crypto/ct/ct_sct_ctx.c

   1 /*
   2  * Copyright 2016-2020 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(OPENSSL_CTX *libctx, const char *propq)
  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     sctx->libctx = libctx;
  31     if (propq != NULL) {
  32         sctx->propq = OPENSSL_strdup(propq);
  33         if (sctx->propq == NULL) {
  34             CTerr(CT_F_SCT_CTX_NEW, ERR_R_MALLOC_FAILURE);
  35             OPENSSL_free(sctx);
  36             return NULL;
  37         }
  38     }
  39
  40     return sctx;
  41 }
  42
  43 void SCT_CTX_free(SCT_CTX *sctx)
  44 {
  45     if (sctx == NULL)
  46         return;
  47     EVP_PKEY_free(sctx->pkey);
  48     OPENSSL_free(sctx->pkeyhash);
  49     OPENSSL_free(sctx->ihash);
  50     OPENSSL_free(sctx->certder);
  51     OPENSSL_free(sctx->preder);
  52     OPENSSL_free(sctx->propq);
  53     OPENSSL_free(sctx);
  54 }
  55
  56 /*
  57  * Finds the index of the first extension with the given NID in cert.
  58  * If there is more than one extension with that NID, *is_duplicated is set to
  59  * 1, otherwise 0 (unless it is NULL).
  60  */
  61 static int ct_x509_get_ext(X509 *cert, int nid, int *is_duplicated)
  62 {
  63     int ret = X509_get_ext_by_NID(cert, nid, -1);
  64
  65     if (is_duplicated != NULL)
  66         *is_duplicated = ret >= 0 && X509_get_ext_by_NID(cert, nid, ret) >= 0;
  67
  68     return ret;
  69 }
  70
  71 /*
  72  * Modifies a certificate by deleting extensions and copying the issuer and
  73  * AKID from the presigner certificate, if necessary.
  74  * Returns 1 on success, 0 otherwise.
  75  */
  76 __owur static int ct_x509_cert_fixup(X509 *cert, X509 *presigner)
  77 {
  78     int preidx, certidx;
  79     int pre_akid_ext_is_dup, cert_akid_ext_is_dup;
  80
  81     if (presigner == NULL)
  82         return 1;
  83
  84     preidx = ct_x509_get_ext(presigner, NID_authority_key_identifier,
  85                              &pre_akid_ext_is_dup);
  86     certidx = ct_x509_get_ext(cert, NID_authority_key_identifier,
  87                               &cert_akid_ext_is_dup);
  88
  89     /* An error occurred whilst searching for the extension */
  90     if (preidx < -1 || certidx < -1)
  91         return 0;
  92     /* Invalid certificate if they contain duplicate extensions */
  93     if (pre_akid_ext_is_dup || cert_akid_ext_is_dup)
  94         return 0;
  95     /* AKID must be present in both certificate or absent in both */
  96     if (preidx >= 0 && certidx == -1)
  97         return 0;
  98     if (preidx == -1 && certidx >= 0)
  99         return 0;
 100     /* Copy issuer name */
 101     if (!X509_set_issuer_name(cert, X509_get_issuer_name(presigner)))
 102         return 0;
 103     if (preidx != -1) {
 104         /* Retrieve and copy AKID encoding */
 105         X509_EXTENSION *preext = X509_get_ext(presigner, preidx);
 106         X509_EXTENSION *certext = X509_get_ext(cert, certidx);
 107         ASN1_OCTET_STRING *preextdata;
 108
 109         /* Should never happen */
 110         if (preext == NULL || certext == NULL)
 111             return 0;
 112         preextdata = X509_EXTENSION_get_data(preext);
 113         if (preextdata == NULL ||
 114             !X509_EXTENSION_set_data(certext, preextdata))
 115             return 0;
 116     }
 117     return 1;
 118 }
 119
 120 int SCT_CTX_set1_cert(SCT_CTX *sctx, X509 *cert, X509 *presigner)
 121 {
 122     unsigned char *certder = NULL, *preder = NULL;
 123     X509 *pretmp = NULL;
 124     int certderlen = 0, prederlen = 0;
 125     int idx = -1;
 126     int poison_ext_is_dup, sct_ext_is_dup;
 127     int poison_idx = ct_x509_get_ext(cert, NID_ct_precert_poison, &poison_ext_is_dup);
 128
 129     /* Duplicate poison extensions are present - error */
 130     if (poison_ext_is_dup)
 131         goto err;
 132
 133     /* If *cert doesn't have a poison extension, it isn't a precert */
 134     if (poison_idx == -1) {
 135         /* cert isn't a precert, so we shouldn't have a presigner */
 136         if (presigner != NULL)
 137             goto err;
 138
 139         certderlen = i2d_X509(cert, &certder);
 140         if (certderlen < 0)
 141             goto err;
 142     }
 143
 144     /* See if cert has a precert SCTs extension */
 145     idx = ct_x509_get_ext(cert, NID_ct_precert_scts, &sct_ext_is_dup);
 146     /* Duplicate SCT extensions are present - error */
 147     if (sct_ext_is_dup)
 148         goto err;
 149
 150     if (idx >= 0 && poison_idx >= 0) {
 151         /*
 152          * cert can't both contain SCTs (i.e. have an SCT extension) and be a
 153          * precert (i.e. have a poison extension).
 154          */
 155         goto err;
 156     }
 157
 158     if (idx == -1) {
 159         idx = poison_idx;
 160     }
 161
 162     /*
 163      * If either a poison or SCT extension is present, remove it before encoding
 164      * cert. This, along with ct_x509_cert_fixup(), gets a TBSCertificate (see
 165      * RFC5280) from cert, which is what the CT log signed when it produced the
 166      * SCT.
 167      */
 168     if (idx >= 0) {
 169         X509_EXTENSION *ext;
 170
 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         ext = X509_delete_ext(pretmp, idx);
 177         X509_EXTENSION_free(ext);
 178
 179         if (!ct_x509_cert_fixup(pretmp, presigner))
 180             goto err;
 181
 182         prederlen = i2d_re_X509_tbs(pretmp, &preder);
 183         if (prederlen <= 0)
 184             goto err;
 185     }
 186
 187     X509_free(pretmp);
 188
 189     OPENSSL_free(sctx->certder);
 190     sctx->certder = certder;
 191     sctx->certderlen = certderlen;
 192
 193     OPENSSL_free(sctx->preder);
 194     sctx->preder = preder;
 195     sctx->prederlen = prederlen;
 196
 197     return 1;
 198 err:
 199     OPENSSL_free(certder);
 200     OPENSSL_free(preder);
 201     X509_free(pretmp);
 202     return 0;
 203 }
 204
 205 __owur static int ct_public_key_hash(SCT_CTX *sctx, X509_PUBKEY *pkey,
 206                                      unsigned char **hash, size_t *hash_len)
 207 {
 208     int ret = 0;
 209     unsigned char *md = NULL, *der = NULL;
 210     int der_len;
 211     unsigned int md_len;
 212     EVP_MD *sha256 = EVP_MD_fetch(sctx->libctx, "SHA2-256", sctx->propq);
 213
 214     if (sha256 == NULL)
 215         goto err;
 216
 217     /* Reuse buffer if possible */
 218     if (*hash != NULL && *hash_len >= SHA256_DIGEST_LENGTH) {
 219         md = *hash;
 220     } else {
 221         md = OPENSSL_malloc(SHA256_DIGEST_LENGTH);
 222         if (md == NULL)
 223             goto err;
 224     }
 225
 226     /* Calculate key hash */
 227     der_len = i2d_X509_PUBKEY(pkey, &der);
 228     if (der_len <= 0)
 229         goto err;
 230
 231     if (!EVP_Digest(der, der_len, md, &md_len, sha256, NULL))
 232         goto err;
 233
 234     if (md != *hash) {
 235         OPENSSL_free(*hash);
 236         *hash = md;
 237         *hash_len = SHA256_DIGEST_LENGTH;
 238     }
 239
 240     md = NULL;
 241     ret = 1;
 242  err:
 243     EVP_MD_free(sha256);
 244     OPENSSL_free(md);
 245     OPENSSL_free(der);
 246     return ret;
 247 }
 248
 249 int SCT_CTX_set1_issuer(SCT_CTX *sctx, const X509 *issuer)
 250 {
 251     return SCT_CTX_set1_issuer_pubkey(sctx, X509_get_X509_PUBKEY(issuer));
 252 }
 253
 254 int SCT_CTX_set1_issuer_pubkey(SCT_CTX *sctx, X509_PUBKEY *pubkey)
 255 {
 256     return ct_public_key_hash(sctx, pubkey, &sctx->ihash, &sctx->ihashlen);
 257 }
 258
 259 int SCT_CTX_set1_pubkey(SCT_CTX *sctx, X509_PUBKEY *pubkey)
 260 {
 261     EVP_PKEY *pkey = X509_PUBKEY_get(pubkey);
 262
 263     if (pkey == NULL)
 264         return 0;
 265
 266     if (!ct_public_key_hash(sctx, pubkey, &sctx->pkeyhash, &sctx->pkeyhashlen)) {
 267         EVP_PKEY_free(pkey);
 268         return 0;
 269     }
 270
 271     EVP_PKEY_free(sctx->pkey);
 272     sctx->pkey = pkey;
 273     return 1;
 274 }
 275
 276 void SCT_CTX_set_time(SCT_CTX *sctx, uint64_t time_in_ms)
 277 {
 278     sctx->epoch_time_in_ms = time_in_ms;
 279 }