crypto/ct/ct_sct_ctx.c

   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
  23 SCT_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
  45 void 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  */
  63 static 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
 122 int 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;
 197 err:
 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
 248 int 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
 253 int 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
 258 int 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
 275 void SCT_CTX_set_time(SCT_CTX *sctx, uint64_t time_in_ms)
 276 {
 277     sctx->epoch_time_in_ms = time_in_ms;
 278 }