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ANDROID: android-verity: Add API to verify signature with builtin keys.

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The builtin keyring was exported prior to this which allowed
android-verity to simply lookup the key in the builtin keyring and
verify the signature of the verity metadata.

This is now broken as the kernel expects the signature to be
in pkcs#7 format (same used for module signing). Obviously, this doesn't
work with the verity metadata as we just append the raw signature in the
metadata .. sigh.

*This one time*, add an API to accept arbitrary signature and verify
that with a key from system's trusted keyring.

Bug: 72722987
Test:
 $ adb push verity_fs.img /data/local/tmp/
 $ adb root && adb shell
 > cd /data/local/tmp
 > losetup /dev/block/loop0 verity_fs.img
 > dmctl create verity-fs android-verity 0 4200 Android:#7e4333f9bba00adfe0ede979e28ed1920492b40f 7:0
 > mount -t ext4 /dev/block/dm-0 temp/
 > cat temp/foo.txt temp/bar.txt

Change-Id: I0c14f3cb2b587b73a4c75907367769688756213e
Signed-off-by: Sandeep Patil <sspatil@google.com>
This commit is contained in:
Sandeep Patil 2018-07-24 09:40:07 -07:00 committed by Amit Pundir
parent 7ef7473dc0
commit 4c2a8d2ef8
2 changed files with 48 additions and 3 deletions
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43
certs/system_keyring.c
View file

@ -264,5 +264,46 @@ int verify_pkcs7_signature(const void *data, size_t len,
return ret; return ret;
} }
EXPORT_SYMBOL_GPL(verify_pkcs7_signature); EXPORT_SYMBOL_GPL(verify_pkcs7_signature);
#endif /* CONFIG_SYSTEM_DATA_VERIFICATION */ #endif /* CONFIG_SYSTEM_DATA_VERIFICATION */
/**
* verify_signature_one - Verify a signature with keys from given keyring
* @sig: The signature to be verified
* @trusted_keys: Trusted keys to use (NULL for builtin trusted keys only,
* (void *)1UL for all trusted keys).
* @keyid: key description (not partial)
*/
int verify_signature_one(const struct public_key_signature *sig,
struct key *trusted_keys, const char *keyid)
{
key_ref_t ref;
struct key *key;
int ret;
if (!sig)
return -EBADMSG;
if (!trusted_keys) {
trusted_keys = builtin_trusted_keys;
} else if (trusted_keys == (void *)1UL) {
#ifdef CONFIG_SECONDARY_TRUSTED_KEYRING
trusted_keys = secondary_trusted_keys;
#else
trusted_keys = builtin_trusted_keys;
#endif
}
ref = keyring_search(make_key_ref(trusted_keys, 1),
&key_type_asymmetric, keyid);
if (IS_ERR(ref)) {
pr_err("Asymmetric key (%s) not found in keyring(%s)\n",
keyid, trusted_keys->description);
return -ENOKEY;
}
key = key_ref_to_ptr(ref);
ret = verify_signature(key, sig);
key_put(key);
return ret;
}
EXPORT_SYMBOL_GPL(verify_signature_one);

8
include/linux/verification.h
View file

@ -32,9 +32,13 @@ enum key_being_used_for {
}; };
extern const char *const key_being_used_for[NR__KEY_BEING_USED_FOR]; extern const char *const key_being_used_for[NR__KEY_BEING_USED_FOR];
#ifdef CONFIG_SYSTEM_DATA_VERIFICATION
struct key; struct key;
struct public_key_signature;
extern int verify_signature_one(const struct public_key_signature *sig,
struct key *trusted_keys, const char *keyid);
#ifdef CONFIG_SYSTEM_DATA_VERIFICATION
extern int verify_pkcs7_signature(const void *data, size_t len, extern int verify_pkcs7_signature(const void *data, size_t len,
const void *raw_pkcs7, size_t pkcs7_len, const void *raw_pkcs7, size_t pkcs7_len,