Commit | Line | Data |
---|---|---|
2ea97746 CE |
1 | /* |
2 | * PDKIM - a RFC4871 (DKIM) implementation | |
3 | * | |
4 | * Copyright (C) 1995 - 2018 Exim maintainers | |
5 | * | |
6 | * signing/verification interface | |
7 | */ | |
8 | ||
9 | #include "../exim.h" | |
10 | #include "crypt_ver.h" | |
11 | #include "signing.h" | |
12 | ||
13 | ||
14 | #ifdef MACRO_PREDEF | |
15 | # include "../macro_predef.h" | |
16 | ||
17 | void | |
18 | features_crypto(void) | |
19 | { | |
20 | # ifdef SIGN_HAVE_ED25519 | |
21 | builtin_macro_create(US"_CRYPTO_SIGN_ED25519"); | |
22 | # endif | |
23 | # ifdef EXIM_HAVE_SHA3 | |
24 | builtin_macro_create(US"_CRYPTO_HASH_SHA3"); | |
25 | # endif | |
26 | } | |
27 | #else | |
28 | ||
29 | #ifndef DISABLE_DKIM /* rest of file */ | |
30 | ||
31 | #ifndef SUPPORT_TLS | |
32 | # error Need SUPPORT_TLS for DKIM | |
33 | #endif | |
34 | ||
35 | ||
36 | /******************************************************************************/ | |
37 | #ifdef SIGN_GNUTLS | |
38 | # define EXIM_GNUTLS_LIBRARY_LOG_LEVEL 3 | |
39 | ||
40 | ||
41 | /* Logging function which can be registered with | |
42 | * gnutls_global_set_log_function() | |
43 | * gnutls_global_set_log_level() 0..9 | |
44 | */ | |
45 | #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 | |
46 | static void | |
47 | exim_gnutls_logger_cb(int level, const char *message) | |
48 | { | |
49 | size_t len = strlen(message); | |
50 | if (len < 1) | |
51 | { | |
52 | DEBUG(D_tls) debug_printf("GnuTLS<%d> empty debug message\n", level); | |
53 | return; | |
54 | } | |
55 | DEBUG(D_tls) debug_printf("GnuTLS<%d>: %s%s", level, message, | |
56 | message[len-1] == '\n' ? "" : "\n"); | |
57 | } | |
58 | #endif | |
59 | ||
60 | ||
61 | ||
62 | void | |
63 | exim_dkim_init(void) | |
64 | { | |
65 | #if EXIM_GNUTLS_LIBRARY_LOG_LEVEL >= 0 | |
66 | DEBUG(D_tls) | |
67 | { | |
68 | gnutls_global_set_log_function(exim_gnutls_logger_cb); | |
69 | /* arbitrarily chosen level; bump upto 9 for more */ | |
70 | gnutls_global_set_log_level(EXIM_GNUTLS_LIBRARY_LOG_LEVEL); | |
71 | } | |
72 | #endif | |
73 | } | |
74 | ||
75 | ||
76 | /* accumulate data (gnutls-only). String to be appended must be nul-terminated. */ | |
77 | gstring * | |
78 | exim_dkim_data_append(gstring * g, uschar * s) | |
79 | { | |
80 | return string_cat(g, s); | |
81 | } | |
82 | ||
83 | ||
84 | ||
85 | /* import private key from PEM string in memory. | |
86 | Return: NULL for success, or an error string */ | |
87 | ||
88 | const uschar * | |
89 | exim_dkim_signing_init(const uschar * privkey_pem, es_ctx * sign_ctx) | |
90 | { | |
91 | gnutls_datum_t k = { .data = (void *)privkey_pem, .size = Ustrlen(privkey_pem) }; | |
92 | gnutls_x509_privkey_t x509_key; | |
93 | const uschar * where; | |
94 | int rc; | |
95 | ||
96 | if ( (where = US"internal init", rc = gnutls_x509_privkey_init(&x509_key)) | |
97 | || (rc = gnutls_privkey_init(&sign_ctx->key)) | |
98 | || (where = US"privkey PEM-block import", | |
99 | rc = gnutls_x509_privkey_import(x509_key, &k, GNUTLS_X509_FMT_PEM)) | |
100 | || (where = US"internal privkey transfer", | |
101 | rc = gnutls_privkey_import_x509(sign_ctx->key, x509_key, 0)) | |
102 | ) | |
103 | return string_sprintf("%s: %s", where, gnutls_strerror(rc)); | |
104 | ||
105 | switch (rc = gnutls_privkey_get_pk_algorithm(sign_ctx->key, NULL)) | |
106 | { | |
107 | case GNUTLS_PK_RSA: sign_ctx->keytype = KEYTYPE_RSA; break; | |
108 | #ifdef SIGN_HAVE_ED25519 | |
109 | case GNUTLS_PK_EDDSA_ED25519: sign_ctx->keytype = KEYTYPE_ED25519; break; | |
110 | #endif | |
111 | default: return rc < 0 | |
112 | ? CUS gnutls_strerror(rc) | |
113 | : string_sprintf("Unhandled key type: %d '%s'", rc, gnutls_pk_get_name(rc)); | |
114 | } | |
115 | ||
116 | return NULL; | |
117 | } | |
118 | ||
119 | ||
120 | ||
121 | /* allocate mem for signature (when signing) */ | |
122 | /* hash & sign data. No way to do incremental. | |
123 | ||
124 | Return: NULL for success, or an error string */ | |
125 | ||
126 | const uschar * | |
127 | exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig) | |
128 | { | |
129 | gnutls_datum_t k_data = { .data = data->data, .size = data->len }; | |
130 | gnutls_digest_algorithm_t dig; | |
131 | gnutls_datum_t k_sig; | |
132 | int rc; | |
133 | ||
134 | switch (hash) | |
135 | { | |
136 | case HASH_SHA1: dig = GNUTLS_DIG_SHA1; break; | |
137 | case HASH_SHA2_256: dig = GNUTLS_DIG_SHA256; break; | |
138 | case HASH_SHA2_512: dig = GNUTLS_DIG_SHA512; break; | |
139 | default: return US"nonhandled hash type"; | |
140 | } | |
141 | ||
142 | if ((rc = gnutls_privkey_sign_data(sign_ctx->key, dig, 0, &k_data, &k_sig))) | |
143 | return CUS gnutls_strerror(rc); | |
144 | ||
145 | /* Don't care about deinit for the key; shortlived process */ | |
146 | ||
147 | sig->data = k_sig.data; | |
148 | sig->len = k_sig.size; | |
149 | return NULL; | |
150 | } | |
151 | ||
152 | ||
153 | ||
154 | /* import public key (from blob in memory) | |
155 | Return: NULL for success, or an error string */ | |
156 | ||
157 | const uschar * | |
158 | exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx) | |
159 | { | |
160 | gnutls_datum_t k; | |
161 | int rc; | |
162 | const uschar * ret = NULL; | |
163 | ||
164 | gnutls_pubkey_init(&verify_ctx->key); | |
165 | k.data = pubkey->data; | |
166 | k.size = pubkey->len; | |
167 | ||
168 | switch(fmt) | |
169 | { | |
170 | case KEYFMT_DER: | |
171 | if ((rc = gnutls_pubkey_import(verify_ctx->key, &k, GNUTLS_X509_FMT_DER))) | |
172 | ret = US gnutls_strerror(rc); | |
173 | break; | |
174 | #ifdef SIGN_HAVE_ED25519 | |
175 | case KEYFMT_ED25519_BARE: | |
176 | if ((rc = gnutls_pubkey_import_ecc_raw(verify_ctx->key, | |
177 | GNUTLS_ECC_CURVE_ED25519, &k, NULL))) | |
178 | ret = US gnutls_strerror(rc); | |
179 | break; | |
180 | #endif | |
181 | default: | |
182 | ret = US"pubkey format not handled"; | |
183 | break; | |
184 | } | |
185 | return ret; | |
186 | } | |
187 | ||
188 | ||
189 | /* verify signature (of hash if RSA sig, of data if EC sig. No way to do incremental) | |
190 | (given pubkey & alleged sig) | |
191 | Return: NULL for success, or an error string */ | |
192 | ||
193 | const uschar * | |
194 | exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data_hash, blob * sig) | |
195 | { | |
196 | gnutls_datum_t k = { .data = data_hash->data, .size = data_hash->len }; | |
197 | gnutls_datum_t s = { .data = sig->data, .size = sig->len }; | |
198 | int rc; | |
199 | const uschar * ret = NULL; | |
200 | ||
201 | #ifdef SIGN_HAVE_ED25519 | |
202 | if (verify_ctx->keytype == KEYTYPE_ED25519) | |
203 | { | |
204 | if ((rc = gnutls_pubkey_verify_data2(verify_ctx->key, | |
205 | GNUTLS_SIGN_EDDSA_ED25519, 0, &k, &s)) < 0) | |
206 | ret = US gnutls_strerror(rc); | |
207 | } | |
208 | else | |
209 | #endif | |
210 | { | |
211 | gnutls_sign_algorithm_t algo; | |
212 | switch (hash) | |
213 | { | |
214 | case HASH_SHA1: algo = GNUTLS_SIGN_RSA_SHA1; break; | |
215 | case HASH_SHA2_256: algo = GNUTLS_SIGN_RSA_SHA256; break; | |
216 | case HASH_SHA2_512: algo = GNUTLS_SIGN_RSA_SHA512; break; | |
217 | default: return US"nonhandled hash type"; | |
218 | } | |
219 | ||
220 | if ((rc = gnutls_pubkey_verify_hash2(verify_ctx->key, algo, 0, &k, &s)) < 0) | |
221 | ret = US gnutls_strerror(rc); | |
222 | } | |
223 | ||
224 | gnutls_pubkey_deinit(verify_ctx->key); | |
225 | return ret; | |
226 | } | |
227 | ||
228 | ||
229 | ||
230 | ||
231 | #elif defined(SIGN_GCRYPT) | |
232 | /******************************************************************************/ | |
233 | /* This variant is used under pre-3.0.0 GnuTLS. Only rsa-sha1 and rsa-sha256 */ | |
234 | ||
235 | ||
236 | /* Internal service routine: | |
237 | Read and move past an asn.1 header, checking class & tag, | |
238 | optionally returning the data-length */ | |
239 | ||
240 | static int | |
241 | as_tag(blob * der, uschar req_cls, long req_tag, long * alen) | |
242 | { | |
243 | int rc; | |
244 | uschar tag_class; | |
245 | int taglen; | |
246 | long tag, len; | |
247 | ||
248 | debug_printf_indent("as_tag: %02x %02x %02x %02x\n", | |
249 | der->data[0], der->data[1], der->data[2], der->data[3]); | |
250 | ||
251 | if ((rc = asn1_get_tag_der(der->data++, der->len--, &tag_class, &taglen, &tag)) | |
252 | != ASN1_SUCCESS) | |
253 | return rc; | |
254 | ||
255 | if (tag_class != req_cls || tag != req_tag) return ASN1_ELEMENT_NOT_FOUND; | |
256 | ||
257 | if ((len = asn1_get_length_der(der->data, der->len, &taglen)) < 0) | |
258 | return ASN1_DER_ERROR; | |
259 | if (alen) *alen = len; | |
260 | ||
261 | /* debug_printf_indent("as_tag: tlen %d dlen %d\n", taglen, (int)len); */ | |
262 | ||
263 | der->data += taglen; | |
264 | der->len -= taglen; | |
265 | return rc; | |
266 | } | |
267 | ||
268 | /* Internal service routine: | |
269 | Read and move over an asn.1 integer, setting an MPI to the value | |
270 | */ | |
271 | ||
272 | static uschar * | |
273 | as_mpi(blob * der, gcry_mpi_t * mpi) | |
274 | { | |
275 | long alen; | |
276 | int rc; | |
277 | gcry_error_t gerr; | |
278 | ||
279 | debug_printf_indent("%s\n", __FUNCTION__); | |
280 | ||
281 | /* integer; move past the header */ | |
282 | if ((rc = as_tag(der, 0, ASN1_TAG_INTEGER, &alen)) != ASN1_SUCCESS) | |
283 | return US asn1_strerror(rc); | |
284 | ||
285 | /* read to an MPI */ | |
286 | if ((gerr = gcry_mpi_scan(mpi, GCRYMPI_FMT_STD, der->data, alen, NULL))) | |
287 | return US gcry_strerror(gerr); | |
288 | ||
289 | /* move over the data */ | |
290 | der->data += alen; der->len -= alen; | |
291 | return NULL; | |
292 | } | |
293 | ||
294 | ||
295 | ||
296 | void | |
297 | exim_dkim_init(void) | |
298 | { | |
299 | /* Version check should be the very first call because it | |
300 | makes sure that important subsystems are initialized. */ | |
301 | if (!gcry_check_version (GCRYPT_VERSION)) | |
302 | { | |
303 | fputs ("libgcrypt version mismatch\n", stderr); | |
304 | exit (2); | |
305 | } | |
306 | ||
307 | /* We don't want to see any warnings, e.g. because we have not yet | |
308 | parsed program options which might be used to suppress such | |
309 | warnings. */ | |
310 | gcry_control (GCRYCTL_SUSPEND_SECMEM_WARN); | |
311 | ||
312 | /* ... If required, other initialization goes here. Note that the | |
313 | process might still be running with increased privileges and that | |
314 | the secure memory has not been initialized. */ | |
315 | ||
316 | /* Allocate a pool of 16k secure memory. This make the secure memory | |
317 | available and also drops privileges where needed. */ | |
318 | gcry_control (GCRYCTL_INIT_SECMEM, 16384, 0); | |
319 | ||
320 | /* It is now okay to let Libgcrypt complain when there was/is | |
321 | a problem with the secure memory. */ | |
322 | gcry_control (GCRYCTL_RESUME_SECMEM_WARN); | |
323 | ||
324 | /* ... If required, other initialization goes here. */ | |
325 | ||
326 | /* Tell Libgcrypt that initialization has completed. */ | |
327 | gcry_control (GCRYCTL_INITIALIZATION_FINISHED, 0); | |
328 | ||
329 | return; | |
330 | } | |
331 | ||
332 | ||
333 | ||
334 | ||
335 | /* Accumulate data (gnutls-only). | |
336 | String to be appended must be nul-terminated. */ | |
337 | ||
338 | gstring * | |
339 | exim_dkim_data_append(gstring * g, uschar * s) | |
340 | { | |
341 | return g; /*dummy*/ | |
342 | } | |
343 | ||
344 | ||
345 | ||
346 | /* import private key from PEM string in memory. | |
347 | Only handles RSA keys. | |
348 | Return: NULL for success, or an error string */ | |
349 | ||
350 | const uschar * | |
351 | exim_dkim_signing_init(const uschar * privkey_pem, es_ctx * sign_ctx) | |
352 | { | |
353 | uschar * s1, * s2; | |
354 | blob der; | |
355 | long alen; | |
356 | int rc; | |
357 | ||
358 | /*XXX will need extension to _spot_ as well as handle a | |
359 | non-RSA key? I think... | |
360 | So... this is not a PrivateKeyInfo - which would have a field | |
361 | identifying the keytype - PrivateKeyAlgorithmIdentifier - | |
362 | but a plain RSAPrivateKey (wrapped in PEM-headers. Can we | |
363 | use those as a type tag? What forms are there? "BEGIN EC PRIVATE KEY" (cf. ec(1ssl)) | |
364 | ||
365 | How does OpenSSL PEM_read_bio_PrivateKey() deal with it? | |
366 | gnutls_x509_privkey_import() ? | |
367 | */ | |
368 | ||
369 | /* | |
370 | * RSAPrivateKey ::= SEQUENCE | |
371 | * version Version, | |
372 | * modulus INTEGER, -- n | |
373 | * publicExponent INTEGER, -- e | |
374 | * privateExponent INTEGER, -- d | |
375 | * prime1 INTEGER, -- p | |
376 | * prime2 INTEGER, -- q | |
377 | * exponent1 INTEGER, -- d mod (p-1) | |
378 | * exponent2 INTEGER, -- d mod (q-1) | |
379 | * coefficient INTEGER, -- (inverse of q) mod p | |
380 | * otherPrimeInfos OtherPrimeInfos OPTIONAL | |
381 | ||
382 | * ECPrivateKey ::= SEQUENCE { | |
383 | * version INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1), | |
384 | * privateKey OCTET STRING, | |
385 | * parameters [0] ECParameters {{ NamedCurve }} OPTIONAL, | |
386 | * publicKey [1] BIT STRING OPTIONAL | |
387 | * } | |
388 | * Hmm, only 1 useful item, and not even an integer? Wonder how we might use it... | |
389 | ||
390 | - actually, gnutls_x509_privkey_import() appears to require a curve name parameter | |
391 | value for that is an OID? a local-only integer (it's an enum in GnuTLS)? | |
392 | ||
393 | ||
394 | Useful cmds: | |
395 | ssh-keygen -t ecdsa -f foo.privkey | |
396 | ssh-keygen -t ecdsa -b384 -f foo.privkey | |
397 | ssh-keygen -t ecdsa -b521 -f foo.privkey | |
398 | ssh-keygen -t ed25519 -f foo.privkey | |
399 | ||
400 | < foo openssl pkcs8 -in /dev/stdin -inform PEM -nocrypt -topk8 -outform DER | od -x | |
401 | ||
402 | openssl asn1parse -in foo -inform PEM -dump | |
403 | openssl asn1parse -in foo -inform PEM -dump -stroffset 24 (??) | |
404 | (not good for ed25519) | |
405 | ||
406 | */ | |
407 | ||
408 | if ( !(s1 = Ustrstr(CS privkey_pem, "-----BEGIN RSA PRIVATE KEY-----")) | |
409 | || !(s2 = Ustrstr(CS (s1+=31), "-----END RSA PRIVATE KEY-----" )) | |
410 | ) | |
411 | return US"Bad PEM wrapper"; | |
412 | ||
413 | *s2 = '\0'; | |
414 | ||
415 | if ((der.len = b64decode(s1, &der.data)) < 0) | |
416 | return US"Bad PEM-DER b64 decode"; | |
417 | ||
418 | /* untangle asn.1 */ | |
419 | ||
420 | /* sequence; just move past the header */ | |
421 | if ((rc = as_tag(&der, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL)) | |
422 | != ASN1_SUCCESS) goto asn_err; | |
423 | ||
424 | /* integer version; move past the header, check is zero */ | |
425 | if ((rc = as_tag(&der, 0, ASN1_TAG_INTEGER, &alen)) != ASN1_SUCCESS) | |
426 | goto asn_err; | |
427 | if (alen != 1 || *der.data != 0) | |
428 | return US"Bad version number"; | |
429 | der.data++; der.len--; | |
430 | ||
431 | if ( (s1 = as_mpi(&der, &sign_ctx->n)) | |
432 | || (s1 = as_mpi(&der, &sign_ctx->e)) | |
433 | || (s1 = as_mpi(&der, &sign_ctx->d)) | |
434 | || (s1 = as_mpi(&der, &sign_ctx->p)) | |
435 | || (s1 = as_mpi(&der, &sign_ctx->q)) | |
436 | || (s1 = as_mpi(&der, &sign_ctx->dp)) | |
437 | || (s1 = as_mpi(&der, &sign_ctx->dq)) | |
438 | || (s1 = as_mpi(&der, &sign_ctx->qp)) | |
439 | ) | |
440 | return s1; | |
441 | ||
442 | #ifdef extreme_debug | |
443 | DEBUG(D_acl) debug_printf_indent("rsa_signing_init:\n"); | |
444 | { | |
445 | uschar * s; | |
446 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->n); | |
447 | debug_printf_indent(" N : %s\n", s); | |
448 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->e); | |
449 | debug_printf_indent(" E : %s\n", s); | |
450 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->d); | |
451 | debug_printf_indent(" D : %s\n", s); | |
452 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->p); | |
453 | debug_printf_indent(" P : %s\n", s); | |
454 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->q); | |
455 | debug_printf_indent(" Q : %s\n", s); | |
456 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->dp); | |
457 | debug_printf_indent(" DP: %s\n", s); | |
458 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->dq); | |
459 | debug_printf_indent(" DQ: %s\n", s); | |
460 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->qp); | |
461 | debug_printf_indent(" QP: %s\n", s); | |
462 | } | |
463 | #endif | |
464 | ||
465 | sign_ctx->keytype = KEYTYPE_RSA; | |
466 | return NULL; | |
467 | ||
468 | asn_err: return US asn1_strerror(rc); | |
469 | } | |
470 | ||
471 | ||
472 | ||
473 | /* allocate mem for signature (when signing) */ | |
474 | /* sign already-hashed data. | |
475 | ||
476 | Return: NULL for success, or an error string */ | |
477 | ||
478 | const uschar * | |
479 | exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig) | |
480 | { | |
481 | char * sexp_hash; | |
482 | gcry_sexp_t s_hash = NULL, s_key = NULL, s_sig = NULL; | |
483 | gcry_mpi_t m_sig; | |
484 | uschar * errstr; | |
485 | gcry_error_t gerr; | |
486 | ||
487 | /*XXX will need extension for hash types (though, possibly, should | |
488 | be re-specced to not rehash but take an already-hashed value? Actually | |
489 | current impl looks WRONG - it _is_ given a hash so should not be | |
490 | re-hashing. Has this been tested? | |
491 | ||
492 | Will need extension for non-RSA sugning algos. */ | |
493 | ||
494 | switch (hash) | |
495 | { | |
496 | case HASH_SHA1: sexp_hash = "(data(flags pkcs1)(hash sha1 %b))"; break; | |
497 | case HASH_SHA2_256: sexp_hash = "(data(flags pkcs1)(hash sha256 %b))"; break; | |
498 | default: return US"nonhandled hash type"; | |
499 | } | |
500 | ||
501 | #define SIGSPACE 128 | |
502 | sig->data = store_get(SIGSPACE); | |
503 | ||
504 | if (gcry_mpi_cmp (sign_ctx->p, sign_ctx->q) > 0) | |
505 | { | |
506 | gcry_mpi_swap (sign_ctx->p, sign_ctx->q); | |
507 | gcry_mpi_invm (sign_ctx->qp, sign_ctx->p, sign_ctx->q); | |
508 | } | |
509 | ||
510 | if ( (gerr = gcry_sexp_build (&s_key, NULL, | |
511 | "(private-key (rsa (n%m)(e%m)(d%m)(p%m)(q%m)(u%m)))", | |
512 | sign_ctx->n, sign_ctx->e, | |
513 | sign_ctx->d, sign_ctx->p, | |
514 | sign_ctx->q, sign_ctx->qp)) | |
515 | || (gerr = gcry_sexp_build (&s_hash, NULL, sexp_hash, | |
516 | (int) data->len, CS data->data)) | |
517 | || (gerr = gcry_pk_sign (&s_sig, s_hash, s_key)) | |
518 | ) | |
519 | return US gcry_strerror(gerr); | |
520 | ||
521 | /* gcry_sexp_dump(s_sig); */ | |
522 | ||
523 | if ( !(s_sig = gcry_sexp_find_token(s_sig, "s", 0)) | |
524 | ) | |
525 | return US"no sig result"; | |
526 | ||
527 | m_sig = gcry_sexp_nth_mpi(s_sig, 1, GCRYMPI_FMT_USG); | |
528 | ||
529 | #ifdef extreme_debug | |
530 | DEBUG(D_acl) | |
531 | { | |
532 | uschar * s; | |
533 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, m_sig); | |
534 | debug_printf_indent(" SG: %s\n", s); | |
535 | } | |
536 | #endif | |
537 | ||
538 | gerr = gcry_mpi_print(GCRYMPI_FMT_USG, sig->data, SIGSPACE, &sig->len, m_sig); | |
539 | if (gerr) | |
540 | { | |
541 | debug_printf_indent("signature conversion from MPI to buffer failed\n"); | |
542 | return US gcry_strerror(gerr); | |
543 | } | |
544 | #undef SIGSPACE | |
545 | ||
546 | return NULL; | |
547 | } | |
548 | ||
549 | ||
550 | /* import public key (from blob in memory) | |
551 | Return: NULL for success, or an error string */ | |
552 | ||
553 | const uschar * | |
554 | exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx) | |
555 | { | |
556 | /* | |
557 | in code sequence per b81207d2bfa92 rsa_parse_public_key() and asn1_get_mpi() | |
558 | */ | |
559 | uschar tag_class; | |
560 | int taglen; | |
561 | long alen; | |
562 | int rc; | |
563 | uschar * errstr; | |
564 | gcry_error_t gerr; | |
565 | uschar * stage = US"S1"; | |
566 | ||
567 | if (fmt != KEYFMT_DER) return US"pubkey format not handled"; | |
568 | ||
569 | /* | |
570 | sequence | |
571 | sequence | |
572 | OBJECT:rsaEncryption | |
573 | NULL | |
574 | BIT STRING:RSAPublicKey | |
575 | sequence | |
576 | INTEGER:Public modulus | |
577 | INTEGER:Public exponent | |
578 | ||
579 | openssl rsa -in aux-fixed/dkim/dkim.private -pubout -outform DER | od -t x1 | head; | |
580 | openssl rsa -in aux-fixed/dkim/dkim.private -pubout | openssl asn1parse -dump; | |
581 | openssl rsa -in aux-fixed/dkim/dkim.private -pubout | openssl asn1parse -dump -offset 22; | |
582 | */ | |
583 | ||
584 | /* sequence; just move past the header */ | |
585 | if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL)) | |
586 | != ASN1_SUCCESS) goto asn_err; | |
587 | ||
588 | /* sequence; skip the entire thing */ | |
589 | DEBUG(D_acl) stage = US"S2"; | |
590 | if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, &alen)) | |
591 | != ASN1_SUCCESS) goto asn_err; | |
592 | pubkey->data += alen; pubkey->len -= alen; | |
593 | ||
594 | ||
595 | /* bitstring: limit range to size of bitstring; | |
596 | move over header + content wrapper */ | |
597 | DEBUG(D_acl) stage = US"BS"; | |
598 | if ((rc = as_tag(pubkey, 0, ASN1_TAG_BIT_STRING, &alen)) != ASN1_SUCCESS) | |
599 | goto asn_err; | |
600 | pubkey->len = alen; | |
601 | pubkey->data++; pubkey->len--; | |
602 | ||
603 | /* sequence; just move past the header */ | |
604 | DEBUG(D_acl) stage = US"S3"; | |
605 | if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL)) | |
606 | != ASN1_SUCCESS) goto asn_err; | |
607 | ||
608 | /* read two integers */ | |
609 | DEBUG(D_acl) stage = US"MPI"; | |
610 | if ( (errstr = as_mpi(pubkey, &verify_ctx->n)) | |
611 | || (errstr = as_mpi(pubkey, &verify_ctx->e)) | |
612 | ) | |
613 | return errstr; | |
614 | ||
615 | #ifdef extreme_debug | |
616 | DEBUG(D_acl) debug_printf_indent("rsa_verify_init:\n"); | |
617 | { | |
618 | uschar * s; | |
619 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, verify_ctx->n); | |
620 | debug_printf_indent(" N : %s\n", s); | |
621 | gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, verify_ctx->e); | |
622 | debug_printf_indent(" E : %s\n", s); | |
623 | } | |
624 | ||
625 | #endif | |
626 | return NULL; | |
627 | ||
628 | asn_err: | |
629 | DEBUG(D_acl) return string_sprintf("%s: %s", stage, asn1_strerror(rc)); | |
630 | return US asn1_strerror(rc); | |
631 | } | |
632 | ||
633 | ||
634 | /* verify signature (of hash) | |
635 | XXX though we appear to be doing a hash, too! | |
636 | (given pubkey & alleged sig) | |
637 | Return: NULL for success, or an error string */ | |
638 | ||
639 | const uschar * | |
640 | exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data_hash, blob * sig) | |
641 | { | |
642 | /* | |
643 | cf. libgnutls 2.8.5 _wrap_gcry_pk_verify() | |
644 | */ | |
645 | char * sexp_hash; | |
646 | gcry_mpi_t m_sig; | |
647 | gcry_sexp_t s_sig = NULL, s_hash = NULL, s_pkey = NULL; | |
648 | gcry_error_t gerr; | |
649 | uschar * stage; | |
650 | ||
651 | /*XXX needs extension for SHA512 */ | |
652 | switch (hash) | |
653 | { | |
654 | case HASH_SHA1: sexp_hash = "(data(flags pkcs1)(hash sha1 %b))"; break; | |
655 | case HASH_SHA2_256: sexp_hash = "(data(flags pkcs1)(hash sha256 %b))"; break; | |
656 | default: return US"nonhandled hash type"; | |
657 | } | |
658 | ||
659 | if ( (stage = US"pkey sexp build", | |
660 | gerr = gcry_sexp_build (&s_pkey, NULL, "(public-key(rsa(n%m)(e%m)))", | |
661 | verify_ctx->n, verify_ctx->e)) | |
662 | || (stage = US"data sexp build", | |
663 | gerr = gcry_sexp_build (&s_hash, NULL, sexp_hash, | |
664 | (int) data_hash->len, CS data_hash->data)) | |
665 | || (stage = US"sig mpi scan", | |
666 | gerr = gcry_mpi_scan(&m_sig, GCRYMPI_FMT_USG, sig->data, sig->len, NULL)) | |
667 | || (stage = US"sig sexp build", | |
668 | gerr = gcry_sexp_build (&s_sig, NULL, "(sig-val(rsa(s%m)))", m_sig)) | |
669 | || (stage = US"verify", | |
670 | gerr = gcry_pk_verify (s_sig, s_hash, s_pkey)) | |
671 | ) | |
672 | { | |
673 | DEBUG(D_acl) debug_printf_indent("verify: error in stage '%s'\n", stage); | |
674 | return US gcry_strerror(gerr); | |
675 | } | |
676 | ||
677 | if (s_sig) gcry_sexp_release (s_sig); | |
678 | if (s_hash) gcry_sexp_release (s_hash); | |
679 | if (s_pkey) gcry_sexp_release (s_pkey); | |
680 | gcry_mpi_release (m_sig); | |
681 | gcry_mpi_release (verify_ctx->n); | |
682 | gcry_mpi_release (verify_ctx->e); | |
683 | ||
684 | return NULL; | |
685 | } | |
686 | ||
687 | ||
688 | ||
689 | ||
690 | #elif defined(SIGN_OPENSSL) | |
691 | /******************************************************************************/ | |
692 | ||
693 | void | |
694 | exim_dkim_init(void) | |
695 | { | |
696 | ERR_load_crypto_strings(); | |
697 | } | |
698 | ||
699 | ||
700 | /* accumulate data (was gnutls-only but now needed for OpenSSL non-EC too | |
701 | because now using hash-and-sign interface) */ | |
702 | gstring * | |
703 | exim_dkim_data_append(gstring * g, uschar * s) | |
704 | { | |
705 | return string_cat(g, s); | |
706 | } | |
707 | ||
708 | ||
709 | /* import private key from PEM string in memory. | |
710 | Return: NULL for success, or an error string */ | |
711 | ||
712 | const uschar * | |
713 | exim_dkim_signing_init(const uschar * privkey_pem, es_ctx * sign_ctx) | |
714 | { | |
715 | BIO * bp = BIO_new_mem_buf(privkey_pem, -1); | |
716 | ||
717 | if (!(sign_ctx->key = PEM_read_bio_PrivateKey(bp, NULL, NULL, NULL))) | |
718 | return string_sprintf("privkey PEM-block import: %s", | |
719 | ERR_error_string(ERR_get_error(), NULL)); | |
720 | ||
721 | sign_ctx->keytype = | |
722 | #ifdef SIGN_HAVE_ED25519 | |
723 | EVP_PKEY_type(EVP_PKEY_id(sign_ctx->key)) == EVP_PKEY_ED25519 | |
724 | ? KEYTYPE_ED25519 : KEYTYPE_RSA; | |
725 | #else | |
726 | KEYTYPE_RSA; | |
727 | #endif | |
728 | return NULL; | |
729 | } | |
730 | ||
731 | ||
732 | ||
733 | /* allocate mem for signature (when signing) */ | |
734 | /* hash & sign data. Incremental not supported. | |
735 | ||
736 | Return: NULL for success with the signaature in the sig blob, or an error string */ | |
737 | ||
738 | const uschar * | |
739 | exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig) | |
740 | { | |
741 | const EVP_MD * md; | |
742 | EVP_MD_CTX * ctx; | |
743 | size_t siglen; | |
744 | ||
745 | switch (hash) | |
746 | { | |
747 | case HASH_NULL: md = NULL; break; /* Ed25519 signing */ | |
748 | case HASH_SHA1: md = EVP_sha1(); break; | |
749 | case HASH_SHA2_256: md = EVP_sha256(); break; | |
750 | case HASH_SHA2_512: md = EVP_sha512(); break; | |
751 | default: return US"nonhandled hash type"; | |
752 | } | |
753 | ||
754 | #ifdef SIGN_HAVE_ED25519 | |
755 | if ( (ctx = EVP_MD_CTX_new()) | |
756 | && EVP_DigestSignInit(ctx, NULL, md, NULL, sign_ctx->key) > 0 | |
757 | && EVP_DigestSign(ctx, NULL, &siglen, NULL, 0) > 0 | |
758 | && (sig->data = store_get(siglen)) | |
759 | ||
760 | /* Obtain the signature (slen could change here!) */ | |
761 | && EVP_DigestSign(ctx, sig->data, &siglen, data->data, data->len) > 0 | |
762 | ) | |
763 | { | |
764 | EVP_MD_CTX_destroy(ctx); | |
765 | sig->len = siglen; | |
766 | return NULL; | |
767 | } | |
768 | #else | |
769 | /*XXX renamed to EVP_MD_CTX_new() in 1.1.0 */ | |
770 | if ( (ctx = EVP_MD_CTX_create()) | |
771 | && EVP_DigestSignInit(ctx, NULL, md, NULL, sign_ctx->key) > 0 | |
772 | && EVP_DigestSignUpdate(ctx, data->data, data->len) > 0 | |
773 | && EVP_DigestSignFinal(ctx, NULL, &siglen) > 0 | |
774 | && (sig->data = store_get(siglen)) | |
775 | ||
776 | /* Obtain the signature (slen could change here!) */ | |
777 | && EVP_DigestSignFinal(ctx, sig->data, &siglen) > 0 | |
778 | ) | |
779 | { | |
780 | EVP_MD_CTX_destroy(ctx); | |
781 | sig->len = siglen; | |
782 | return NULL; | |
783 | } | |
784 | #endif | |
785 | ||
786 | if (ctx) EVP_MD_CTX_destroy(ctx); | |
787 | return US ERR_error_string(ERR_get_error(), NULL); | |
788 | } | |
789 | ||
790 | ||
791 | ||
792 | /* import public key (from blob in memory) | |
793 | Return: NULL for success, or an error string */ | |
794 | ||
795 | const uschar * | |
796 | exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx) | |
797 | { | |
798 | const uschar * s = pubkey->data; | |
799 | uschar * ret = NULL; | |
800 | ||
801 | switch(fmt) | |
802 | { | |
803 | case KEYFMT_DER: | |
804 | /*XXX hmm, we never free this */ | |
805 | if (!(verify_ctx->key = d2i_PUBKEY(NULL, &s, pubkey->len))) | |
806 | ret = US ERR_error_string(ERR_get_error(), NULL); | |
807 | break; | |
808 | #ifdef SIGN_HAVE_ED25519 | |
809 | case KEYFMT_ED25519_BARE: | |
810 | if (!(verify_ctx->key = EVP_PKEY_new_raw_public_key(EVP_PKEY_ED25519, NULL, | |
811 | s, pubkey->len))) | |
812 | ret = US ERR_error_string(ERR_get_error(), NULL); | |
813 | break; | |
814 | #endif | |
815 | default: | |
816 | ret = US"pubkey format not handled"; | |
817 | break; | |
818 | } | |
819 | ||
820 | return ret; | |
821 | } | |
822 | ||
823 | ||
824 | ||
825 | ||
826 | /* verify signature (of hash, except Ed25519 where of-data) | |
827 | (given pubkey & alleged sig) | |
828 | Return: NULL for success, or an error string */ | |
829 | ||
830 | const uschar * | |
831 | exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data, blob * sig) | |
832 | { | |
833 | const EVP_MD * md; | |
834 | ||
835 | switch (hash) | |
836 | { | |
837 | case HASH_NULL: md = NULL; break; | |
838 | case HASH_SHA1: md = EVP_sha1(); break; | |
839 | case HASH_SHA2_256: md = EVP_sha256(); break; | |
840 | case HASH_SHA2_512: md = EVP_sha512(); break; | |
841 | default: return US"nonhandled hash type"; | |
842 | } | |
843 | ||
844 | #ifdef SIGN_HAVE_ED25519 | |
845 | if (!md) | |
846 | { | |
847 | EVP_MD_CTX * ctx; | |
848 | ||
849 | if ((ctx = EVP_MD_CTX_new())) | |
850 | { | |
851 | if ( EVP_DigestVerifyInit(ctx, NULL, md, NULL, verify_ctx->key) > 0 | |
852 | && EVP_DigestVerify(ctx, sig->data, sig->len, data->data, data->len) > 0 | |
853 | ) | |
854 | { EVP_MD_CTX_free(ctx); return NULL; } | |
855 | EVP_MD_CTX_free(ctx); | |
856 | } | |
857 | } | |
858 | else | |
859 | #endif | |
860 | { | |
861 | EVP_PKEY_CTX * ctx; | |
862 | ||
863 | if ((ctx = EVP_PKEY_CTX_new(verify_ctx->key, NULL))) | |
864 | { | |
865 | if ( EVP_PKEY_verify_init(ctx) > 0 | |
866 | && EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) > 0 | |
867 | && EVP_PKEY_CTX_set_signature_md(ctx, md) > 0 | |
868 | && EVP_PKEY_verify(ctx, sig->data, sig->len, | |
869 | data->data, data->len) == 1 | |
870 | ) | |
871 | { EVP_PKEY_CTX_free(ctx); return NULL; } | |
872 | EVP_PKEY_CTX_free(ctx); | |
873 | ||
874 | DEBUG(D_tls) | |
875 | if (Ustrcmp(ERR_reason_error_string(ERR_peek_error()), "wrong signature length") == 0) | |
876 | debug_printf("sig len (from msg hdr): %d, expected (from dns pubkey) %d\n", | |
877 | (int) sig->len, EVP_PKEY_size(verify_ctx->key)); | |
878 | } | |
879 | } | |
880 | ||
881 | return US ERR_error_string(ERR_get_error(), NULL); | |
882 | } | |
883 | ||
884 | ||
885 | ||
886 | #endif | |
887 | /******************************************************************************/ | |
888 | ||
889 | #endif /*DISABLE_DKIM*/ | |
890 | #endif /*MACRO_PREDEF*/ | |
891 | /* End of File */ |