| /* Verify the signature on a PKCS#7 message. |
| * |
| * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. |
| * Written by David Howells (dhowells@redhat.com) |
| * |
| * This program is free software; you can redistribute it and/or |
| * modify it under the terms of the GNU General Public Licence |
| * as published by the Free Software Foundation; either version |
| * 2 of the Licence, or (at your option) any later version. |
| */ |
| |
| #define pr_fmt(fmt) "PKCS7: "fmt |
| #include <linux/kernel.h> |
| #include <linux/export.h> |
| #include <linux/slab.h> |
| #include <linux/err.h> |
| #include <linux/asn1.h> |
| #include <crypto/hash.h> |
| #include "public_key.h" |
| #include "pkcs7_parser.h" |
| |
| /* |
| * Digest the relevant parts of the PKCS#7 data |
| */ |
| static int pkcs7_digest(struct pkcs7_message *pkcs7, |
| struct pkcs7_signed_info *sinfo) |
| { |
| struct crypto_shash *tfm; |
| struct shash_desc *desc; |
| size_t digest_size, desc_size; |
| void *digest; |
| int ret; |
| |
| kenter(",%u,%u", sinfo->index, sinfo->sig.pkey_hash_algo); |
| |
| if (sinfo->sig.pkey_hash_algo >= PKEY_HASH__LAST || |
| !hash_algo_name[sinfo->sig.pkey_hash_algo]) |
| return -ENOPKG; |
| |
| /* Allocate the hashing algorithm we're going to need and find out how |
| * big the hash operational data will be. |
| */ |
| tfm = crypto_alloc_shash(hash_algo_name[sinfo->sig.pkey_hash_algo], |
| 0, 0); |
| if (IS_ERR(tfm)) |
| return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm); |
| |
| desc_size = crypto_shash_descsize(tfm) + sizeof(*desc); |
| sinfo->sig.digest_size = digest_size = crypto_shash_digestsize(tfm); |
| |
| ret = -ENOMEM; |
| digest = kzalloc(digest_size + desc_size, GFP_KERNEL); |
| if (!digest) |
| goto error_no_desc; |
| |
| desc = digest + digest_size; |
| desc->tfm = tfm; |
| desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP; |
| |
| /* Digest the message [RFC2315 9.3] */ |
| ret = crypto_shash_init(desc); |
| if (ret < 0) |
| goto error; |
| ret = crypto_shash_finup(desc, pkcs7->data, pkcs7->data_len, digest); |
| if (ret < 0) |
| goto error; |
| pr_devel("MsgDigest = [%*ph]\n", 8, digest); |
| |
| /* However, if there are authenticated attributes, there must be a |
| * message digest attribute amongst them which corresponds to the |
| * digest we just calculated. |
| */ |
| if (sinfo->authattrs) { |
| u8 tag; |
| |
| if (!sinfo->msgdigest) { |
| pr_warn("Sig %u: No messageDigest\n", sinfo->index); |
| ret = -EKEYREJECTED; |
| goto error; |
| } |
| |
| if (sinfo->msgdigest_len != sinfo->sig.digest_size) { |
| pr_debug("Sig %u: Invalid digest size (%u)\n", |
| sinfo->index, sinfo->msgdigest_len); |
| ret = -EBADMSG; |
| goto error; |
| } |
| |
| if (memcmp(digest, sinfo->msgdigest, sinfo->msgdigest_len) != 0) { |
| pr_debug("Sig %u: Message digest doesn't match\n", |
| sinfo->index); |
| ret = -EKEYREJECTED; |
| goto error; |
| } |
| |
| /* We then calculate anew, using the authenticated attributes |
| * as the contents of the digest instead. Note that we need to |
| * convert the attributes from a CONT.0 into a SET before we |
| * hash it. |
| */ |
| memset(digest, 0, sinfo->sig.digest_size); |
| |
| ret = crypto_shash_init(desc); |
| if (ret < 0) |
| goto error; |
| tag = ASN1_CONS_BIT | ASN1_SET; |
| ret = crypto_shash_update(desc, &tag, 1); |
| if (ret < 0) |
| goto error; |
| ret = crypto_shash_finup(desc, sinfo->authattrs, |
| sinfo->authattrs_len, digest); |
| if (ret < 0) |
| goto error; |
| pr_devel("AADigest = [%*ph]\n", 8, digest); |
| } |
| |
| sinfo->sig.digest = digest; |
| digest = NULL; |
| |
| error: |
| kfree(digest); |
| error_no_desc: |
| crypto_free_shash(tfm); |
| kleave(" = %d", ret); |
| return ret; |
| } |
| |
| /* |
| * 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", sinfo->index); |
| |
| 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 (!asymmetric_key_id_same(x509->id, sinfo->signing_cert_id)) |
| continue; |
| pr_devel("Sig %u: Found cert serial match X.509[%u]\n", |
| sinfo->index, certix); |
| |
| 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; |
| } |
| |
| /* The relevant X.509 cert isn't found here, but it might be found in |
| * the trust keyring. |
| */ |
| pr_debug("Sig %u: Issuing X.509 cert not found (#%*phN)\n", |
| sinfo->index, |
| sinfo->signing_cert_id->len, sinfo->signing_cert_id->data); |
| return 0; |
| } |
| |
| /* |
| * Verify the internal certificate chain as best we can. |
| */ |
| static int pkcs7_verify_sig_chain(struct pkcs7_message *pkcs7, |
| struct pkcs7_signed_info *sinfo) |
| { |
| struct x509_certificate *x509 = sinfo->signer, *p; |
| struct asymmetric_key_id *auth; |
| int ret; |
| |
| kenter(""); |
| |
| for (p = pkcs7->certs; p; p = p->next) |
| p->seen = false; |
| |
| for (;;) { |
| pr_debug("verify %s: %*phN\n", |
| x509->subject, |
| x509->raw_serial_size, x509->raw_serial); |
| x509->seen = true; |
| ret = x509_get_sig_params(x509); |
| if (ret < 0) |
| goto maybe_missing_crypto_in_x509; |
| |
| pr_debug("- issuer %s\n", x509->issuer); |
| if (x509->akid_id) |
| pr_debug("- authkeyid.id %*phN\n", |
| x509->akid_id->len, x509->akid_id->data); |
| if (x509->akid_skid) |
| pr_debug("- authkeyid.skid %*phN\n", |
| x509->akid_skid->len, x509->akid_skid->data); |
| |
| if ((!x509->akid_id && !x509->akid_skid) || |
| strcmp(x509->subject, x509->issuer) == 0) { |
| /* If there's no authority certificate specified, then |
| * the certificate must be self-signed and is the root |
| * of the chain. Likewise if the cert is its own |
| * authority. |
| */ |
| pr_debug("- no auth?\n"); |
| if (x509->raw_subject_size != x509->raw_issuer_size || |
| memcmp(x509->raw_subject, x509->raw_issuer, |
| x509->raw_issuer_size) != 0) |
| return 0; |
| |
| ret = x509_check_signature(x509->pub, x509); |
| if (ret < 0) |
| goto maybe_missing_crypto_in_x509; |
| x509->signer = x509; |
| pr_debug("- self-signed\n"); |
| return 0; |
| } |
| |
| /* Look through the X.509 certificates in the PKCS#7 message's |
| * list to see if the next one is there. |
| */ |
| auth = x509->akid_id; |
| if (auth) { |
| pr_debug("- want %*phN\n", auth->len, auth->data); |
| for (p = pkcs7->certs; p; p = p->next) { |
| pr_debug("- cmp [%u] %*phN\n", |
| p->index, p->id->len, p->id->data); |
| if (asymmetric_key_id_same(p->id, auth)) |
| goto found_issuer_check_skid; |
| } |
| } else { |
| auth = x509->akid_skid; |
| pr_debug("- want %*phN\n", auth->len, auth->data); |
| for (p = pkcs7->certs; p; p = p->next) { |
| if (!p->skid) |
| continue; |
| pr_debug("- cmp [%u] %*phN\n", |
| p->index, p->skid->len, p->skid->data); |
| if (asymmetric_key_id_same(p->skid, auth)) |
| goto found_issuer; |
| } |
| } |
| |
| /* We didn't find the root of this chain */ |
| pr_debug("- top\n"); |
| return 0; |
| |
| found_issuer_check_skid: |
| /* We matched issuer + serialNumber, but if there's an |
| * authKeyId.keyId, that must match the CA subjKeyId also. |
| */ |
| if (x509->akid_skid && |
| !asymmetric_key_id_same(p->skid, x509->akid_skid)) { |
| pr_warn("Sig %u: X.509 chain contains auth-skid nonmatch (%u->%u)\n", |
| sinfo->index, x509->index, p->index); |
| return -EKEYREJECTED; |
| } |
| found_issuer: |
| pr_debug("- subject %s\n", p->subject); |
| if (p->seen) { |
| pr_warn("Sig %u: X.509 chain contains loop\n", |
| sinfo->index); |
| return 0; |
| } |
| ret = x509_check_signature(p->pub, x509); |
| if (ret < 0) |
| return ret; |
| x509->signer = p; |
| if (x509 == p) { |
| pr_debug("- self-signed\n"); |
| return 0; |
| } |
| x509 = p; |
| might_sleep(); |
| } |
| |
| maybe_missing_crypto_in_x509: |
| /* Just prune the certificate chain at this point if we lack some |
| * crypto module to go further. Note, however, we don't want to set |
| * sinfo->missing_crypto as the signed info block may still be |
| * validatable against an X.509 cert lower in the chain that we have a |
| * trusted copy of. |
| */ |
| if (ret == -ENOPKG) |
| return 0; |
| return ret; |
| } |
| |
| /* |
| * Verify one signed information block from a PKCS#7 message. |
| */ |
| static int pkcs7_verify_one(struct pkcs7_message *pkcs7, |
| struct pkcs7_signed_info *sinfo) |
| { |
| int ret; |
| |
| kenter(",%u", sinfo->index); |
| |
| /* First of all, digest the data in the PKCS#7 message and the |
| * signed information block |
| */ |
| ret = pkcs7_digest(pkcs7, sinfo); |
| if (ret < 0) |
| return ret; |
| |
| /* Find the key for the signature if there is one */ |
| ret = pkcs7_find_key(pkcs7, sinfo); |
| if (ret < 0) |
| return ret; |
| |
| if (!sinfo->signer) |
| return 0; |
| |
| pr_devel("Using X.509[%u] for sig %u\n", |
| sinfo->signer->index, sinfo->index); |
| |
| /* Check that the PKCS#7 signing time is valid according to the X.509 |
| * certificate. We can't, however, check against the system clock |
| * since that may not have been set yet and may be wrong. |
| */ |
| if (test_bit(sinfo_has_signing_time, &sinfo->aa_set)) { |
| if (sinfo->signing_time < sinfo->signer->valid_from || |
| sinfo->signing_time > sinfo->signer->valid_to) { |
| pr_warn("Message signed outside of X.509 validity window\n"); |
| return -EKEYREJECTED; |
| } |
| } |
| |
| /* 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); |
| |
| /* Verify the internal certificate chain */ |
| return pkcs7_verify_sig_chain(pkcs7, sinfo); |
| } |
| |
| /** |
| * pkcs7_verify - Verify a PKCS#7 message |
| * @pkcs7: The PKCS#7 message to be verified |
| * @usage: The use to which the key is being put |
| * |
| * Verify a PKCS#7 message is internally consistent - that is, the data digest |
| * matches the digest in the AuthAttrs and any signature in the message or one |
| * of the X.509 certificates it carries that matches another X.509 cert in the |
| * message can be verified. |
| * |
| * This does not look to match the contents of the PKCS#7 message against any |
| * external public keys. |
| * |
| * Returns, in order of descending priority: |
| * |
| * (*) -EKEYREJECTED if a key was selected that had a usage restriction at |
| * odds with the specified usage, or: |
| * |
| * (*) -EKEYREJECTED if a signature failed to match for which we found an |
| * appropriate X.509 certificate, or: |
| * |
| * (*) -EBADMSG if some part of the message was invalid, or: |
| * |
| * (*) -ENOPKG if none of the signature chains are verifiable because suitable |
| * crypto modules couldn't be found, or: |
| * |
| * (*) 0 if all the signature chains that don't incur -ENOPKG can be verified |
| * (note that a signature chain may be of zero length), or: |
| */ |
| int pkcs7_verify(struct pkcs7_message *pkcs7, |
| enum key_being_used_for usage) |
| { |
| struct pkcs7_signed_info *sinfo; |
| struct x509_certificate *x509; |
| int enopkg = -ENOPKG; |
| int ret, n; |
| |
| kenter(""); |
| |
| switch (usage) { |
| case VERIFYING_MODULE_SIGNATURE: |
| if (pkcs7->data_type != OID_data) { |
| pr_warn("Invalid module sig (not pkcs7-data)\n"); |
| return -EKEYREJECTED; |
| } |
| if (pkcs7->have_authattrs) { |
| pr_warn("Invalid module sig (has authattrs)\n"); |
| return -EKEYREJECTED; |
| } |
| break; |
| case VERIFYING_FIRMWARE_SIGNATURE: |
| if (pkcs7->data_type != OID_data) { |
| pr_warn("Invalid firmware sig (not pkcs7-data)\n"); |
| return -EKEYREJECTED; |
| } |
| if (!pkcs7->have_authattrs) { |
| pr_warn("Invalid firmware sig (missing authattrs)\n"); |
| return -EKEYREJECTED; |
| } |
| break; |
| case VERIFYING_KEXEC_PE_SIGNATURE: |
| if (pkcs7->data_type != OID_msIndirectData) { |
| pr_warn("Invalid kexec sig (not Authenticode)\n"); |
| return -EKEYREJECTED; |
| } |
| /* Authattr presence checked in parser */ |
| break; |
| case VERIFYING_UNSPECIFIED_SIGNATURE: |
| if (pkcs7->data_type != OID_data) { |
| pr_warn("Invalid unspecified sig (not pkcs7-data)\n"); |
| return -EKEYREJECTED; |
| } |
| break; |
| default: |
| return -EINVAL; |
| } |
| |
| for (n = 0, x509 = pkcs7->certs; x509; x509 = x509->next, n++) { |
| ret = x509_get_sig_params(x509); |
| if (ret < 0) |
| return ret; |
| } |
| |
| for (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) { |
| ret = pkcs7_verify_one(pkcs7, sinfo); |
| if (ret < 0) { |
| if (ret == -ENOPKG) { |
| sinfo->unsupported_crypto = true; |
| continue; |
| } |
| kleave(" = %d", ret); |
| return ret; |
| } |
| enopkg = 0; |
| } |
| |
| kleave(" = %d", enopkg); |
| return enopkg; |
| } |
| EXPORT_SYMBOL_GPL(pkcs7_verify); |
| |
| /** |
| * pkcs7_supply_detached_data - Supply the data needed to verify a PKCS#7 message |
| * @pkcs7: The PKCS#7 message |
| * @data: The data to be verified |
| * @datalen: The amount of data |
| * |
| * Supply the detached data needed to verify a PKCS#7 message. Note that no |
| * attempt to retain/pin the data is made. That is left to the caller. The |
| * data will not be modified by pkcs7_verify() and will not be freed when the |
| * PKCS#7 message is freed. |
| * |
| * Returns -EINVAL if data is already supplied in the message, 0 otherwise. |
| */ |
| int pkcs7_supply_detached_data(struct pkcs7_message *pkcs7, |
| const void *data, size_t datalen) |
| { |
| if (pkcs7->data) { |
| pr_debug("Data already supplied\n"); |
| return -EINVAL; |
| } |
| pkcs7->data = data; |
| pkcs7->data_len = datalen; |
| return 0; |
| } |