1/*
2 * Copyright 2016 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the OpenSSL license (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#ifdef OPENSSL_NO_CT
11# error "CT is disabled"
12#endif
13
14#include <stddef.h>
15#include <string.h>
16
17#include <openssl/err.h>
18#include <openssl/obj_mac.h>
19#include <openssl/x509.h>
20
21#include "ct_local.h"
22
23SCT_CTX *SCT_CTX_new(void)
24{
25    SCT_CTX *sctx = OPENSSL_zalloc(sizeof(*sctx));
26
27    if (sctx == NULL)
28        CTerr(CT_F_SCT_CTX_NEW, ERR_R_MALLOC_FAILURE);
29
30    return sctx;
31}
32
33void SCT_CTX_free(SCT_CTX *sctx)
34{
35    if (sctx == NULL)
36        return;
37    EVP_PKEY_free(sctx->pkey);
38    OPENSSL_free(sctx->pkeyhash);
39    OPENSSL_free(sctx->ihash);
40    OPENSSL_free(sctx->certder);
41    OPENSSL_free(sctx->preder);
42    OPENSSL_free(sctx);
43}
44
45/*
46 * Finds the index of the first extension with the given NID in cert.
47 * If there is more than one extension with that NID, *is_duplicated is set to
48 * 1, otherwise 0 (unless it is NULL).
49 */
50static int ct_x509_get_ext(X509 *cert, int nid, int *is_duplicated)
51{
52    int ret = X509_get_ext_by_NID(cert, nid, -1);
53
54    if (is_duplicated != NULL)
55        *is_duplicated = ret >= 0 && X509_get_ext_by_NID(cert, nid, ret) >= 0;
56
57    return ret;
58}
59
60/*
61 * Modifies a certificate by deleting extensions and copying the issuer and
62 * AKID from the presigner certificate, if necessary.
63 * Returns 1 on success, 0 otherwise.
64 */
65__owur static int ct_x509_cert_fixup(X509 *cert, X509 *presigner)
66{
67    int preidx, certidx;
68    int pre_akid_ext_is_dup, cert_akid_ext_is_dup;
69
70    if (presigner == NULL)
71        return 1;
72
73    preidx = ct_x509_get_ext(presigner, NID_authority_key_identifier,
74                             &pre_akid_ext_is_dup);
75    certidx = ct_x509_get_ext(cert, NID_authority_key_identifier,
76                              &cert_akid_ext_is_dup);
77
78    /* An error occurred whilst searching for the extension */
79    if (preidx < -1 || certidx < -1)
80        return 0;
81    /* Invalid certificate if they contain duplicate extensions */
82    if (pre_akid_ext_is_dup || cert_akid_ext_is_dup)
83        return 0;
84    /* AKID must be present in both certificate or absent in both */
85    if (preidx >= 0 && certidx == -1)
86        return 0;
87    if (preidx == -1 && certidx >= 0)
88        return 0;
89    /* Copy issuer name */
90    if (!X509_set_issuer_name(cert, X509_get_issuer_name(presigner)))
91        return 0;
92    if (preidx != -1) {
93        /* Retrieve and copy AKID encoding */
94        X509_EXTENSION *preext = X509_get_ext(presigner, preidx);
95        X509_EXTENSION *certext = X509_get_ext(cert, certidx);
96        ASN1_OCTET_STRING *preextdata;
97
98        /* Should never happen */
99        if (preext == NULL || certext == NULL)
100            return 0;
101        preextdata = X509_EXTENSION_get_data(preext);
102        if (preextdata == NULL ||
103            !X509_EXTENSION_set_data(certext, preextdata))
104            return 0;
105    }
106    return 1;
107}
108
109int SCT_CTX_set1_cert(SCT_CTX *sctx, X509 *cert, X509 *presigner)
110{
111    unsigned char *certder = NULL, *preder = NULL;
112    X509 *pretmp = NULL;
113    int certderlen = 0, prederlen = 0;
114    int idx = -1;
115    int poison_ext_is_dup, sct_ext_is_dup;
116    int poison_idx = ct_x509_get_ext(cert, NID_ct_precert_poison, &poison_ext_is_dup);
117
118    /* Duplicate poison extensions are present - error */
119    if (poison_ext_is_dup)
120        goto err;
121
122    /* If *cert doesn't have a poison extension, it isn't a precert */
123    if (poison_idx == -1) {
124        /* cert isn't a precert, so we shouldn't have a presigner */
125        if (presigner != NULL)
126            goto err;
127
128        certderlen = i2d_X509(cert, &certder);
129        if (certderlen < 0)
130            goto err;
131    }
132
133    /* See if cert has a precert SCTs extension */
134    idx = ct_x509_get_ext(cert, NID_ct_precert_scts, &sct_ext_is_dup);
135    /* Duplicate SCT extensions are present - error */
136    if (sct_ext_is_dup)
137        goto err;
138
139    if (idx >= 0 && poison_idx >= 0) {
140        /*
141         * cert can't both contain SCTs (i.e. have an SCT extension) and be a
142         * precert (i.e. have a poison extension).
143         */
144        goto err;
145    }
146
147    if (idx == -1) {
148        idx = poison_idx;
149    }
150
151    /*
152     * If either a poison or SCT extension is present, remove it before encoding
153     * cert. This, along with ct_x509_cert_fixup(), gets a TBSCertificate (see
154     * RFC5280) from cert, which is what the CT log signed when it produced the
155     * SCT.
156     */
157    if (idx >= 0) {
158        X509_EXTENSION *ext;
159
160        /* Take a copy of certificate so we don't modify passed version */
161        pretmp = X509_dup(cert);
162        if (pretmp == NULL)
163            goto err;
164
165        ext = X509_delete_ext(pretmp, idx);
166        X509_EXTENSION_free(ext);
167
168        if (!ct_x509_cert_fixup(pretmp, presigner))
169            goto err;
170
171        prederlen = i2d_re_X509_tbs(pretmp, &preder);
172        if (prederlen <= 0)
173            goto err;
174    }
175
176    X509_free(pretmp);
177
178    OPENSSL_free(sctx->certder);
179    sctx->certder = certder;
180    sctx->certderlen = certderlen;
181
182    OPENSSL_free(sctx->preder);
183    sctx->preder = preder;
184    sctx->prederlen = prederlen;
185
186    return 1;
187err:
188    OPENSSL_free(certder);
189    OPENSSL_free(preder);
190    X509_free(pretmp);
191    return 0;
192}
193
194__owur static int ct_public_key_hash(X509_PUBKEY *pkey, unsigned char **hash,
195                                     size_t *hash_len)
196{
197    int ret = 0;
198    unsigned char *md = NULL, *der = NULL;
199    int der_len;
200    unsigned int md_len;
201
202    /* Reuse buffer if possible */
203    if (*hash != NULL && *hash_len >= SHA256_DIGEST_LENGTH) {
204        md = *hash;
205    } else {
206        md = OPENSSL_malloc(SHA256_DIGEST_LENGTH);
207        if (md == NULL)
208            goto err;
209    }
210
211    /* Calculate key hash */
212    der_len = i2d_X509_PUBKEY(pkey, &der);
213    if (der_len <= 0)
214        goto err;
215
216    if (!EVP_Digest(der, der_len, md, &md_len, EVP_sha256(), NULL))
217        goto err;
218
219    if (md != *hash) {
220        OPENSSL_free(*hash);
221        *hash = md;
222        *hash_len = SHA256_DIGEST_LENGTH;
223    }
224
225    md = NULL;
226    ret = 1;
227 err:
228    OPENSSL_free(md);
229    OPENSSL_free(der);
230    return ret;
231}
232
233int SCT_CTX_set1_issuer(SCT_CTX *sctx, const X509 *issuer)
234{
235    return SCT_CTX_set1_issuer_pubkey(sctx, X509_get_X509_PUBKEY(issuer));
236}
237
238int SCT_CTX_set1_issuer_pubkey(SCT_CTX *sctx, X509_PUBKEY *pubkey)
239{
240    return ct_public_key_hash(pubkey, &sctx->ihash, &sctx->ihashlen);
241}
242
243int SCT_CTX_set1_pubkey(SCT_CTX *sctx, X509_PUBKEY *pubkey)
244{
245    EVP_PKEY *pkey = X509_PUBKEY_get(pubkey);
246
247    if (pkey == NULL)
248        return 0;
249
250    if (!ct_public_key_hash(pubkey, &sctx->pkeyhash, &sctx->pkeyhashlen)) {
251        EVP_PKEY_free(pkey);
252        return 0;
253    }
254
255    EVP_PKEY_free(sctx->pkey);
256    sctx->pkey = pkey;
257    return 1;
258}
259
260void SCT_CTX_set_time(SCT_CTX *sctx, uint64_t time_in_ms)
261{
262    sctx->epoch_time_in_ms = time_in_ms;
263}
264