1 /*
2 * Copyright 2016-2021 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the Apache License 2.0 (the "License"). You may not use
5 * this file except in compliance with the License. You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
8 */
9
10 #include <string.h>
11
12 #include <openssl/ct.h>
13 #include <openssl/err.h>
14 #include <openssl/evp.h>
15 #include <openssl/x509.h>
16
17 #include "ct_local.h"
18
19 typedef enum sct_signature_type_t {
20 SIGNATURE_TYPE_NOT_SET = -1,
21 SIGNATURE_TYPE_CERT_TIMESTAMP,
22 SIGNATURE_TYPE_TREE_HASH
23 } SCT_SIGNATURE_TYPE;
24
25 /*
26 * Update encoding for SCT signature verification/generation to supplied
27 * EVP_MD_CTX.
28 */
sct_ctx_update(EVP_MD_CTX * ctx,const SCT_CTX * sctx,const SCT * sct)29 static int sct_ctx_update(EVP_MD_CTX *ctx, const SCT_CTX *sctx, const SCT *sct)
30 {
31 unsigned char tmpbuf[12];
32 unsigned char *p, *der;
33 size_t derlen;
34 /*+
35 * digitally-signed struct {
36 * (1 byte) Version sct_version;
37 * (1 byte) SignatureType signature_type = certificate_timestamp;
38 * (8 bytes) uint64 timestamp;
39 * (2 bytes) LogEntryType entry_type;
40 * (? bytes) select(entry_type) {
41 * case x509_entry: ASN.1Cert;
42 * case precert_entry: PreCert;
43 * } signed_entry;
44 * (2 bytes + sct->ext_len) CtExtensions extensions;
45 * }
46 */
47 if (sct->entry_type == CT_LOG_ENTRY_TYPE_NOT_SET)
48 return 0;
49 if (sct->entry_type == CT_LOG_ENTRY_TYPE_PRECERT && sctx->ihash == NULL)
50 return 0;
51
52 p = tmpbuf;
53 *p++ = sct->version;
54 *p++ = SIGNATURE_TYPE_CERT_TIMESTAMP;
55 l2n8(sct->timestamp, p);
56 s2n(sct->entry_type, p);
57
58 if (!EVP_DigestUpdate(ctx, tmpbuf, p - tmpbuf))
59 return 0;
60
61 if (sct->entry_type == CT_LOG_ENTRY_TYPE_X509) {
62 der = sctx->certder;
63 derlen = sctx->certderlen;
64 } else {
65 if (!EVP_DigestUpdate(ctx, sctx->ihash, sctx->ihashlen))
66 return 0;
67 der = sctx->preder;
68 derlen = sctx->prederlen;
69 }
70
71 /* If no encoding available, fatal error */
72 if (der == NULL)
73 return 0;
74
75 /* Include length first */
76 p = tmpbuf;
77 l2n3(derlen, p);
78
79 if (!EVP_DigestUpdate(ctx, tmpbuf, 3))
80 return 0;
81 if (!EVP_DigestUpdate(ctx, der, derlen))
82 return 0;
83
84 /* Add any extensions */
85 p = tmpbuf;
86 s2n(sct->ext_len, p);
87 if (!EVP_DigestUpdate(ctx, tmpbuf, 2))
88 return 0;
89
90 if (sct->ext_len && !EVP_DigestUpdate(ctx, sct->ext, sct->ext_len))
91 return 0;
92
93 return 1;
94 }
95
SCT_CTX_verify(const SCT_CTX * sctx,const SCT * sct)96 int SCT_CTX_verify(const SCT_CTX *sctx, const SCT *sct)
97 {
98 EVP_MD_CTX *ctx = NULL;
99 int ret = 0;
100
101 if (!SCT_is_complete(sct) || sctx->pkey == NULL ||
102 sct->entry_type == CT_LOG_ENTRY_TYPE_NOT_SET ||
103 (sct->entry_type == CT_LOG_ENTRY_TYPE_PRECERT && sctx->ihash == NULL)) {
104 ERR_raise(ERR_LIB_CT, CT_R_SCT_NOT_SET);
105 return 0;
106 }
107 if (sct->version != SCT_VERSION_V1) {
108 ERR_raise(ERR_LIB_CT, CT_R_SCT_UNSUPPORTED_VERSION);
109 return 0;
110 }
111 if (sct->log_id_len != sctx->pkeyhashlen ||
112 memcmp(sct->log_id, sctx->pkeyhash, sctx->pkeyhashlen) != 0) {
113 ERR_raise(ERR_LIB_CT, CT_R_SCT_LOG_ID_MISMATCH);
114 return 0;
115 }
116 if (sct->timestamp > sctx->epoch_time_in_ms) {
117 ERR_raise(ERR_LIB_CT, CT_R_SCT_FUTURE_TIMESTAMP);
118 return 0;
119 }
120
121 ctx = EVP_MD_CTX_new();
122 if (ctx == NULL)
123 goto end;
124
125 if (!EVP_DigestVerifyInit_ex(ctx, NULL, "SHA2-256", sctx->libctx,
126 sctx->propq, sctx->pkey, NULL))
127 goto end;
128
129 if (!sct_ctx_update(ctx, sctx, sct))
130 goto end;
131
132 /* Verify signature */
133 ret = EVP_DigestVerifyFinal(ctx, sct->sig, sct->sig_len);
134 /* If ret < 0 some other error: fall through without setting error */
135 if (ret == 0)
136 ERR_raise(ERR_LIB_CT, CT_R_SCT_INVALID_SIGNATURE);
137
138 end:
139 EVP_MD_CTX_free(ctx);
140 return ret;
141 }
142
