[linux-block.git] / crypto / asymmetric_keys / verify_pefile.c

// SPDX-License-Identifier: GPL-2.0-or-later
/* Parse a signed PE binary
 *
 * Copyright (C) 2014 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#define pr_fmt(fmt) "PEFILE: "fmt
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/err.h>
#include <linux/pe.h>
#include <linux/asn1.h>
#include <linux/verification.h>
#include <crypto/hash.h>
#include "verify_pefile.h"

/*
 * Parse a PE binary.
 */
static int pefile_parse_binary(const void *pebuf, unsigned int pelen,
			       struct pefile_context *ctx)
{
	const struct mz_hdr *mz = pebuf;
	const struct pe_hdr *pe;
	const struct pe32_opt_hdr *pe32;
	const struct pe32plus_opt_hdr *pe64;
	const struct data_directory *ddir;
	const struct data_dirent *dde;
	const struct section_header *secs, *sec;
	size_t cursor, datalen = pelen;

	kenter("");

#define chkaddr(base, x, s)						\
	do {								\
		if ((x) < base || (s) >= datalen || (x) > datalen - (s)) \
			return -ELIBBAD;				\
	} while (0)

	chkaddr(0, 0, sizeof(*mz));
	if (mz->magic != MZ_MAGIC)
		return -ELIBBAD;
	cursor = sizeof(*mz);

	chkaddr(cursor, mz->peaddr, sizeof(*pe));
	pe = pebuf + mz->peaddr;
	if (pe->magic != PE_MAGIC)
		return -ELIBBAD;
	cursor = mz->peaddr + sizeof(*pe);

	chkaddr(0, cursor, sizeof(pe32->magic));
	pe32 = pebuf + cursor;
	pe64 = pebuf + cursor;

	switch (pe32->magic) {
	case PE_OPT_MAGIC_PE32:
		chkaddr(0, cursor, sizeof(*pe32));
		ctx->image_checksum_offset =
			(unsigned long)&pe32->csum - (unsigned long)pebuf;
		ctx->header_size = pe32->header_size;
		cursor += sizeof(*pe32);
		ctx->n_data_dirents = pe32->data_dirs;
		break;

	case PE_OPT_MAGIC_PE32PLUS:
		chkaddr(0, cursor, sizeof(*pe64));
		ctx->image_checksum_offset =
			(unsigned long)&pe64->csum - (unsigned long)pebuf;
		ctx->header_size = pe64->header_size;
		cursor += sizeof(*pe64);
		ctx->n_data_dirents = pe64->data_dirs;
		break;

	default:
		pr_debug("Unknown PEOPT magic = %04hx\n", pe32->magic);
		return -ELIBBAD;
	}

	pr_debug("checksum @ %x\n", ctx->image_checksum_offset);
	pr_debug("header size = %x\n", ctx->header_size);

	if (cursor >= ctx->header_size || ctx->header_size >= datalen)
		return -ELIBBAD;

	if (ctx->n_data_dirents > (ctx->header_size - cursor) / sizeof(*dde))
		return -ELIBBAD;

	ddir = pebuf + cursor;
	cursor += sizeof(*dde) * ctx->n_data_dirents;

	ctx->cert_dirent_offset =
		(unsigned long)&ddir->certs - (unsigned long)pebuf;
	ctx->certs_size = ddir->certs.size;

	if (!ddir->certs.virtual_address || !ddir->certs.size) {
		pr_debug("Unsigned PE binary\n");
		return -EKEYREJECTED;
	}

	chkaddr(ctx->header_size, ddir->certs.virtual_address,
		ddir->certs.size);
	ctx->sig_offset = ddir->certs.virtual_address;
	ctx->sig_len = ddir->certs.size;
	pr_debug("cert = %x @%x [%*ph]\n",
		 ctx->sig_len, ctx->sig_offset,
		 ctx->sig_len, pebuf + ctx->sig_offset);

	ctx->n_sections = pe->sections;
	if (ctx->n_sections > (ctx->header_size - cursor) / sizeof(*sec))
		return -ELIBBAD;
	ctx->secs = secs = pebuf + cursor;

	return 0;
}

/*
 * Check and strip the PE wrapper from around the signature and check that the
 * remnant looks something like PKCS#7.
 */
static int pefile_strip_sig_wrapper(const void *pebuf,
				    struct pefile_context *ctx)
{
	struct win_certificate wrapper;
	const u8 *pkcs7;
	unsigned len;

	if (ctx->sig_len < sizeof(wrapper)) {
		pr_debug("Signature wrapper too short\n");
		return -ELIBBAD;
	}

	memcpy(&wrapper, pebuf + ctx->sig_offset, sizeof(wrapper));
	pr_debug("sig wrapper = { %x, %x, %x }\n",
		 wrapper.length, wrapper.revision, wrapper.cert_type);

	/* Both pesign and sbsign round up the length of certificate table
	 * (in optional header data directories) to 8 byte alignment.
	 */
	if (round_up(wrapper.length, 8) != ctx->sig_len) {
		pr_debug("Signature wrapper len wrong\n");
		return -ELIBBAD;
	}
	if (wrapper.revision != WIN_CERT_REVISION_2_0) {
		pr_debug("Signature is not revision 2.0\n");
		return -ENOTSUPP;
	}
	if (wrapper.cert_type != WIN_CERT_TYPE_PKCS_SIGNED_DATA) {
		pr_debug("Signature certificate type is not PKCS\n");
		return -ENOTSUPP;
	}

	/* It looks like the pkcs signature length in wrapper->length and the
	 * size obtained from the data dir entries, which lists the total size
	 * of certificate table, are both aligned to an octaword boundary, so
	 * we may have to deal with some padding.
	 */
	ctx->sig_len = wrapper.length;
	ctx->sig_offset += sizeof(wrapper);
	ctx->sig_len -= sizeof(wrapper);
	if (ctx->sig_len < 4) {
		pr_debug("Signature data missing\n");
		return -EKEYREJECTED;
	}

	/* What's left should be a PKCS#7 cert */
	pkcs7 = pebuf + ctx->sig_offset;
	if (pkcs7[0] != (ASN1_CONS_BIT | ASN1_SEQ))
		goto not_pkcs7;

	switch (pkcs7[1]) {
	case 0 ... 0x7f:
		len = pkcs7[1] + 2;
		goto check_len;
	case ASN1_INDEFINITE_LENGTH:
		return 0;
	case 0x81:
		len = pkcs7[2] + 3;
		goto check_len;
	case 0x82:
		len = ((pkcs7[2] << 8) | pkcs7[3]) + 4;
		goto check_len;
	case 0x83 ... 0xff:
		return -EMSGSIZE;
	default:
		goto not_pkcs7;
	}

check_len:
	if (len <= ctx->sig_len) {
		/* There may be padding */
		ctx->sig_len = len;
		return 0;
	}
not_pkcs7:
	pr_debug("Signature data not PKCS#7\n");
	return -ELIBBAD;
}

/*
 * Compare two sections for canonicalisation.
 */
static int pefile_compare_shdrs(const void *a, const void *b)
{
	const struct section_header *shdra = a;
	const struct section_header *shdrb = b;
	int rc;

	if (shdra->data_addr > shdrb->data_addr)
		return 1;
	if (shdrb->data_addr > shdra->data_addr)
		return -1;

	if (shdra->virtual_address > shdrb->virtual_address)
		return 1;
	if (shdrb->virtual_address > shdra->virtual_address)
		return -1;

	rc = strcmp(shdra->name, shdrb->name);
	if (rc != 0)
		return rc;

	if (shdra->virtual_size > shdrb->virtual_size)
		return 1;
	if (shdrb->virtual_size > shdra->virtual_size)
		return -1;

	if (shdra->raw_data_size > shdrb->raw_data_size)
		return 1;
	if (shdrb->raw_data_size > shdra->raw_data_size)
		return -1;

	return 0;
}

/*
 * Load the contents of the PE binary into the digest, leaving out the image
 * checksum and the certificate data block.
 */
static int pefile_digest_pe_contents(const void *pebuf, unsigned int pelen,
				     struct pefile_context *ctx,
				     struct shash_desc *desc)
{
	unsigned *canon, tmp, loop, i, hashed_bytes;
	int ret;

	/* Digest the header and data directory, but leave out the image
	 * checksum and the data dirent for the signature.
	 */
	ret = crypto_shash_update(desc, pebuf, ctx->image_checksum_offset);
	if (ret < 0)
		return ret;

	tmp = ctx->image_checksum_offset + sizeof(uint32_t);
	ret = crypto_shash_update(desc, pebuf + tmp,
				  ctx->cert_dirent_offset - tmp);
	if (ret < 0)
		return ret;

	tmp = ctx->cert_dirent_offset + sizeof(struct data_dirent);
	ret = crypto_shash_update(desc, pebuf + tmp, ctx->header_size - tmp);
	if (ret < 0)
		return ret;

	canon = kcalloc(ctx->n_sections, sizeof(unsigned), GFP_KERNEL);
	if (!canon)
		return -ENOMEM;

	/* We have to canonicalise the section table, so we perform an
	 * insertion sort.
	 */
	canon[0] = 0;
	for (loop = 1; loop < ctx->n_sections; loop++) {
		for (i = 0; i < loop; i++) {
			if (pefile_compare_shdrs(&ctx->secs[canon[i]],
						 &ctx->secs[loop]) > 0) {
				memmove(&canon[i + 1], &canon[i],
					(loop - i) * sizeof(canon[0]));
				break;
			}
		}
		canon[i] = loop;
	}

	hashed_bytes = ctx->header_size;
	for (loop = 0; loop < ctx->n_sections; loop++) {
		i = canon[loop];
		if (ctx->secs[i].raw_data_size == 0)
			continue;
		ret = crypto_shash_update(desc,
					  pebuf + ctx->secs[i].data_addr,
					  ctx->secs[i].raw_data_size);
		if (ret < 0) {
			kfree(canon);
			return ret;
		}
		hashed_bytes += ctx->secs[i].raw_data_size;
	}
	kfree(canon);

	if (pelen > hashed_bytes) {
		tmp = hashed_bytes + ctx->certs_size;
		ret = crypto_shash_update(desc,
					  pebuf + hashed_bytes,
					  pelen - tmp);
		if (ret < 0)
			return ret;
	}

	return 0;
}

/*
 * Digest the contents of the PE binary, leaving out the image checksum and the
 * certificate data block.
 */
static int pefile_digest_pe(const void *pebuf, unsigned int pelen,
			    struct pefile_context *ctx)
{
	struct crypto_shash *tfm;
	struct shash_desc *desc;
	size_t digest_size, desc_size;
	void *digest;
	int ret;

	kenter(",%s", ctx->digest_algo);

	/* Allocate the hashing algorithm we're going to need and find out how
	 * big the hash operational data will be.
	 */
	tfm = crypto_alloc_shash(ctx->digest_algo, 0, 0);
	if (IS_ERR(tfm))
		return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm);

	desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
	digest_size = crypto_shash_digestsize(tfm);

	if (digest_size != ctx->digest_len) {
		pr_debug("Digest size mismatch (%zx != %x)\n",
			 digest_size, ctx->digest_len);
		ret = -EBADMSG;
		goto error_no_desc;
	}
	pr_debug("Digest: desc=%zu size=%zu\n", desc_size, digest_size);

	ret = -ENOMEM;
	desc = kzalloc(desc_size + digest_size, GFP_KERNEL);
	if (!desc)
		goto error_no_desc;

	desc->tfm   = tfm;
	ret = crypto_shash_init(desc);
	if (ret < 0)
		goto error;

	ret = pefile_digest_pe_contents(pebuf, pelen, ctx, desc);
	if (ret < 0)
		goto error;

	digest = (void *)desc + desc_size;
	ret = crypto_shash_final(desc, digest);
	if (ret < 0)
		goto error;

	pr_debug("Digest calc = [%*ph]\n", ctx->digest_len, digest);

	/* Check that the PE file digest matches that in the MSCODE part of the
	 * PKCS#7 certificate.
	 */
	if (memcmp(digest, ctx->digest, ctx->digest_len) != 0) {
		pr_debug("Digest mismatch\n");
		ret = -EKEYREJECTED;
	} else {
		pr_debug("The digests match!\n");
	}

error:
	kzfree(desc);
error_no_desc:
	crypto_free_shash(tfm);
	kleave(" = %d", ret);
	return ret;
}

/**
 * verify_pefile_signature - Verify the signature on a PE binary image
 * @pebuf: Buffer containing the PE binary image
 * @pelen: Length of the binary image
 * @trust_keys: Signing certificate(s) to use as starting points
 * @usage: The use to which the key is being put.
 *
 * Validate that the certificate chain inside the PKCS#7 message inside the PE
 * binary image intersects keys we already know and trust.
 *
 * Returns, in order of descending priority:
 *
 *  (*) -ELIBBAD if the image cannot be parsed, or:
 *
 *  (*) -EKEYREJECTED if a signature failed to match for which we have a valid
 *	key, or:
 *
 *  (*) 0 if at least one signature chain intersects with the keys in the trust
 *	keyring, or:
 *
 *  (*) -ENOPKG if a suitable crypto module couldn't be found for a check on a
 *	chain.
 *
 *  (*) -ENOKEY if we couldn't find a match for any of the signature chains in
 *	the message.
 *
 * May also return -ENOMEM.
 */
int verify_pefile_signature(const void *pebuf, unsigned pelen,
			    struct key *trusted_keys,
			    enum key_being_used_for usage)
{
	struct pefile_context ctx;
	int ret;

	kenter("");

	memset(&ctx, 0, sizeof(ctx));
	ret = pefile_parse_binary(pebuf, pelen, &ctx);
	if (ret < 0)
		return ret;

	ret = pefile_strip_sig_wrapper(pebuf, &ctx);
	if (ret < 0)
		return ret;

	ret = verify_pkcs7_signature(NULL, 0,
				     pebuf + ctx.sig_offset, ctx.sig_len,
				     trusted_keys, usage,
				     mscode_parse, &ctx);
	if (ret < 0)
		goto error;

	pr_debug("Digest: %u [%*ph]\n",
		 ctx.digest_len, ctx.digest_len, ctx.digest);

	/* Generate the digest and check against the PKCS7 certificate
	 * contents.
	 */
	ret = pefile_digest_pe(pebuf, pelen, &ctx);

error:
	kzfree(ctx.digest);
	return ret;
}
Commit	Line	Data
b4d0d230	1	// SPDX-License-Identifier: GPL-2.0-or-later
26d1164b DH	2	/* Parse a signed PE binary
	3	*
	4	* Copyright (C) 2014 Red Hat, Inc. All Rights Reserved.
	5	* Written by David Howells (dhowells@redhat.com)
26d1164b DH	6	*/
	7
	8	#define pr_fmt(fmt) "PEFILE: "fmt
	9	#include <linux/module.h>
	10	#include <linux/kernel.h>
	11	#include <linux/slab.h>
	12	#include <linux/err.h>
	13	#include <linux/pe.h>
09dacbbd	14	#include <linux/asn1.h>
e68503bd	15	#include <linux/verification.h>
26d1164b DH	16	#include <crypto/hash.h>
	17	#include "verify_pefile.h"
	18
	19	/*
	20	* Parse a PE binary.
	21	*/
	22	static int pefile_parse_binary(const void *pebuf, unsigned int pelen,
	23	struct pefile_context *ctx)
	24	{
	25	const struct mz_hdr *mz = pebuf;
	26	const struct pe_hdr *pe;
	27	const struct pe32_opt_hdr *pe32;
	28	const struct pe32plus_opt_hdr *pe64;
	29	const struct data_directory *ddir;
	30	const struct data_dirent *dde;
	31	const struct section_header secs, sec;
	32	size_t cursor, datalen = pelen;
	33
	34	kenter("");
	35
	36	#define chkaddr(base, x, s) \
	37	do { \
	38	if ((x) < base \|\| (s) >= datalen \|\| (x) > datalen - (s)) \
	39	return -ELIBBAD; \
	40	} while (0)
	41
	42	chkaddr(0, 0, sizeof(*mz));
	43	if (mz->magic != MZ_MAGIC)
	44	return -ELIBBAD;
	45	cursor = sizeof(*mz);
	46
	47	chkaddr(cursor, mz->peaddr, sizeof(*pe));
	48	pe = pebuf + mz->peaddr;
	49	if (pe->magic != PE_MAGIC)
	50	return -ELIBBAD;
	51	cursor = mz->peaddr + sizeof(*pe);
	52
	53	chkaddr(0, cursor, sizeof(pe32->magic));
	54	pe32 = pebuf + cursor;
	55	pe64 = pebuf + cursor;
	56
	57	switch (pe32->magic) {
	58	case PE_OPT_MAGIC_PE32:
	59	chkaddr(0, cursor, sizeof(*pe32));
	60	ctx->image_checksum_offset =
	61	(unsigned long)&pe32->csum - (unsigned long)pebuf;
	62	ctx->header_size = pe32->header_size;
	63	cursor += sizeof(*pe32);
	64	ctx->n_data_dirents = pe32->data_dirs;
	65	break;
	66
	67	case PE_OPT_MAGIC_PE32PLUS:
	68	chkaddr(0, cursor, sizeof(*pe64));
	69	ctx->image_checksum_offset =
	70	(unsigned long)&pe64->csum - (unsigned long)pebuf;
	71	ctx->header_size = pe64->header_size;
	72	cursor += sizeof(*pe64);
	73	ctx->n_data_dirents = pe64->data_dirs;
	74	break;
	75
	76	default:
	77	pr_debug("Unknown PEOPT magic = %04hx\n", pe32->magic);
	78	return -ELIBBAD;
	79	}
80
81	pr_debug("checksum @ %x\n", ctx->image_checksum_offset);
82	pr_debug("header size = %x\n", ctx->header_size);
83
84	if (cursor >= ctx->header_size \|\| ctx->header_size >= datalen)
85	return -ELIBBAD;
86
87	if (ctx->n_data_dirents > (ctx->header_size - cursor) / sizeof(*dde))
88	return -ELIBBAD;
89
90	ddir = pebuf + cursor;
91	cursor += sizeof(dde) ctx->n_data_dirents;
92
93	ctx->cert_dirent_offset =
94	(unsigned long)&ddir->certs - (unsigned long)pebuf;
95	ctx->certs_size = ddir->certs.size;
96
97	if (!ddir->certs.virtual_address \|\| !ddir->certs.size) {
98	pr_debug("Unsigned PE binary\n");
99	return -EKEYREJECTED;
100	}
101
102	chkaddr(ctx->header_size, ddir->certs.virtual_address,
103	ddir->certs.size);
104	ctx->sig_offset = ddir->certs.virtual_address;
105	ctx->sig_len = ddir->certs.size;
106	pr_debug("cert = %x @%x [%*ph]\n",
107	ctx->sig_len, ctx->sig_offset,
108	ctx->sig_len, pebuf + ctx->sig_offset);
109
110	ctx->n_sections = pe->sections;
111	if (ctx->n_sections > (ctx->header_size - cursor) / sizeof(*sec))
112	return -ELIBBAD;
113	ctx->secs = secs = pebuf + cursor;
114
115	return 0;
116	}
117
09dacbbd DH	118	/*
	119	* Check and strip the PE wrapper from around the signature and check that the
	120	* remnant looks something like PKCS#7.
	121	*/
	122	static int pefile_strip_sig_wrapper(const void *pebuf,
	123	struct pefile_context *ctx)
	124	{
	125	struct win_certificate wrapper;
	126	const u8 *pkcs7;
0aa04094	127	unsigned len;
09dacbbd DH	128
	129	if (ctx->sig_len < sizeof(wrapper)) {
	130	pr_debug("Signature wrapper too short\n");
	131	return -ELIBBAD;
	132	}
	133
	134	memcpy(&wrapper, pebuf + ctx->sig_offset, sizeof(wrapper));
	135	pr_debug("sig wrapper = { %x, %x, %x }\n",
	136	wrapper.length, wrapper.revision, wrapper.cert_type);
	137
	138	/* Both pesign and sbsign round up the length of certificate table
	139	* (in optional header data directories) to 8 byte alignment.
	140	*/
	141	if (round_up(wrapper.length, 8) != ctx->sig_len) {
	142	pr_debug("Signature wrapper len wrong\n");
	143	return -ELIBBAD;
	144	}
	145	if (wrapper.revision != WIN_CERT_REVISION_2_0) {
	146	pr_debug("Signature is not revision 2.0\n");
	147	return -ENOTSUPP;
	148	}
	149	if (wrapper.cert_type != WIN_CERT_TYPE_PKCS_SIGNED_DATA) {
	150	pr_debug("Signature certificate type is not PKCS\n");
	151	return -ENOTSUPP;
	152	}
	153
0aa04094 DH	154	/* It looks like the pkcs signature length in wrapper->length and the
	155	* size obtained from the data dir entries, which lists the total size
	156	* of certificate table, are both aligned to an octaword boundary, so
	157	* we may have to deal with some padding.
09dacbbd DH	158	*/
	159	ctx->sig_len = wrapper.length;
	160	ctx->sig_offset += sizeof(wrapper);
	161	ctx->sig_len -= sizeof(wrapper);
0aa04094	162	if (ctx->sig_len < 4) {
09dacbbd DH	163	pr_debug("Signature data missing\n");
	164	return -EKEYREJECTED;
	165	}
	166
0aa04094	167	/* What's left should be a PKCS#7 cert */
09dacbbd	168	pkcs7 = pebuf + ctx->sig_offset;
0aa04094 DH	169	if (pkcs7[0] != (ASN1_CONS_BIT \| ASN1_SEQ))
	170	goto not_pkcs7;
	171
	172	switch (pkcs7[1]) {
	173	case 0 ... 0x7f:
	174	len = pkcs7[1] + 2;
	175	goto check_len;
	176	case ASN1_INDEFINITE_LENGTH:
	177	return 0;
	178	case 0x81:
	179	len = pkcs7[2] + 3;
	180	goto check_len;
	181	case 0x82:
	182	len = ((pkcs7[2] << 8) \| pkcs7[3]) + 4;
	183	goto check_len;
	184	case 0x83 ... 0xff:
	185	return -EMSGSIZE;
	186	default:
	187	goto not_pkcs7;
09dacbbd DH	188	}
09dacbbd DH	189
0aa04094 DH	190	check_len:
	191	if (len <= ctx->sig_len) {
	192	/* There may be padding */
	193	ctx->sig_len = len;
	194	return 0;
	195	}
	196	not_pkcs7:
09dacbbd DH	197	pr_debug("Signature data not PKCS#7\n");
	198	return -ELIBBAD;
	199	}
	200
af316fc4 DH	201	/*
	202	* Compare two sections for canonicalisation.
	203	*/
	204	static int pefile_compare_shdrs(const void a, const void b)
	205	{
	206	const struct section_header *shdra = a;
	207	const struct section_header *shdrb = b;
	208	int rc;
	209
	210	if (shdra->data_addr > shdrb->data_addr)
	211	return 1;
	212	if (shdrb->data_addr > shdra->data_addr)
	213	return -1;
	214
	215	if (shdra->virtual_address > shdrb->virtual_address)
	216	return 1;
	217	if (shdrb->virtual_address > shdra->virtual_address)
	218	return -1;
	219
	220	rc = strcmp(shdra->name, shdrb->name);
	221	if (rc != 0)
	222	return rc;
	223
	224	if (shdra->virtual_size > shdrb->virtual_size)
	225	return 1;
	226	if (shdrb->virtual_size > shdra->virtual_size)
	227	return -1;
	228
	229	if (shdra->raw_data_size > shdrb->raw_data_size)
	230	return 1;
	231	if (shdrb->raw_data_size > shdra->raw_data_size)
	232	return -1;
	233
	234	return 0;
	235	}
	236
	237	/*
	238	* Load the contents of the PE binary into the digest, leaving out the image
	239	* checksum and the certificate data block.
	240	*/
	241	static int pefile_digest_pe_contents(const void *pebuf, unsigned int pelen,
	242	struct pefile_context *ctx,
	243	struct shash_desc *desc)
	244	{
	245	unsigned *canon, tmp, loop, i, hashed_bytes;
	246	int ret;
	247
	248	/* Digest the header and data directory, but leave out the image
	249	* checksum and the data dirent for the signature.
	250	*/
	251	ret = crypto_shash_update(desc, pebuf, ctx->image_checksum_offset);
	252	if (ret < 0)
	253	return ret;
	254
	255	tmp = ctx->image_checksum_offset + sizeof(uint32_t);
	256	ret = crypto_shash_update(desc, pebuf + tmp,
	257	ctx->cert_dirent_offset - tmp);
	258	if (ret < 0)
	259	return ret;
	260
	261	tmp = ctx->cert_dirent_offset + sizeof(struct data_dirent);
	262	ret = crypto_shash_update(desc, pebuf + tmp, ctx->header_size - tmp);
	263	if (ret < 0)
	264	return ret;
265
266	canon = kcalloc(ctx->n_sections, sizeof(unsigned), GFP_KERNEL);
267	if (!canon)
268	return -ENOMEM;
269
270	/* We have to canonicalise the section table, so we perform an
271	* insertion sort.
272	*/
273	canon[0] = 0;
274	for (loop = 1; loop < ctx->n_sections; loop++) {
275	for (i = 0; i < loop; i++) {
276	if (pefile_compare_shdrs(&ctx->secs[canon[i]],
277	&ctx->secs[loop]) > 0) {
278	memmove(&canon[i + 1], &canon[i],
279	(loop - i) * sizeof(canon[0]));
280	break;
281	}
282	}
283	canon[i] = loop;
284	}
285
286	hashed_bytes = ctx->header_size;
287	for (loop = 0; loop < ctx->n_sections; loop++) {
288	i = canon[loop];
289	if (ctx->secs[i].raw_data_size == 0)
290	continue;
291	ret = crypto_shash_update(desc,
292	pebuf + ctx->secs[i].data_addr,
293	ctx->secs[i].raw_data_size);
294	if (ret < 0) {
295	kfree(canon);
296	return ret;
297	}
298	hashed_bytes += ctx->secs[i].raw_data_size;
299	}
300	kfree(canon);
301
302	if (pelen > hashed_bytes) {
303	tmp = hashed_bytes + ctx->certs_size;
304	ret = crypto_shash_update(desc,
305	pebuf + hashed_bytes,
306	pelen - tmp);
307	if (ret < 0)
308	return ret;
309	}
310
311	return 0;
312	}
313
314	/*
315	* Digest the contents of the PE binary, leaving out the image checksum and the
316	* certificate data block.
317	*/
318	static int pefile_digest_pe(const void *pebuf, unsigned int pelen,
319	struct pefile_context *ctx)
320	{
321	struct crypto_shash *tfm;
322	struct shash_desc *desc;
323	size_t digest_size, desc_size;
324	void *digest;
325	int ret;
326
4e8ae72a	327	kenter(",%s", ctx->digest_algo);
af316fc4 DH	328
	329	/* Allocate the hashing algorithm we're going to need and find out how
	330	* big the hash operational data will be.
	331	*/
4e8ae72a	332	tfm = crypto_alloc_shash(ctx->digest_algo, 0, 0);
af316fc4 DH	333	if (IS_ERR(tfm))
	334	return (PTR_ERR(tfm) == -ENOENT) ? -ENOPKG : PTR_ERR(tfm);
	335
	336	desc_size = crypto_shash_descsize(tfm) + sizeof(*desc);
	337	digest_size = crypto_shash_digestsize(tfm);
	338
	339	if (digest_size != ctx->digest_len) {
	340	pr_debug("Digest size mismatch (%zx != %x)\n",
	341	digest_size, ctx->digest_len);
	342	ret = -EBADMSG;
	343	goto error_no_desc;
	344	}
	345	pr_debug("Digest: desc=%zu size=%zu\n", desc_size, digest_size);
	346
	347	ret = -ENOMEM;
	348	desc = kzalloc(desc_size + digest_size, GFP_KERNEL);
	349	if (!desc)
	350	goto error_no_desc;
	351
	352	desc->tfm = tfm;
af316fc4 DH	353	ret = crypto_shash_init(desc);
	354	if (ret < 0)
	355	goto error;
	356
	357	ret = pefile_digest_pe_contents(pebuf, pelen, ctx, desc);
	358	if (ret < 0)
	359	goto error;
	360
	361	digest = (void *)desc + desc_size;
	362	ret = crypto_shash_final(desc, digest);
	363	if (ret < 0)
	364	goto error;
	365
	366	pr_debug("Digest calc = [%*ph]\n", ctx->digest_len, digest);
	367
	368	/* Check that the PE file digest matches that in the MSCODE part of the
	369	* PKCS#7 certificate.
	370	*/
	371	if (memcmp(digest, ctx->digest, ctx->digest_len) != 0) {
	372	pr_debug("Digest mismatch\n");
	373	ret = -EKEYREJECTED;
	374	} else {
	375	pr_debug("The digests match!\n");
	376	}
	377
	378	error:
da7798a7	379	kzfree(desc);
af316fc4 DH	380	error_no_desc:
	381	crypto_free_shash(tfm);
	382	kleave(" = %d", ret);
	383	return ret;
	384	}
	385
26d1164b DH	386	/**
	387	* verify_pefile_signature - Verify the signature on a PE binary image
	388	* @pebuf: Buffer containing the PE binary image
	389	* @pelen: Length of the binary image
e68503bd	390	* @trust_keys: Signing certificate(s) to use as starting points
99db4435	391	* @usage: The use to which the key is being put.
26d1164b DH	392	*
	393	* Validate that the certificate chain inside the PKCS#7 message inside the PE
	394	* binary image intersects keys we already know and trust.
	395	*
	396	* Returns, in order of descending priority:
	397	*
	398	* (*) -ELIBBAD if the image cannot be parsed, or:
	399	*
	400	* (*) -EKEYREJECTED if a signature failed to match for which we have a valid
	401	* key, or:
	402	*
	403	* (*) 0 if at least one signature chain intersects with the keys in the trust
	404	* keyring, or:
	405	*
	406	* (*) -ENOPKG if a suitable crypto module couldn't be found for a check on a
	407	* chain.
	408	*
	409	* (*) -ENOKEY if we couldn't find a match for any of the signature chains in
	410	* the message.
	411	*
	412	* May also return -ENOMEM.
	413	*/
	414	int verify_pefile_signature(const void *pebuf, unsigned pelen,
e68503bd DH	415	struct key *trusted_keys,
e68503bd DH	416	enum key_being_used_for usage)
26d1164b DH	417	{
	418	struct pefile_context ctx;
	419	int ret;
	420
	421	kenter("");
	422
	423	memset(&ctx, 0, sizeof(ctx));
	424	ret = pefile_parse_binary(pebuf, pelen, &ctx);
	425	if (ret < 0)
	426	return ret;
	427
09dacbbd DH	428	ret = pefile_strip_sig_wrapper(pebuf, &ctx);
	429	if (ret < 0)
	430	return ret;
	431
e68503bd DH	432	ret = verify_pkcs7_signature(NULL, 0,
e68503bd DH	433	pebuf + ctx.sig_offset, ctx.sig_len,
bda850cd	434	trusted_keys, usage,
e68503bd	435	mscode_parse, &ctx);
4c0b4b1d DH	436	if (ret < 0)
	437	goto error;
	438
	439	pr_debug("Digest: %u [%*ph]\n",
	440	ctx.digest_len, ctx.digest_len, ctx.digest);
	441
af316fc4 DH	442	/* Generate the digest and check against the PKCS7 certificate
	443	* contents.
	444	*/
	445	ret = pefile_digest_pe(pebuf, pelen, &ctx);
3968280c DH	446
3968280c DH	447	error:
da7798a7	448	kzfree(ctx.digest);
3968280c	449	return ret;
26d1164b	450	}