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1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * MSCode parser using MbedTLS ASN1 library
4 *
5 * Copyright (c) 2024 Linaro Limited
6 * Author: Raymond Mao <raymond.mao@linaro.org>
7 */
8
9#include <linux/kernel.h>
10#include <linux/err.h>
11#include <crypto/pkcs7.h>
12#include <crypto/mscode.h>
13
14/*
15 * Parse a Microsoft Individual Code Signing blob
16 *
17 * U.P.SEQUENCE {
18 * U.P.OBJECTIDENTIFIER 1.3.6.1.4.1.311.2.1.15 (SPC_PE_IMAGE_DATA_OBJID)
19 * U.P.SEQUENCE {
20 * U.P.BITSTRING NaN : 0 unused bit(s);
21 * [C.P.0] {
22 * [C.P.2] {
23 * [C.P.0] <arbitrary string>
24 * }
25 * }
26 * }
27 * }
28 * U.P.SEQUENCE {
29 * U.P.SEQUENCE {
30 * U.P.OBJECTIDENTIFIER <digest algorithm OID>
31 * U.P.NULL
32 * }
33 * U.P.OCTETSTRING <PE image digest>
34 * }
35 *
36 * @ctx: PE file context.
37 * @content_data: content data pointer.
38 * @data_len: content data length.
39 * @asn1hdrlen: ASN1 header length.
40 */
41int mscode_parse(void *ctx, const void *content_data, size_t data_len,
42 size_t asn1hdrlen)
43{
44 struct pefile_context *_ctx = ctx;
45 unsigned char *p = (unsigned char *)content_data;
46 unsigned char *end = (unsigned char *)content_data + data_len;
47 size_t len = 0;
48 int ret;
49 unsigned char *inner_p;
50 size_t seq_len = 0;
51
52 ret = mbedtls_asn1_get_tag(&p, end, &seq_len,
53 MBEDTLS_ASN1_CONSTRUCTED |
54 MBEDTLS_ASN1_SEQUENCE);
55 if (ret)
56 return ret;
57
58 inner_p = p;
59 ret = mbedtls_asn1_get_tag(&inner_p, inner_p + seq_len, &len,
60 MBEDTLS_ASN1_OID);
61 if (ret)
62 return ret;
63
64 /* Sanity check on the PE Image Data OID (1.3.6.1.4.1.311.2.1.15) */
65 if (MBEDTLS_OID_CMP_RAW(MBEDTLS_OID_MICROSOFT_PEIMAGEDATA, inner_p,
66 len))
67 return -EINVAL;
68
69 p += seq_len;
70 ret = mbedtls_asn1_get_tag(&p, end, &seq_len,
71 MBEDTLS_ASN1_CONSTRUCTED |
72 MBEDTLS_ASN1_SEQUENCE);
73 if (ret)
74 return ret;
75
76 ret = mbedtls_asn1_get_tag(&p, p + seq_len, &seq_len,
77 MBEDTLS_ASN1_CONSTRUCTED |
78 MBEDTLS_ASN1_SEQUENCE);
79 if (ret)
80 return ret;
81
82 inner_p = p;
83
84 /*
85 * Check if the inner sequence contains a supported hash
86 * algorithm OID
87 */
88 ret = mbedtls_asn1_get_tag(&inner_p, inner_p + seq_len, &len,
89 MBEDTLS_ASN1_OID);
90 if (ret)
91 return ret;
92
93 if (!MBEDTLS_OID_CMP_RAW(MBEDTLS_OID_DIGEST_ALG_MD5, inner_p, len))
94 _ctx->digest_algo = "md5";
95 else if (!MBEDTLS_OID_CMP_RAW(MBEDTLS_OID_DIGEST_ALG_SHA1, inner_p,
96 len))
97 _ctx->digest_algo = "sha1";
98 else if (!MBEDTLS_OID_CMP_RAW(MBEDTLS_OID_DIGEST_ALG_SHA224, inner_p,
99 len))
100 _ctx->digest_algo = "sha224";
101 else if (!MBEDTLS_OID_CMP_RAW(MBEDTLS_OID_DIGEST_ALG_SHA256, inner_p,
102 len))
103 _ctx->digest_algo = "sha256";
104 else if (!MBEDTLS_OID_CMP_RAW(MBEDTLS_OID_DIGEST_ALG_SHA384, inner_p,
105 len))
106 _ctx->digest_algo = "sha384";
107 else if (!MBEDTLS_OID_CMP_RAW(MBEDTLS_OID_DIGEST_ALG_SHA512, inner_p,
108 len))
109 _ctx->digest_algo = "sha512";
110
111 if (!_ctx->digest_algo)
112 return -EINVAL;
113
114 p += seq_len;
115 ret = mbedtls_asn1_get_tag(&p, end, &len, MBEDTLS_ASN1_OCTET_STRING);
116 if (ret)
117 return ret;
118
119 _ctx->digest = p;
120 _ctx->digest_len = len;
121
122 return 0;
123}