b55bd9f5f5c70373463fee4fd2a706205997386c
[exim.git] / src / src / pdkim / signing.c
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 #ifdef DISABLE_TLS
32 # error Must no DISABLE_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 unsigned * bits)
160 {
161 gnutls_datum_t k;
162 int rc;
163 const uschar * ret = NULL;
164
165 gnutls_pubkey_init(&verify_ctx->key);
166 k.data = pubkey->data;
167 k.size = pubkey->len;
168
169 switch(fmt)
170 {
171 case KEYFMT_DER:
172 if ((rc = gnutls_pubkey_import(verify_ctx->key, &k, GNUTLS_X509_FMT_DER)))
173 ret = US gnutls_strerror(rc);
174 break;
175 #ifdef SIGN_HAVE_ED25519
176 case KEYFMT_ED25519_BARE:
177 if ((rc = gnutls_pubkey_import_ecc_raw(verify_ctx->key,
178 GNUTLS_ECC_CURVE_ED25519, &k, NULL)))
179 ret = US gnutls_strerror(rc);
180 break;
181 #endif
182 default:
183 ret = US"pubkey format not handled";
184 break;
185 }
186 if (!ret && bits) gnutls_pubkey_get_pk_algorithm(verify_ctx->key, bits);
187 return ret;
188 }
189
190
191 /* verify signature (of hash if RSA sig, of data if EC sig. No way to do incremental)
192 (given pubkey & alleged sig)
193 Return: NULL for success, or an error string */
194
195 const uschar *
196 exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data_hash, blob * sig)
197 {
198 gnutls_datum_t k = { .data = data_hash->data, .size = data_hash->len };
199 gnutls_datum_t s = { .data = sig->data, .size = sig->len };
200 int rc;
201 const uschar * ret = NULL;
202
203 #ifdef SIGN_HAVE_ED25519
204 if (verify_ctx->keytype == KEYTYPE_ED25519)
205 {
206 if ((rc = gnutls_pubkey_verify_data2(verify_ctx->key,
207 GNUTLS_SIGN_EDDSA_ED25519, 0, &k, &s)) < 0)
208 ret = US gnutls_strerror(rc);
209 }
210 else
211 #endif
212 {
213 gnutls_sign_algorithm_t algo;
214 switch (hash)
215 {
216 case HASH_SHA1: algo = GNUTLS_SIGN_RSA_SHA1; break;
217 case HASH_SHA2_256: algo = GNUTLS_SIGN_RSA_SHA256; break;
218 case HASH_SHA2_512: algo = GNUTLS_SIGN_RSA_SHA512; break;
219 default: return US"nonhandled hash type";
220 }
221
222 if ((rc = gnutls_pubkey_verify_hash2(verify_ctx->key, algo, 0, &k, &s)) < 0)
223 ret = US gnutls_strerror(rc);
224 }
225
226 gnutls_pubkey_deinit(verify_ctx->key);
227 return ret;
228 }
229
230
231
232
233 #elif defined(SIGN_GCRYPT)
234 /******************************************************************************/
235 /* This variant is used under pre-3.0.0 GnuTLS. Only rsa-sha1 and rsa-sha256 */
236
237
238 /* Internal service routine:
239 Read and move past an asn.1 header, checking class & tag,
240 optionally returning the data-length */
241
242 static int
243 as_tag(blob * der, uschar req_cls, long req_tag, long * alen)
244 {
245 int rc;
246 uschar tag_class;
247 int taglen;
248 long tag, len;
249
250 debug_printf_indent("as_tag: %02x %02x %02x %02x\n",
251 der->data[0], der->data[1], der->data[2], der->data[3]);
252
253 if ((rc = asn1_get_tag_der(der->data++, der->len--, &tag_class, &taglen, &tag))
254 != ASN1_SUCCESS)
255 return rc;
256
257 if (tag_class != req_cls || tag != req_tag) return ASN1_ELEMENT_NOT_FOUND;
258
259 if ((len = asn1_get_length_der(der->data, der->len, &taglen)) < 0)
260 return ASN1_DER_ERROR;
261 if (alen) *alen = len;
262
263 /* debug_printf_indent("as_tag: tlen %d dlen %d\n", taglen, (int)len); */
264
265 der->data += taglen;
266 der->len -= taglen;
267 return rc;
268 }
269
270 /* Internal service routine:
271 Read and move over an asn.1 integer, setting an MPI to the value
272 */
273
274 static uschar *
275 as_mpi(blob * der, gcry_mpi_t * mpi)
276 {
277 long alen;
278 int rc;
279 gcry_error_t gerr;
280
281 debug_printf_indent("%s\n", __FUNCTION__);
282
283 /* integer; move past the header */
284 if ((rc = as_tag(der, 0, ASN1_TAG_INTEGER, &alen)) != ASN1_SUCCESS)
285 return US asn1_strerror(rc);
286
287 /* read to an MPI */
288 if ((gerr = gcry_mpi_scan(mpi, GCRYMPI_FMT_STD, der->data, alen, NULL)))
289 return US gcry_strerror(gerr);
290
291 /* move over the data */
292 der->data += alen; der->len -= alen;
293 return NULL;
294 }
295
296
297
298 void
299 exim_dkim_init(void)
300 {
301 /* Version check should be the very first call because it
302 makes sure that important subsystems are initialized. */
303 if (!gcry_check_version (GCRYPT_VERSION))
304 {
305 fputs ("libgcrypt version mismatch\n", stderr);
306 exit (2);
307 }
308
309 /* We don't want to see any warnings, e.g. because we have not yet
310 parsed program options which might be used to suppress such
311 warnings. */
312 gcry_control (GCRYCTL_SUSPEND_SECMEM_WARN);
313
314 /* ... If required, other initialization goes here. Note that the
315 process might still be running with increased privileges and that
316 the secure memory has not been initialized. */
317
318 /* Allocate a pool of 16k secure memory. This make the secure memory
319 available and also drops privileges where needed. */
320 gcry_control (GCRYCTL_INIT_SECMEM, 16384, 0);
321
322 /* It is now okay to let Libgcrypt complain when there was/is
323 a problem with the secure memory. */
324 gcry_control (GCRYCTL_RESUME_SECMEM_WARN);
325
326 /* ... If required, other initialization goes here. */
327
328 /* Tell Libgcrypt that initialization has completed. */
329 gcry_control (GCRYCTL_INITIALIZATION_FINISHED, 0);
330
331 return;
332 }
333
334
335
336
337 /* Accumulate data (gnutls-only).
338 String to be appended must be nul-terminated. */
339
340 gstring *
341 exim_dkim_data_append(gstring * g, uschar * s)
342 {
343 return g; /*dummy*/
344 }
345
346
347
348 /* import private key from PEM string in memory.
349 Only handles RSA keys.
350 Return: NULL for success, or an error string */
351
352 const uschar *
353 exim_dkim_signing_init(const uschar * privkey_pem, es_ctx * sign_ctx)
354 {
355 uschar * s1, * s2;
356 blob der;
357 long alen;
358 int rc;
359
360 /*XXX will need extension to _spot_ as well as handle a
361 non-RSA key? I think...
362 So... this is not a PrivateKeyInfo - which would have a field
363 identifying the keytype - PrivateKeyAlgorithmIdentifier -
364 but a plain RSAPrivateKey (wrapped in PEM-headers. Can we
365 use those as a type tag? What forms are there? "BEGIN EC PRIVATE KEY" (cf. ec(1ssl))
366
367 How does OpenSSL PEM_read_bio_PrivateKey() deal with it?
368 gnutls_x509_privkey_import() ?
369 */
370
371 /*
372 * RSAPrivateKey ::= SEQUENCE
373 * version Version,
374 * modulus INTEGER, -- n
375 * publicExponent INTEGER, -- e
376 * privateExponent INTEGER, -- d
377 * prime1 INTEGER, -- p
378 * prime2 INTEGER, -- q
379 * exponent1 INTEGER, -- d mod (p-1)
380 * exponent2 INTEGER, -- d mod (q-1)
381 * coefficient INTEGER, -- (inverse of q) mod p
382 * otherPrimeInfos OtherPrimeInfos OPTIONAL
383
384 * ECPrivateKey ::= SEQUENCE {
385 * version INTEGER { ecPrivkeyVer1(1) } (ecPrivkeyVer1),
386 * privateKey OCTET STRING,
387 * parameters [0] ECParameters {{ NamedCurve }} OPTIONAL,
388 * publicKey [1] BIT STRING OPTIONAL
389 * }
390 * Hmm, only 1 useful item, and not even an integer? Wonder how we might use it...
391
392 - actually, gnutls_x509_privkey_import() appears to require a curve name parameter
393 value for that is an OID? a local-only integer (it's an enum in GnuTLS)?
394
395
396 Useful cmds:
397 ssh-keygen -t ecdsa -f foo.privkey
398 ssh-keygen -t ecdsa -b384 -f foo.privkey
399 ssh-keygen -t ecdsa -b521 -f foo.privkey
400 ssh-keygen -t ed25519 -f foo.privkey
401
402 < foo openssl pkcs8 -in /dev/stdin -inform PEM -nocrypt -topk8 -outform DER | od -x
403
404 openssl asn1parse -in foo -inform PEM -dump
405 openssl asn1parse -in foo -inform PEM -dump -stroffset 24 (??)
406 (not good for ed25519)
407
408 */
409
410 if ( !(s1 = Ustrstr(CS privkey_pem, "-----BEGIN RSA PRIVATE KEY-----"))
411 || !(s2 = Ustrstr(CS (s1+=31), "-----END RSA PRIVATE KEY-----" ))
412 )
413 return US"Bad PEM wrapper";
414
415 *s2 = '\0';
416
417 if ((rc = b64decode(s1, &der.data) < 0))
418 return US"Bad PEM-DER b64 decode";
419 der.len = rc;
420
421 /* untangle asn.1 */
422
423 /* sequence; just move past the header */
424 if ((rc = as_tag(&der, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL))
425 != ASN1_SUCCESS) goto asn_err;
426
427 /* integer version; move past the header, check is zero */
428 if ((rc = as_tag(&der, 0, ASN1_TAG_INTEGER, &alen)) != ASN1_SUCCESS)
429 goto asn_err;
430 if (alen != 1 || *der.data != 0)
431 return US"Bad version number";
432 der.data++; der.len--;
433
434 if ( (s1 = as_mpi(&der, &sign_ctx->n))
435 || (s1 = as_mpi(&der, &sign_ctx->e))
436 || (s1 = as_mpi(&der, &sign_ctx->d))
437 || (s1 = as_mpi(&der, &sign_ctx->p))
438 || (s1 = as_mpi(&der, &sign_ctx->q))
439 || (s1 = as_mpi(&der, &sign_ctx->dp))
440 || (s1 = as_mpi(&der, &sign_ctx->dq))
441 || (s1 = as_mpi(&der, &sign_ctx->qp))
442 )
443 return s1;
444
445 #ifdef extreme_debug
446 DEBUG(D_acl) debug_printf_indent("rsa_signing_init:\n");
447 {
448 uschar * s;
449 gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->n);
450 debug_printf_indent(" N : %s\n", s);
451 gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->e);
452 debug_printf_indent(" E : %s\n", s);
453 gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->d);
454 debug_printf_indent(" D : %s\n", s);
455 gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->p);
456 debug_printf_indent(" P : %s\n", s);
457 gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->q);
458 debug_printf_indent(" Q : %s\n", s);
459 gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->dp);
460 debug_printf_indent(" DP: %s\n", s);
461 gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->dq);
462 debug_printf_indent(" DQ: %s\n", s);
463 gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, sign_ctx->qp);
464 debug_printf_indent(" QP: %s\n", s);
465 }
466 #endif
467
468 sign_ctx->keytype = KEYTYPE_RSA;
469 return NULL;
470
471 asn_err: return US asn1_strerror(rc);
472 }
473
474
475
476 /* allocate mem for signature (when signing) */
477 /* sign already-hashed data.
478
479 Return: NULL for success, or an error string */
480
481 const uschar *
482 exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig)
483 {
484 char * sexp_hash;
485 gcry_sexp_t s_hash = NULL, s_key = NULL, s_sig = NULL;
486 gcry_mpi_t m_sig;
487 uschar * errstr;
488 gcry_error_t gerr;
489
490 /*XXX will need extension for hash types (though, possibly, should
491 be re-specced to not rehash but take an already-hashed value? Actually
492 current impl looks WRONG - it _is_ given a hash so should not be
493 re-hashing. Has this been tested?
494
495 Will need extension for non-RSA sugning algos. */
496
497 switch (hash)
498 {
499 case HASH_SHA1: sexp_hash = "(data(flags pkcs1)(hash sha1 %b))"; break;
500 case HASH_SHA2_256: sexp_hash = "(data(flags pkcs1)(hash sha256 %b))"; break;
501 default: return US"nonhandled hash type";
502 }
503
504 #define SIGSPACE 128
505 sig->data = store_get(SIGSPACE, FALSE);
506
507 if (gcry_mpi_cmp (sign_ctx->p, sign_ctx->q) > 0)
508 {
509 gcry_mpi_swap (sign_ctx->p, sign_ctx->q);
510 gcry_mpi_invm (sign_ctx->qp, sign_ctx->p, sign_ctx->q);
511 }
512
513 if ( (gerr = gcry_sexp_build (&s_key, NULL,
514 "(private-key (rsa (n%m)(e%m)(d%m)(p%m)(q%m)(u%m)))",
515 sign_ctx->n, sign_ctx->e,
516 sign_ctx->d, sign_ctx->p,
517 sign_ctx->q, sign_ctx->qp))
518 || (gerr = gcry_sexp_build (&s_hash, NULL, sexp_hash,
519 (int) data->len, CS data->data))
520 || (gerr = gcry_pk_sign (&s_sig, s_hash, s_key))
521 )
522 return US gcry_strerror(gerr);
523
524 /* gcry_sexp_dump(s_sig); */
525
526 if ( !(s_sig = gcry_sexp_find_token(s_sig, "s", 0))
527 )
528 return US"no sig result";
529
530 m_sig = gcry_sexp_nth_mpi(s_sig, 1, GCRYMPI_FMT_USG);
531
532 #ifdef extreme_debug
533 DEBUG(D_acl)
534 {
535 uschar * s;
536 gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, m_sig);
537 debug_printf_indent(" SG: %s\n", s);
538 }
539 #endif
540
541 gerr = gcry_mpi_print(GCRYMPI_FMT_USG, sig->data, SIGSPACE, &sig->len, m_sig);
542 if (gerr)
543 {
544 debug_printf_indent("signature conversion from MPI to buffer failed\n");
545 return US gcry_strerror(gerr);
546 }
547 #undef SIGSPACE
548
549 return NULL;
550 }
551
552
553 /* import public key (from blob in memory)
554 Return: NULL for success, or an error string */
555
556 const uschar *
557 exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx,
558 unsigned * bits)
559 {
560 /*
561 in code sequence per b81207d2bfa92 rsa_parse_public_key() and asn1_get_mpi()
562 */
563 uschar tag_class;
564 int taglen;
565 long alen;
566 unsigned nbits;
567 int rc;
568 uschar * errstr;
569 gcry_error_t gerr;
570 uschar * stage = US"S1";
571
572 if (fmt != KEYFMT_DER) return US"pubkey format not handled";
573
574 /*
575 sequence
576 sequence
577 OBJECT:rsaEncryption
578 NULL
579 BIT STRING:RSAPublicKey
580 sequence
581 INTEGER:Public modulus
582 INTEGER:Public exponent
583
584 openssl rsa -in aux-fixed/dkim/dkim.private -pubout -outform DER | od -t x1 | head;
585 openssl rsa -in aux-fixed/dkim/dkim.private -pubout | openssl asn1parse -dump;
586 openssl rsa -in aux-fixed/dkim/dkim.private -pubout | openssl asn1parse -dump -offset 22;
587 */
588
589 /* sequence; just move past the header */
590 if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL))
591 != ASN1_SUCCESS) goto asn_err;
592
593 /* sequence; skip the entire thing */
594 DEBUG(D_acl) stage = US"S2";
595 if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, &alen))
596 != ASN1_SUCCESS) goto asn_err;
597 pubkey->data += alen; pubkey->len -= alen;
598
599
600 /* bitstring: limit range to size of bitstring;
601 move over header + content wrapper */
602 DEBUG(D_acl) stage = US"BS";
603 if ((rc = as_tag(pubkey, 0, ASN1_TAG_BIT_STRING, &alen)) != ASN1_SUCCESS)
604 goto asn_err;
605 pubkey->len = alen;
606 pubkey->data++; pubkey->len--;
607
608 /* sequence; just move past the header */
609 DEBUG(D_acl) stage = US"S3";
610 if ((rc = as_tag(pubkey, ASN1_CLASS_STRUCTURED, ASN1_TAG_SEQUENCE, NULL))
611 != ASN1_SUCCESS) goto asn_err;
612
613 /* read two integers */
614 DEBUG(D_acl) stage = US"MPI";
615 nbits = pubkey->len;
616 if ((errstr = as_mpi(pubkey, &verify_ctx->n))) return errstr;
617 nbits = (nbits - pubkey->len) * 8;
618 if ((errstr = as_mpi(pubkey, &verify_ctx->e))) return errstr;
619
620 #ifdef extreme_debug
621 DEBUG(D_acl) debug_printf_indent("rsa_verify_init:\n");
622 {
623 uschar * s;
624 gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, verify_ctx->n);
625 debug_printf_indent(" N : %s\n", s);
626 gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, verify_ctx->e);
627 debug_printf_indent(" E : %s\n", s);
628 }
629
630 #endif
631 if (bits) *bits = nbits;
632 return NULL;
633
634 asn_err:
635 DEBUG(D_acl) return string_sprintf("%s: %s", stage, asn1_strerror(rc));
636 return US asn1_strerror(rc);
637 }
638
639
640 /* verify signature (of hash)
641 XXX though we appear to be doing a hash, too!
642 (given pubkey & alleged sig)
643 Return: NULL for success, or an error string */
644
645 const uschar *
646 exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data_hash, blob * sig)
647 {
648 /*
649 cf. libgnutls 2.8.5 _wrap_gcry_pk_verify()
650 */
651 char * sexp_hash;
652 gcry_mpi_t m_sig;
653 gcry_sexp_t s_sig = NULL, s_hash = NULL, s_pkey = NULL;
654 gcry_error_t gerr;
655 uschar * stage;
656
657 /*XXX needs extension for SHA512 */
658 switch (hash)
659 {
660 case HASH_SHA1: sexp_hash = "(data(flags pkcs1)(hash sha1 %b))"; break;
661 case HASH_SHA2_256: sexp_hash = "(data(flags pkcs1)(hash sha256 %b))"; break;
662 default: return US"nonhandled hash type";
663 }
664
665 if ( (stage = US"pkey sexp build",
666 gerr = gcry_sexp_build (&s_pkey, NULL, "(public-key(rsa(n%m)(e%m)))",
667 verify_ctx->n, verify_ctx->e))
668 || (stage = US"data sexp build",
669 gerr = gcry_sexp_build (&s_hash, NULL, sexp_hash,
670 (int) data_hash->len, CS data_hash->data))
671 || (stage = US"sig mpi scan",
672 gerr = gcry_mpi_scan(&m_sig, GCRYMPI_FMT_USG, sig->data, sig->len, NULL))
673 || (stage = US"sig sexp build",
674 gerr = gcry_sexp_build (&s_sig, NULL, "(sig-val(rsa(s%m)))", m_sig))
675 || (stage = US"verify",
676 gerr = gcry_pk_verify (s_sig, s_hash, s_pkey))
677 )
678 {
679 DEBUG(D_acl) debug_printf_indent("verify: error in stage '%s'\n", stage);
680 return US gcry_strerror(gerr);
681 }
682
683 if (s_sig) gcry_sexp_release (s_sig);
684 if (s_hash) gcry_sexp_release (s_hash);
685 if (s_pkey) gcry_sexp_release (s_pkey);
686 gcry_mpi_release (m_sig);
687 gcry_mpi_release (verify_ctx->n);
688 gcry_mpi_release (verify_ctx->e);
689
690 return NULL;
691 }
692
693
694
695
696 #elif defined(SIGN_OPENSSL)
697 /******************************************************************************/
698
699 void
700 exim_dkim_init(void)
701 {
702 ERR_load_crypto_strings();
703 }
704
705
706 /* accumulate data (was gnutls-only but now needed for OpenSSL non-EC too
707 because now using hash-and-sign interface) */
708 gstring *
709 exim_dkim_data_append(gstring * g, uschar * s)
710 {
711 return string_cat(g, s);
712 }
713
714
715 /* import private key from PEM string in memory.
716 Return: NULL for success, or an error string */
717
718 const uschar *
719 exim_dkim_signing_init(const uschar * privkey_pem, es_ctx * sign_ctx)
720 {
721 BIO * bp = BIO_new_mem_buf((void *)privkey_pem, -1);
722
723 if (!(sign_ctx->key = PEM_read_bio_PrivateKey(bp, NULL, NULL, NULL)))
724 return string_sprintf("privkey PEM-block import: %s",
725 ERR_error_string(ERR_get_error(), NULL));
726
727 sign_ctx->keytype =
728 #ifdef SIGN_HAVE_ED25519
729 EVP_PKEY_type(EVP_PKEY_id(sign_ctx->key)) == EVP_PKEY_ED25519
730 ? KEYTYPE_ED25519 : KEYTYPE_RSA;
731 #else
732 KEYTYPE_RSA;
733 #endif
734 return NULL;
735 }
736
737
738
739 /* allocate mem for signature (when signing) */
740 /* hash & sign data. Incremental not supported.
741
742 Return: NULL for success with the signaature in the sig blob, or an error string */
743
744 const uschar *
745 exim_dkim_sign(es_ctx * sign_ctx, hashmethod hash, blob * data, blob * sig)
746 {
747 const EVP_MD * md;
748 EVP_MD_CTX * ctx;
749 size_t siglen;
750
751 switch (hash)
752 {
753 case HASH_NULL: md = NULL; break; /* Ed25519 signing */
754 case HASH_SHA1: md = EVP_sha1(); break;
755 case HASH_SHA2_256: md = EVP_sha256(); break;
756 case HASH_SHA2_512: md = EVP_sha512(); break;
757 default: return US"nonhandled hash type";
758 }
759
760 #ifdef SIGN_HAVE_ED25519
761 if ( (ctx = EVP_MD_CTX_new())
762 && EVP_DigestSignInit(ctx, NULL, md, NULL, sign_ctx->key) > 0
763 && EVP_DigestSign(ctx, NULL, &siglen, NULL, 0) > 0
764 && (sig->data = store_get(siglen, FALSE))
765
766 /* Obtain the signature (slen could change here!) */
767 && EVP_DigestSign(ctx, sig->data, &siglen, data->data, data->len) > 0
768 )
769 {
770 EVP_MD_CTX_destroy(ctx);
771 sig->len = siglen;
772 return NULL;
773 }
774 #else
775 /*XXX renamed to EVP_MD_CTX_new() in 1.1.0 */
776 if ( (ctx = EVP_MD_CTX_create())
777 && EVP_DigestSignInit(ctx, NULL, md, NULL, sign_ctx->key) > 0
778 && EVP_DigestSignUpdate(ctx, data->data, data->len) > 0
779 && EVP_DigestSignFinal(ctx, NULL, &siglen) > 0
780 && (sig->data = store_get(siglen, FALSE))
781
782 /* Obtain the signature (slen could change here!) */
783 && EVP_DigestSignFinal(ctx, sig->data, &siglen) > 0
784 )
785 {
786 EVP_MD_CTX_destroy(ctx);
787 sig->len = siglen;
788 return NULL;
789 }
790 #endif
791
792 if (ctx) EVP_MD_CTX_destroy(ctx);
793 return US ERR_error_string(ERR_get_error(), NULL);
794 }
795
796
797
798 /* import public key (from blob in memory)
799 Return: NULL for success, or an error string */
800
801 const uschar *
802 exim_dkim_verify_init(blob * pubkey, keyformat fmt, ev_ctx * verify_ctx,
803 unsigned * bits)
804 {
805 const uschar * s = pubkey->data;
806 uschar * ret = NULL;
807
808 switch(fmt)
809 {
810 case KEYFMT_DER:
811 /*XXX hmm, we never free this */
812 if (!(verify_ctx->key = d2i_PUBKEY(NULL, &s, pubkey->len)))
813 ret = US ERR_error_string(ERR_get_error(), NULL);
814 break;
815 #ifdef SIGN_HAVE_ED25519
816 case KEYFMT_ED25519_BARE:
817 if (!(verify_ctx->key = EVP_PKEY_new_raw_public_key(EVP_PKEY_ED25519, NULL,
818 s, pubkey->len)))
819 ret = US ERR_error_string(ERR_get_error(), NULL);
820 break;
821 #endif
822 default:
823 ret = US"pubkey format not handled";
824 break;
825 }
826
827 if (!ret && bits) *bits = EVP_PKEY_bits(verify_ctx->key);
828 return ret;
829 }
830
831
832
833
834 /* verify signature (of hash, except Ed25519 where of-data)
835 (given pubkey & alleged sig)
836 Return: NULL for success, or an error string */
837
838 const uschar *
839 exim_dkim_verify(ev_ctx * verify_ctx, hashmethod hash, blob * data, blob * sig)
840 {
841 const EVP_MD * md;
842
843 switch (hash)
844 {
845 case HASH_NULL: md = NULL; break;
846 case HASH_SHA1: md = EVP_sha1(); break;
847 case HASH_SHA2_256: md = EVP_sha256(); break;
848 case HASH_SHA2_512: md = EVP_sha512(); break;
849 default: return US"nonhandled hash type";
850 }
851
852 #ifdef SIGN_HAVE_ED25519
853 if (!md)
854 {
855 EVP_MD_CTX * ctx;
856
857 if ((ctx = EVP_MD_CTX_new()))
858 {
859 if ( EVP_DigestVerifyInit(ctx, NULL, md, NULL, verify_ctx->key) > 0
860 && EVP_DigestVerify(ctx, sig->data, sig->len, data->data, data->len) > 0
861 )
862 { EVP_MD_CTX_free(ctx); return NULL; }
863 EVP_MD_CTX_free(ctx);
864 }
865 }
866 else
867 #endif
868 {
869 EVP_PKEY_CTX * ctx;
870
871 if ((ctx = EVP_PKEY_CTX_new(verify_ctx->key, NULL)))
872 {
873 if ( EVP_PKEY_verify_init(ctx) > 0
874 && EVP_PKEY_CTX_set_rsa_padding(ctx, RSA_PKCS1_PADDING) > 0
875 && EVP_PKEY_CTX_set_signature_md(ctx, md) > 0
876 && EVP_PKEY_verify(ctx, sig->data, sig->len,
877 data->data, data->len) == 1
878 )
879 { EVP_PKEY_CTX_free(ctx); return NULL; }
880 EVP_PKEY_CTX_free(ctx);
881
882 DEBUG(D_tls)
883 if (Ustrcmp(ERR_reason_error_string(ERR_peek_error()), "wrong signature length") == 0)
884 debug_printf("sig len (from msg hdr): %d, expected (from dns pubkey) %d\n",
885 (int) sig->len, EVP_PKEY_size(verify_ctx->key));
886 }
887 }
888
889 return US ERR_error_string(ERR_get_error(), NULL);
890 }
891
892
893
894 #endif
895 /******************************************************************************/
896
897 #endif /*DISABLE_DKIM*/
898 #endif /*MACRO_PREDEF*/
899 /* End of File */