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#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(OSSL_LIB_CTX *libctx, const char *propq)
24{
25    SCT_CTX *sctx = OPENSSL_zalloc(sizeof(*sctx));
26
27    if (sctx == NULL) {
28        ERR_raise(ERR_LIB_CT, ERR_R_MALLOC_FAILURE);
29        return NULL;
30    }
31
32    sctx->libctx = libctx;
33    if (propq != NULL) {
34        sctx->propq = OPENSSL_strdup(propq);
35        if (sctx->propq == NULL) {
36            ERR_raise(ERR_LIB_CT, ERR_R_MALLOC_FAILURE);
37            OPENSSL_free(sctx);
38            return NULL;
39        }
40    }
41
42    return sctx;
43}
44
45void SCT_CTX_free(SCT_CTX *sctx)
46{
47    if (sctx == NULL)
48        return;
49    EVP_PKEY_free(sctx->pkey);
50    OPENSSL_free(sctx->pkeyhash);
51    OPENSSL_free(sctx->ihash);
52    OPENSSL_free(sctx->certder);
53    OPENSSL_free(sctx->preder);
54    OPENSSL_free(sctx->propq);
55    OPENSSL_free(sctx);
56}
57
58/*
59 * Finds the index of the first extension with the given NID in cert.
60 * If there is more than one extension with that NID, *is_duplicated is set to
61 * 1, otherwise 0 (unless it is NULL).
62 */
63static int ct_x509_get_ext(X509 *cert, int nid, int *is_duplicated)
64{
65    int ret = X509_get_ext_by_NID(cert, nid, -1);
66
67    if (is_duplicated != NULL)
68        *is_duplicated = ret >= 0 && X509_get_ext_by_NID(cert, nid, ret) >= 0;
69
70    return ret;
71}
72
73/*
74 * Modifies a certificate by deleting extensions and copying the issuer and
75 * AKID from the presigner certificate, if necessary.
76 * Returns 1 on success, 0 otherwise.
77 */
78__owur static int ct_x509_cert_fixup(X509 *cert, X509 *presigner)
79{
80    int preidx, certidx;
81    int pre_akid_ext_is_dup, cert_akid_ext_is_dup;
82
83    if (presigner == NULL)
84        return 1;
85
86    preidx = ct_x509_get_ext(presigner, NID_authority_key_identifier,
87                             &pre_akid_ext_is_dup);
88    certidx = ct_x509_get_ext(cert, NID_authority_key_identifier,
89                              &cert_akid_ext_is_dup);
90
91    /* An error occurred whilst searching for the extension */
92    if (preidx < -1 || certidx < -1)
93        return 0;
94    /* Invalid certificate if they contain duplicate extensions */
95    if (pre_akid_ext_is_dup || cert_akid_ext_is_dup)
96        return 0;
97    /* AKID must be present in both certificate or absent in both */
98    if (preidx >= 0 && certidx == -1)
99        return 0;
100    if (preidx == -1 && certidx >= 0)
101        return 0;
102    /* Copy issuer name */
103    if (!X509_set_issuer_name(cert, X509_get_issuer_name(presigner)))
104        return 0;
105    if (preidx != -1) {
106        /* Retrieve and copy AKID encoding */
107        X509_EXTENSION *preext = X509_get_ext(presigner, preidx);
108        X509_EXTENSION *certext = X509_get_ext(cert, certidx);
109        ASN1_OCTET_STRING *preextdata;
110
111        /* Should never happen */
112        if (preext == NULL || certext == NULL)
113            return 0;
114        preextdata = X509_EXTENSION_get_data(preext);
115        if (preextdata == NULL ||
116            !X509_EXTENSION_set_data(certext, preextdata))
117            return 0;
118    }
119    return 1;
120}
121
122int SCT_CTX_set1_cert(SCT_CTX *sctx, X509 *cert, X509 *presigner)
123{
124    unsigned char *certder = NULL, *preder = NULL;
125    X509 *pretmp = NULL;
126    int certderlen = 0, prederlen = 0;
127    int idx = -1;
128    int poison_ext_is_dup, sct_ext_is_dup;
129    int poison_idx = ct_x509_get_ext(cert, NID_ct_precert_poison, &poison_ext_is_dup);
130
131    /* Duplicate poison extensions are present - error */
132    if (poison_ext_is_dup)
133        goto err;
134
135    /* If *cert doesn't have a poison extension, it isn't a precert */
136    if (poison_idx == -1) {
137        /* cert isn't a precert, so we shouldn't have a presigner */
138        if (presigner != NULL)
139            goto err;
140
141        certderlen = i2d_X509(cert, &certder);
142        if (certderlen < 0)
143            goto err;
144    }
145
146    /* See if cert has a precert SCTs extension */
147    idx = ct_x509_get_ext(cert, NID_ct_precert_scts, &sct_ext_is_dup);
148    /* Duplicate SCT extensions are present - error */
149    if (sct_ext_is_dup)
150        goto err;
151
152    if (idx >= 0 && poison_idx >= 0) {
153        /*
154         * cert can't both contain SCTs (i.e. have an SCT extension) and be a
155         * precert (i.e. have a poison extension).
156         */
157        goto err;
158    }
159
160    if (idx == -1) {
161        idx = poison_idx;
162    }
163
164    /*
165     * If either a poison or SCT extension is present, remove it before encoding
166     * cert. This, along with ct_x509_cert_fixup(), gets a TBSCertificate (see
167     * RFC5280) from cert, which is what the CT log signed when it produced the
168     * SCT.
169     */
170    if (idx >= 0) {
171        /* Take a copy of certificate so we don't modify passed version */
172        pretmp = X509_dup(cert);
173        if (pretmp == NULL)
174            goto err;
175
176        X509_EXTENSION_free(X509_delete_ext(pretmp, idx));
177
178        if (!ct_x509_cert_fixup(pretmp, presigner))
179            goto err;
180
181        prederlen = i2d_re_X509_tbs(pretmp, &preder);
182        if (prederlen <= 0)
183            goto err;
184    }
185
186    X509_free(pretmp);
187
188    OPENSSL_free(sctx->certder);
189    sctx->certder = certder;
190    sctx->certderlen = certderlen;
191
192    OPENSSL_free(sctx->preder);
193    sctx->preder = preder;
194    sctx->prederlen = prederlen;
195
196    return 1;
197err:
198    OPENSSL_free(certder);
199    OPENSSL_free(preder);
200    X509_free(pretmp);
201    return 0;
202}
203
204__owur static int ct_public_key_hash(SCT_CTX *sctx, X509_PUBKEY *pkey,
205                                     unsigned char **hash, size_t *hash_len)
206{
207    int ret = 0;
208    unsigned char *md = NULL, *der = NULL;
209    int der_len;
210    unsigned int md_len;
211    EVP_MD *sha256 = EVP_MD_fetch(sctx->libctx, "SHA2-256", sctx->propq);
212
213    if (sha256 == NULL)
214        goto err;
215
216    /* Reuse buffer if possible */
217    if (*hash != NULL && *hash_len >= SHA256_DIGEST_LENGTH) {
218        md = *hash;
219    } else {
220        md = OPENSSL_malloc(SHA256_DIGEST_LENGTH);
221        if (md == NULL)
222            goto err;
223    }
224
225    /* Calculate key hash */
226    der_len = i2d_X509_PUBKEY(pkey, &der);
227    if (der_len <= 0)
228        goto err;
229
230    if (!EVP_Digest(der, der_len, md, &md_len, sha256, NULL))
231        goto err;
232
233    if (md != *hash) {
234        OPENSSL_free(*hash);
235        *hash = md;
236        *hash_len = SHA256_DIGEST_LENGTH;
237    }
238
239    md = NULL;
240    ret = 1;
241 err:
242    EVP_MD_free(sha256);
243    OPENSSL_free(md);
244    OPENSSL_free(der);
245    return ret;
246}
247
248int SCT_CTX_set1_issuer(SCT_CTX *sctx, const X509 *issuer)
249{
250    return SCT_CTX_set1_issuer_pubkey(sctx, X509_get_X509_PUBKEY(issuer));
251}
252
253int SCT_CTX_set1_issuer_pubkey(SCT_CTX *sctx, X509_PUBKEY *pubkey)
254{
255    return ct_public_key_hash(sctx, pubkey, &sctx->ihash, &sctx->ihashlen);
256}
257
258int SCT_CTX_set1_pubkey(SCT_CTX *sctx, X509_PUBKEY *pubkey)
259{
260    EVP_PKEY *pkey = X509_PUBKEY_get(pubkey);
261
262    if (pkey == NULL)
263        return 0;
264
265    if (!ct_public_key_hash(sctx, pubkey, &sctx->pkeyhash, &sctx->pkeyhashlen)) {
266        EVP_PKEY_free(pkey);
267        return 0;
268    }
269
270    EVP_PKEY_free(sctx->pkey);
271    sctx->pkey = pkey;
272    return 1;
273}
274
275void SCT_CTX_set_time(SCT_CTX *sctx, uint64_t time_in_ms)
276{
277    sctx->epoch_time_in_ms = time_in_ms;
278}
279