[RFC PATCH 04/15] PKCS#7: Make trust determination dependent on contents of trust keyring

From: David Howells
Date: Fri Jan 08 2016 - 13:33:57 EST

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Make the determination of the trustworthiness of a key dependent on whether
a key that can verify it is present in the ring of trusted keys rather than
whether or not the verifying key has KEY_FLAG_TRUSTED set.

verify_pkcs7_signature() will return -ENOKEY if the PKCS#7 message trust
chain cannot be verified.

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
---

certs/system_keyring.c | 13 ++++---------
crypto/asymmetric_keys/pkcs7_key_type.c | 2 +-
crypto/asymmetric_keys/pkcs7_parser.h | 1 -
crypto/asymmetric_keys/pkcs7_trust.c | 16 +++-------------
crypto/asymmetric_keys/verify_pefile.c | 2 +-
crypto/asymmetric_keys/x509_parser.h | 1 -
include/crypto/pkcs7.h | 3 +--
include/linux/verification.h | 1 -
kernel/module_signing.c | 2 +-
9 files changed, 11 insertions(+), 30 deletions(-)

diff --git a/certs/system_keyring.c b/certs/system_keyring.c
index cf55bd3a072a..e7f286413276 100644
--- a/certs/system_keyring.c
+++ b/certs/system_keyring.c
@@ -121,7 +121,6 @@ late_initcall(load_system_certificate_list);
int verify_pkcs7_signature(const void *data, size_t len,
const void *raw_pkcs7, size_t pkcs7_len,
struct key *trusted_keys,
- int untrusted_error,
enum key_being_used_for usage,
int (*view_content)(void *ctx,
const void *data, size_t len,
@@ -129,7 +128,6 @@ int verify_pkcs7_signature(const void *data, size_t len,
void *ctx)
{
struct pkcs7_message *pkcs7;
- bool trusted;
int ret;

pkcs7 = pkcs7_parse_message(raw_pkcs7, pkcs7_len);
@@ -149,13 +147,10 @@ int verify_pkcs7_signature(const void *data, size_t len,

if (!trusted_keys)
trusted_keys = system_trusted_keyring;
- ret = pkcs7_validate_trust(pkcs7, trusted_keys, &trusted);
- if (ret < 0)
- goto error;
-
- if (!trusted && untrusted_error) {
- pr_err("PKCS#7 signature not signed with a trusted key\n");
- ret = untrusted_error;
+ ret = pkcs7_validate_trust(pkcs7, trusted_keys);
+ if (ret < 0) {
+ if (ret == -ENOKEY)
+ pr_err("PKCS#7 signature not signed with a trusted key\n");
goto error;
}

diff --git a/crypto/asymmetric_keys/pkcs7_key_type.c b/crypto/asymmetric_keys/pkcs7_key_type.c
index 240a5303ebb7..89b75477868d 100644
--- a/crypto/asymmetric_keys/pkcs7_key_type.c
+++ b/crypto/asymmetric_keys/pkcs7_key_type.c
@@ -71,7 +71,7 @@ static int pkcs7_preparse(struct key_preparsed_payload *prep)

ret = verify_pkcs7_signature(NULL, 0,
prep->data, prep->datalen,
- NULL, -ENOKEY, usage,
+ NULL, usage,
pkcs7_view_content, prep);

kleave(" = %d", ret);
diff --git a/crypto/asymmetric_keys/pkcs7_parser.h b/crypto/asymmetric_keys/pkcs7_parser.h
index a66b19ebcf47..c8159983ed8f 100644
--- a/crypto/asymmetric_keys/pkcs7_parser.h
+++ b/crypto/asymmetric_keys/pkcs7_parser.h
@@ -22,7 +22,6 @@ struct pkcs7_signed_info {
struct pkcs7_signed_info *next;
struct x509_certificate *signer; /* Signing certificate (in msg->certs) */
unsigned index;
- bool trusted;
bool unsupported_crypto; /* T if not usable due to missing crypto */

/* Message digest - the digest of the Content Data (or NULL) */
diff --git a/crypto/asymmetric_keys/pkcs7_trust.c b/crypto/asymmetric_keys/pkcs7_trust.c
index 90d6d47965b0..388007fed3b2 100644
--- a/crypto/asymmetric_keys/pkcs7_trust.c
+++ b/crypto/asymmetric_keys/pkcs7_trust.c
@@ -30,7 +30,6 @@ static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7,
struct public_key_signature *sig = &sinfo->sig;
struct x509_certificate *x509, *last = NULL, *p;
struct key *key;
- bool trusted;
int ret;

kenter(",%u,", sinfo->index);
@@ -42,10 +41,8 @@ static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7,

for (x509 = sinfo->signer; x509; x509 = x509->signer) {
if (x509->seen) {
- if (x509->verified) {
- trusted = x509->trusted;
+ if (x509->verified)
goto verified;
- }
kleave(" = -ENOKEY [cached]");
return -ENOKEY;
}
@@ -122,7 +119,6 @@ static int pkcs7_validate_trust_one(struct pkcs7_message *pkcs7,

matched:
ret = verify_signature(key, sig);
- trusted = test_bit(KEY_FLAG_TRUSTED, &key->flags);
key_put(key);
if (ret < 0) {
if (ret == -ENOMEM)
@@ -134,12 +130,9 @@ matched:
verified:
if (x509) {
x509->verified = true;
- for (p = sinfo->signer; p != x509; p = p->signer) {
+ for (p = sinfo->signer; p != x509; p = p->signer)
p->verified = true;
- p->trusted = trusted;
- }
}
- sinfo->trusted = trusted;
kleave(" = 0");
return 0;
}
@@ -148,7 +141,6 @@ verified:
* pkcs7_validate_trust - Validate PKCS#7 trust chain
* @pkcs7: The PKCS#7 certificate to validate
* @trust_keyring: Signing certificates to use as starting points
- * @_trusted: Set to true if trustworth, false otherwise
*
* Validate that the certificate chain inside the PKCS#7 message intersects
* keys we already know and trust.
@@ -170,8 +162,7 @@ verified:
* May also return -ENOMEM.
*/
int pkcs7_validate_trust(struct pkcs7_message *pkcs7,
- struct key *trust_keyring,
- bool *_trusted)
+ struct key *trust_keyring)
{
struct pkcs7_signed_info *sinfo;
struct x509_certificate *p;
@@ -191,7 +182,6 @@ int pkcs7_validate_trust(struct pkcs7_message *pkcs7,
cached_ret = -ENOPKG;
continue;
case 0:
- *_trusted |= sinfo->trusted;
cached_ret = 0;
continue;
default:
diff --git a/crypto/asymmetric_keys/verify_pefile.c b/crypto/asymmetric_keys/verify_pefile.c
index 443a00f9cd7a..4112f922cc66 100644
--- a/crypto/asymmetric_keys/verify_pefile.c
+++ b/crypto/asymmetric_keys/verify_pefile.c
@@ -436,7 +436,7 @@ int verify_pefile_signature(const void *pebuf, unsigned pelen,

ret = verify_pkcs7_signature(NULL, 0,
pebuf + ctx.sig_offset, ctx.sig_len,
- trusted_keys, -EKEYREJECTED, usage,
+ trusted_keys, usage,
mscode_parse, &ctx);
if (ret < 0)
goto error;
diff --git a/crypto/asymmetric_keys/x509_parser.h b/crypto/asymmetric_keys/x509_parser.h
index dbeed6018e63..36b7c47335b5 100644
--- a/crypto/asymmetric_keys/x509_parser.h
+++ b/crypto/asymmetric_keys/x509_parser.h
@@ -41,7 +41,6 @@ struct x509_certificate {
unsigned index;
bool seen; /* Infinite recursion prevention */
bool verified;
- bool trusted;
bool unsupported_crypto; /* T if can't be verified due to missing crypto */
};

diff --git a/include/crypto/pkcs7.h b/include/crypto/pkcs7.h
index 8323e3e57131..583f199400a3 100644
--- a/include/crypto/pkcs7.h
+++ b/include/crypto/pkcs7.h
@@ -33,8 +33,7 @@ extern int pkcs7_get_content_data(const struct pkcs7_message *pkcs7,
* pkcs7_trust.c
*/
extern int pkcs7_validate_trust(struct pkcs7_message *pkcs7,
- struct key *trust_keyring,
- bool *_trusted);
+ struct key *trust_keyring);

/*
* pkcs7_verify.c
diff --git a/include/linux/verification.h b/include/linux/verification.h
index bb0fcf941cb7..a10549a6c7cd 100644
--- a/include/linux/verification.h
+++ b/include/linux/verification.h
@@ -33,7 +33,6 @@ struct key;
extern int verify_pkcs7_signature(const void *data, size_t len,
const void *raw_pkcs7, size_t pkcs7_len,
struct key *trusted_keys,
- int untrusted_error,
enum key_being_used_for usage,
int (*view_content)(void *ctx,
const void *data, size_t len,
diff --git a/kernel/module_signing.c b/kernel/module_signing.c
index 70cf0220efeb..b3dafe4fd320 100644
--- a/kernel/module_signing.c
+++ b/kernel/module_signing.c
@@ -74,6 +74,6 @@ int mod_verify_sig(const void *mod, unsigned long *_modlen)
}

return verify_pkcs7_signature(mod, modlen, mod + modlen, sig_len,
- NULL, -ENOKEY, VERIFYING_MODULE_SIGNATURE,
+ NULL, VERIFYING_MODULE_SIGNATURE,
NULL, NULL);
}

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