| 1 | /* |
| 2 | * PDKIM - a RFC4871 (DKIM) implementation |
| 3 | * |
| 4 | * Copyright (C) 2017 Exim maintainers |
| 5 | * |
| 6 | * signing/verification interface |
| 7 | */ |
| 8 | |
| 9 | #include "../exim.h" |
| 10 | |
| 11 | #ifndef DISABLE_DKIM /* entire file */ |
| 12 | |
| 13 | #ifndef SUPPORT_TLS |
| 14 | # error Need SUPPORT_TLS for DKIM |
| 15 | #endif |
| 16 | |
| 17 | #include "crypt_ver.h" |
| 18 | #include "signing.h" |
| 19 | |
| 20 | |
| 21 | /******************************************************************************/ |
| 22 | #ifdef SIGN_GNUTLS |
| 23 | # define EXIM_GNUTLS_LIBRARY_LOG_LEVEL 3 |
| 24 | |
| 25 | |
| 26 | /* Logging function which can be registered with |
| 27 | * gnutls_global_set_log_function() |
| 28 | * gnutls_global_set_log_level() 0..9 |
| 29 | */ |
| 30 | #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 |
| 31 | static void |
| 32 | exim_gnutls_logger_cb(int level, const char *message) |
| 33 | { |
| 34 | size_t len = strlen(message); |
| 35 | if (len < 1) |
| 36 | { |
| 37 | DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level); |
| 38 | return; |
| 39 | } |
| 40 | DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message, |
| 41 | message[len-1] == '\n' ? "" : "\n"); |
| 42 | } |
| 43 | #endif |
| 44 | |
| 45 | |
| 46 | |
| 47 | void |
| 48 | exim_dkim_init(void) |
| 49 | { |
| 50 | #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 |
| 51 | DEBUG(D_tls) |
| 52 | { |
| 53 | gnutls_global_set_log_function(exim_gnutls_logger_cb); |
| 54 | /* arbitrarily chosen level; bump upto 9 for more */ |
| 55 | gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL); |
| 56 | } |
| 57 | #endif |
| 58 | } |
| 59 | |
| 60 | |
| 61 | /* accumulate data (gnutls-only). String to be appended must be nul-terminated. */ |
| 62 | gstring * |
| 63 | exim_dkim_data_append(gstring * g, uschar * s) |
| 64 | { |
| 65 | return string_cat(g, s); |
| 66 | } |
| 67 | |
| 68 | |
| 69 | |
| 70 | /* import private key from PEM string in memory. |
| 71 | Return: NULL for success, or an error string */ |
| 72 | |
| 73 | const uschar * |
| 74 | exim_dkim_signing_init(uschar * privkey_pem, es_ctx * sign_ctx) |
| 75 | { |
| 76 | gnutls_datum_t k = { .data = privkey_pem, .size = Ustrlen(privkey_pem) }; |
| 77 | gnutls_x509_privkey_t x509_key; |
| 78 | int rc; |
| 79 | |
| 80 | if ( (rc = gnutls_x509_privkey_init(&x509_key)) |
| 81 | || (rc = gnutls_x509_privkey_import(x509_key, &k, GNUTLS_X509_FMT_PEM)) |
| 82 | || (rc = gnutls_privkey_init(&sign_ctx->key)) |
| 83 | || (rc = gnutls_privkey_import_x509(sign_ctx->key, x509_key, 0)) |
| 84 | ) |
| 85 | return CUS gnutls_strerror(rc); |
| 86 | |
| 87 | switch (rc = gnutls_privkey_get_pk_algorithm(sign_ctx->key, NULL)) |
| 88 | { |
| 89 | case GNUTLS_PK_RSA: sign_ctx->keytype = KEYTYPE_RSA; break; |
| 90 | #ifdef SIGN_HAVE_ED25519 |
| 91 | case GNUTLS_PK_EDDSA_ED25519: sign_ctx->keytype = KEYTYPE_ED25519; break; |
| 92 | #endif |
| 93 | default: return rc < 0 |
| 94 | ? CUS gnutls_strerror(rc) |
| 95 | : string_sprintf("Unhandled key type: %d '%s'", rc, gnutls_pk_get_name(rc)); |
| 96 | } |
| 97 | |
| 98 | return NULL; |
| 99 | } |
| 100 | |
| 101 | |
| 102 | |
| 103 | /* allocate mem for signature (when signing) */ |
| 104 | /* hash & sign data. No way to do incremental. |
| 105 | |
| 106 | Return: NULL for success, or an error string */ |
| 107 | |
| 108 | const uschar * |
| 109 | exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig) |
| 110 | { |
| 111 | gnutls_datum_t k_data = { .data = data->data, .size = data->len }; |
| 112 | gnutls_digest_algorithm_t dig; |
| 113 | gnutls_datum_t k_sig; |
| 114 | int rc; |
| 115 | |
| 116 | switch (hash) |
| 117 | { |
| 118 | case HASH_SHA1: dig = GNUTLS_DIG_SHA1; break; |
| 119 | case HASH_SHA2_256: dig = GNUTLS_DIG_SHA256; break; |
| 120 | case HASH_SHA2_512: dig = GNUTLS_DIG_SHA512; break; |
| 121 | default: return US"nonhandled hash type"; |
| 122 | } |
| 123 | |
| 124 | if ((rc = gnutls_privkey_sign_data(sign_ctx->key, dig, 0, &k_data, &k_sig))) |
| 125 | return CUS gnutls_strerror(rc); |
| 126 | |
| 127 | /* Don't care about deinit for the key; shortlived process */ |
| 128 | |
| 129 | sig->data = k_sig.data; |
| 130 | sig->len = k_sig.size; |
| 131 | return NULL; |
| 132 | } |
| 133 | |
| 134 | |
| 135 | |
| 136 | /* import public key (from blob in memory) |
| 137 | Return: NULL for success, or an error string */ |
| 138 | |
| 139 | const uschar * |
| 140 | exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx) |
| 141 | { |
| 142 | gnutls_datum_t k; |
| 143 | int rc; |
| 144 | const uschar * ret = NULL; |
| 145 | |
| 146 | gnutls_pubkey_init(&verify_ctx->key); |
| 147 | k.data = pubkey->data; |
| 148 | k.size = pubkey->len; |
| 149 | |
| 150 | switch(fmt) |
| 151 | { |
| 152 | case KEYFMT_DER: |
| 153 | if ((rc = gnutls_pubkey_import(verify_ctx->key, &k, GNUTLS_X509_FMT_DER))) |
| 154 | ret = gnutls_strerror(rc); |
| 155 | break; |
| 156 | #ifdef SIGN_HAVE_ED25519 |
| 157 | case KEYFMT_ED25519_BARE: |
| 158 | if ((rc = gnutls_pubkey_import_ecc_raw(verify_ctx->key, |
| 159 | GNUTLS_ECC_CURVE_ED25519, &k, NULL))) |
| 160 | ret = gnutls_strerror(rc); |
| 161 | break; |
| 162 | #endif |
| 163 | default: |
| 164 | ret = US"pubkey format not handled"; |
| 165 | break; |
| 166 | } |
| 167 | return ret; |
| 168 | } |
| 169 | |
| 170 | |
| 171 | /* verify signature (of hash if RSA sig, of data if EC sig. No way to do incremental) |
| 172 | (given pubkey & alleged sig) |
| 173 | Return: NULL for success, or an error string */ |
| 174 | |
| 175 | const uschar * |
| 176 | exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data_hash, blob * sig) |
| 177 | { |
| 178 | gnutls_datum_t k = { .data = data_hash->data, .size = data_hash->len }; |
| 179 | gnutls_datum_t s = { .data = sig->data, .size = sig->len }; |
| 180 | int rc; |
| 181 | const uschar * ret = NULL; |
| 182 | |
| 183 | #ifdef SIGN_HAVE_ED25519 |
| 184 | if (verify_ctx->keytype == KEYTYPE_ED25519) |
| 185 | { |
| 186 | if ((rc = gnutls_pubkey_verify_data2(verify_ctx->key, |
| 187 | GNUTLS_SIGN_EDDSA_ED25519, 0, &k, &s)) < 0) |
| 188 | ret = gnutls_strerror(rc); |
| 189 | } |
| 190 | else |
| 191 | #endif |
| 192 | { |
| 193 | gnutls_sign_algorithm_t algo; |
| 194 | switch (hash) |
| 195 | { |
| 196 | case HASH_SHA1: algo = GNUTLS_SIGN_RSA_SHA1; break; |
| 197 | case HASH_SHA2_256: algo = GNUTLS_SIGN_RSA_SHA256; break; |
| 198 | case HASH_SHA2_512: algo = GNUTLS_SIGN_RSA_SHA512; break; |
| 199 | default: return US"nonhandled hash type"; |
| 200 | } |
| 201 | |
| 202 | if ((rc = gnutls_pubkey_verify_hash2(verify_ctx->key, algo, 0, &k, &s)) < 0) |
| 203 | ret = gnutls_strerror(rc); |
| 204 | } |
| 205 | |
| 206 | gnutls_pubkey_deinit(verify_ctx->key); |
| 207 | return ret; |
| 208 | } |
| 209 | |
| 210 | |
| 211 | |
| 212 | |
| 213 | #elif defined(SIGN_GCRYPT) |
| 214 | /******************************************************************************/ |
| 215 | /* This variant is used under pre-3.0.0 GnuTLS. Only rsa-sha1 and rsa-sha256 */ |
| 216 | |
| 217 | |
| 218 | /* Internal service routine: |
| 219 | Read and move past an asn.1 header, checking class & tag, |
| 220 | optionally returning the data-length */ |
| 221 | |
| 222 | static int |
| 223 | as_tag(blob * der, uschar req_cls, long req_tag, long * alen) |
| 224 | { |
| 225 | int rc; |
| 226 | uschar tag_class; |
| 227 | int taglen; |
| 228 | long tag, len; |
| 229 | |
| 230 | debug_printf_indent("as_tag: %02x %02x %02x %02x\n", |
| 231 | der->data[0], der->data[1], der->data[2], der->data[3]); |
| 232 | |
| 233 | if ((rc = asn1_get_tag_der(der->data++, der->len--, &tag_class, &taglen, &tag)) |
| 234 | != ASN1_SUCCESS) |
| 235 | return rc; |
| 236 | |
| 237 | if (tag_class != req_cls || tag != req_tag) return ASN1_ELEMENT_NOT_FOUND; |
| 238 | |
| 239 | if ((len = asn1_get_length_der(der->data, der->len, &taglen)) < 0) |
| 240 | return ASN1_DER_ERROR; |
| 241 | if (alen) *alen = len; |
| 242 | |
| 243 | /* debug_printf_indent("as_tag: tlen %d dlen %d\n", taglen, (int)len); */ |
| 244 | |
| 245 | der->data += taglen; |
| 246 | der->len -= taglen; |
| 247 | return rc; |
| 248 | } |
| 249 | |
| 250 | /* Internal service routine: |
| 251 | Read and move over an asn.1 integer, setting an MPI to the value |
| 252 | */ |
| 253 | |
| 254 | static uschar * |
| 255 | as_mpi(blob * der, gcry_mpi_t * mpi) |
| 256 | { |
| 257 | long alen; |
| 258 | int rc; |
| 259 | gcry_error_t gerr; |
| 260 | |
| 261 | debug_printf_indent("%s\n", __FUNCTION__); |
| 262 | |
| 263 | /* integer; move past the header */ |
| 264 | if ((rc = as_tag(der, 0, ASN1_TAG_INTEGER, &alen)) != ASN1_SUCCESS) |
| 265 | return US asn1_strerror(rc); |
| 266 | |
| 267 | /* read to an MPI */ |
| 268 | if ((gerr = gcry_mpi_scan(mpi, GCRYMPI_FMT_STD, der->data, alen, NULL))) |
| 269 | return US gcry_strerror(gerr); |
| 270 | |
| 271 | /* move over the data */ |
| 272 | der->data += alen; der->len -= alen; |
| 273 | return NULL; |
| 274 | } |
| 275 | |
| 276 | |
| 277 | |
| 278 | void |
| 279 | exim_dkim_init(void) |
| 280 | { |
| 281 | /* Version check should be the very first call because it |
| 282 | makes sure that important subsystems are initialized. */ |
| 283 | if (!gcry_check_version (GCRYPT_VERSION)) |
| 284 | { |
| 285 | fputs ("libgcrypt version mismatch\n", stderr); |
| 286 | exit (2); |
| 287 | } |
| 288 | |
| 289 | /* We don't want to see any warnings, e.g. because we have not yet |
| 290 | parsed program options which might be used to suppress such |
| 291 | warnings. */ |
| 292 | gcry_control (GCRYCTL_SUSPEND_SECMEM_WARN); |
| 293 | |
| 294 | /* ... If required, other initialization goes here. Note that the |
| 295 | process might still be running with increased privileges and that |
| 296 | the secure memory has not been initialized. */ |
| 297 | |
| 298 | /* Allocate a pool of 16k secure memory. This make the secure memory |
| 299 | available and also drops privileges where needed. */ |
| 300 | gcry_control (GCRYCTL_INIT_SECMEM, 16384, 0); |
| 301 | |
| 302 | /* It is now okay to let Libgcrypt complain when there was/is |
| 303 | a problem with the secure memory. */ |
| 304 | gcry_control (GCRYCTL_RESUME_SECMEM_WARN); |
| 305 | |
| 306 | /* ... If required, other initialization goes here. */ |
| 307 | |
| 308 | /* Tell Libgcrypt that initialization has completed. */ |
| 309 | gcry_control (GCRYCTL_INITIALIZATION_FINISHED, 0); |
| 310 | |
| 311 | return; |
| 312 | } |
| 313 | |
| 314 | |
| 315 | |
| 316 | |
| 317 | /* Accumulate data (gnutls-only). |
| 318 | String to be appended must be nul-terminated. */ |
| 319 | |
| 320 | gstring * |
| 321 | exim_dkim_data_append(gstring * g, uschar * s) |
| 322 | { |
| 323 | return g; /*dummy*/ |
| 324 | } |
| 325 | |
| 326 | |
| 327 | |
| 328 | /* import private key from PEM string in memory. |
| 329 | Only handles RSA keys. |
| 330 | Return: NULL for success, or an error string */ |
| 331 | |
| 332 | const uschar * |
| 333 | exim_dkim_signing_init(uschar * privkey_pem, es_ctx * sign_ctx) |
| 334 | { |
| 335 | uschar * s1, * s2; |
| 336 | blob der; |
| 337 | long alen; |
| 338 | int rc; |
| 339 | |
| 340 | /*XXX will need extension to _spot_ as well as handle a |
| 341 | non-RSA key? I think... |
| 342 | So... this is not a PrivateKeyInfo - which would have a field |
| 343 | identifying the keytype - PrivateKeyAlgorithmIdentifier - |
| 344 | but a plain RSAPrivateKey (wrapped in PEM-headers. Can we |
| 345 | use those as a type tag? What forms are there? "BEGIN EC PRIVATE KEY" (cf. ec(1ssl)) |
| 346 | |
| 347 | How does OpenSSL PEM_read_bio_PrivateKey() deal with it? |
| 348 | gnutls_x509_privkey_import() ? |
| 349 | */ |
| 350 | |
| 351 | /* |
| 352 | * RSAPrivateKey ::= SEQUENCE |
| 353 | * version Version, |
| 354 | * modulus INTEGER, -- n |
| 355 | * publicExponent INTEGER, -- e |
| 356 | * privateExponent INTEGER, -- d |
| 357 | * prime1 INTEGER, -- p |
| 358 | * prime2 INTEGER, -- q |
| 359 | * exponent1 INTEGER, -- d mod (p-1) |
| 360 | * exponent2 INTEGER, -- d mod (q-1) |
| 361 | * coefficient INTEGER, -- (inverse of q) mod p |
| 362 | * otherPrimeInfos OtherPrimeInfos OPTIONAL |
| 363 | |
| 364 | * ECPrivateKey ::= SEQUENCE { |
| 365 | * version INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1), |
| 366 | * privateKey OCTET STRING, |
| 367 | * parameters [0] ECParameters {{ NamedCurve }} OPTIONAL, |
| 368 | * publicKey [1] BIT STRING OPTIONAL |
| 369 | * } |
| 370 | * Hmm, only 1 useful item, and not even an integer? Wonder how we might use it... |
| 371 | |
| 372 | - actually, gnutls_x509_privkey_import() appears to require a curve name parameter |
| 373 | value for that is an OID? a local-only integer (it's an enum in GnuTLS)? |
| 374 | |
| 375 | |
| 376 | Useful cmds: |
| 377 | ssh-keygen -t ecdsa -f foo.privkey |
| 378 | ssh-keygen -t ecdsa -b384 -f foo.privkey |
| 379 | ssh-keygen -t ecdsa -b521 -f foo.privkey |
| 380 | ssh-keygen -t ed25519 -f foo.privkey |
| 381 | |
| 382 | < foo openssl pkcs8 -in /dev/stdin -inform PEM -nocrypt -topk8 -outform DER | od -x |
| 383 | |
| 384 | openssl asn1parse -in foo -inform PEM -dump |
| 385 | openssl asn1parse -in foo -inform PEM -dump -stroffset 24 (??) |
| 386 | (not good for ed25519) |
| 387 | |
| 388 | */ |
| 389 | |
| 390 | if ( !(s1 = Ustrstr(CS privkey_pem, "-----BEGIN RSA PRIVATE KEY-----")) |
| 391 | || !(s2 = Ustrstr(CS (s1+=31), "-----END RSA PRIVATE KEY-----" )) |
| 392 | ) |
| 393 | return US"Bad PEM wrapper"; |
| 394 | |
| 395 | *s2 = '\0'; |
| 396 | |
| 397 | if ((der.len = b64decode(s1, &der.data)) < 0) |
| 398 | return US"Bad PEM-DER b64 decode"; |
| 399 | |
| 400 | /* untangle asn.1 */ |
| 401 | |
| 402 | /* sequence; just move past the header */ |
| 403 | if ((rc = as_tag(&der, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL)) |
| 404 | != ASN1_SUCCESS) goto asn_err; |
| 405 | |
| 406 | /* integer version; move past the header, check is zero */ |
| 407 | if ((rc = as_tag(&der, 0, ASN1_TAG_INTEGER, &alen)) != ASN1_SUCCESS) |
| 408 | goto asn_err; |
| 409 | if (alen != 1 || *der.data != 0) |
| 410 | return US"Bad version number"; |
| 411 | der.data++; der.len--; |
| 412 | |
| 413 | if ( (s1 = as_mpi(&der, &sign_ctx->n)) |
| 414 | || (s1 = as_mpi(&der, &sign_ctx->e)) |
| 415 | || (s1 = as_mpi(&der, &sign_ctx->d)) |
| 416 | || (s1 = as_mpi(&der, &sign_ctx->p)) |
| 417 | || (s1 = as_mpi(&der, &sign_ctx->q)) |
| 418 | || (s1 = as_mpi(&der, &sign_ctx->dp)) |
| 419 | || (s1 = as_mpi(&der, &sign_ctx->dq)) |
| 420 | || (s1 = as_mpi(&der, &sign_ctx->qp)) |
| 421 | ) |
| 422 | return s1; |
| 423 | |
| 424 | #ifdef extreme_debug |
| 425 | DEBUG(D_acl) debug_printf_indent("rsa_signing_init:\n"); |
| 426 | { |
| 427 | uschar * s; |
| 428 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->n); |
| 429 | debug_printf_indent(" N : %s\n", s); |
| 430 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->e); |
| 431 | debug_printf_indent(" E : %s\n", s); |
| 432 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->d); |
| 433 | debug_printf_indent(" D : %s\n", s); |
| 434 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->p); |
| 435 | debug_printf_indent(" P : %s\n", s); |
| 436 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->q); |
| 437 | debug_printf_indent(" Q : %s\n", s); |
| 438 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->dp); |
| 439 | debug_printf_indent(" DP: %s\n", s); |
| 440 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->dq); |
| 441 | debug_printf_indent(" DQ: %s\n", s); |
| 442 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->qp); |
| 443 | debug_printf_indent(" QP: %s\n", s); |
| 444 | } |
| 445 | #endif |
| 446 | |
| 447 | sign_ctx->keytype = KEYTYPE_RSA; |
| 448 | return NULL; |
| 449 | |
| 450 | asn_err: return US asn1_strerror(rc); |
| 451 | } |
| 452 | |
| 453 | |
| 454 | |
| 455 | /* allocate mem for signature (when signing) */ |
| 456 | /* sign already-hashed data. |
| 457 | |
| 458 | Return: NULL for success, or an error string */ |
| 459 | |
| 460 | const uschar * |
| 461 | exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig) |
| 462 | { |
| 463 | char * sexp_hash; |
| 464 | gcry_sexp_t s_hash = NULL, s_key = NULL, s_sig = NULL; |
| 465 | gcry_mpi_t m_sig; |
| 466 | uschar * errstr; |
| 467 | gcry_error_t gerr; |
| 468 | |
| 469 | /*XXX will need extension for hash types (though, possibly, should |
| 470 | be re-specced to not rehash but take an already-hashed value? Actually |
| 471 | current impl looks WRONG - it _is_ given a hash so should not be |
| 472 | re-hashing. Has this been tested? |
| 473 | |
| 474 | Will need extension for non-RSA sugning algos. */ |
| 475 | |
| 476 | switch (hash) |
| 477 | { |
| 478 | case HASH_SHA1: sexp_hash = "(data(flags pkcs1)(hash sha1 %b))"; break; |
| 479 | case HASH_SHA2_256: sexp_hash = "(data(flags pkcs1)(hash sha256 %b))"; break; |
| 480 | default: return US"nonhandled hash type"; |
| 481 | } |
| 482 | |
| 483 | #define SIGSPACE 128 |
| 484 | sig->data = store_get(SIGSPACE); |
| 485 | |
| 486 | if (gcry_mpi_cmp (sign_ctx->p, sign_ctx->q) > 0) |
| 487 | { |
| 488 | gcry_mpi_swap (sign_ctx->p, sign_ctx->q); |
| 489 | gcry_mpi_invm (sign_ctx->qp, sign_ctx->p, sign_ctx->q); |
| 490 | } |
| 491 | |
| 492 | if ( (gerr = gcry_sexp_build (&s_key, NULL, |
| 493 | "(private-key (rsa (n%m)(e%m)(d%m)(p%m)(q%m)(u%m)))", |
| 494 | sign_ctx->n, sign_ctx->e, |
| 495 | sign_ctx->d, sign_ctx->p, |
| 496 | sign_ctx->q, sign_ctx->qp)) |
| 497 | || (gerr = gcry_sexp_build (&s_hash, NULL, sexp_hash, |
| 498 | (int) data->len, CS data->data)) |
| 499 | || (gerr = gcry_pk_sign (&s_sig, s_hash, s_key)) |
| 500 | ) |
| 501 | return US gcry_strerror(gerr); |
| 502 | |
| 503 | /* gcry_sexp_dump(s_sig); */ |
| 504 | |
| 505 | if ( !(s_sig = gcry_sexp_find_token(s_sig, "s", 0)) |
| 506 | ) |
| 507 | return US"no sig result"; |
| 508 | |
| 509 | m_sig = gcry_sexp_nth_mpi(s_sig, 1, GCRYMPI_FMT_USG); |
| 510 | |
| 511 | #ifdef extreme_debug |
| 512 | DEBUG(D_acl) |
| 513 | { |
| 514 | uschar * s; |
| 515 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, m_sig); |
| 516 | debug_printf_indent(" SG: %s\n", s); |
| 517 | } |
| 518 | #endif |
| 519 | |
| 520 | gerr = gcry_mpi_print(GCRYMPI_FMT_USG, sig->data, SIGSPACE, &sig->len, m_sig); |
| 521 | if (gerr) |
| 522 | { |
| 523 | debug_printf_indent("signature conversion from MPI to buffer failed\n"); |
| 524 | return US gcry_strerror(gerr); |
| 525 | } |
| 526 | #undef SIGSPACE |
| 527 | |
| 528 | return NULL; |
| 529 | } |
| 530 | |
| 531 | |
| 532 | /* import public key (from blob in memory) |
| 533 | Return: NULL for success, or an error string */ |
| 534 | |
| 535 | const uschar * |
| 536 | exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx) |
| 537 | { |
| 538 | /* |
| 539 | in code sequence per b81207d2bfa92 rsa_parse_public_key() and asn1_get_mpi() |
| 540 | */ |
| 541 | uschar tag_class; |
| 542 | int taglen; |
| 543 | long alen; |
| 544 | int rc; |
| 545 | uschar * errstr; |
| 546 | gcry_error_t gerr; |
| 547 | uschar * stage = US"S1"; |
| 548 | |
| 549 | if (fmt != KEYFMT_DER) return US"pubkey format not handled"; |
| 550 | |
| 551 | /* |
| 552 | sequence |
| 553 | sequence |
| 554 | OBJECT:rsaEncryption |
| 555 | NULL |
| 556 | BIT STRING:RSAPublicKey |
| 557 | sequence |
| 558 | INTEGER:Public modulus |
| 559 | INTEGER:Public exponent |
| 560 | |
| 561 | openssl rsa -in aux-fixed/dkim/dkim.private -pubout -outform DER | od -t x1 | head; |
| 562 | openssl rsa -in aux-fixed/dkim/dkim.private -pubout | openssl asn1parse -dump; |
| 563 | openssl rsa -in aux-fixed/dkim/dkim.private -pubout | openssl asn1parse -dump -offset 22; |
| 564 | */ |
| 565 | |
| 566 | /* sequence; just move past the header */ |
| 567 | if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL)) |
| 568 | != ASN1_SUCCESS) goto asn_err; |
| 569 | |
| 570 | /* sequence; skip the entire thing */ |
| 571 | DEBUG(D_acl) stage = US"S2"; |
| 572 | if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, &alen)) |
| 573 | != ASN1_SUCCESS) goto asn_err; |
| 574 | pubkey->data += alen; pubkey->len -= alen; |
| 575 | |
| 576 | |
| 577 | /* bitstring: limit range to size of bitstring; |
| 578 | move over header + content wrapper */ |
| 579 | DEBUG(D_acl) stage = US"BS"; |
| 580 | if ((rc = as_tag(pubkey, 0, ASN1_TAG_BIT_STRING, &alen)) != ASN1_SUCCESS) |
| 581 | goto asn_err; |
| 582 | pubkey->len = alen; |
| 583 | pubkey->data++; pubkey->len--; |
| 584 | |
| 585 | /* sequence; just move past the header */ |
| 586 | DEBUG(D_acl) stage = US"S3"; |
| 587 | if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL)) |
| 588 | != ASN1_SUCCESS) goto asn_err; |
| 589 | |
| 590 | /* read two integers */ |
| 591 | DEBUG(D_acl) stage = US"MPI"; |
| 592 | if ( (errstr = as_mpi(pubkey, &verify_ctx->n)) |
| 593 | || (errstr = as_mpi(pubkey, &verify_ctx->e)) |
| 594 | ) |
| 595 | return errstr; |
| 596 | |
| 597 | #ifdef extreme_debug |
| 598 | DEBUG(D_acl) debug_printf_indent("rsa_verify_init:\n"); |
| 599 | { |
| 600 | uschar * s; |
| 601 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, verify_ctx->n); |
| 602 | debug_printf_indent(" N : %s\n", s); |
| 603 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, verify_ctx->e); |
| 604 | debug_printf_indent(" E : %s\n", s); |
| 605 | } |
| 606 | |
| 607 | #endif |
| 608 | return NULL; |
| 609 | |
| 610 | asn_err: |
| 611 | DEBUG(D_acl) return string_sprintf("%s: %s", stage, asn1_strerror(rc)); |
| 612 | return US asn1_strerror(rc); |
| 613 | } |
| 614 | |
| 615 | |
| 616 | /* verify signature (of hash) |
| 617 | XXX though we appear to be doing a hash, too! |
| 618 | (given pubkey & alleged sig) |
| 619 | Return: NULL for success, or an error string */ |
| 620 | |
| 621 | const uschar * |
| 622 | exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data_hash, blob * sig) |
| 623 | { |
| 624 | /* |
| 625 | cf. libgnutls 2.8.5 _wrap_gcry_pk_verify() |
| 626 | */ |
| 627 | char * sexp_hash; |
| 628 | gcry_mpi_t m_sig; |
| 629 | gcry_sexp_t s_sig = NULL, s_hash = NULL, s_pkey = NULL; |
| 630 | gcry_error_t gerr; |
| 631 | uschar * stage; |
| 632 | |
| 633 | /*XXX needs extension for SHA512 */ |
| 634 | switch (hash) |
| 635 | { |
| 636 | case HASH_SHA1: sexp_hash = "(data(flags pkcs1)(hash sha1 %b))"; break; |
| 637 | case HASH_SHA2_256: sexp_hash = "(data(flags pkcs1)(hash sha256 %b))"; break; |
| 638 | default: return US"nonhandled hash type"; |
| 639 | } |
| 640 | |
| 641 | if ( (stage = US"pkey sexp build", |
| 642 | gerr = gcry_sexp_build (&s_pkey, NULL, "(public-key(rsa(n%m)(e%m)))", |
| 643 | verify_ctx->n, verify_ctx->e)) |
| 644 | || (stage = US"data sexp build", |
| 645 | gerr = gcry_sexp_build (&s_hash, NULL, sexp_hash, |
| 646 | (int) data_hash->len, CS data_hash->data)) |
| 647 | || (stage = US"sig mpi scan", |
| 648 | gerr = gcry_mpi_scan(&m_sig, GCRYMPI_FMT_USG, sig->data, sig->len, NULL)) |
| 649 | || (stage = US"sig sexp build", |
| 650 | gerr = gcry_sexp_build (&s_sig, NULL, "(sig-val(rsa(s%m)))", m_sig)) |
| 651 | || (stage = US"verify", |
| 652 | gerr = gcry_pk_verify (s_sig, s_hash, s_pkey)) |
| 653 | ) |
| 654 | { |
| 655 | DEBUG(D_acl) debug_printf_indent("verify: error in stage '%s'\n", stage); |
| 656 | return US gcry_strerror(gerr); |
| 657 | } |
| 658 | |
| 659 | if (s_sig) gcry_sexp_release (s_sig); |
| 660 | if (s_hash) gcry_sexp_release (s_hash); |
| 661 | if (s_pkey) gcry_sexp_release (s_pkey); |
| 662 | gcry_mpi_release (m_sig); |
| 663 | gcry_mpi_release (verify_ctx->n); |
| 664 | gcry_mpi_release (verify_ctx->e); |
| 665 | |
| 666 | return NULL; |
| 667 | } |
| 668 | |
| 669 | |
| 670 | |
| 671 | |
| 672 | #elif defined(SIGN_OPENSSL) |
| 673 | /******************************************************************************/ |
| 674 | |
| 675 | void |
| 676 | exim_dkim_init(void) |
| 677 | { |
| 678 | ERR_load_crypto_strings(); |
| 679 | } |
| 680 | |
| 681 | |
| 682 | /* accumulate data (was gnutls-onl but now needed for OpenSSL non-EC too |
| 683 | because now using hash-and-sign interface) */ |
| 684 | gstring * |
| 685 | exim_dkim_data_append(gstring * g, uschar * s) |
| 686 | { |
| 687 | return string_cat(g, s); |
| 688 | } |
| 689 | |
| 690 | |
| 691 | /* import private key from PEM string in memory. |
| 692 | Return: NULL for success, or an error string */ |
| 693 | |
| 694 | const uschar * |
| 695 | exim_dkim_signing_init(uschar * privkey_pem, es_ctx * sign_ctx) |
| 696 | { |
| 697 | BIO * bp = BIO_new_mem_buf(privkey_pem, -1); |
| 698 | |
| 699 | if (!(sign_ctx->key = PEM_read_bio_PrivateKey(bp, NULL, NULL, NULL))) |
| 700 | return US ERR_error_string(ERR_get_error(), NULL); |
| 701 | |
| 702 | sign_ctx->keytype = |
| 703 | #ifdef SIGN_HAVE_ED25519 |
| 704 | EVP_PKEY_type(EVP_PKEY_id(sign_ctx->key)) == EVP_PKEY_EC |
| 705 | ? KEYTYPE_ED25519 : KEYTYPE_RSA; |
| 706 | #else |
| 707 | KEYTYPE_RSA; |
| 708 | #endif |
| 709 | return NULL; |
| 710 | } |
| 711 | |
| 712 | |
| 713 | |
| 714 | /* allocate mem for signature (when signing) */ |
| 715 | /* hash & sign data. Could be incremental |
| 716 | |
| 717 | Return: NULL for success with the signaature in the sig blob, or an error string */ |
| 718 | |
| 719 | const uschar * |
| 720 | exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig) |
| 721 | { |
| 722 | const EVP_MD * md; |
| 723 | EVP_MD_CTX * ctx; |
| 724 | size_t siglen; |
| 725 | |
| 726 | switch (hash) |
| 727 | { |
| 728 | case HASH_SHA1: md = EVP_sha1(); break; |
| 729 | case HASH_SHA2_256: md = EVP_sha256(); break; |
| 730 | case HASH_SHA2_512: md = EVP_sha512(); break; |
| 731 | default: return US"nonhandled hash type"; |
| 732 | } |
| 733 | |
| 734 | /* Create the Message Digest Context */ |
| 735 | /*XXX renamed to EVP_MD_CTX_new() in 1.1.0 */ |
| 736 | if( (ctx = EVP_MD_CTX_create()) |
| 737 | |
| 738 | /* Initialise the DigestSign operation */ |
| 739 | && EVP_DigestSignInit(ctx, NULL, md, NULL, sign_ctx->key) > 0 |
| 740 | |
| 741 | /* Call update with the message */ |
| 742 | && EVP_DigestSignUpdate(ctx, data->data, data->len) > 0 |
| 743 | |
| 744 | /* Finalise the DigestSign operation */ |
| 745 | /* First call EVP_DigestSignFinal with a NULL sig parameter to obtain the length of the |
| 746 | * signature. Length is returned in slen */ |
| 747 | && EVP_DigestSignFinal(ctx, NULL, &siglen) > 0 |
| 748 | |
| 749 | /* Allocate memory for the signature based on size in slen */ |
| 750 | && (sig->data = store_get(siglen)) |
| 751 | |
| 752 | /* Obtain the signature (slen could change here!) */ |
| 753 | && EVP_DigestSignFinal(ctx, sig->data, &siglen) > 0 |
| 754 | ) |
| 755 | { |
| 756 | EVP_MD_CTX_destroy(ctx); |
| 757 | sig->len = siglen; |
| 758 | return NULL; |
| 759 | } |
| 760 | |
| 761 | if (ctx) EVP_MD_CTX_destroy(ctx); |
| 762 | return US ERR_error_string(ERR_get_error(), NULL); |
| 763 | } |
| 764 | |
| 765 | |
| 766 | |
| 767 | /* import public key (from blob in memory) |
| 768 | Return: NULL for success, or an error string */ |
| 769 | |
| 770 | const uschar * |
| 771 | exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx) |
| 772 | { |
| 773 | const uschar * s = pubkey->data; |
| 774 | uschar * ret = NULL; |
| 775 | |
| 776 | if (fmt != KEYFMT_DER) return US"pubkey format not handled"; |
| 777 | switch(fmt) |
| 778 | { |
| 779 | case KEYFMT_DER: |
| 780 | /*XXX ok, this fails for EC: |
| 781 | error:0609E09C:digital envelope routines:pkey_set_type:unsupported algorithm |
| 782 | */ |
| 783 | |
| 784 | /*XXX hmm, we never free this */ |
| 785 | if (!(verify_ctx->key = d2i_PUBKEY(NULL, &s, pubkey->len))) |
| 786 | ret = US ERR_error_string(ERR_get_error(), NULL); |
| 787 | break; |
| 788 | #ifdef SIGN_HAVE_ED25519 |
| 789 | case KEYFMT_ED25519_BARE: |
| 790 | { |
| 791 | BIGNUM * x; |
| 792 | EC_KEY * eck; |
| 793 | if ( !(x = BN_bin2bn(s, pubkey->len, NULL)) |
| 794 | || !(eck = EC_KEY_new_by_curve_name(NID_ED25519)) |
| 795 | || !EC_KEY_set_public_key_affine_coordinates(eck, x, NULL) |
| 796 | || !(verify_ctx->key = EVP_PKEY_new()) |
| 797 | || !EVP_PKEY_assign_EC_KEY(verify_ctx->key, eck) |
| 798 | ) |
| 799 | ret = US ERR_error_string(ERR_get_error(), NULL); |
| 800 | } |
| 801 | break; |
| 802 | #endif |
| 803 | default: |
| 804 | ret = US"pubkey format not handled"; |
| 805 | break; |
| 806 | } |
| 807 | |
| 808 | return ret; |
| 809 | } |
| 810 | |
| 811 | |
| 812 | |
| 813 | |
| 814 | /* verify signature (of hash) |
| 815 | (pre-EC coding; of data if "notyet" code, The latter could be incremental) |
| 816 | (given pubkey & alleged sig) |
| 817 | Return: NULL for success, or an error string */ |
| 818 | |
| 819 | const uschar * |
| 820 | exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data, blob * sig) |
| 821 | { |
| 822 | const EVP_MD * md; |
| 823 | |
| 824 | /*XXX OpenSSL does not seem to have Ed25519 support yet. Reportedly BoringSSL does, |
| 825 | but that's a nonstable API and not recommended (by its owner, Google) for external use. */ |
| 826 | |
| 827 | switch (hash) |
| 828 | { |
| 829 | case HASH_SHA1: md = EVP_sha1(); break; |
| 830 | case HASH_SHA2_256: md = EVP_sha256(); break; |
| 831 | case HASH_SHA2_512: md = EVP_sha512(); break; |
| 832 | default: return US"nonhandled hash type"; |
| 833 | } |
| 834 | |
| 835 | #ifdef notyet_SIGN_HAVE_ED25519 |
| 836 | { |
| 837 | EVP_MD_CTX * ctx; |
| 838 | |
| 839 | /*XXX renamed to EVP_MD_CTX_new() in 1.1.0 */ |
| 840 | if ( |
| 841 | (ctx = EVP_MD_CTX_create()) |
| 842 | |
| 843 | /* Initialize `key` with a public key */ |
| 844 | && EVP_DigestVerifyInit(ctx, NULL, md, NULL, verify_ctx->key) > 0 |
| 845 | |
| 846 | /* add data to be hashed (call multiple times if needed) */ |
| 847 | |
| 848 | && EVP_DigestVerifyUpdate(ctx, data->data, data->len) > 0 |
| 849 | |
| 850 | /* finish off the hash and check the offered signature */ |
| 851 | |
| 852 | && EVP_DigestVerifyFinal(ctx, sig->data, sig->len) > 0 |
| 853 | ) |
| 854 | { |
| 855 | EVP_MD_CTX_destroy(ctx); /* renamed to _free in 1.1.0 */ |
| 856 | return NULL; |
| 857 | } |
| 858 | |
| 859 | if (ctx) EVP_MD_CTX_free(ctx); |
| 860 | return US ERR_error_string(ERR_get_error(), NULL); |
| 861 | } |
| 862 | #else |
| 863 | { |
| 864 | EVP_PKEY_CTX * ctx; |
| 865 | |
| 866 | if ( (ctx = EVP_PKEY_CTX_new(verify_ctx->key, NULL)) |
| 867 | && EVP_PKEY_verify_init(ctx) > 0 |
| 868 | && EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) > 0 |
| 869 | && EVP_PKEY_CTX_set_signature_md(ctx, md) > 0 |
| 870 | && EVP_PKEY_verify(ctx, sig->data, sig->len, |
| 871 | data->data, data->len) == 1 |
| 872 | ) |
| 873 | { EVP_PKEY_CTX_free(ctx); return NULL; } |
| 874 | |
| 875 | if (ctx) EVP_PKEY_CTX_free(ctx); |
| 876 | return US ERR_error_string(ERR_get_error(), NULL); |
| 877 | } |
| 878 | #endif |
| 879 | } |
| 880 | |
| 881 | |
| 882 | |
| 883 | #endif |
| 884 | /******************************************************************************/ |
| 885 | |
| 886 | #endif /*DISABLE_DKIM*/ |
| 887 | /* End of File */ |