Find the appropriate key in the PKCS#7 key list and verify the signature with
it. There may be several keys in there forming a chain. Any link in that
chain or the root of that chain may be in our keyrings.
Signed-off-by: David Howells <dhowells at redhat.com>
Acked-by: Vivek Goyal <vgoyal at redhat.com>
Reviewed-by: Kees Cook <keescook at chromium.org>
---
crypto/asymmetric_keys/pkcs7_verify.c | 64 +++++++++++++++++++++++++++++++++
include/crypto/pkcs7.h | 5 +++
2 files changed, 69 insertions(+)
diff --git a/crypto/asymmetric_keys/pkcs7_verify.c b/crypto/asymmetric_keys/pkcs7_verify.c
index 0bb408a..745e5c8 100644
--- a/crypto/asymmetric_keys/pkcs7_verify.c
+++ b/crypto/asymmetric_keys/pkcs7_verify.c
@@ -120,6 +120,55 @@ error_no_desc:
}
/*
+ * Find the key (X.509 certificate) to use to verify a PKCS#7 message. PKCS#7
+ * uses the issuer's name and the issuing certificate serial number for
+ * matching purposes. These must match the certificate issuer's name (not
+ * subject's name) and the certificate serial number [RFC 2315 6.7].
+ */
+static int pkcs7_find_key(struct pkcs7_message *pkcs7,
+ struct pkcs7_signed_info *sinfo)
+{
+ struct x509_certificate *x509;
+ unsigned certix = 1;
+
+ kenter("%u,%u,%u",
+ sinfo->index, sinfo->raw_serial_size, sinfo->raw_issuer_size);
+
+ for (x509 = pkcs7->certs; x509; x509 = x509->next, certix++) {
+ /* I'm _assuming_ that the generator of the PKCS#7 message will
+ * encode the fields from the X.509 cert in the same way in the
+ * PKCS#7 message - but I can't be 100% sure of that. It's
+ * possible this will need element-by-element comparison.
+ */
+ if (x509->raw_serial_size != sinfo->raw_serial_size ||
+ memcmp(x509->raw_serial, sinfo->raw_serial,
+ sinfo->raw_serial_size) != 0)
+ continue;
+ pr_devel("Sig %u: Found cert serial match X.509[%u]\n",
+ sinfo->index, certix);
+
+ if (x509->raw_issuer_size != sinfo->raw_issuer_size ||
+ memcmp(x509->raw_issuer, sinfo->raw_issuer,
+ sinfo->raw_issuer_size) != 0) {
+ pr_warn("Sig %u: X.509 subject and PKCS#7 issuer don't match\n",
+ sinfo->index);
+ continue;
+ }
+
+ if (x509->pub->pkey_algo != sinfo->sig.pkey_algo) {
+ pr_warn("Sig %u: X.509 algo and PKCS#7 sig algo don't match\n",
+ sinfo->index);
+ continue;
+ }
+
+ sinfo->signer = x509;
+ return 0;
+ }
+ pr_warn("Sig %u: Issuing X.509 cert not found (#%*ph)\n",
+ sinfo->index, sinfo->raw_serial_size, sinfo->raw_serial);
+ return -ENOKEY;
+}
+
/*
* Verify one signed information block from a PKCS#7 message.
*/
@@ -137,6 +186,21 @@ static int pkcs7_verify_one(struct pkcs7_message *pkcs7,
if (ret < 0)
return ret;
+ /* Find the key for the signature */
+ ret = pkcs7_find_key(pkcs7, sinfo);
+ if (ret < 0)
+ return ret;
+
+ pr_devel("Using X.509[%u] for sig %u\n",
+ sinfo->signer->index, sinfo->index);
+
+ /* Verify the PKCS#7 binary against the key */
+ ret = public_key_verify_signature(sinfo->signer->pub, &sinfo->sig);
+ if (ret < 0)
+ return ret;
+
+ pr_devel("Verified signature %u\n", sinfo->index);
+
return 0;
}
diff --git a/include/crypto/pkcs7.h b/include/crypto/pkcs7.h
index 8f2628f..8ba0f38 100644
--- a/include/crypto/pkcs7.h
+++ b/include/crypto/pkcs7.h
@@ -21,3 +21,8 @@ extern void pkcs7_free_message(struct pkcs7_message *pkcs7);
extern int pkcs7_get_content_data(const struct pkcs7_message *pkcs7,
const void **_data, size_t *_datalen,
bool want_wrapper);
+
+/*
+ * pkcs7_verify.c
+ */
+extern int pkcs7_verify(struct pkcs7_message *pkcs7);
