO: + log = requested && seccomp_actions_logged & SECCOMP_LOG_ERRNO; + break; case SECCOMP_RET_TRACE: + log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE; break; case SECCOMP_RET_KILL: default: @@ -548,8 +561,9 @@ static inline void seccomp_log(unsigned long syscall, long signr, u32 action) } /* - * Force an audit message to be emitted when the action is RET_KILL and - * the action is allowed to be logged by the admin. + * Force an audit message to be emitted when the action is RET_KILL or + * the FILTER_FLAG_LOG bit was set and the action is allowed to be + * logged by the admin. */ if (log) return __audit_seccomp(syscall, signr, action); @@ -586,7 +600,7 @@ static void __secure_computing_strict(int this_syscall) #ifdef SECCOMP_DEBUG dump_stack(); #endif - seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL); + seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL, true); do_exit(SIGKILL); } @@ -695,7 +709,7 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, case SECCOMP_RET_KILL: default: - seccomp_log(this_syscall, SIGSYS, action); + seccomp_log(this_syscall, SIGSYS, action, true); /* Dump core only if this is the last remaining thread. */ if (get_nr_threads(current) == 1) { siginfo_t info; @@ -712,7 +726,7 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, unreachable(); skip: - seccomp_log(this_syscall, 0, action); + seccomp_log(this_syscall, 0, action, match ? match->log : false); return -1; } #else diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c index abf708e09892..1c8c22ce7740 100644 --- a/tools/testing/selftests/seccomp/seccomp_bpf.c +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c @@ -1739,6 +1739,10 @@ TEST_F_SIGNAL(TRACE_syscall, kill_after_ptrace, SIGSYS) #define SECCOMP_FILTER_FLAG_TSYNC 1 #endif +#ifndef SECCOMP_FILTER_FLAG_LOG +#define SECCOMP_FILTER_FLAG_LOG 2 +#endif + #ifndef seccomp int seccomp(unsigned int op, unsigned int flags, void *args) { @@ -1844,7 +1848,8 @@ TEST(seccomp_syscall_mode_lock) */ TEST(detect_seccomp_filter_flags) { - unsigned int flags[] = { SECCOMP_FILTER_FLAG_TSYNC }; + unsigned int flags[] = { SECCOMP_FILTER_FLAG_TSYNC, + SECCOMP_FILTER_FLAG_LOG }; unsigned int flag, all_flags; int i; long ret; @@ -2533,6 +2538,67 @@ TEST(syscall_restart) _metadata->passed = 0; } +TEST_SIGNAL(filter_flag_log, SIGSYS) +{ + struct sock_filter allow_filter[] = { + BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW), + }; + struct sock_filter kill_filter[] = { + BPF_STMT(BPF_LD|BPF_W|BPF_ABS, + offsetof(struct seccomp_data, nr)), + BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_getpid, 0, 1), + BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL), + BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW), + }; + struct sock_fprog allow_prog = { + .len = (unsigned short)ARRAY_SIZE(allow_filter), + .filter = allow_filter, + }; + struct sock_fprog kill_prog = { + .len = (unsigned short)ARRAY_SIZE(kill_filter), + .filter = kill_filter, + }; + long ret; + pid_t parent = getppid(); + + ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); + ASSERT_EQ(0, ret); + + /* Verify that the FILTER_FLAG_LOG flag isn't accepted in strict mode */ + ret = seccomp(SECCOMP_SET_MODE_STRICT, SECCOMP_FILTER_FLAG_LOG, + &allow_prog); + ASSERT_NE(ENOSYS, errno) { + TH_LOG("Kernel does not support seccomp syscall!"); + } + EXPECT_NE(0, ret) { + TH_LOG("Kernel accepted FILTER_FLAG_LOG flag in strict mode!"); + } + EXPECT_EQ(EINVAL, errno) { + TH_LOG("Kernel returned unexpected errno for FILTER_FLAG_LOG flag in strict mode!"); + } + + /* Verify that a simple, permissive filter can be added with no flags */ + ret = seccomp(SECCOMP_SET_MODE_FILTER, 0, &allow_prog); + EXPECT_EQ(0, ret); + + /* See if the same filter can be added with the FILTER_FLAG_LOG flag */ + ret = seccomp(SECCOMP_SET_MODE_FILTER, SECCOMP_FILTER_FLAG_LOG, + &allow_prog); + ASSERT_NE(EINVAL, errno) { + TH_LOG("Kernel does not support the FILTER_FLAG_LOG flag!"); + } + EXPECT_EQ(0, ret); + + /* Ensure that the kill filter works with the FILTER_FLAG_LOG flag */ + ret = seccomp(SECCOMP_SET_MODE_FILTER, SECCOMP_FILTER_FLAG_LOG, + &kill_prog); + EXPECT_EQ(0, ret); + + EXPECT_EQ(parent, syscall(__NR_getppid)); + /* getpid() should never return. */ + EXPECT_EQ(0, syscall(__NR_getpid)); +} + TEST(get_action_avail) { __u32 actions[] = { SECCOMP_RET_KILL, SECCOMP_RET_TRAP, @@ -2573,6 +2639,7 @@ TEST(get_action_avail) * - endianness checking when appropriate * - 64-bit arg prodding * - arch value testing (x86 modes especially) + * - verify that FILTER_FLAG_LOG filters generate log messages * - ... */ -- cgit v1.2.3-59-g8ed1b From 59f5cf44a38284eb9e76270c786fb6cc62ef8ac4 Mon Sep 17 00:00:00 2001 From: Tyler Hicks Date: Fri, 11 Aug 2017 04:33:57 +0000 Subject: seccomp: Action to log before allowing Add a new action, SECCOMP_RET_LOG, that logs a syscall before allowing the syscall. At the implementation level, this action is identical to the existing SECCOMP_RET_ALLOW action. However, it can be very useful when initially developing a seccomp filter for an application. The developer can set the default action to be SECCOMP_RET_LOG, maybe mark any obviously needed syscalls with SECCOMP_RET_ALLOW, and then put the application through its paces. A list of syscalls that triggered the default action (SECCOMP_RET_LOG) can be easily gleaned from the logs and that list can be used to build the syscall whitelist. Finally, the developer can change the default action to the desired value. This provides a more friendly experience than seeing the application get killed, then updating the filter and rebuilding the app, seeing the application get killed due to a different syscall, then updating the filter and rebuilding the app, etc. The functionality is similar to what's supported by the various LSMs. SELinux has permissive mode, AppArmor has complain mode, SMACK has bring-up mode, etc. SECCOMP_RET_LOG is given a lower value than SECCOMP_RET_ALLOW as allow while logging is slightly more restrictive than quietly allowing. Unfortunately, the tests added for SECCOMP_RET_LOG are not capable of inspecting the audit log to verify that the syscall was logged. With this patch, the logic for deciding if an action will be logged is: if action == RET_ALLOW: do not log else if action == RET_KILL && RET_KILL in actions_logged: log else if action == RET_LOG && RET_LOG in actions_logged: log else if filter-requests-logging && action in actions_logged: log else if audit_enabled && process-is-being-audited: log else: do not log Signed-off-by: Tyler Hicks Signed-off-by: Kees Cook --- Documentation/userspace-api/seccomp_filter.rst | 9 +++ include/uapi/linux/seccomp.h | 1 + kernel/seccomp.c | 23 ++++-- tools/testing/selftests/seccomp/seccomp_bpf.c | 98 +++++++++++++++++++++++++- 4 files changed, 125 insertions(+), 6 deletions(-) diff --git a/Documentation/userspace-api/seccomp_filter.rst b/Documentation/userspace-api/seccomp_filter.rst index 2d1d8ab04ac5..f4977357daf2 100644 --- a/Documentation/userspace-api/seccomp_filter.rst +++ b/Documentation/userspace-api/seccomp_filter.rst @@ -141,6 +141,15 @@ In precedence order, they are: allow use of ptrace, even of other sandboxed processes, without extreme care; ptracers can use this mechanism to escape.) +``SECCOMP_RET_LOG``: + Results in the system call being executed after it is logged. This + should be used by application developers to learn which syscalls their + application needs without having to iterate through multiple test and + development cycles to build the list. + + This action will only be logged if "log" is present in the + actions_logged sysctl string. + ``SECCOMP_RET_ALLOW``: Results in the system call being executed. diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h index 19a611d0712e..f94433263e4b 100644 --- a/include/uapi/linux/seccomp.h +++ b/include/uapi/linux/seccomp.h @@ -31,6 +31,7 @@ #define SECCOMP_RET_TRAP 0x00030000U /* disallow and force a SIGSYS */ #define SECCOMP_RET_ERRNO 0x00050000U /* returns an errno */ #define SECCOMP_RET_TRACE 0x7ff00000U /* pass to a tracer or disallow */ +#define SECCOMP_RET_LOG 0x7ffc0000U /* allow after logging */ #define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */ /* Masks for the return value sections. */ diff --git a/kernel/seccomp.c b/kernel/seccomp.c index ed9fde418fc4..59cde2ed3b92 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -533,10 +533,12 @@ static void seccomp_send_sigsys(int syscall, int reason) #define SECCOMP_LOG_TRAP (1 << 2) #define SECCOMP_LOG_ERRNO (1 << 3) #define SECCOMP_LOG_TRACE (1 << 4) -#define SECCOMP_LOG_ALLOW (1 << 5) +#define SECCOMP_LOG_LOG (1 << 5) +#define SECCOMP_LOG_ALLOW (1 << 6) static u32 seccomp_actions_logged = SECCOMP_LOG_KILL | SECCOMP_LOG_TRAP | - SECCOMP_LOG_ERRNO | SECCOMP_LOG_TRACE; + SECCOMP_LOG_ERRNO | SECCOMP_LOG_TRACE | + SECCOMP_LOG_LOG; static inline void seccomp_log(unsigned long syscall, long signr, u32 action, bool requested) @@ -555,15 +557,18 @@ static inline void seccomp_log(unsigned long syscall, long signr, u32 action, case SECCOMP_RET_TRACE: log = requested && seccomp_actions_logged & SECCOMP_LOG_TRACE; break; + case SECCOMP_RET_LOG: + log = seccomp_actions_logged & SECCOMP_LOG_LOG; + break; case SECCOMP_RET_KILL: default: log = seccomp_actions_logged & SECCOMP_LOG_KILL; } /* - * Force an audit message to be emitted when the action is RET_KILL or - * the FILTER_FLAG_LOG bit was set and the action is allowed to be - * logged by the admin. + * Force an audit message to be emitted when the action is RET_KILL, + * RET_LOG, or the FILTER_FLAG_LOG bit was set and the action is + * allowed to be logged by the admin. */ if (log) return __audit_seccomp(syscall, signr, action); @@ -699,6 +704,10 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, return 0; + case SECCOMP_RET_LOG: + seccomp_log(this_syscall, 0, action, true); + return 0; + case SECCOMP_RET_ALLOW: /* * Note that the "match" filter will always be NULL for @@ -873,6 +882,7 @@ static long seccomp_get_action_avail(const char __user *uaction) case SECCOMP_RET_TRAP: case SECCOMP_RET_ERRNO: case SECCOMP_RET_TRACE: + case SECCOMP_RET_LOG: case SECCOMP_RET_ALLOW: break; default: @@ -1023,12 +1033,14 @@ out: #define SECCOMP_RET_TRAP_NAME "trap" #define SECCOMP_RET_ERRNO_NAME "errno" #define SECCOMP_RET_TRACE_NAME "trace" +#define SECCOMP_RET_LOG_NAME "log" #define SECCOMP_RET_ALLOW_NAME "allow" static const char seccomp_actions_avail[] = SECCOMP_RET_KILL_NAME " " SECCOMP_RET_TRAP_NAME " " SECCOMP_RET_ERRNO_NAME " " SECCOMP_RET_TRACE_NAME " " + SECCOMP_RET_LOG_NAME " " SECCOMP_RET_ALLOW_NAME; struct seccomp_log_name { @@ -1041,6 +1053,7 @@ static const struct seccomp_log_name seccomp_log_names[] = { { SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME }, { SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME }, { SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME }, + { SECCOMP_LOG_LOG, SECCOMP_RET_LOG_NAME }, { SECCOMP_LOG_ALLOW, SECCOMP_RET_ALLOW_NAME }, { } }; diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c index 1c8c22ce7740..7372958eccb5 100644 --- a/tools/testing/selftests/seccomp/seccomp_bpf.c +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c @@ -74,7 +74,12 @@ #define SECCOMP_RET_ERRNO 0x00050000U /* returns an errno */ #define SECCOMP_RET_TRACE 0x7ff00000U /* pass to a tracer or disallow */ #define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */ +#endif +#ifndef SECCOMP_RET_LOG +#define SECCOMP_RET_LOG 0x7ffc0000U /* allow after logging */ +#endif +#ifndef SECCOMP_RET_ACTION /* Masks for the return value sections. */ #define SECCOMP_RET_ACTION 0x7fff0000U #define SECCOMP_RET_DATA 0x0000ffffU @@ -342,6 +347,28 @@ TEST(empty_prog) EXPECT_EQ(EINVAL, errno); } +TEST(log_all) +{ + struct sock_filter filter[] = { + BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_LOG), + }; + struct sock_fprog prog = { + .len = (unsigned short)ARRAY_SIZE(filter), + .filter = filter, + }; + long ret; + pid_t parent = getppid(); + + ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); + ASSERT_EQ(0, ret); + + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &prog); + ASSERT_EQ(0, ret); + + /* getppid() should succeed and be logged (no check for logging) */ + EXPECT_EQ(parent, syscall(__NR_getppid)); +} + TEST_SIGNAL(unknown_ret_is_kill_inside, SIGSYS) { struct sock_filter filter[] = { @@ -756,6 +783,7 @@ TEST_F(TRAP, handler) FIXTURE_DATA(precedence) { struct sock_fprog allow; + struct sock_fprog log; struct sock_fprog trace; struct sock_fprog error; struct sock_fprog trap; @@ -767,6 +795,13 @@ FIXTURE_SETUP(precedence) struct sock_filter allow_insns[] = { BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW), }; + struct sock_filter log_insns[] = { + BPF_STMT(BPF_LD|BPF_W|BPF_ABS, + offsetof(struct seccomp_data, nr)), + BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_getpid, 1, 0), + BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW), + BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_LOG), + }; struct sock_filter trace_insns[] = { BPF_STMT(BPF_LD|BPF_W|BPF_ABS, offsetof(struct seccomp_data, nr)), @@ -803,6 +838,7 @@ FIXTURE_SETUP(precedence) memcpy(self->_x.filter, &_x##_insns, sizeof(_x##_insns)); \ self->_x.len = (unsigned short)ARRAY_SIZE(_x##_insns) FILTER_ALLOC(allow); + FILTER_ALLOC(log); FILTER_ALLOC(trace); FILTER_ALLOC(error); FILTER_ALLOC(trap); @@ -813,6 +849,7 @@ FIXTURE_TEARDOWN(precedence) { #define FILTER_FREE(_x) if (self->_x.filter) free(self->_x.filter) FILTER_FREE(allow); + FILTER_FREE(log); FILTER_FREE(trace); FILTER_FREE(error); FILTER_FREE(trap); @@ -830,6 +867,8 @@ TEST_F(precedence, allow_ok) ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow); ASSERT_EQ(0, ret); + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log); + ASSERT_EQ(0, ret); ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace); ASSERT_EQ(0, ret); ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error); @@ -854,6 +893,8 @@ TEST_F_SIGNAL(precedence, kill_is_highest, SIGSYS) ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow); ASSERT_EQ(0, ret); + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log); + ASSERT_EQ(0, ret); ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace); ASSERT_EQ(0, ret); ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error); @@ -885,6 +926,8 @@ TEST_F_SIGNAL(precedence, kill_is_highest_in_any_order, SIGSYS) ASSERT_EQ(0, ret); ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error); ASSERT_EQ(0, ret); + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log); + ASSERT_EQ(0, ret); ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace); ASSERT_EQ(0, ret); ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trap); @@ -906,6 +949,8 @@ TEST_F_SIGNAL(precedence, trap_is_second, SIGSYS) ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow); ASSERT_EQ(0, ret); + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log); + ASSERT_EQ(0, ret); ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace); ASSERT_EQ(0, ret); ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error); @@ -931,6 +976,8 @@ TEST_F_SIGNAL(precedence, trap_is_second_in_any_order, SIGSYS) ASSERT_EQ(0, ret); ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trap); ASSERT_EQ(0, ret); + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log); + ASSERT_EQ(0, ret); ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace); ASSERT_EQ(0, ret); ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error); @@ -952,6 +999,8 @@ TEST_F(precedence, errno_is_third) ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow); ASSERT_EQ(0, ret); + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log); + ASSERT_EQ(0, ret); ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace); ASSERT_EQ(0, ret); ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error); @@ -970,6 +1019,8 @@ TEST_F(precedence, errno_is_third_in_any_order) ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); ASSERT_EQ(0, ret); + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log); + ASSERT_EQ(0, ret); ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->error); ASSERT_EQ(0, ret); ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace); @@ -992,6 +1043,8 @@ TEST_F(precedence, trace_is_fourth) ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow); ASSERT_EQ(0, ret); + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log); + ASSERT_EQ(0, ret); ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->trace); ASSERT_EQ(0, ret); /* Should work just fine. */ @@ -1013,12 +1066,54 @@ TEST_F(precedence, trace_is_fourth_in_any_order) ASSERT_EQ(0, ret); ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow); ASSERT_EQ(0, ret); + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log); + ASSERT_EQ(0, ret); /* Should work just fine. */ EXPECT_EQ(parent, syscall(__NR_getppid)); /* No ptracer */ EXPECT_EQ(-1, syscall(__NR_getpid)); } +TEST_F(precedence, log_is_fifth) +{ + pid_t mypid, parent; + long ret; + + mypid = getpid(); + parent = getppid(); + ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); + ASSERT_EQ(0, ret); + + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow); + ASSERT_EQ(0, ret); + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log); + ASSERT_EQ(0, ret); + /* Should work just fine. */ + EXPECT_EQ(parent, syscall(__NR_getppid)); + /* Should also work just fine */ + EXPECT_EQ(mypid, syscall(__NR_getpid)); +} + +TEST_F(precedence, log_is_fifth_in_any_order) +{ + pid_t mypid, parent; + long ret; + + mypid = getpid(); + parent = getppid(); + ret = prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0); + ASSERT_EQ(0, ret); + + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->log); + ASSERT_EQ(0, ret); + ret = prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &self->allow); + ASSERT_EQ(0, ret); + /* Should work just fine. */ + EXPECT_EQ(parent, syscall(__NR_getppid)); + /* Should also work just fine */ + EXPECT_EQ(mypid, syscall(__NR_getpid)); +} + #ifndef PTRACE_O_TRACESECCOMP #define PTRACE_O_TRACESECCOMP 0x00000080 #endif @@ -2603,7 +2698,7 @@ TEST(get_action_avail) { __u32 actions[] = { SECCOMP_RET_KILL, SECCOMP_RET_TRAP, SECCOMP_RET_ERRNO, SECCOMP_RET_TRACE, - SECCOMP_RET_ALLOW }; + SECCOMP_RET_LOG, SECCOMP_RET_ALLOW }; __u32 unknown_action = 0x10000000U; int i; long ret; @@ -2640,6 +2735,7 @@ TEST(get_action_avail) * - 64-bit arg prodding * - arch value testing (x86 modes especially) * - verify that FILTER_FLAG_LOG filters generate log messages + * - verify that RET_LOG generates log messages * - ... */ -- cgit v1.2.3-59-g8ed1b From fd76875ca289a3d4722f266fd2d5532a27083903 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Fri, 11 Aug 2017 12:53:18 -0700 Subject: seccomp: Rename SECCOMP_RET_KILL to SECCOMP_RET_KILL_THREAD In preparation for adding SECCOMP_RET_KILL_PROCESS, rename SECCOMP_RET_KILL to the more accurate SECCOMP_RET_KILL_THREAD. The existing selftest values are intentionally left as SECCOMP_RET_KILL just to be sure we're exercising the alias. Signed-off-by: Kees Cook --- Documentation/networking/filter.txt | 2 +- Documentation/userspace-api/seccomp_filter.rst | 4 +-- include/uapi/linux/seccomp.h | 3 +- kernel/seccomp.c | 39 ++++++++++++++------------ samples/seccomp/bpf-direct.c | 4 +-- samples/seccomp/bpf-helper.h | 2 +- tools/testing/selftests/seccomp/seccomp_bpf.c | 17 ++++++----- 7 files changed, 39 insertions(+), 32 deletions(-) diff --git a/Documentation/networking/filter.txt b/Documentation/networking/filter.txt index b69b205501de..73aa0f12156d 100644 --- a/Documentation/networking/filter.txt +++ b/Documentation/networking/filter.txt @@ -337,7 +337,7 @@ Examples for low-level BPF: jeq #14, good /* __NR_rt_sigprocmask */ jeq #13, good /* __NR_rt_sigaction */ jeq #35, good /* __NR_nanosleep */ - bad: ret #0 /* SECCOMP_RET_KILL */ + bad: ret #0 /* SECCOMP_RET_KILL_THREAD */ good: ret #0x7fff0000 /* SECCOMP_RET_ALLOW */ The above example code can be placed into a file (here called "foo"), and diff --git a/Documentation/userspace-api/seccomp_filter.rst b/Documentation/userspace-api/seccomp_filter.rst index f4977357daf2..d76396f2d8ed 100644 --- a/Documentation/userspace-api/seccomp_filter.rst +++ b/Documentation/userspace-api/seccomp_filter.rst @@ -87,11 +87,11 @@ Return values A seccomp filter may return any of the following values. If multiple filters exist, the return value for the evaluation of a given system call will always use the highest precedent value. (For example, -``SECCOMP_RET_KILL`` will always take precedence.) +``SECCOMP_RET_KILL_THREAD`` will always take precedence.) In precedence order, they are: -``SECCOMP_RET_KILL``: +``SECCOMP_RET_KILL_THREAD``: Results in the task exiting immediately without executing the system call. The exit status of the task (``status & 0x7f``) will be ``SIGSYS``, not ``SIGKILL``. diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h index f94433263e4b..5a03f699eb17 100644 --- a/include/uapi/linux/seccomp.h +++ b/include/uapi/linux/seccomp.h @@ -27,7 +27,8 @@ * The ordering ensures that a min_t() over composed return values always * selects the least permissive choice. */ -#define SECCOMP_RET_KILL 0x00000000U /* kill the task immediately */ +#define SECCOMP_RET_KILL_THREAD 0x00000000U /* kill the thread */ +#define SECCOMP_RET_KILL SECCOMP_RET_KILL_THREAD #define SECCOMP_RET_TRAP 0x00030000U /* disallow and force a SIGSYS */ #define SECCOMP_RET_ERRNO 0x00050000U /* returns an errno */ #define SECCOMP_RET_TRACE 0x7ff00000U /* pass to a tracer or disallow */ diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 59cde2ed3b92..95ac54cff00f 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -192,7 +192,7 @@ static u32 seccomp_run_filters(const struct seccomp_data *sd, /* Ensure unexpected behavior doesn't result in failing open. */ if (unlikely(WARN_ON(f == NULL))) - return SECCOMP_RET_KILL; + return SECCOMP_RET_KILL_THREAD; if (!sd) { populate_seccomp_data(&sd_local); @@ -529,15 +529,17 @@ static void seccomp_send_sigsys(int syscall, int reason) #endif /* CONFIG_SECCOMP_FILTER */ /* For use with seccomp_actions_logged */ -#define SECCOMP_LOG_KILL (1 << 0) +#define SECCOMP_LOG_KILL_THREAD (1 << 0) #define SECCOMP_LOG_TRAP (1 << 2) #define SECCOMP_LOG_ERRNO (1 << 3) #define SECCOMP_LOG_TRACE (1 << 4) #define SECCOMP_LOG_LOG (1 << 5) #define SECCOMP_LOG_ALLOW (1 << 6) -static u32 seccomp_actions_logged = SECCOMP_LOG_KILL | SECCOMP_LOG_TRAP | - SECCOMP_LOG_ERRNO | SECCOMP_LOG_TRACE | +static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_THREAD | + SECCOMP_LOG_TRAP | + SECCOMP_LOG_ERRNO | + SECCOMP_LOG_TRACE | SECCOMP_LOG_LOG; static inline void seccomp_log(unsigned long syscall, long signr, u32 action, @@ -560,13 +562,13 @@ static inline void seccomp_log(unsigned long syscall, long signr, u32 action, case SECCOMP_RET_LOG: log = seccomp_actions_logged & SECCOMP_LOG_LOG; break; - case SECCOMP_RET_KILL: + case SECCOMP_RET_KILL_THREAD: default: - log = seccomp_actions_logged & SECCOMP_LOG_KILL; + log = seccomp_actions_logged & SECCOMP_LOG_KILL_THREAD; } /* - * Force an audit message to be emitted when the action is RET_KILL, + * Force an audit message to be emitted when the action is RET_KILL_*, * RET_LOG, or the FILTER_FLAG_LOG bit was set and the action is * allowed to be logged by the admin. */ @@ -605,7 +607,7 @@ static void __secure_computing_strict(int this_syscall) #ifdef SECCOMP_DEBUG dump_stack(); #endif - seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL, true); + seccomp_log(this_syscall, SIGKILL, SECCOMP_RET_KILL_THREAD, true); do_exit(SIGKILL); } @@ -716,7 +718,7 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, */ return 0; - case SECCOMP_RET_KILL: + case SECCOMP_RET_KILL_THREAD: default: seccomp_log(this_syscall, SIGSYS, action, true); /* Dump core only if this is the last remaining thread. */ @@ -878,7 +880,7 @@ static long seccomp_get_action_avail(const char __user *uaction) return -EFAULT; switch (action) { - case SECCOMP_RET_KILL: + case SECCOMP_RET_KILL_THREAD: case SECCOMP_RET_TRAP: case SECCOMP_RET_ERRNO: case SECCOMP_RET_TRACE: @@ -1029,19 +1031,20 @@ out: #ifdef CONFIG_SYSCTL /* Human readable action names for friendly sysctl interaction */ -#define SECCOMP_RET_KILL_NAME "kill" +#define SECCOMP_RET_KILL_THREAD_NAME "kill_thread" #define SECCOMP_RET_TRAP_NAME "trap" #define SECCOMP_RET_ERRNO_NAME "errno" #define SECCOMP_RET_TRACE_NAME "trace" #define SECCOMP_RET_LOG_NAME "log" #define SECCOMP_RET_ALLOW_NAME "allow" -static const char seccomp_actions_avail[] = SECCOMP_RET_KILL_NAME " " - SECCOMP_RET_TRAP_NAME " " - SECCOMP_RET_ERRNO_NAME " " - SECCOMP_RET_TRACE_NAME " " - SECCOMP_RET_LOG_NAME " " - SECCOMP_RET_ALLOW_NAME; +static const char seccomp_actions_avail[] = + SECCOMP_RET_KILL_THREAD_NAME " " + SECCOMP_RET_TRAP_NAME " " + SECCOMP_RET_ERRNO_NAME " " + SECCOMP_RET_TRACE_NAME " " + SECCOMP_RET_LOG_NAME " " + SECCOMP_RET_ALLOW_NAME; struct seccomp_log_name { u32 log; @@ -1049,7 +1052,7 @@ struct seccomp_log_name { }; static const struct seccomp_log_name seccomp_log_names[] = { - { SECCOMP_LOG_KILL, SECCOMP_RET_KILL_NAME }, + { SECCOMP_LOG_KILL_THREAD, SECCOMP_RET_KILL_THREAD_NAME }, { SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME }, { SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME }, { SECCOMP_LOG_TRACE, SECCOMP_RET_TRACE_NAME }, diff --git a/samples/seccomp/bpf-direct.c b/samples/seccomp/bpf-direct.c index 151ec3f52189..235ce3c49ee9 100644 --- a/samples/seccomp/bpf-direct.c +++ b/samples/seccomp/bpf-direct.c @@ -129,7 +129,7 @@ static int install_filter(void) /* Check that read is only using stdin. */ BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_arg(0)), BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDIN_FILENO, 4, 0), - BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL), + BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL_THREAD), /* Check that write is only using stdout */ BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_arg(0)), @@ -139,7 +139,7 @@ static int install_filter(void) BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW), BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_TRAP), - BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL), + BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL_THREAD), }; struct sock_fprog prog = { .len = (unsigned short)(sizeof(filter)/sizeof(filter[0])), diff --git a/samples/seccomp/bpf-helper.h b/samples/seccomp/bpf-helper.h index 1d8de9edd858..83dbe79cbe2c 100644 --- a/samples/seccomp/bpf-helper.h +++ b/samples/seccomp/bpf-helper.h @@ -44,7 +44,7 @@ void seccomp_bpf_print(struct sock_filter *filter, size_t count); #define ALLOW \ BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW) #define DENY \ - BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL) + BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL_THREAD) #define JUMP(labels, label) \ BPF_JUMP(BPF_JMP+BPF_JA, FIND_LABEL((labels), (label)), \ JUMP_JT, JUMP_JF) diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c index 7372958eccb5..a3ba39a32449 100644 --- a/tools/testing/selftests/seccomp/seccomp_bpf.c +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c @@ -68,15 +68,18 @@ #define SECCOMP_MODE_FILTER 2 #endif +#ifndef SECCOMP_RET_KILL_THREAD +#define SECCOMP_RET_KILL_THREAD 0x00000000U /* kill the thread */ +#endif #ifndef SECCOMP_RET_KILL -#define SECCOMP_RET_KILL 0x00000000U /* kill the task immediately */ -#define SECCOMP_RET_TRAP 0x00030000U /* disallow and force a SIGSYS */ -#define SECCOMP_RET_ERRNO 0x00050000U /* returns an errno */ -#define SECCOMP_RET_TRACE 0x7ff00000U /* pass to a tracer or disallow */ -#define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */ +#define SECCOMP_RET_KILL SECCOMP_RET_KILL_THREAD +#define SECCOMP_RET_TRAP 0x00030000U /* disallow and force a SIGSYS */ +#define SECCOMP_RET_ERRNO 0x00050000U /* returns an errno */ +#define SECCOMP_RET_TRACE 0x7ff00000U /* pass to a tracer or disallow */ +#define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */ #endif #ifndef SECCOMP_RET_LOG -#define SECCOMP_RET_LOG 0x7ffc0000U /* allow after logging */ +#define SECCOMP_RET_LOG 0x7ffc0000U /* allow after logging */ #endif #ifndef SECCOMP_RET_ACTION @@ -2696,7 +2699,7 @@ TEST_SIGNAL(filter_flag_log, SIGSYS) TEST(get_action_avail) { - __u32 actions[] = { SECCOMP_RET_KILL, SECCOMP_RET_TRAP, + __u32 actions[] = { SECCOMP_RET_KILL_THREAD, SECCOMP_RET_TRAP, SECCOMP_RET_ERRNO, SECCOMP_RET_TRACE, SECCOMP_RET_LOG, SECCOMP_RET_ALLOW }; __u32 unknown_action = 0x10000000U; -- cgit v1.2.3-59-g8ed1b From 4d3b0b05aae9ee9ce0970dc4cc0fb3fad5e85945 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Fri, 11 Aug 2017 13:01:39 -0700 Subject: seccomp: Introduce SECCOMP_RET_KILL_PROCESS This introduces the BPF return value for SECCOMP_RET_KILL_PROCESS to kill an entire process. This cannot yet be reached by seccomp, but it changes the default-kill behavior (for unknown return values) from kill-thread to kill-process. Signed-off-by: Kees Cook --- include/uapi/linux/seccomp.h | 18 ++++++++++-------- kernel/seccomp.c | 22 ++++++++++++++++------ 2 files changed, 26 insertions(+), 14 deletions(-) diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h index 5a03f699eb17..7e77c92df78a 100644 --- a/include/uapi/linux/seccomp.h +++ b/include/uapi/linux/seccomp.h @@ -22,18 +22,20 @@ /* * All BPF programs must return a 32-bit value. * The bottom 16-bits are for optional return data. - * The upper 16-bits are ordered from least permissive values to most. + * The upper 16-bits are ordered from least permissive values to most, + * as a signed value (so 0x8000000 is negative). * * The ordering ensures that a min_t() over composed return values always * selects the least permissive choice. */ -#define SECCOMP_RET_KILL_THREAD 0x00000000U /* kill the thread */ -#define SECCOMP_RET_KILL SECCOMP_RET_KILL_THREAD -#define SECCOMP_RET_TRAP 0x00030000U /* disallow and force a SIGSYS */ -#define SECCOMP_RET_ERRNO 0x00050000U /* returns an errno */ -#define SECCOMP_RET_TRACE 0x7ff00000U /* pass to a tracer or disallow */ -#define SECCOMP_RET_LOG 0x7ffc0000U /* allow after logging */ -#define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */ +#define SECCOMP_RET_KILL_PROCESS 0x80000000U /* kill the process */ +#define SECCOMP_RET_KILL_THREAD 0x00000000U /* kill the thread */ +#define SECCOMP_RET_KILL SECCOMP_RET_KILL_THREAD +#define SECCOMP_RET_TRAP 0x00030000U /* disallow and force a SIGSYS */ +#define SECCOMP_RET_ERRNO 0x00050000U /* returns an errno */ +#define SECCOMP_RET_TRACE 0x7ff00000U /* pass to a tracer or disallow */ +#define SECCOMP_RET_LOG 0x7ffc0000U /* allow after logging */ +#define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */ /* Masks for the return value sections. */ #define SECCOMP_RET_ACTION 0x7fff0000U diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 95ac54cff00f..5c7299b9d953 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -192,7 +192,7 @@ static u32 seccomp_run_filters(const struct seccomp_data *sd, /* Ensure unexpected behavior doesn't result in failing open. */ if (unlikely(WARN_ON(f == NULL))) - return SECCOMP_RET_KILL_THREAD; + return SECCOMP_RET_KILL_PROCESS; if (!sd) { populate_seccomp_data(&sd_local); @@ -529,14 +529,16 @@ static void seccomp_send_sigsys(int syscall, int reason) #endif /* CONFIG_SECCOMP_FILTER */ /* For use with seccomp_actions_logged */ -#define SECCOMP_LOG_KILL_THREAD (1 << 0) +#define SECCOMP_LOG_KILL_PROCESS (1 << 0) +#define SECCOMP_LOG_KILL_THREAD (1 << 1) #define SECCOMP_LOG_TRAP (1 << 2) #define SECCOMP_LOG_ERRNO (1 << 3) #define SECCOMP_LOG_TRACE (1 << 4) #define SECCOMP_LOG_LOG (1 << 5) #define SECCOMP_LOG_ALLOW (1 << 6) -static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_THREAD | +static u32 seccomp_actions_logged = SECCOMP_LOG_KILL_PROCESS | + SECCOMP_LOG_KILL_THREAD | SECCOMP_LOG_TRAP | SECCOMP_LOG_ERRNO | SECCOMP_LOG_TRACE | @@ -563,8 +565,11 @@ static inline void seccomp_log(unsigned long syscall, long signr, u32 action, log = seccomp_actions_logged & SECCOMP_LOG_LOG; break; case SECCOMP_RET_KILL_THREAD: - default: log = seccomp_actions_logged & SECCOMP_LOG_KILL_THREAD; + break; + case SECCOMP_RET_KILL_PROCESS: + default: + log = seccomp_actions_logged & SECCOMP_LOG_KILL_PROCESS; } /* @@ -719,10 +724,12 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, return 0; case SECCOMP_RET_KILL_THREAD: + case SECCOMP_RET_KILL_PROCESS: default: seccomp_log(this_syscall, SIGSYS, action, true); /* Dump core only if this is the last remaining thread. */ - if (get_nr_threads(current) == 1) { + if (action == SECCOMP_RET_KILL_PROCESS || + get_nr_threads(current) == 1) { siginfo_t info; /* Show the original registers in the dump. */ @@ -731,7 +738,10 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, seccomp_init_siginfo(&info, this_syscall, data); do_coredump(&info); } - do_exit(SIGSYS); + if (action == SECCOMP_RET_KILL_PROCESS) + do_group_exit(SIGSYS); + else + do_exit(SIGSYS); } unreachable(); -- cgit v1.2.3-59-g8ed1b From 0466bdb99e8744bc9befa8d62a317f0fd7fd7421 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Fri, 11 Aug 2017 13:12:11 -0700 Subject: seccomp: Implement SECCOMP_RET_KILL_PROCESS action MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Right now, SECCOMP_RET_KILL_THREAD (neé SECCOMP_RET_KILL) kills the current thread. There have been a few requests for this to kill the entire process (the thread group). This cannot be just changed (discovered when adding coredump support since coredumping kills the entire process) because there are userspace programs depending on the thread-kill behavior. Instead, implement SECCOMP_RET_KILL_PROCESS, which is 0x80000000, and can be processed as "-1" by the kernel, below the existing RET_KILL that is ABI-set to "0". For userspace, SECCOMP_RET_ACTION_FULL is added to expand the mask to the signed bit. Old userspace using the SECCOMP_RET_ACTION mask will see SECCOMP_RET_KILL_PROCESS as 0 still, but this would only be visible when examining the siginfo in a core dump from a RET_KILL_*, where it will think it was thread-killed instead of process-killed. Attempts to introduce this behavior via other ways (filter flags, seccomp struct flags, masked RET_DATA bits) all come with weird side-effects and baggage. This change preserves the central behavioral expectations of the seccomp filter engine without putting too great a burden on changes needed in userspace to use the new action. The new action is discoverable by userspace through either the new actions_avail sysctl or through the SECCOMP_GET_ACTION_AVAIL seccomp operation. If used without checking for availability, old kernels will treat RET_KILL_PROCESS as RET_KILL_THREAD (since the old mask will produce RET_KILL_THREAD). Cc: Paul Moore Cc: Fabricio Voznika Signed-off-by: Kees Cook --- Documentation/userspace-api/seccomp_filter.rst | 7 ++++++- include/uapi/linux/seccomp.h | 1 + kernel/seccomp.c | 9 +++++++-- 3 files changed, 14 insertions(+), 3 deletions(-) diff --git a/Documentation/userspace-api/seccomp_filter.rst b/Documentation/userspace-api/seccomp_filter.rst index d76396f2d8ed..099c412951d6 100644 --- a/Documentation/userspace-api/seccomp_filter.rst +++ b/Documentation/userspace-api/seccomp_filter.rst @@ -87,10 +87,15 @@ Return values A seccomp filter may return any of the following values. If multiple filters exist, the return value for the evaluation of a given system call will always use the highest precedent value. (For example, -``SECCOMP_RET_KILL_THREAD`` will always take precedence.) +``SECCOMP_RET_KILL_PROCESS`` will always take precedence.) In precedence order, they are: +``SECCOMP_RET_KILL_PROCESS``: + Results in the entire process exiting immediately without executing + the system call. The exit status of the task (``status & 0x7f``) + will be ``SIGSYS``, not ``SIGKILL``. + ``SECCOMP_RET_KILL_THREAD``: Results in the task exiting immediately without executing the system call. The exit status of the task (``status & 0x7f``) will diff --git a/include/uapi/linux/seccomp.h b/include/uapi/linux/seccomp.h index 7e77c92df78a..f6bc1dea3247 100644 --- a/include/uapi/linux/seccomp.h +++ b/include/uapi/linux/seccomp.h @@ -38,6 +38,7 @@ #define SECCOMP_RET_ALLOW 0x7fff0000U /* allow */ /* Masks for the return value sections. */ +#define SECCOMP_RET_ACTION_FULL 0xffff0000U #define SECCOMP_RET_ACTION 0x7fff0000U #define SECCOMP_RET_DATA 0x0000ffffU diff --git a/kernel/seccomp.c b/kernel/seccomp.c index 5c7299b9d953..c24579dfa7a1 100644 --- a/kernel/seccomp.c +++ b/kernel/seccomp.c @@ -181,6 +181,7 @@ static int seccomp_check_filter(struct sock_filter *filter, unsigned int flen) * * Returns valid seccomp BPF response codes. */ +#define ACTION_ONLY(ret) ((s32)((ret) & (SECCOMP_RET_ACTION_FULL))) static u32 seccomp_run_filters(const struct seccomp_data *sd, struct seccomp_filter **match) { @@ -206,7 +207,7 @@ static u32 seccomp_run_filters(const struct seccomp_data *sd, for (; f; f = f->prev) { u32 cur_ret = BPF_PROG_RUN(f->prog, sd); - if ((cur_ret & SECCOMP_RET_ACTION) < (ret & SECCOMP_RET_ACTION)) { + if (ACTION_ONLY(cur_ret) < ACTION_ONLY(ret)) { ret = cur_ret; *match = f; } @@ -650,7 +651,7 @@ static int __seccomp_filter(int this_syscall, const struct seccomp_data *sd, filter_ret = seccomp_run_filters(sd, &match); data = filter_ret & SECCOMP_RET_DATA; - action = filter_ret & SECCOMP_RET_ACTION; + action = filter_ret & SECCOMP_RET_ACTION_FULL; switch (action) { case SECCOMP_RET_ERRNO: @@ -890,6 +891,7 @@ static long seccomp_get_action_avail(const char __user *uaction) return -EFAULT; switch (action) { + case SECCOMP_RET_KILL_PROCESS: case SECCOMP_RET_KILL_THREAD: case SECCOMP_RET_TRAP: case SECCOMP_RET_ERRNO: @@ -1041,6 +1043,7 @@ out: #ifdef CONFIG_SYSCTL /* Human readable action names for friendly sysctl interaction */ +#define SECCOMP_RET_KILL_PROCESS_NAME "kill_process" #define SECCOMP_RET_KILL_THREAD_NAME "kill_thread" #define SECCOMP_RET_TRAP_NAME "trap" #define SECCOMP_RET_ERRNO_NAME "errno" @@ -1049,6 +1052,7 @@ out: #define SECCOMP_RET_ALLOW_NAME "allow" static const char seccomp_actions_avail[] = + SECCOMP_RET_KILL_PROCESS_NAME " " SECCOMP_RET_KILL_THREAD_NAME " " SECCOMP_RET_TRAP_NAME " " SECCOMP_RET_ERRNO_NAME " " @@ -1062,6 +1066,7 @@ struct seccomp_log_name { }; static const struct seccomp_log_name seccomp_log_names[] = { + { SECCOMP_LOG_KILL_PROCESS, SECCOMP_RET_KILL_PROCESS_NAME }, { SECCOMP_LOG_KILL_THREAD, SECCOMP_RET_KILL_THREAD_NAME }, { SECCOMP_LOG_TRAP, SECCOMP_RET_TRAP_NAME }, { SECCOMP_LOG_ERRNO, SECCOMP_RET_ERRNO_NAME }, -- cgit v1.2.3-59-g8ed1b From f3e1821d9e1cc3fb434d7763001791dcd6720c90 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Fri, 11 Aug 2017 13:20:33 -0700 Subject: selftests/seccomp: Test thread vs process killing This verifies that SECCOMP_RET_KILL_PROCESS is higher priority than SECCOMP_RET_KILL_THREAD. (This also moves a bunch of defines up earlier in the file to use them earlier.) Signed-off-by: Kees Cook Reviewed-by: Tyler Hicks --- tools/testing/selftests/seccomp/seccomp_bpf.c | 228 +++++++++++++++++++------- 1 file changed, 168 insertions(+), 60 deletions(-) diff --git a/tools/testing/selftests/seccomp/seccomp_bpf.c b/tools/testing/selftests/seccomp/seccomp_bpf.c index a3ba39a32449..0683cd543cd5 100644 --- a/tools/testing/selftests/seccomp/seccomp_bpf.c +++ b/tools/testing/selftests/seccomp/seccomp_bpf.c @@ -68,7 +68,17 @@ #define SECCOMP_MODE_FILTER 2 #endif -#ifndef SECCOMP_RET_KILL_THREAD +#ifndef SECCOMP_RET_ALLOW +struct seccomp_data { + int nr; + __u32 arch; + __u64 instruction_pointer; + __u64 args[6]; +}; +#endif + +#ifndef SECCOMP_RET_KILL_PROCESS +#define SECCOMP_RET_KILL_PROCESS 0x80000000U /* kill the process */ #define SECCOMP_RET_KILL_THREAD 0x00000000U /* kill the thread */ #endif #ifndef SECCOMP_RET_KILL @@ -82,17 +92,53 @@ #define SECCOMP_RET_LOG 0x7ffc0000U /* allow after logging */ #endif -#ifndef SECCOMP_RET_ACTION -/* Masks for the return value sections. */ -#define SECCOMP_RET_ACTION 0x7fff0000U -#define SECCOMP_RET_DATA 0x0000ffffU +#ifndef __NR_seccomp +# if defined(__i386__) +# define __NR_seccomp 354 +# elif defined(__x86_64__) +# define __NR_seccomp 317 +# elif defined(__arm__) +# define __NR_seccomp 383 +# elif defined(__aarch64__) +# define __NR_seccomp 277 +# elif defined(__hppa__) +# define __NR_seccomp 338 +# elif defined(__powerpc__) +# define __NR_seccomp 358 +# elif defined(__s390__) +# define __NR_seccomp 348 +# else +# warning "seccomp syscall number unknown for this architecture" +# define __NR_seccomp 0xffff +# endif +#endif -struct seccomp_data { - int nr; - __u32 arch; - __u64 instruction_pointer; - __u64 args[6]; -}; +#ifndef SECCOMP_SET_MODE_STRICT +#define SECCOMP_SET_MODE_STRICT 0 +#endif + +#ifndef SECCOMP_SET_MODE_FILTER +#define SECCOMP_SET_MODE_FILTER 1 +#endif + +#ifndef SECCOMP_GET_ACTION_AVAIL +#define SECCOMP_GET_ACTION_AVAIL 2 +#endif + +#ifndef SECCOMP_FILTER_FLAG_TSYNC +#define SECCOMP_FILTER_FLAG_TSYNC 1 +#endif + +#ifndef SECCOMP_FILTER_FLAG_LOG +#define SECCOMP_FILTER_FLAG_LOG 2 +#endif + +#ifndef seccomp +int seccomp(unsigned int op, unsigned int flags, void *args) +{ + errno = 0; + return syscall(__NR_seccomp, op, flags, args); +} #endif #if __BYTE_ORDER == __LITTLE_ENDIAN @@ -550,6 +596,117 @@ TEST_SIGNAL(KILL_one_arg_six, SIGSYS) close(fd); } +/* This is a thread task to die via seccomp filter violation. */ +void *kill_thread(void *data) +{ + bool die = (bool)data; + + if (die) { + prctl(PR_GET_SECCOMP, 0, 0, 0, 0); + return (void *)SIBLING_EXIT_FAILURE; + } + + return (void *)SIBLING_EXIT_UNKILLED; +} + +/* Prepare a thread that will kill itself or both of us. */ +void kill_thread_or_group(struct __test_metadata *_metadata, bool kill_process) +{ + pthread_t thread; + void *status; + /* Kill only when calling __NR_prctl. */ + struct sock_filter filter_thread[] = { + BPF_STMT(BPF_LD|BPF_W|BPF_ABS, + offsetof(struct seccomp_data, nr)), + BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_prctl, 0, 1), + BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL_THREAD), + BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW), + }; + struct sock_fprog prog_thread = { + .len = (unsigned short)ARRAY_SIZE(filter_thread), + .filter = filter_thread, + }; + struct sock_filter filter_process[] = { + BPF_STMT(BPF_LD|BPF_W|BPF_ABS, + offsetof(struct seccomp_data, nr)), + BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, __NR_prctl, 0, 1), + BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_KILL_PROCESS), + BPF_STMT(BPF_RET|BPF_K, SECCOMP_RET_ALLOW), + }; + struct sock_fprog prog_process = { + .len = (unsigned short)ARRAY_SIZE(filter_process), + .filter = filter_process, + }; + + ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) { + TH_LOG("Kernel does not support PR_SET_NO_NEW_PRIVS!"); + } + + ASSERT_EQ(0, seccomp(SECCOMP_SET_MODE_FILTER, 0, + kill_process ? &prog_process : &prog_thread)); + + /* + * Add the KILL_THREAD rule again to make sure that the KILL_PROCESS + * flag cannot be downgraded by a new filter. + */ + ASSERT_EQ(0, seccomp(SECCOMP_SET_MODE_FILTER, 0, &prog_thread)); + + /* Start a thread that will exit immediately. */ + ASSERT_EQ(0, pthread_create(&thread, NULL, kill_thread, (void *)false)); + ASSERT_EQ(0, pthread_join(thread, &status)); + ASSERT_EQ(SIBLING_EXIT_UNKILLED, (unsigned long)status); + + /* Start a thread that will die immediately. */ + ASSERT_EQ(0, pthread_create(&thread, NULL, kill_thread, (void *)true)); + ASSERT_EQ(0, pthread_join(thread, &status)); + ASSERT_NE(SIBLING_EXIT_FAILURE, (unsigned long)status); + + /* + * If we get here, only the spawned thread died. Let the parent know + * the whole process didn't die (i.e. this thread, the spawner, + * stayed running). + */ + exit(42); +} + +TEST(KILL_thread) +{ + int status; + pid_t child_pid; + + child_pid = fork(); + ASSERT_LE(0, child_pid); + if (child_pid == 0) { + kill_thread_or_group(_metadata, false); + _exit(38); + } + + ASSERT_EQ(child_pid, waitpid(child_pid, &status, 0)); + + /* If only the thread was killed, we'll see exit 42. */ + ASSERT_TRUE(WIFEXITED(status)); + ASSERT_EQ(42, WEXITSTATUS(status)); +} + +TEST(KILL_process) +{ + int status; + pid_t child_pid; + + child_pid = fork(); + ASSERT_LE(0, child_pid); + if (child_pid == 0) { + kill_thread_or_group(_metadata, true); + _exit(38); + } + + ASSERT_EQ(child_pid, waitpid(child_pid, &status, 0)); + + /* If the entire process was killed, we'll see SIGSYS. */ + ASSERT_TRUE(WIFSIGNALED(status)); + ASSERT_EQ(SIGSYS, WTERMSIG(status)); +} + /* TODO(wad) add 64-bit versus 32-bit arg tests. */ TEST(arg_out_of_range) { @@ -1800,55 +1957,6 @@ TEST_F_SIGNAL(TRACE_syscall, kill_after_ptrace, SIGSYS) EXPECT_NE(self->mypid, syscall(__NR_getpid)); } -#ifndef __NR_seccomp -# if defined(__i386__) -# define __NR_seccomp 354 -# elif defined(__x86_64__) -# define __NR_seccomp 317 -# elif defined(__arm__) -# define __NR_seccomp 383 -# elif defined(__aarch64__) -# define __NR_seccomp 277 -# elif defined(__hppa__) -# define __NR_seccomp 338 -# elif defined(__powerpc__) -# define __NR_seccomp 358 -# elif defined(__s390__) -# define __NR_seccomp 348 -# else -# warning "seccomp syscall number unknown for this architecture" -# define __NR_seccomp 0xffff -# endif -#endif - -#ifndef SECCOMP_SET_MODE_STRICT -#define SECCOMP_SET_MODE_STRICT 0 -#endif - -#ifndef SECCOMP_SET_MODE_FILTER -#define SECCOMP_SET_MODE_FILTER 1 -#endif - -#ifndef SECCOMP_GET_ACTION_AVAIL -#define SECCOMP_GET_ACTION_AVAIL 2 -#endif - -#ifndef SECCOMP_FILTER_FLAG_TSYNC -#define SECCOMP_FILTER_FLAG_TSYNC 1 -#endif - -#ifndef SECCOMP_FILTER_FLAG_LOG -#define SECCOMP_FILTER_FLAG_LOG 2 -#endif - -#ifndef seccomp -int seccomp(unsigned int op, unsigned int flags, void *args) -{ - errno = 0; - return syscall(__NR_seccomp, op, flags, args); -} -#endif - TEST(seccomp_syscall) { struct sock_filter filter[] = { -- cgit v1.2.3-59-g8ed1b From 6849243bf4c6155151b294e9f0e0dc9540d6f083 Mon Sep 17 00:00:00 2001 From: Kees Cook Date: Wed, 16 Aug 2017 20:26:57 -0700 Subject: samples: Unrename SECCOMP_RET_KILL Since samples can still be built before header installs, avoid the cosmetic renaming of SECCOMP_RET_KILL to avoid build failures in -next. Cc: Stephen Rothwell Signed-off-by: Kees Cook --- samples/seccomp/bpf-direct.c | 4 ++-- samples/seccomp/bpf-helper.h | 2 +- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/samples/seccomp/bpf-direct.c b/samples/seccomp/bpf-direct.c index 235ce3c49ee9..151ec3f52189 100644 --- a/samples/seccomp/bpf-direct.c +++ b/samples/seccomp/bpf-direct.c @@ -129,7 +129,7 @@ static int install_filter(void) /* Check that read is only using stdin. */ BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_arg(0)), BPF_JUMP(BPF_JMP+BPF_JEQ+BPF_K, STDIN_FILENO, 4, 0), - BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL_THREAD), + BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL), /* Check that write is only using stdout */ BPF_STMT(BPF_LD+BPF_W+BPF_ABS, syscall_arg(0)), @@ -139,7 +139,7 @@ static int install_filter(void) BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW), BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_TRAP), - BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL_THREAD), + BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL), }; struct sock_fprog prog = { .len = (unsigned short)(sizeof(filter)/sizeof(filter[0])), diff --git a/samples/seccomp/bpf-helper.h b/samples/seccomp/bpf-helper.h index 83dbe79cbe2c..1d8de9edd858 100644 --- a/samples/seccomp/bpf-helper.h +++ b/samples/seccomp/bpf-helper.h @@ -44,7 +44,7 @@ void seccomp_bpf_print(struct sock_filter *filter, size_t count); #define ALLOW \ BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_ALLOW) #define DENY \ - BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL_THREAD) + BPF_STMT(BPF_RET+BPF_K, SECCOMP_RET_KILL) #define JUMP(labels, label) \ BPF_JUMP(BPF_JMP+BPF_JA, FIND_LABEL((labels), (label)), \ JUMP_JT, JUMP_JF) -- cgit v1.2.3-59-g8ed1b