path: root/security/security.c
diff options
authorMikhail Kurinnoi <viewizard@viewizard.com>2018-06-27 16:33:42 +0300
committerMimi Zohar <zohar@linux.vnet.ibm.com>2018-07-18 07:27:22 -0400
commit6eb864c1d9dd1ef32b88e03c3f49d8be0dab7dcf (patch)
tree3484d390ade78e5dcdffdb67cb11b00ecefa10b9 /security/security.c
parentevm: Allow non-SHA1 digital signatures (diff)
integrity: prevent deadlock during digsig verification.
This patch aimed to prevent deadlock during digsig verification.The point of issue - user space utility modprobe and/or it's dependencies (ld-*.so, libz.so.*, libc-*.so and /lib/modules/ files) that could be used for kernel modules load during digsig verification and could be signed by digsig in the same time. First at all, look at crypto_alloc_tfm() work algorithm: crypto_alloc_tfm() will first attempt to locate an already loaded algorithm. If that fails and the kernel supports dynamically loadable modules, it will then attempt to load a module of the same name or alias. If that fails it will send a query to any loaded crypto manager to construct an algorithm on the fly. We have situation, when public_key_verify_signature() in case of RSA algorithm use alg_name to store internal information in order to construct an algorithm on the fly, but crypto_larval_lookup() will try to use alg_name in order to load kernel module with same name. 1) we can't do anything with crypto module work, since it designed to work exactly in this way; 2) we can't globally filter module requests for modprobe, since it designed to work with any requests. In this patch, I propose add an exception for "crypto-pkcs1pad(rsa,*)" module requests only in case of enabled integrity asymmetric keys support. Since we don't have any real "crypto-pkcs1pad(rsa,*)" kernel modules for sure, we are safe to fail such module request from crypto_larval_lookup(). In this way we prevent modprobe execution during digsig verification and avoid possible deadlock if modprobe and/or it's dependencies also signed with digsig. Requested "crypto-pkcs1pad(rsa,*)" kernel module name formed by: 1) "pkcs1pad(rsa,%s)" in public_key_verify_signature(); 2) "crypto-%s" / "crypto-%s-all" in crypto_larval_lookup(). "crypto-pkcs1pad(rsa," part of request is a constant and unique and could be used as filter. Signed-off-by: Mikhail Kurinnoi <viewizard@viewizard.com> Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com> include/linux/integrity.h | 13 +++++++++++++ security/integrity/digsig_asymmetric.c | 23 +++++++++++++++++++++++ security/security.c | 7 ++++++- 3 files changed, 42 insertions(+), 1 deletion(-)
Diffstat (limited to 'security/security.c')
1 files changed, 6 insertions, 1 deletions
diff --git a/security/security.c b/security/security.c
index b49ee810371b..dbca03d3629b 100644
--- a/security/security.c
+++ b/security/security.c
@@ -1032,7 +1032,12 @@ int security_kernel_create_files_as(struct cred *new, struct inode *inode)
int security_kernel_module_request(char *kmod_name)
- return call_int_hook(kernel_module_request, 0, kmod_name);
+ int ret;
+ ret = call_int_hook(kernel_module_request, 0, kmod_name);
+ if (ret)
+ return ret;
+ return integrity_kernel_module_request(kmod_name);
int security_kernel_read_file(struct file *file, enum kernel_read_file_id id)