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-rw-r--r--fs/proc/array.c5
-rw-r--r--include/linux/cred.h8
-rw-r--r--include/uapi/linux/prctl.h7
-rw-r--r--kernel/user_namespace.c1
-rw-r--r--security/commoncap.c102
-rw-r--r--security/keys/process_keys.c1
6 files changed, 113 insertions, 11 deletions
diff --git a/fs/proc/array.c b/fs/proc/array.c
index ce065cf3104f..f60f0121e331 100644
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -308,7 +308,8 @@ static void render_cap_t(struct seq_file *m, const char *header,
static inline void task_cap(struct seq_file *m, struct task_struct *p)
{
const struct cred *cred;
- kernel_cap_t cap_inheritable, cap_permitted, cap_effective, cap_bset;
+ kernel_cap_t cap_inheritable, cap_permitted, cap_effective,
+ cap_bset, cap_ambient;
rcu_read_lock();
cred = __task_cred(p);
@@ -316,12 +317,14 @@ static inline void task_cap(struct seq_file *m, struct task_struct *p)
cap_permitted = cred->cap_permitted;
cap_effective = cred->cap_effective;
cap_bset = cred->cap_bset;
+ cap_ambient = cred->cap_ambient;
rcu_read_unlock();
render_cap_t(m, "CapInh:\t", &cap_inheritable);
render_cap_t(m, "CapPrm:\t", &cap_permitted);
render_cap_t(m, "CapEff:\t", &cap_effective);
render_cap_t(m, "CapBnd:\t", &cap_bset);
+ render_cap_t(m, "CapAmb:\t", &cap_ambient);
}
static inline void task_seccomp(struct seq_file *m, struct task_struct *p)
diff --git a/include/linux/cred.h b/include/linux/cred.h
index 8b6c083e68a7..8d70e1361ecd 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -137,6 +137,7 @@ struct cred {
kernel_cap_t cap_permitted; /* caps we're permitted */
kernel_cap_t cap_effective; /* caps we can actually use */
kernel_cap_t cap_bset; /* capability bounding set */
+ kernel_cap_t cap_ambient; /* Ambient capability set */
#ifdef CONFIG_KEYS
unsigned char jit_keyring; /* default keyring to attach requested
* keys to */
@@ -212,6 +213,13 @@ static inline void validate_process_creds(void)
}
#endif
+static inline bool cap_ambient_invariant_ok(const struct cred *cred)
+{
+ return cap_issubset(cred->cap_ambient,
+ cap_intersect(cred->cap_permitted,
+ cred->cap_inheritable));
+}
+
/**
* get_new_cred - Get a reference on a new set of credentials
* @cred: The new credentials to reference
diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
index 31891d9535e2..a8d0759a9e40 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -190,4 +190,11 @@ struct prctl_mm_map {
# define PR_FP_MODE_FR (1 << 0) /* 64b FP registers */
# define PR_FP_MODE_FRE (1 << 1) /* 32b compatibility */
+/* Control the ambient capability set */
+#define PR_CAP_AMBIENT 47
+# define PR_CAP_AMBIENT_IS_SET 1
+# define PR_CAP_AMBIENT_RAISE 2
+# define PR_CAP_AMBIENT_LOWER 3
+# define PR_CAP_AMBIENT_CLEAR_ALL 4
+
#endif /* _LINUX_PRCTL_H */
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c
index f65a0a06a8c0..88fefa68c516 100644
--- a/kernel/user_namespace.c
+++ b/kernel/user_namespace.c
@@ -39,6 +39,7 @@ static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns)
cred->cap_inheritable = CAP_EMPTY_SET;
cred->cap_permitted = CAP_FULL_SET;
cred->cap_effective = CAP_FULL_SET;
+ cred->cap_ambient = CAP_EMPTY_SET;
cred->cap_bset = CAP_FULL_SET;
#ifdef CONFIG_KEYS
key_put(cred->request_key_auth);
diff --git a/security/commoncap.c b/security/commoncap.c
index d103f5a4043d..1f74dde1063e 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -267,6 +267,16 @@ int cap_capset(struct cred *new,
new->cap_effective = *effective;
new->cap_inheritable = *inheritable;
new->cap_permitted = *permitted;
+
+ /*
+ * Mask off ambient bits that are no longer both permitted and
+ * inheritable.
+ */
+ new->cap_ambient = cap_intersect(new->cap_ambient,
+ cap_intersect(*permitted,
+ *inheritable));
+ if (WARN_ON(!cap_ambient_invariant_ok(new)))
+ return -EINVAL;
return 0;
}
@@ -347,6 +357,7 @@ static inline int bprm_caps_from_vfs_caps(struct cpu_vfs_cap_data *caps,
/*
* pP' = (X & fP) | (pI & fI)
+ * The addition of pA' is handled later.
*/
new->cap_permitted.cap[i] =
(new->cap_bset.cap[i] & permitted) |
@@ -474,10 +485,13 @@ int cap_bprm_set_creds(struct linux_binprm *bprm)
{
const struct cred *old = current_cred();
struct cred *new = bprm->cred;
- bool effective, has_cap = false;
+ bool effective, has_cap = false, is_setid;
int ret;
kuid_t root_uid;
+ if (WARN_ON(!cap_ambient_invariant_ok(old)))
+ return -EPERM;
+
effective = false;
ret = get_file_caps(bprm, &effective, &has_cap);
if (ret < 0)
@@ -522,8 +536,9 @@ skip:
*
* In addition, if NO_NEW_PRIVS, then ensure we get no new privs.
*/
- if ((!uid_eq(new->euid, old->uid) ||
- !gid_eq(new->egid, old->gid) ||
+ is_setid = !uid_eq(new->euid, old->uid) || !gid_eq(new->egid, old->gid);
+
+ if ((is_setid ||
!cap_issubset(new->cap_permitted, old->cap_permitted)) &&
bprm->unsafe & ~LSM_UNSAFE_PTRACE_CAP) {
/* downgrade; they get no more than they had, and maybe less */
@@ -539,10 +554,28 @@ skip:
new->suid = new->fsuid = new->euid;
new->sgid = new->fsgid = new->egid;
+ /* File caps or setid cancels ambient. */
+ if (has_cap || is_setid)
+ cap_clear(new->cap_ambient);
+
+ /*
+ * Now that we've computed pA', update pP' to give:
+ * pP' = (X & fP) | (pI & fI) | pA'
+ */
+ new->cap_permitted = cap_combine(new->cap_permitted, new->cap_ambient);
+
+ /*
+ * Set pE' = (fE ? pP' : pA'). Because pA' is zero if fE is set,
+ * this is the same as pE' = (fE ? pP' : 0) | pA'.
+ */
if (effective)
new->cap_effective = new->cap_permitted;
else
- cap_clear(new->cap_effective);
+ new->cap_effective = new->cap_ambient;
+
+ if (WARN_ON(!cap_ambient_invariant_ok(new)))
+ return -EPERM;
+
bprm->cap_effective = effective;
/*
@@ -557,7 +590,7 @@ skip:
* Number 1 above might fail if you don't have a full bset, but I think
* that is interesting information to audit.
*/
- if (!cap_isclear(new->cap_effective)) {
+ if (!cap_issubset(new->cap_effective, new->cap_ambient)) {
if (!cap_issubset(CAP_FULL_SET, new->cap_effective) ||
!uid_eq(new->euid, root_uid) || !uid_eq(new->uid, root_uid) ||
issecure(SECURE_NOROOT)) {
@@ -568,6 +601,10 @@ skip:
}
new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
+
+ if (WARN_ON(!cap_ambient_invariant_ok(new)))
+ return -EPERM;
+
return 0;
}
@@ -589,7 +626,7 @@ int cap_bprm_secureexec(struct linux_binprm *bprm)
if (!uid_eq(cred->uid, root_uid)) {
if (bprm->cap_effective)
return 1;
- if (!cap_isclear(cred->cap_permitted))
+ if (!cap_issubset(cred->cap_permitted, cred->cap_ambient))
return 1;
}
@@ -691,10 +728,18 @@ static inline void cap_emulate_setxuid(struct cred *new, const struct cred *old)
uid_eq(old->suid, root_uid)) &&
(!uid_eq(new->uid, root_uid) &&
!uid_eq(new->euid, root_uid) &&
- !uid_eq(new->suid, root_uid)) &&
- !issecure(SECURE_KEEP_CAPS)) {
- cap_clear(new->cap_permitted);
- cap_clear(new->cap_effective);
+ !uid_eq(new->suid, root_uid))) {
+ if (!issecure(SECURE_KEEP_CAPS)) {
+ cap_clear(new->cap_permitted);
+ cap_clear(new->cap_effective);
+ }
+
+ /*
+ * Pre-ambient programs expect setresuid to nonroot followed
+ * by exec to drop capabilities. We should make sure that
+ * this remains the case.
+ */
+ cap_clear(new->cap_ambient);
}
if (uid_eq(old->euid, root_uid) && !uid_eq(new->euid, root_uid))
cap_clear(new->cap_effective);
@@ -924,6 +969,43 @@ int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
new->securebits &= ~issecure_mask(SECURE_KEEP_CAPS);
return commit_creds(new);
+ case PR_CAP_AMBIENT:
+ if (arg2 == PR_CAP_AMBIENT_CLEAR_ALL) {
+ if (arg3 | arg4 | arg5)
+ return -EINVAL;
+
+ new = prepare_creds();
+ if (!new)
+ return -ENOMEM;
+ cap_clear(new->cap_ambient);
+ return commit_creds(new);
+ }
+
+ if (((!cap_valid(arg3)) | arg4 | arg5))
+ return -EINVAL;
+
+ if (arg2 == PR_CAP_AMBIENT_IS_SET) {
+ return !!cap_raised(current_cred()->cap_ambient, arg3);
+ } else if (arg2 != PR_CAP_AMBIENT_RAISE &&
+ arg2 != PR_CAP_AMBIENT_LOWER) {
+ return -EINVAL;
+ } else {
+ if (arg2 == PR_CAP_AMBIENT_RAISE &&
+ (!cap_raised(current_cred()->cap_permitted, arg3) ||
+ !cap_raised(current_cred()->cap_inheritable,
+ arg3)))
+ return -EPERM;
+
+ new = prepare_creds();
+ if (!new)
+ return -ENOMEM;
+ if (arg2 == PR_CAP_AMBIENT_RAISE)
+ cap_raise(new->cap_ambient, arg3);
+ else
+ cap_lower(new->cap_ambient, arg3);
+ return commit_creds(new);
+ }
+
default:
/* No functionality available - continue with default */
return -ENOSYS;
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index bd536cb221e2..43b4cddbf2b3 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -848,6 +848,7 @@ void key_change_session_keyring(struct callback_head *twork)
new->cap_inheritable = old->cap_inheritable;
new->cap_permitted = old->cap_permitted;
new->cap_effective = old->cap_effective;
+ new->cap_ambient = old->cap_ambient;
new->cap_bset = old->cap_bset;
new->jit_keyring = old->jit_keyring;
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.