src/src/pdkim/rsa.c

   1 /*
   2  *  PDKIM - a RFC4871 (DKIM) implementation
   3  *
   4  *  Copyright (C) 2016  Exim maintainers
   5  *
   6  *  RSA 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 "rsa.h"
  19
  20
  21 /******************************************************************************/
  22 #ifdef RSA_GNUTLS
  23
  24 void
  25 exim_rsa_init(void)
  26 {
  27 }
  28
  29
  30 /* accumulate data (gnutls-only).  String to be appended must be nul-terminated. */
  31 blob *
  32 exim_rsa_data_append(blob * b, int * alloc, uschar * s)
  33 {
  34 int len = b->len;
  35 b->data = string_append(b->data, alloc, &len, 1, s);
  36 b->len = len;
  37 return b;
  38 }
  39
  40
  41
  42 /* import private key from PEM string in memory.
  43 Return: NULL for success, or an error string */
  44
  45 const uschar *
  46 exim_rsa_signing_init(uschar * privkey_pem, es_ctx * sign_ctx)
  47 {
  48 gnutls_datum_t k;
  49 int rc;
  50
  51 k.data = privkey_pem;
  52 k.size = strlen(privkey_pem);
  53
  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 */
  57    )
  58   return gnutls_strerror(rc);
  59
  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
  63    )
  64   return gnutls_strerror(rc);
  65
  66 return NULL;
  67 }
  68
  69
  70
  71 /* allocate mem for signature (when signing) */
  72 /* sign data (gnutls_only)
  73 OR
  74 sign hash.
  75
  76 Return: NULL for success, or an error string */
  77
  78 const uschar *
  79 exim_rsa_sign(es_ctx * sign_ctx, BOOL is_sha1, blob * data, blob * sig)
  80 {
  81 gnutls_datum_t k;
  82 size_t sigsize = 0;
  83 int rc;
  84 const uschar * ret = NULL;
  85
  86 /* Allocate mem for signature */
  87 k.data = data->data;
  88 k.size = data->len;
  89 (void) gnutls_x509_privkey_sign_data(sign_ctx->rsa,
  90   is_sha1 ? GNUTLS_DIG_SHA1 : GNUTLS_DIG_SHA256,
  91   0, &k, NULL, &sigsize);
  92
  93 sig->data = store_get(sigsize);
  94 sig->len = sigsize;
  95
  96 /* Do signing */
  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
 100    )
 101   ret = gnutls_strerror(rc);
 102
 103 gnutls_x509_privkey_deinit(sign_ctx->rsa);
 104 return ret;
 105 }
 106
 107
 108
 109 /* import public key (from DER in memory)
 110 Return: NULL for success, or an error string */
 111
 112 const uschar *
 113 exim_rsa_verify_init(blob * pubkey_der, ev_ctx * verify_ctx)
 114 {
 115 gnutls_datum_t k;
 116 int rc;
 117 const uschar * ret = NULL;
 118
 119 gnutls_pubkey_init(&verify_ctx->rsa);
 120
 121 k.data = pubkey_der->data;
 122 k.size = pubkey_der->len;
 123
 124 if ((rc = gnutls_pubkey_import(verify_ctx->rsa, &k, GNUTLS_X509_FMT_DER))
 125        != GNUTLS_E_SUCCESS)
 126   ret = gnutls_strerror(rc);
 127 return ret;
 128 }
 129
 130
 131 /* verify signature (of hash)  (given pubkey & alleged sig)
 132 Return: NULL for success, or an error string */
 133
 134 const uschar *
 135 exim_rsa_verify(ev_ctx * verify_ctx, BOOL is_sha1, blob * data_hash, blob * sig)
 136 {
 137 gnutls_datum_t k, s;
 138 int rc;
 139 const uschar * ret = NULL;
 140
 141 k.data = data_hash->data;
 142 k.size = data_hash->len;
 143 s.data = sig->data;
 144 s.size = sig->len;
 145 if ((rc = gnutls_pubkey_verify_hash2(verify_ctx->rsa,
 146             is_sha1 ? GNUTLS_SIGN_RSA_SHA1 : GNUTLS_SIGN_RSA_SHA256,
 147             0, &k, &s)) < 0)
 148   ret = gnutls_strerror(rc);
 149
 150 gnutls_pubkey_deinit(verify_ctx->rsa);
 151 return ret;
 152 }
 153
 154
 155
 156
 157 #elif defined(RSA_GCRYPT)
 158 /******************************************************************************/
 159
 160
 161 /* Internal service routine:
 162 Read and move past an asn.1 header, checking class & tag,
 163 optionally returning the data-length */
 164
 165 static int
 166 as_tag(blob * der, uschar req_cls, long req_tag, long * alen)
 167 {
 168 int rc;
 169 uschar tag_class;
 170 int taglen;
 171 long tag, len;
 172
 173 /* debug_printf("as_tag: %02x %02x %02x %02x\n",
 174         der->data[0], der->data[1], der->data[2], der->data[3]); */
 175
 176 if ((rc = asn1_get_tag_der(der->data++, der->len--, &tag_class, &taglen, &tag))
 177     != ASN1_SUCCESS)
 178   return rc;
 179
 180 if (tag_class != req_cls || tag != req_tag) return ASN1_ELEMENT_NOT_FOUND;
 181
 182 if ((len = asn1_get_length_der(der->data, der->len, &taglen)) < 0)
 183   return ASN1_DER_ERROR;
 184 if (alen) *alen = len;
 185
 186 /* debug_printf("as_tag:  tlen %d dlen %d\n", taglen, (int)len); */
 187
 188 der->data += taglen;
 189 der->len -= taglen;
 190 return rc;
 191 }
 192
 193 /* Internal service routine:
 194 Read and move over an asn.1 integer, setting an MPI to the value
 195 */
 196
 197 static uschar *
 198 as_mpi(blob * der, gcry_mpi_t * mpi)
 199 {
 200 long alen;
 201 int rc;
 202 gcry_error_t gerr;
 203
 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);
 207
 208 /* read to an MPI */
 209 if ((gerr = gcry_mpi_scan(mpi, GCRYMPI_FMT_STD, der->data, alen, NULL)))
 210   return US gcry_strerror(gerr);
 211
 212 /* move over the data */
 213 der->data += alen; der->len -= alen;
 214 return NULL;
 215 }
 216
 217
 218
 219 void
 220 exim_rsa_init(void)
 221 {
 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))
 225   {
 226   fputs ("libgcrypt version mismatch\n", stderr);
 227   exit (2);
 228   }
 229
 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
 232 warnings. */
 233 gcry_control (GCRYCTL_SUSPEND_SECMEM_WARN);
 234
 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.  */
 238
 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);
 242
 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);
 246
 247 /* ... If required, other initialization goes here.  */
 248
 249 /* Tell Libgcrypt that initialization has completed. */
 250 gcry_control (GCRYCTL_INITIALIZATION_FINISHED, 0);
 251
 252 return;
 253 }
 254
 255
 256
 257
 258 /* Accumulate data (gnutls-only).
 259 String to be appended must be nul-terminated. */
 260
 261 blob *
 262 exim_rsa_data_append(blob * b, int * alloc, uschar * s)
 263 {
 264 return b;       /*dummy*/
 265 }
 266
 267
 268
 269 /* import private key from PEM string in memory.
 270 Return: NULL for success, or an error string */
 271
 272 const uschar *
 273 exim_rsa_signing_init(uschar * privkey_pem, es_ctx * sign_ctx)
 274 {
 275 uschar * s1, * s2;
 276 blob der;
 277 long alen;
 278 int rc;
 279
 280 /*
 281  *  RSAPrivateKey ::= SEQUENCE
 282  *      version           Version,
 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
 292  */
 293
 294 if (  !(s1 = Ustrstr(CS privkey_pem, "-----BEGIN RSA PRIVATE KEY-----"))
 295    || !(s2 = Ustrstr(CS (s1+=31),    "-----END RSA PRIVATE KEY-----" ))
 296    )
 297   return US"Bad PEM wrapper";
 298
 299 *s2 = '\0';
 300
 301 if ((der.len = b64decode(s1, &der.data)) < 0)
 302   return US"Bad PEM-DER b64 decode";
 303
 304 /* untangle asn.1 */
 305
 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;
 309
 310 /* integer version; move past the header, check is zero */
 311 if ((rc = as_tag(&der, 0, ASN1_TAG_INTEGER, &alen)) != ASN1_SUCCESS)
 312   goto asn_err;
 313 if (alen != 1 || *der.data != 0)
 314   return US"Bad version number";
 315 der.data++; der.len--;
 316
 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))
 325    )
 326   return s1;
 327
 328 DEBUG(D_acl) debug_printf("rsa_signing_init:\n");
 329   {
 330   uschar * s;
 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);
 347   }
 348 return NULL;
 349
 350 asn_err: return US asn1_strerror(rc);
 351 }
 352
 353
 354
 355 /* allocate mem for signature (when signing) */
 356 /* sign data (gnutls_only)
 357 OR
 358 sign hash.
 359
 360 Return: NULL for success, or an error string */
 361
 362 const uschar *
 363 exim_rsa_sign(es_ctx * sign_ctx, BOOL is_sha1, blob * data, blob * sig)
 364 {
 365 gcry_sexp_t s_hash = NULL, s_key = NULL, s_sig = NULL;
 366 gcry_mpi_t m_sig;
 367 uschar * errstr;
 368 gcry_error_t gerr;
 369
 370 #define SIGSPACE 128
 371 sig->data = store_get(SIGSPACE);
 372
 373 if (gcry_mpi_cmp (sign_ctx->p, sign_ctx->q) > 0)
 374   {
 375   gcry_mpi_swap (sign_ctx->p, sign_ctx->q);
 376   gcry_mpi_invm (sign_ctx->qp, sign_ctx->p, sign_ctx->q);
 377   }
 378
 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,
 385                 is_sha1
 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))
 390    )
 391   return US gcry_strerror(gerr);
 392
 393 /* gcry_sexp_dump(s_sig); */
 394
 395 if (  !(s_sig = gcry_sexp_find_token(s_sig, "s", 0))
 396    )
 397   return US"no sig result";
 398
 399 m_sig = gcry_sexp_nth_mpi(s_sig, 1, GCRYMPI_FMT_USG);
 400
 401 DEBUG(D_acl)
 402   {
 403   uschar * s;
 404   gcry_mpi_aprint (GCRYMPI_FMT_HEX, &s, NULL, m_sig);
 405   debug_printf(" SG: %s\n", s);
 406   }
 407
 408 gerr = gcry_mpi_print(GCRYMPI_FMT_USG, sig->data, SIGSPACE, &sig->len, m_sig);
 409 if (gerr)
 410   {
 411   debug_printf("signature conversion from MPI to buffer failed\n");
 412   return US gcry_strerror(gerr);
 413   }
 414 #undef SIGSPACE
 415
 416 return NULL;
 417 }
 418
 419
 420 /* import public key (from DER in memory)
 421 Return: NULL for success, or an error string */
 422
 423 const uschar *
 424 exim_rsa_verify_init(blob * pubkey_der, ev_ctx * verify_ctx)
 425 {
 426 /*
 427 in code sequence per b81207d2bfa92 rsa_parse_public_key() and asn1_get_mpi()
 428 */
 429 uschar tag_class;
 430 int taglen;
 431 long alen;
 432 int rc;
 433 uschar * errstr;
 434 gcry_error_t gerr;
 435 uschar * stage = US"S1";
 436
 437 /*
 438 sequence
 439  sequence
 440   OBJECT:rsaEncryption
 441   NULL
 442  BIT STRING:RSAPublicKey
 443   sequence
 444    INTEGER:Public modulus
 445    INTEGER:Public exponent
 446
 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;
 450 */
 451
 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;
 455
 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;
 461
 462
 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)
 467   goto asn_err;
 468 pubkey_der->len = alen;
 469 pubkey_der->data++; pubkey_der->len--;
 470
 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;
 475
 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))
 480    )
 481   return errstr;
 482
 483 DEBUG(D_acl) debug_printf("rsa_verify_init:\n");
 484         {
 485         uschar * s;
 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);
 490         }
 491
 492 return NULL;
 493
 494 asn_err:
 495 DEBUG(D_acl) return string_sprintf("%s: %s", stage, asn1_strerror(rc));
 496              return US asn1_strerror(rc);
 497 }
 498
 499
 500 /* verify signature (of hash)  (given pubkey & alleged sig)
 501 Return: NULL for success, or an error string */
 502
 503 const uschar *
 504 exim_rsa_verify(ev_ctx * verify_ctx, BOOL is_sha1, blob * data_hash, blob * sig)
 505 {
 506 /*
 507 cf. libgnutls 2.8.5 _wrap_gcry_pk_verify()
 508 */
 509 gcry_mpi_t m_sig;
 510 gcry_sexp_t s_sig = NULL, s_hash = NULL, s_pkey = NULL;
 511 gcry_error_t gerr;
 512 uschar * stage;
 513
 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,
 519                 is_sha1
 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))
 529    )
 530   {
 531   DEBUG(D_acl) debug_printf("verify: error in stage '%s'\n", stage);
 532   return US gcry_strerror(gerr);
 533   }
 534
 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);
 541
 542 return NULL;
 543 }
 544
 545
 546
 547
 548 #elif defined(RSA_OPENSSL)
 549 /******************************************************************************/
 550
 551 void
 552 exim_rsa_init(void)
 553 {
 554 }
 555
 556
 557 /* accumulate data (gnutls-only) */
 558 blob *
 559 exim_rsa_data_append(blob * b, int * alloc, uschar * s)
 560 {
 561 return b;       /*dummy*/
 562 }
 563
 564
 565 /* import private key from PEM string in memory.
 566 Return: NULL for success, or an error string */
 567
 568 const uschar *
 569 exim_rsa_signing_init(uschar * privkey_pem, es_ctx * sign_ctx)
 570 {
 571 uschar * p, * q;
 572 int len;
 573
 574 /* Convert PEM to DER */
 575 if (  !(p = Ustrstr(privkey_pem, "-----BEGIN RSA PRIVATE KEY-----"))
 576    || !(q = Ustrstr(p+=31,       "-----END RSA PRIVATE KEY-----"))
 577    )
 578   return US"Bad PEM wrapping";
 579
 580 *q = '\0';
 581 if ((len = b64decode(p, &p)) < 0)
 582   return US"b64decode failed";
 583
 584 if (!(sign_ctx->rsa = d2i_RSAPrivateKey(NULL, CUSS &p, len)))
 585   {
 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);
 590   }
 591
 592 return NULL;
 593 }
 594
 595
 596
 597 /* allocate mem for signature (when signing) */
 598 /* sign data (gnutls_only)
 599 OR
 600 sign hash.
 601
 602 Return: NULL for success, or an error string */
 603
 604 const uschar *
 605 exim_rsa_sign(es_ctx * sign_ctx, BOOL is_sha1, blob * data, blob * sig)
 606 {
 607 uint len;
 608 const uschar * ret = NULL;
 609
 610 /* Allocate mem for signature */
 611 len = RSA_size(sign_ctx->rsa);
 612 sig->data = store_get(len);
 613 sig->len = len;
 614
 615 /* Do signing */
 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)
 619   {
 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);
 624   }
 625
 626 RSA_free(sign_ctx->rsa);
 627 return ret;;
 628 }
 629
 630
 631
 632 /* import public key (from DER in memory)
 633 Return: nULL for success, or an error string */
 634
 635 const uschar *
 636 exim_rsa_verify_init(blob * pubkey_der, ev_ctx * verify_ctx)
 637 {
 638 const uschar * p = CUS pubkey_der->data;
 639 const uschar * ret = NULL;
 640
 641 if (!(verify_ctx->rsa = d2i_RSA_PUBKEY(NULL, &p, (long) pubkey_der->len)))
 642   {
 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);
 647   }
 648 return ret;
 649 }
 650
 651
 652
 653
 654 /* verify signature (of hash)  (given pubkey & alleged sig)
 655 Return: NULL for success, or an error string */
 656
 657 const uschar *
 658 exim_rsa_verify(ev_ctx * verify_ctx, BOOL is_sha1, blob * data_hash, blob * sig)
 659 {
 660 const uschar * ret = NULL;
 661
 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)
 665   {
 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);
 670   }
 671 return ret;
 672 }
 673
 674
 675 #endif
 676 /******************************************************************************/
 677
 678 #endif  /*DISABLE_DKIM*/
 679 /* End of File */