digest.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright (C) 2020-2024 Microsoft Corporation. All rights reserved.
  4 */
  5
  6#include "digest.h"
  7
  8/**
  9 * ipe_digest_parse() - parse a digest in IPE's policy.
 10 * @valstr: Supplies the string parsed from the policy.
 11 *
 12 * Digests in IPE are defined in a standard way:
 13 *	<alg_name>:<hex>
 14 *
 15 * Use this function to create a property to parse the digest
 16 * consistently. The parsed digest will be saved in @value in IPE's
 17 * policy.
 18 *
 19 * Return: The parsed digest_info structure on success. If an error occurs,
 20 * the function will return the error value (via ERR_PTR).
 21 */
 22struct digest_info *ipe_digest_parse(const char *valstr)
 23{
 24	struct digest_info *info = NULL;
 25	char *sep, *raw_digest;
 26	size_t raw_digest_len;
 27	u8 *digest = NULL;
 28	char *alg = NULL;
 29	int rc = 0;
 30
 31	info = kzalloc(sizeof(*info), GFP_KERNEL);
 32	if (!info)
 33		return ERR_PTR(-ENOMEM);
 34
 35	sep = strchr(valstr, ':');
 36	if (!sep) {
 37		rc = -EBADMSG;
 38		goto err;
 39	}
 40
 41	alg = kstrndup(valstr, sep - valstr, GFP_KERNEL);
 42	if (!alg) {
 43		rc = -ENOMEM;
 44		goto err;
 45	}
 46
 47	raw_digest = sep + 1;
 48	raw_digest_len = strlen(raw_digest);
 49
 50	info->digest_len = (raw_digest_len + 1) / 2;
 51	digest = kzalloc(info->digest_len, GFP_KERNEL);
 52	if (!digest) {
 53		rc = -ENOMEM;
 54		goto err;
 55	}
 56
 57	rc = hex2bin(digest, raw_digest, info->digest_len);
 58	if (rc < 0) {
 59		rc = -EINVAL;
 60		goto err;
 61	}
 62
 63	info->alg = alg;
 64	info->digest = digest;
 65	return info;
 66
 67err:
 68	kfree(alg);
 69	kfree(digest);
 70	kfree(info);
 71	return ERR_PTR(rc);
 72}
 73
 74/**
 75 * ipe_digest_eval() - evaluate an IPE digest against another digest.
 76 * @expected: Supplies the policy-provided digest value.
 77 * @digest: Supplies the digest to compare against the policy digest value.
 78 *
 79 * Return:
 80 * * %true	- digests match
 81 * * %false	- digests do not match
 82 */
 83bool ipe_digest_eval(const struct digest_info *expected,
 84		     const struct digest_info *digest)
 85{
 86	return (expected->digest_len == digest->digest_len) &&
 87	       (!strcmp(expected->alg, digest->alg)) &&
 88	       (!memcmp(expected->digest, digest->digest, expected->digest_len));
 89}
 90
 91/**
 92 * ipe_digest_free() - free an IPE digest.
 93 * @info: Supplies a pointer the policy-provided digest to free.
 94 */
 95void ipe_digest_free(struct digest_info *info)
 96{
 97	if (IS_ERR_OR_NULL(info))
 98		return;
 99
100	kfree(info->alg);
101	kfree(info->digest);
102	kfree(info);
103}
104
105/**
106 * ipe_digest_audit() - audit a digest that was sourced from IPE's policy.
107 * @ab: Supplies the audit_buffer to append the formatted result.
108 * @info: Supplies a pointer to source the audit record from.
109 *
110 * Digests in IPE are audited in this format:
111 *	<alg_name>:<hex>
112 */
113void ipe_digest_audit(struct audit_buffer *ab, const struct digest_info *info)
114{
115	audit_log_untrustedstring(ab, info->alg);
116	audit_log_format(ab, ":");
117	audit_log_n_hex(ab, info->digest, info->digest_len);
118}