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