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KEYS: encrypted: fix buffer overread in valid_master_desc()

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With the 'encrypted' key type it was possible for userspace to provide a
data blob ending with a master key description shorter than expected,
e.g. 'keyctl add encrypted desc "new x" @s'.  When validating such a
master key description, validate_master_desc() could read beyond the end
of the buffer.  Fix this by using strncmp() instead of memcmp().  [Also
clean up the code to deduplicate some logic.]

Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
This commit is contained in:
Eric Biggers 2017-06-08 14:48:18 +01:00 committed by James Morris
parent e9ff56ac35
commit 794b4bc292
1 changed files with 15 additions and 16 deletions
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31
security/keys/encrypted-keys/encrypted.c
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@ -141,23 +141,22 @@ static int valid_ecryptfs_desc(const char *ecryptfs_desc)
*/
static int valid_master_desc(const char *new_desc, const char *orig_desc)
{
if (!memcmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN)) {
if (strlen(new_desc) == KEY_TRUSTED_PREFIX_LEN)
goto out;
if (orig_desc)
if (memcmp(new_desc, orig_desc, KEY_TRUSTED_PREFIX_LEN))
goto out;
} else if (!memcmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN)) {
if (strlen(new_desc) == KEY_USER_PREFIX_LEN)
goto out;
if (orig_desc)
if (memcmp(new_desc, orig_desc, KEY_USER_PREFIX_LEN))
goto out;
} else
goto out;
int prefix_len;
if (!strncmp(new_desc, KEY_TRUSTED_PREFIX, KEY_TRUSTED_PREFIX_LEN))
prefix_len = KEY_TRUSTED_PREFIX_LEN;
else if (!strncmp(new_desc, KEY_USER_PREFIX, KEY_USER_PREFIX_LEN))
prefix_len = KEY_USER_PREFIX_LEN;
else
return -EINVAL;
if (!new_desc[prefix_len])
return -EINVAL;
if (orig_desc && strncmp(new_desc, orig_desc, prefix_len))
return -EINVAL;
return 0;
out:
return -EINVAL;
}
/*