2 * PDKIM - a RFC4871 (DKIM) implementation
4 * Copyright (C) 2016 Exim maintainers
6 * RSA signing/verification interface
11 #ifndef DISABLE_DKIM /* entire file */
14 # error Need SUPPORT_TLS for DKIM
17 #include "crypt_ver.h"
21 /******************************************************************************/
30 /* accumulate data (gnutls-only). String to be appended must be nul-terminated. */
32 exim_rsa_data_append(blob
* b
, int * alloc
, uschar
* s
)
35 b
->data
= string_append(b
->data
, alloc
, &len
, 1, s
);
42 /* import private key from PEM string in memory.
43 Return: NULL for success, or an error string */
46 exim_rsa_signing_init(uschar
* privkey_pem
, es_ctx
* sign_ctx
)
52 k
.size
= strlen(privkey_pem
);
54 if ( (rc
= gnutls_x509_privkey_init(&sign_ctx
->rsa
)) != GNUTLS_E_SUCCESS
55 /*|| (rc = gnutls_x509_privkey_import(sign_ctx->rsa, &k,
56 GNUTLS_X509_FMT_PEM)) != GNUTLS_E_SUCCESS */
58 return gnutls_strerror(rc
);
60 if ( /* (rc = gnutls_x509_privkey_init(&sign_ctx->rsa)) != GNUTLS_E_SUCCESS
61 ||*/ (rc
= gnutls_x509_privkey_import(sign_ctx
->rsa
, &k
,
62 GNUTLS_X509_FMT_PEM
)) != GNUTLS_E_SUCCESS
64 return gnutls_strerror(rc
);
71 /* allocate mem for signature (when signing) */
72 /* sign data (gnutls_only)
76 Return: NULL for success, or an error string */
79 exim_rsa_sign(es_ctx
* sign_ctx
, BOOL is_sha1
, blob
* data
, blob
* sig
)
84 const uschar
* ret
= NULL
;
86 /* Allocate mem for signature */
89 (void) gnutls_x509_privkey_sign_data(sign_ctx
->rsa
,
90 is_sha1
? GNUTLS_DIG_SHA1
: GNUTLS_DIG_SHA256
,
91 0, &k
, NULL
, &sigsize
);
93 sig
->data
= store_get(sigsize
);
97 if ((rc
= gnutls_x509_privkey_sign_data(sign_ctx
->rsa
,
98 is_sha1
? GNUTLS_DIG_SHA1
: GNUTLS_DIG_SHA256
,
99 0, &k
, sig
->data
, &sigsize
)) != GNUTLS_E_SUCCESS
101 ret
= gnutls_strerror(rc
);
103 gnutls_x509_privkey_deinit(sign_ctx
->rsa
);
109 /* import public key (from DER in memory)
110 Return: NULL for success, or an error string */
113 exim_rsa_verify_init(blob
* pubkey_der
, ev_ctx
* verify_ctx
)
117 const uschar
* ret
= NULL
;
119 gnutls_pubkey_init(&verify_ctx
->rsa
);
121 k
.data
= pubkey_der
->data
;
122 k
.size
= pubkey_der
->len
;
124 if ((rc
= gnutls_pubkey_import(verify_ctx
->rsa
, &k
, GNUTLS_X509_FMT_DER
))
126 ret
= gnutls_strerror(rc
);
131 /* verify signature (of hash) (given pubkey & alleged sig)
132 Return: NULL for success, or an error string */
135 exim_rsa_verify(ev_ctx
* verify_ctx
, BOOL is_sha1
, blob
* data_hash
, blob
* sig
)
139 const uschar
* ret
= NULL
;
141 k
.data
= data_hash
->data
;
142 k
.size
= data_hash
->len
;
145 if ((rc
= gnutls_pubkey_verify_hash2(verify_ctx
->rsa
,
146 is_sha1
? GNUTLS_SIGN_RSA_SHA1
: GNUTLS_SIGN_RSA_SHA256
,
148 ret
= gnutls_strerror(rc
);
150 gnutls_pubkey_deinit(verify_ctx
->rsa
);
157 #elif defined(RSA_GCRYPT)
158 /******************************************************************************/
161 /* Internal service routine:
162 Read and move past an asn.1 header, checking class & tag,
163 optionally returning the data-length */
166 as_tag(blob
* der
, uschar req_cls
, long req_tag
, long * alen
)
173 /* debug_printf("as_tag: %02x %02x %02x %02x\n",
174 der->data[0], der->data[1], der->data[2], der->data[3]); */
176 if ((rc
= asn1_get_tag_der(der
->data
++, der
->len
--, &tag_class
, &taglen
, &tag
))
180 if (tag_class
!= req_cls
|| tag
!= req_tag
) return ASN1_ELEMENT_NOT_FOUND
;
182 if ((len
= asn1_get_length_der(der
->data
, der
->len
, &taglen
)) < 0)
183 return ASN1_DER_ERROR
;
184 if (alen
) *alen
= len
;
186 /* debug_printf("as_tag: tlen %d dlen %d\n", taglen, (int)len); */
193 /* Internal service routine:
194 Read and move over an asn.1 integer, setting an MPI to the value
198 as_mpi(blob
* der
, gcry_mpi_t
* mpi
)
204 /* integer; move past the header */
205 if ((rc
= as_tag(der
, 0, ASN1_TAG_INTEGER
, &alen
)) != ASN1_SUCCESS
)
206 return US
asn1_strerror(rc
);
209 if ((gerr
= gcry_mpi_scan(mpi
, GCRYMPI_FMT_STD
, der
->data
, alen
, NULL
)))
210 return US
gcry_strerror(gerr
);
212 /* move over the data */
213 der
->data
+= alen
; der
->len
-= alen
;
222 /* Version check should be the very first call because it
223 makes sure that important subsystems are initialized. */
224 if (!gcry_check_version (GCRYPT_VERSION
))
226 fputs ("libgcrypt version mismatch\n", stderr
);
230 /* We don't want to see any warnings, e.g. because we have not yet
231 parsed program options which might be used to suppress such
233 gcry_control (GCRYCTL_SUSPEND_SECMEM_WARN
);
235 /* ... If required, other initialization goes here. Note that the
236 process might still be running with increased privileges and that
237 the secure memory has not been initialized. */
239 /* Allocate a pool of 16k secure memory. This make the secure memory
240 available and also drops privileges where needed. */
241 gcry_control (GCRYCTL_INIT_SECMEM
, 16384, 0);
243 /* It is now okay to let Libgcrypt complain when there was/is
244 a problem with the secure memory. */
245 gcry_control (GCRYCTL_RESUME_SECMEM_WARN
);
247 /* ... If required, other initialization goes here. */
249 /* Tell Libgcrypt that initialization has completed. */
250 gcry_control (GCRYCTL_INITIALIZATION_FINISHED
, 0);
258 /* Accumulate data (gnutls-only).
259 String to be appended must be nul-terminated. */
262 exim_rsa_data_append(blob
* b
, int * alloc
, uschar
* s
)
269 /* import private key from PEM string in memory.
270 Return: NULL for success, or an error string */
273 exim_rsa_signing_init(uschar
* privkey_pem
, es_ctx
* sign_ctx
)
281 * RSAPrivateKey ::= SEQUENCE
283 * modulus INTEGER, -- n
284 * publicExponent INTEGER, -- e
285 * privateExponent INTEGER, -- d
286 * prime1 INTEGER, -- p
287 * prime2 INTEGER, -- q
288 * exponent1 INTEGER, -- d mod (p-1)
289 * exponent2 INTEGER, -- d mod (q-1)
290 * coefficient INTEGER, -- (inverse of q) mod p
291 * otherPrimeInfos OtherPrimeInfos OPTIONAL
294 if ( !(s1
= Ustrstr(CS privkey_pem
, "-----BEGIN RSA PRIVATE KEY-----"))
295 || !(s2
= Ustrstr(CS (s1
+=31), "-----END RSA PRIVATE KEY-----" ))
297 return US
"Bad PEM wrapper";
301 if ((der
.len
= b64decode(s1
, &der
.data
)) < 0)
302 return US
"Bad PEM-DER b64 decode";
306 /* sequence; just move past the header */
307 if ((rc
= as_tag(&der
, ASN1_CLASS_STRUCTURED
, ASN1_TAG_SEQUENCE
, NULL
))
308 != ASN1_SUCCESS
) goto asn_err
;
310 /* integer version; move past the header, check is zero */
311 if ((rc
= as_tag(&der
, 0, ASN1_TAG_INTEGER
, &alen
)) != ASN1_SUCCESS
)
313 if (alen
!= 1 || *der
.data
!= 0)
314 return US
"Bad version number";
315 der
.data
++; der
.len
--;
317 if ( (s1
= as_mpi(&der
, &sign_ctx
->n
))
318 || (s1
= as_mpi(&der
, &sign_ctx
->e
))
319 || (s1
= as_mpi(&der
, &sign_ctx
->d
))
320 || (s1
= as_mpi(&der
, &sign_ctx
->p
))
321 || (s1
= as_mpi(&der
, &sign_ctx
->q
))
322 || (s1
= as_mpi(&der
, &sign_ctx
->dp
))
323 || (s1
= as_mpi(&der
, &sign_ctx
->dq
))
324 || (s1
= as_mpi(&der
, &sign_ctx
->qp
))
328 DEBUG(D_acl
) debug_printf("rsa_signing_init:\n");
331 gcry_mpi_aprint (GCRYMPI_FMT_HEX
, &s
, NULL
, sign_ctx
->n
);
332 debug_printf(" N : %s\n", s
);
333 gcry_mpi_aprint (GCRYMPI_FMT_HEX
, &s
, NULL
, sign_ctx
->e
);
334 debug_printf(" E : %s\n", s
);
335 gcry_mpi_aprint (GCRYMPI_FMT_HEX
, &s
, NULL
, sign_ctx
->d
);
336 debug_printf(" D : %s\n", s
);
337 gcry_mpi_aprint (GCRYMPI_FMT_HEX
, &s
, NULL
, sign_ctx
->p
);
338 debug_printf(" P : %s\n", s
);
339 gcry_mpi_aprint (GCRYMPI_FMT_HEX
, &s
, NULL
, sign_ctx
->q
);
340 debug_printf(" Q : %s\n", s
);
341 gcry_mpi_aprint (GCRYMPI_FMT_HEX
, &s
, NULL
, sign_ctx
->dp
);
342 debug_printf(" DP: %s\n", s
);
343 gcry_mpi_aprint (GCRYMPI_FMT_HEX
, &s
, NULL
, sign_ctx
->dq
);
344 debug_printf(" DQ: %s\n", s
);
345 gcry_mpi_aprint (GCRYMPI_FMT_HEX
, &s
, NULL
, sign_ctx
->qp
);
346 debug_printf(" QP: %s\n", s
);
350 asn_err
: return US
asn1_strerror(rc
);
355 /* allocate mem for signature (when signing) */
356 /* sign data (gnutls_only)
360 Return: NULL for success, or an error string */
363 exim_rsa_sign(es_ctx
* sign_ctx
, BOOL is_sha1
, blob
* data
, blob
* sig
)
365 gcry_sexp_t s_hash
= NULL
, s_key
= NULL
, s_sig
= NULL
;
371 sig
->data
= store_get(SIGSPACE
);
373 if (gcry_mpi_cmp (sign_ctx
->p
, sign_ctx
->q
) > 0)
375 gcry_mpi_swap (sign_ctx
->p
, sign_ctx
->q
);
376 gcry_mpi_invm (sign_ctx
->qp
, sign_ctx
->p
, sign_ctx
->q
);
379 if ( (gerr
= gcry_sexp_build (&s_key
, NULL
,
380 "(private-key (rsa (n%m)(e%m)(d%m)(p%m)(q%m)(u%m)))",
381 sign_ctx
->n
, sign_ctx
->e
,
382 sign_ctx
->d
, sign_ctx
->p
,
383 sign_ctx
->q
, sign_ctx
->qp
))
384 || (gerr
= gcry_sexp_build (&s_hash
, NULL
,
386 ? "(data(flags pkcs1)(hash sha1 %b))"
387 : "(data(flags pkcs1)(hash sha256 %b))",
388 (int) data
->len
, CS data
->data
))
389 || (gerr
= gcry_pk_sign (&s_sig
, s_hash
, s_key
))
391 return US
gcry_strerror(gerr
);
393 /* gcry_sexp_dump(s_sig); */
395 if ( !(s_sig
= gcry_sexp_find_token(s_sig
, "s", 0))
397 return US
"no sig result";
399 m_sig
= gcry_sexp_nth_mpi(s_sig
, 1, GCRYMPI_FMT_USG
);
404 gcry_mpi_aprint (GCRYMPI_FMT_HEX
, &s
, NULL
, m_sig
);
405 debug_printf(" SG: %s\n", s
);
408 gerr
= gcry_mpi_print(GCRYMPI_FMT_USG
, sig
->data
, SIGSPACE
, &sig
->len
, m_sig
);
411 debug_printf("signature conversion from MPI to buffer failed\n");
412 return US
gcry_strerror(gerr
);
420 /* import public key (from DER in memory)
421 Return: NULL for success, or an error string */
424 exim_rsa_verify_init(blob
* pubkey_der
, ev_ctx
* verify_ctx
)
427 in code sequence per b81207d2bfa92 rsa_parse_public_key() and asn1_get_mpi()
435 uschar
* stage
= US
"S1";
442 BIT STRING:RSAPublicKey
444 INTEGER:Public modulus
445 INTEGER:Public exponent
447 openssl rsa -in aux-fixed/dkim/dkim.private -pubout -outform DER | od -t x1 | head;
448 openssl rsa -in aux-fixed/dkim/dkim.private -pubout | openssl asn1parse -dump;
449 openssl rsa -in aux-fixed/dkim/dkim.private -pubout | openssl asn1parse -dump -offset 22;
452 /* sequence; just move past the header */
453 if ((rc
= as_tag(pubkey_der
, ASN1_CLASS_STRUCTURED
, ASN1_TAG_SEQUENCE
, NULL
))
454 != ASN1_SUCCESS
) goto asn_err
;
456 /* sequence; skip the entire thing */
457 DEBUG(D_acl
) stage
= US
"S2";
458 if ((rc
= as_tag(pubkey_der
, ASN1_CLASS_STRUCTURED
, ASN1_TAG_SEQUENCE
, &alen
))
459 != ASN1_SUCCESS
) goto asn_err
;
460 pubkey_der
->data
+= alen
; pubkey_der
->len
-= alen
;
463 /* bitstring: limit range to size of bitstring;
464 move over header + content wrapper */
465 DEBUG(D_acl
) stage
= US
"BS";
466 if ((rc
= as_tag(pubkey_der
, 0, ASN1_TAG_BIT_STRING
, &alen
)) != ASN1_SUCCESS
)
468 pubkey_der
->len
= alen
;
469 pubkey_der
->data
++; pubkey_der
->len
--;
471 /* sequence; just move past the header */
472 DEBUG(D_acl
) stage
= US
"S3";
473 if ((rc
= as_tag(pubkey_der
, ASN1_CLASS_STRUCTURED
, ASN1_TAG_SEQUENCE
, NULL
))
474 != ASN1_SUCCESS
) goto asn_err
;
476 /* read two integers */
477 DEBUG(D_acl
) stage
= US
"MPI";
478 if ( (errstr
= as_mpi(pubkey_der
, &verify_ctx
->n
))
479 || (errstr
= as_mpi(pubkey_der
, &verify_ctx
->e
))
483 DEBUG(D_acl
) debug_printf("rsa_verify_init:\n");
486 gcry_mpi_aprint (GCRYMPI_FMT_HEX
, &s
, NULL
, verify_ctx
->n
);
487 debug_printf(" N : %s\n", s
);
488 gcry_mpi_aprint (GCRYMPI_FMT_HEX
, &s
, NULL
, verify_ctx
->e
);
489 debug_printf(" E : %s\n", s
);
495 DEBUG(D_acl
) return string_sprintf("%s: %s", stage
, asn1_strerror(rc
));
496 return US
asn1_strerror(rc
);
500 /* verify signature (of hash) (given pubkey & alleged sig)
501 Return: NULL for success, or an error string */
504 exim_rsa_verify(ev_ctx
* verify_ctx
, BOOL is_sha1
, blob
* data_hash
, blob
* sig
)
507 cf. libgnutls 2.8.5 _wrap_gcry_pk_verify()
510 gcry_sexp_t s_sig
= NULL
, s_hash
= NULL
, s_pkey
= NULL
;
514 if ( (stage
= US
"pkey sexp build",
515 gerr
= gcry_sexp_build (&s_pkey
, NULL
, "(public-key(rsa(n%m)(e%m)))",
516 verify_ctx
->n
, verify_ctx
->e
))
517 || (stage
= US
"data sexp build",
518 gerr
= gcry_sexp_build (&s_hash
, NULL
,
520 ? "(data(flags pkcs1)(hash sha1 %b))"
521 : "(data(flags pkcs1)(hash sha256 %b))",
522 (int) data_hash
->len
, CS data_hash
->data
))
523 || (stage
= US
"sig mpi scan",
524 gerr
= gcry_mpi_scan(&m_sig
, GCRYMPI_FMT_USG
, sig
->data
, sig
->len
, NULL
))
525 || (stage
= US
"sig sexp build",
526 gerr
= gcry_sexp_build (&s_sig
, NULL
, "(sig-val(rsa(s%m)))", m_sig
))
527 || (stage
= US
"verify",
528 gerr
= gcry_pk_verify (s_sig
, s_hash
, s_pkey
))
531 DEBUG(D_acl
) debug_printf("verify: error in stage '%s'\n", stage
);
532 return US
gcry_strerror(gerr
);
535 if (s_sig
) gcry_sexp_release (s_sig
);
536 if (s_hash
) gcry_sexp_release (s_hash
);
537 if (s_pkey
) gcry_sexp_release (s_pkey
);
538 gcry_mpi_release (m_sig
);
539 gcry_mpi_release (verify_ctx
->n
);
540 gcry_mpi_release (verify_ctx
->e
);
548 #elif defined(RSA_OPENSSL)
549 /******************************************************************************/
557 /* accumulate data (gnutls-only) */
559 exim_rsa_data_append(blob
* b
, int * alloc
, uschar
* s
)
565 /* import private key from PEM string in memory.
566 Return: NULL for success, or an error string */
569 exim_rsa_signing_init(uschar
* privkey_pem
, es_ctx
* sign_ctx
)
574 /* Convert PEM to DER */
575 if ( !(p
= Ustrstr(privkey_pem
, "-----BEGIN RSA PRIVATE KEY-----"))
576 || !(q
= Ustrstr(p
+=31, "-----END RSA PRIVATE KEY-----"))
578 return US
"Bad PEM wrapping";
581 if ((len
= b64decode(p
, &p
)) < 0)
582 return US
"b64decode failed";
584 if (!(sign_ctx
->rsa
= d2i_RSAPrivateKey(NULL
, CUSS
&p
, len
)))
586 char ssl_errstring
[256];
587 ERR_load_crypto_strings(); /*XXX move to a startup routine */
588 ERR_error_string(ERR_get_error(), ssl_errstring
);
589 return string_copy(US ssl_errstring
);
597 /* allocate mem for signature (when signing) */
598 /* sign data (gnutls_only)
602 Return: NULL for success, or an error string */
605 exim_rsa_sign(es_ctx
* sign_ctx
, BOOL is_sha1
, blob
* data
, blob
* sig
)
608 const uschar
* ret
= NULL
;
610 /* Allocate mem for signature */
611 len
= RSA_size(sign_ctx
->rsa
);
612 sig
->data
= store_get(len
);
616 if (RSA_sign(is_sha1
? NID_sha1
: NID_sha256
,
617 CUS data
->data
, data
->len
,
618 US sig
->data
, &len
, sign_ctx
->rsa
) != 1)
620 char ssl_errstring
[256];
621 ERR_load_crypto_strings(); /*XXX move to a startup routine */
622 ERR_error_string(ERR_get_error(), ssl_errstring
);
623 ret
= string_copy(US ssl_errstring
);
626 RSA_free(sign_ctx
->rsa
);
632 /* import public key (from DER in memory)
633 Return: nULL for success, or an error string */
636 exim_rsa_verify_init(blob
* pubkey_der
, ev_ctx
* verify_ctx
)
638 const uschar
* p
= CUS pubkey_der
->data
;
639 const uschar
* ret
= NULL
;
641 if (!(verify_ctx
->rsa
= d2i_RSA_PUBKEY(NULL
, &p
, (long) pubkey_der
->len
)))
643 char ssl_errstring
[256];
644 ERR_load_crypto_strings(); /*XXX move to a startup routine */
645 ERR_error_string(ERR_get_error(), ssl_errstring
);
646 ret
= string_copy(CUS ssl_errstring
);
654 /* verify signature (of hash) (given pubkey & alleged sig)
655 Return: NULL for success, or an error string */
658 exim_rsa_verify(ev_ctx
* verify_ctx
, BOOL is_sha1
, blob
* data_hash
, blob
* sig
)
660 const uschar
* ret
= NULL
;
662 if (RSA_verify(is_sha1
? NID_sha1
: NID_sha256
,
663 CUS data_hash
->data
, data_hash
->len
,
664 US sig
->data
, (uint
) sig
->len
, verify_ctx
->rsa
) != 1)
666 char ssl_errstring
[256];
667 ERR_load_crypto_strings(); /*XXX move to a startup routine */
668 ERR_error_string(ERR_get_error(), ssl_errstring
);
669 ret
= string_copy(US ssl_errstring
);
676 /******************************************************************************/
678 #endif /*DISABLE_DKIM*/