[PATCH v2 4/8] lib: crypto: import pkcs7_verify.c from linux
Heinrich Schuchardt
xypron.glpk at gmx.de
Tue Jul 7 12:27:49 CEST 2020
On 16.06.20 07:26, AKASHI Takahiro wrote:
> The file, pkcs7_verify.c, will now be imported from linux code and
> modified to fit into U-Boot environment.
>
> In particular, pkcs7_verify_one() function will be used in a later patch
> to rework signature verification logic aiming to support intermediate
> certificates in "chain of trust."
>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
> ---
> lib/crypto/Kconfig | 3 +
> lib/crypto/Makefile | 1 +
> lib/crypto/pkcs7_verify.c | 524 ++++++++++++++++++++++++++++++++++++++
> 3 files changed, 528 insertions(+)
> create mode 100644 lib/crypto/pkcs7_verify.c
>
> diff --git a/lib/crypto/Kconfig b/lib/crypto/Kconfig
> index 2b221b915aa6..6369bafac07b 100644
> --- a/lib/crypto/Kconfig
> +++ b/lib/crypto/Kconfig
> @@ -49,4 +49,7 @@ config PKCS7_MESSAGE_PARSER
> This option provides support for parsing PKCS#7 format messages for
> signature data and provides the ability to verify the signature.
>
> +config PKCS7_VERIFY
> + bool
> +
> endif # ASYMMETRIC_KEY_TYPE
> diff --git a/lib/crypto/Makefile b/lib/crypto/Makefile
> index 8267fee0a7b8..f3a414525d2a 100644
> --- a/lib/crypto/Makefile
> +++ b/lib/crypto/Makefile
> @@ -44,6 +44,7 @@ obj-$(CONFIG_PKCS7_MESSAGE_PARSER) += pkcs7_message.o
> pkcs7_message-y := \
> pkcs7.asn1.o \
> pkcs7_parser.o
> +obj-$(CONFIG_PKCS7_VERIFY) += pkcs7_verify.o
>
> $(obj)/pkcs7_parser.o: $(obj)/pkcs7.asn1.h
> $(obj)/pkcs7.asn1.o: $(obj)/pkcs7.asn1.c $(obj)/pkcs7.asn1.h
> diff --git a/lib/crypto/pkcs7_verify.c b/lib/crypto/pkcs7_verify.c
> new file mode 100644
> index 000000000000..1e8600f7faca
> --- /dev/null
> +++ b/lib/crypto/pkcs7_verify.c
> @@ -0,0 +1,524 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/* Verify the signature on a PKCS#7 message.
> + *
> + * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
> + * Written by David Howells (dhowells at redhat.com)
Please, describe the source from where you copied here:
Copied from Linux crypto/asymmetric_keys/pkcs7_verify.c.
> + */
> +
> +#define pr_fmt(fmt) "PKCS7: "fmt
This define is really meant to create unreadable code.
> +#ifdef __UBOOT__
Who needs those #ifdefs?
If you really think they are necessary to resync with the Linux code,
minimize them. One #ifdef for all headers should be enough.
> +#include <string.h>
> +#include <linux/bitops.h>
> +#include <linux/compat.h>
> +#else
> +#include <linux/kernel.h>
> +#include <linux/export.h>
> +#include <linux/slab.h>
> +#include <linux/err.h>
> +#endif
> +#include <linux/asn1.h>
> +#ifndef __UBOOT__
> +#include <crypto/hash.h>
> +#include <crypto/hash_info.h>
> +#endif
> +#include <crypto/public_key.h>
> +#ifdef __UBOOT__
> +#include <crypto/pkcs7_parser.h>
> +#else
> +#include "pkcs7_parser.h"
> +#endif
> +
> +/*
> + * Digest the relevant parts of the PKCS#7 data
> + */
> +#ifdef __UBOOT__
> +static int pkcs7_digest(struct pkcs7_message *pkcs7,
> + struct pkcs7_signed_info *sinfo)
> +{
> + return 0;
> +}
> +#else
> +static int pkcs7_digest(struct pkcs7_message *pkcs7,
> + struct pkcs7_signed_info *sinfo)
> +{
> + struct public_key_signature *sig = sinfo->sig;
> + struct crypto_shash *tfm;
> + struct shash_desc *desc;
> + size_t desc_size;
> + int ret;
> +
> + kenter(",%u,%s", sinfo->index, sinfo->sig->hash_algo);
Please, use our logging function: log_content(). At least where you
defined kenter or pr_devel.
Best regards
Heinrich
> +
> + /* The digest was calculated already. */
> + if (sig->digest)
> + return 0;
> +
> + if (!sinfo->sig->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(sinfo->sig->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);
> + sig->digest_size = crypto_shash_digestsize(tfm);
> +
> + ret = -ENOMEM;
> + sig->digest = kmalloc(sig->digest_size, GFP_KERNEL);
> + if (!sig->digest)
> + goto error_no_desc;
> +
> + desc = kzalloc(desc_size, GFP_KERNEL);
> + if (!desc)
> + goto error_no_desc;
> +
> + desc->tfm = tfm;
> +
> + /* Digest the message [RFC2315 9.3] */
> + ret = crypto_shash_digest(desc, pkcs7->data, pkcs7->data_len,
> + sig->digest);
> + if (ret < 0)
> + goto error;
> + pr_devel("MsgDigest = [%*ph]\n", 8, sig->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 != sig->digest_size) {
> + pr_debug("Sig %u: Invalid digest size (%u)\n",
> + sinfo->index, sinfo->msgdigest_len);
> + ret = -EBADMSG;
> + goto error;
> + }
> +
> + if (memcmp(sig->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(sig->digest, 0, 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, sig->digest);
> + if (ret < 0)
> + goto error;
> + pr_devel("AADigest = [%*ph]\n", 8, sig->digest);
> + }
> +
> +error:
> + kfree(desc);
> +error_no_desc:
> + crypto_free_shash(tfm);
> + kleave(" = %d", ret);
> + return ret;
> +}
> +
> +int pkcs7_get_digest(struct pkcs7_message *pkcs7, const u8 **buf, u32 *len,
> + enum hash_algo *hash_algo)
> +{
> + struct pkcs7_signed_info *sinfo = pkcs7->signed_infos;
> + int i, ret;
> +
> + /*
> + * This function doesn't support messages with more than one signature.
> + */
> + if (sinfo == NULL || sinfo->next != NULL)
> + return -EBADMSG;
> +
> + ret = pkcs7_digest(pkcs7, sinfo);
> + if (ret)
> + return ret;
> +
> + *buf = sinfo->sig->digest;
> + *len = sinfo->sig->digest_size;
> +
> + for (i = 0; i < HASH_ALGO__LAST; i++)
> + if (!strcmp(hash_algo_name[i], sinfo->sig->hash_algo)) {
> + *hash_algo = i;
> + break;
> + }
> +
> + return 0;
> +}
> +#endif /* !__UBOOT__ */
> +
> +/*
> + * 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->sig->auth_ids[0]))
> + continue;
> + pr_devel("Sig %u: Found cert serial match X.509[%u]\n",
> + sinfo->index, certix);
> +
> + if (strcmp(x509->pub->pkey_algo, sinfo->sig->pkey_algo) != 0) {
> + 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->sig->auth_ids[0]->len, sinfo->sig->auth_ids[0]->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 public_key_signature *sig;
> + 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;
> +
> + if (x509->blacklisted) {
> + /* If this cert is blacklisted, then mark everything
> + * that depends on this as blacklisted too.
> + */
> + sinfo->blacklisted = true;
> + for (p = sinfo->signer; p != x509; p = p->signer)
> + p->blacklisted = true;
> + pr_debug("- blacklisted\n");
> + return 0;
> + }
> +
> + if (x509->unsupported_key)
> + goto unsupported_crypto_in_x509;
> +
> + pr_debug("- issuer %s\n", x509->issuer);
> + sig = x509->sig;
> + if (sig->auth_ids[0])
> + pr_debug("- authkeyid.id %*phN\n",
> + sig->auth_ids[0]->len, sig->auth_ids[0]->data);
> + if (sig->auth_ids[1])
> + pr_debug("- authkeyid.skid %*phN\n",
> + sig->auth_ids[1]->len, sig->auth_ids[1]->data);
> +
> + if (x509->self_signed) {
> + /* 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.
> + */
> + if (x509->unsupported_sig)
> + goto unsupported_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 = sig->auth_ids[0];
> + 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 if (sig->auth_ids[1]) {
> + auth = sig->auth_ids[1];
> + 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 (sig->auth_ids[1] &&
> + !asymmetric_key_id_same(p->skid, sig->auth_ids[1])) {
> + 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 = public_key_verify_signature(p->pub, x509->sig);
> + if (ret < 0)
> + return ret;
> + x509->signer = p;
> + if (x509 == p) {
> + pr_debug("- self-signed\n");
> + return 0;
> + }
> + x509 = p;
> +#ifndef __UBOOT__
> + might_sleep();
> +#endif
> + }
> +
> +unsupported_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->unsupported_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.
> + */
> + return 0;
> +}
> +
> +/*
> + * Verify one signed information block from a PKCS#7 message.
> + */
> +#ifndef __UBOOT__
> +static
> +#endif
> +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);
> +}
> +
> +#ifndef __UBOOT__
> +/**
> + * 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:
> + *
> + * (*) 0 if a signature chain passed verification, or:
> + *
> + * (*) -EKEYREJECTED if a blacklisted key was encountered, or:
> + *
> + * (*) -ENOPKG if none of the signature chains are verifiable because suitable
> + * crypto modules couldn't be found.
> + */
> +int pkcs7_verify(struct pkcs7_message *pkcs7,
> + enum key_being_used_for usage)
> +{
> + struct pkcs7_signed_info *sinfo;
> + int actual_ret = -ENOPKG;
> + int ret;
> +
> + 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 (sinfo = pkcs7->signed_infos; sinfo; sinfo = sinfo->next) {
> + ret = pkcs7_verify_one(pkcs7, sinfo);
> + if (sinfo->blacklisted) {
> + if (actual_ret == -ENOPKG)
> + actual_ret = -EKEYREJECTED;
> + continue;
> + }
> + if (ret < 0) {
> + if (ret == -ENOPKG) {
> + sinfo->unsupported_crypto = true;
> + continue;
> + }
> + kleave(" = %d", ret);
> + return ret;
> + }
> + actual_ret = 0;
> + }
> +
> + kleave(" = %d", actual_ret);
> + return actual_ret;
> +}
> +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;
> +}
> +#endif /* __UBOOT__ */
>
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