PolarSSL v1.2.5
rsa.c
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1 /*
2  * The RSA public-key cryptosystem
3  *
4  * Copyright (C) 2006-2011, Brainspark B.V.
5  *
6  * This file is part of PolarSSL (http://www.polarssl.org)
7  * Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
8  *
9  * All rights reserved.
10  *
11  * This program is free software; you can redistribute it and/or modify
12  * it under the terms of the GNU General Public License as published by
13  * the Free Software Foundation; either version 2 of the License, or
14  * (at your option) any later version.
15  *
16  * This program is distributed in the hope that it will be useful,
17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19  * GNU General Public License for more details.
20  *
21  * You should have received a copy of the GNU General Public License along
22  * with this program; if not, write to the Free Software Foundation, Inc.,
23  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
24  */
25 /*
26  * RSA was designed by Ron Rivest, Adi Shamir and Len Adleman.
27  *
28  * http://theory.lcs.mit.edu/~rivest/rsapaper.pdf
29  * http://www.cacr.math.uwaterloo.ca/hac/about/chap8.pdf
30  */
31 
32 #include "polarssl/config.h"
33 
34 #if defined(POLARSSL_RSA_C)
35 
36 #include "polarssl/rsa.h"
37 
38 #if defined(POLARSSL_PKCS1_V21)
39 #include "polarssl/md.h"
40 #endif
41 
42 #include <stdlib.h>
43 #include <stdio.h>
44 
45 /*
46  * Initialize an RSA context
47  */
48 void rsa_init( rsa_context *ctx,
49  int padding,
50  int hash_id )
51 {
52  memset( ctx, 0, sizeof( rsa_context ) );
53 
54  ctx->padding = padding;
55  ctx->hash_id = hash_id;
56 }
57 
58 #if defined(POLARSSL_GENPRIME)
59 
60 /*
61  * Generate an RSA keypair
62  */
63 int rsa_gen_key( rsa_context *ctx,
64  int (*f_rng)(void *, unsigned char *, size_t),
65  void *p_rng,
66  unsigned int nbits, int exponent )
67 {
68  int ret;
69  mpi P1, Q1, H, G;
70 
71  if( f_rng == NULL || nbits < 128 || exponent < 3 )
73 
74  mpi_init( &P1 ); mpi_init( &Q1 ); mpi_init( &H ); mpi_init( &G );
75 
76  /*
77  * find primes P and Q with Q < P so that:
78  * GCD( E, (P-1)*(Q-1) ) == 1
79  */
80  MPI_CHK( mpi_lset( &ctx->E, exponent ) );
81 
82  do
83  {
84  MPI_CHK( mpi_gen_prime( &ctx->P, ( nbits + 1 ) >> 1, 0,
85  f_rng, p_rng ) );
86 
87  MPI_CHK( mpi_gen_prime( &ctx->Q, ( nbits + 1 ) >> 1, 0,
88  f_rng, p_rng ) );
89 
90  if( mpi_cmp_mpi( &ctx->P, &ctx->Q ) < 0 )
91  mpi_swap( &ctx->P, &ctx->Q );
92 
93  if( mpi_cmp_mpi( &ctx->P, &ctx->Q ) == 0 )
94  continue;
95 
96  MPI_CHK( mpi_mul_mpi( &ctx->N, &ctx->P, &ctx->Q ) );
97  if( mpi_msb( &ctx->N ) != nbits )
98  continue;
99 
100  MPI_CHK( mpi_sub_int( &P1, &ctx->P, 1 ) );
101  MPI_CHK( mpi_sub_int( &Q1, &ctx->Q, 1 ) );
102  MPI_CHK( mpi_mul_mpi( &H, &P1, &Q1 ) );
103  MPI_CHK( mpi_gcd( &G, &ctx->E, &H ) );
104  }
105  while( mpi_cmp_int( &G, 1 ) != 0 );
106 
107  /*
108  * D = E^-1 mod ((P-1)*(Q-1))
109  * DP = D mod (P - 1)
110  * DQ = D mod (Q - 1)
111  * QP = Q^-1 mod P
112  */
113  MPI_CHK( mpi_inv_mod( &ctx->D , &ctx->E, &H ) );
114  MPI_CHK( mpi_mod_mpi( &ctx->DP, &ctx->D, &P1 ) );
115  MPI_CHK( mpi_mod_mpi( &ctx->DQ, &ctx->D, &Q1 ) );
116  MPI_CHK( mpi_inv_mod( &ctx->QP, &ctx->Q, &ctx->P ) );
117 
118  ctx->len = ( mpi_msb( &ctx->N ) + 7 ) >> 3;
119 
120 cleanup:
121 
122  mpi_free( &P1 ); mpi_free( &Q1 ); mpi_free( &H ); mpi_free( &G );
123 
124  if( ret != 0 )
125  {
126  rsa_free( ctx );
127  return( POLARSSL_ERR_RSA_KEY_GEN_FAILED + ret );
128  }
129 
130  return( 0 );
131 }
132 
133 #endif
134 
135 /*
136  * Check a public RSA key
137  */
138 int rsa_check_pubkey( const rsa_context *ctx )
139 {
140  if( !ctx->N.p || !ctx->E.p )
142 
143  if( ( ctx->N.p[0] & 1 ) == 0 ||
144  ( ctx->E.p[0] & 1 ) == 0 )
146 
147  if( mpi_msb( &ctx->N ) < 128 ||
148  mpi_msb( &ctx->N ) > POLARSSL_MPI_MAX_BITS )
150 
151  if( mpi_msb( &ctx->E ) < 2 ||
152  mpi_msb( &ctx->E ) > 64 )
154 
155  return( 0 );
156 }
157 
158 /*
159  * Check a private RSA key
160  */
161 int rsa_check_privkey( const rsa_context *ctx )
162 {
163  int ret;
164  mpi PQ, DE, P1, Q1, H, I, G, G2, L1, L2, DP, DQ, QP;
165 
166  if( ( ret = rsa_check_pubkey( ctx ) ) != 0 )
167  return( ret );
168 
169  if( !ctx->P.p || !ctx->Q.p || !ctx->D.p )
171 
172  mpi_init( &PQ ); mpi_init( &DE ); mpi_init( &P1 ); mpi_init( &Q1 );
173  mpi_init( &H ); mpi_init( &I ); mpi_init( &G ); mpi_init( &G2 );
174  mpi_init( &L1 ); mpi_init( &L2 ); mpi_init( &DP ); mpi_init( &DQ );
175  mpi_init( &QP );
176 
177  MPI_CHK( mpi_mul_mpi( &PQ, &ctx->P, &ctx->Q ) );
178  MPI_CHK( mpi_mul_mpi( &DE, &ctx->D, &ctx->E ) );
179  MPI_CHK( mpi_sub_int( &P1, &ctx->P, 1 ) );
180  MPI_CHK( mpi_sub_int( &Q1, &ctx->Q, 1 ) );
181  MPI_CHK( mpi_mul_mpi( &H, &P1, &Q1 ) );
182  MPI_CHK( mpi_gcd( &G, &ctx->E, &H ) );
183 
184  MPI_CHK( mpi_gcd( &G2, &P1, &Q1 ) );
185  MPI_CHK( mpi_div_mpi( &L1, &L2, &H, &G2 ) );
186  MPI_CHK( mpi_mod_mpi( &I, &DE, &L1 ) );
187 
188  MPI_CHK( mpi_mod_mpi( &DP, &ctx->D, &P1 ) );
189  MPI_CHK( mpi_mod_mpi( &DQ, &ctx->D, &Q1 ) );
190  MPI_CHK( mpi_inv_mod( &QP, &ctx->Q, &ctx->P ) );
191  /*
192  * Check for a valid PKCS1v2 private key
193  */
194  if( mpi_cmp_mpi( &PQ, &ctx->N ) != 0 ||
195  mpi_cmp_mpi( &DP, &ctx->DP ) != 0 ||
196  mpi_cmp_mpi( &DQ, &ctx->DQ ) != 0 ||
197  mpi_cmp_mpi( &QP, &ctx->QP ) != 0 ||
198  mpi_cmp_int( &L2, 0 ) != 0 ||
199  mpi_cmp_int( &I, 1 ) != 0 ||
200  mpi_cmp_int( &G, 1 ) != 0 )
201  {
203  }
204 
205 cleanup:
206  mpi_free( &PQ ); mpi_free( &DE ); mpi_free( &P1 ); mpi_free( &Q1 );
207  mpi_free( &H ); mpi_free( &I ); mpi_free( &G ); mpi_free( &G2 );
208  mpi_free( &L1 ); mpi_free( &L2 ); mpi_free( &DP ); mpi_free( &DQ );
209  mpi_free( &QP );
210 
212  return( ret );
213 
214  if( ret != 0 )
215  return( POLARSSL_ERR_RSA_KEY_CHECK_FAILED + ret );
216 
217  return( 0 );
218 }
219 
220 /*
221  * Do an RSA public key operation
222  */
223 int rsa_public( rsa_context *ctx,
224  const unsigned char *input,
225  unsigned char *output )
226 {
227  int ret;
228  size_t olen;
229  mpi T;
230 
231  mpi_init( &T );
232 
233  MPI_CHK( mpi_read_binary( &T, input, ctx->len ) );
234 
235  if( mpi_cmp_mpi( &T, &ctx->N ) >= 0 )
236  {
237  mpi_free( &T );
239  }
240 
241  olen = ctx->len;
242  MPI_CHK( mpi_exp_mod( &T, &T, &ctx->E, &ctx->N, &ctx->RN ) );
243  MPI_CHK( mpi_write_binary( &T, output, olen ) );
244 
245 cleanup:
246 
247  mpi_free( &T );
248 
249  if( ret != 0 )
250  return( POLARSSL_ERR_RSA_PUBLIC_FAILED + ret );
251 
252  return( 0 );
253 }
254 
255 /*
256  * Do an RSA private key operation
257  */
258 int rsa_private( rsa_context *ctx,
259  const unsigned char *input,
260  unsigned char *output )
261 {
262  int ret;
263  size_t olen;
264  mpi T, T1, T2;
265 
266  mpi_init( &T ); mpi_init( &T1 ); mpi_init( &T2 );
267 
268  MPI_CHK( mpi_read_binary( &T, input, ctx->len ) );
269 
270  if( mpi_cmp_mpi( &T, &ctx->N ) >= 0 )
271  {
272  mpi_free( &T );
274  }
275 
276 #if defined(POLARSSL_RSA_NO_CRT)
277  MPI_CHK( mpi_exp_mod( &T, &T, &ctx->D, &ctx->N, &ctx->RN ) );
278 #else
279  /*
280  * faster decryption using the CRT
281  *
282  * T1 = input ^ dP mod P
283  * T2 = input ^ dQ mod Q
284  */
285  MPI_CHK( mpi_exp_mod( &T1, &T, &ctx->DP, &ctx->P, &ctx->RP ) );
286  MPI_CHK( mpi_exp_mod( &T2, &T, &ctx->DQ, &ctx->Q, &ctx->RQ ) );
287 
288  /*
289  * T = (T1 - T2) * (Q^-1 mod P) mod P
290  */
291  MPI_CHK( mpi_sub_mpi( &T, &T1, &T2 ) );
292  MPI_CHK( mpi_mul_mpi( &T1, &T, &ctx->QP ) );
293  MPI_CHK( mpi_mod_mpi( &T, &T1, &ctx->P ) );
294 
295  /*
296  * output = T2 + T * Q
297  */
298  MPI_CHK( mpi_mul_mpi( &T1, &T, &ctx->Q ) );
299  MPI_CHK( mpi_add_mpi( &T, &T2, &T1 ) );
300 #endif
301 
302  olen = ctx->len;
303  MPI_CHK( mpi_write_binary( &T, output, olen ) );
304 
305 cleanup:
306 
307  mpi_free( &T ); mpi_free( &T1 ); mpi_free( &T2 );
308 
309  if( ret != 0 )
310  return( POLARSSL_ERR_RSA_PRIVATE_FAILED + ret );
311 
312  return( 0 );
313 }
314 
315 #if defined(POLARSSL_PKCS1_V21)
316 
325 static void mgf_mask( unsigned char *dst, size_t dlen, unsigned char *src, size_t slen,
326  md_context_t *md_ctx )
327 {
328  unsigned char mask[POLARSSL_MD_MAX_SIZE];
329  unsigned char counter[4];
330  unsigned char *p;
331  unsigned int hlen;
332  size_t i, use_len;
333 
334  memset( mask, 0, POLARSSL_MD_MAX_SIZE );
335  memset( counter, 0, 4 );
336 
337  hlen = md_ctx->md_info->size;
338 
339  // Generate and apply dbMask
340  //
341  p = dst;
342 
343  while( dlen > 0 )
344  {
345  use_len = hlen;
346  if( dlen < hlen )
347  use_len = dlen;
348 
349  md_starts( md_ctx );
350  md_update( md_ctx, src, slen );
351  md_update( md_ctx, counter, 4 );
352  md_finish( md_ctx, mask );
353 
354  for( i = 0; i < use_len; ++i )
355  *p++ ^= mask[i];
356 
357  counter[3]++;
358 
359  dlen -= use_len;
360  }
361 }
362 #endif
363 
364 /*
365  * Add the message padding, then do an RSA operation
366  */
368  int (*f_rng)(void *, unsigned char *, size_t),
369  void *p_rng,
370  int mode, size_t ilen,
371  const unsigned char *input,
372  unsigned char *output )
373 {
374  size_t nb_pad, olen;
375  int ret;
376  unsigned char *p = output;
377 #if defined(POLARSSL_PKCS1_V21)
378  unsigned int hlen;
379  const md_info_t *md_info;
380  md_context_t md_ctx;
381 #endif
382 
383  olen = ctx->len;
384 
385  if( f_rng == NULL )
387 
388  switch( ctx->padding )
389  {
390  case RSA_PKCS_V15:
391 
392  if( olen < ilen + 11 )
394 
395  nb_pad = olen - 3 - ilen;
396 
397  *p++ = 0;
398  if( mode == RSA_PUBLIC )
399  {
400  *p++ = RSA_CRYPT;
401 
402  while( nb_pad-- > 0 )
403  {
404  int rng_dl = 100;
405 
406  do {
407  ret = f_rng( p_rng, p, 1 );
408  } while( *p == 0 && --rng_dl && ret == 0 );
409 
410  // Check if RNG failed to generate data
411  //
412  if( rng_dl == 0 || ret != 0)
413  return POLARSSL_ERR_RSA_RNG_FAILED + ret;
414 
415  p++;
416  }
417  }
418  else
419  {
420  *p++ = RSA_SIGN;
421 
422  while( nb_pad-- > 0 )
423  *p++ = 0xFF;
424  }
425 
426  *p++ = 0;
427  memcpy( p, input, ilen );
428  break;
429 
430 #if defined(POLARSSL_PKCS1_V21)
431  case RSA_PKCS_V21:
432 
433  md_info = md_info_from_type( ctx->hash_id );
434  if( md_info == NULL )
436 
437  hlen = md_get_size( md_info );
438 
439  if( olen < ilen + 2 * hlen + 2 || f_rng == NULL )
441 
442  memset( output, 0, olen );
443 
444  *p++ = 0;
445 
446  // Generate a random octet string seed
447  //
448  if( ( ret = f_rng( p_rng, p, hlen ) ) != 0 )
449  return( POLARSSL_ERR_RSA_RNG_FAILED + ret );
450 
451  p += hlen;
452 
453  // Construct DB
454  //
455  md( md_info, p, 0, p );
456  p += hlen;
457  p += olen - 2 * hlen - 2 - ilen;
458  *p++ = 1;
459  memcpy( p, input, ilen );
460 
461  md_init_ctx( &md_ctx, md_info );
462 
463  // maskedDB: Apply dbMask to DB
464  //
465  mgf_mask( output + hlen + 1, olen - hlen - 1, output + 1, hlen,
466  &md_ctx );
467 
468  // maskedSeed: Apply seedMask to seed
469  //
470  mgf_mask( output + 1, hlen, output + hlen + 1, olen - hlen - 1,
471  &md_ctx );
472 
473  md_free_ctx( &md_ctx );
474  break;
475 #endif
476 
477  default:
478 
480  }
481 
482  return( ( mode == RSA_PUBLIC )
483  ? rsa_public( ctx, output, output )
484  : rsa_private( ctx, output, output ) );
485 }
486 
487 /*
488  * Do an RSA operation, then remove the message padding
489  */
491  int mode, size_t *olen,
492  const unsigned char *input,
493  unsigned char *output,
494  size_t output_max_len)
495 {
496  int ret;
497  size_t ilen;
498  unsigned char *p;
499  unsigned char bt;
500  unsigned char buf[POLARSSL_MPI_MAX_SIZE];
501 #if defined(POLARSSL_PKCS1_V21)
502  unsigned char lhash[POLARSSL_MD_MAX_SIZE];
503  unsigned int hlen;
504  const md_info_t *md_info;
505  md_context_t md_ctx;
506 #endif
507 
508  ilen = ctx->len;
509 
510  if( ilen < 16 || ilen > sizeof( buf ) )
512 
513  ret = ( mode == RSA_PUBLIC )
514  ? rsa_public( ctx, input, buf )
515  : rsa_private( ctx, input, buf );
516 
517  if( ret != 0 )
518  return( ret );
519 
520  p = buf;
521 
522  switch( ctx->padding )
523  {
524  case RSA_PKCS_V15:
525 
526  if( *p++ != 0 )
528 
529  bt = *p++;
530  if( ( bt != RSA_CRYPT && mode == RSA_PRIVATE ) ||
531  ( bt != RSA_SIGN && mode == RSA_PUBLIC ) )
532  {
534  }
535 
536  if( bt == RSA_CRYPT )
537  {
538  while( *p != 0 && p < buf + ilen - 1 )
539  p++;
540 
541  if( *p != 0 || p >= buf + ilen - 1 )
543 
544  p++;
545  }
546  else
547  {
548  while( *p == 0xFF && p < buf + ilen - 1 )
549  p++;
550 
551  if( *p != 0 || p >= buf + ilen - 1 )
553 
554  p++;
555  }
556 
557  break;
558 
559 #if defined(POLARSSL_PKCS1_V21)
560  case RSA_PKCS_V21:
561 
562  if( *p++ != 0 )
564 
565  md_info = md_info_from_type( ctx->hash_id );
566  if( md_info == NULL )
568 
569  hlen = md_get_size( md_info );
570 
571  md_init_ctx( &md_ctx, md_info );
572 
573  // Generate lHash
574  //
575  md( md_info, lhash, 0, lhash );
576 
577  // seed: Apply seedMask to maskedSeed
578  //
579  mgf_mask( buf + 1, hlen, buf + hlen + 1, ilen - hlen - 1,
580  &md_ctx );
581 
582  // DB: Apply dbMask to maskedDB
583  //
584  mgf_mask( buf + hlen + 1, ilen - hlen - 1, buf + 1, hlen,
585  &md_ctx );
586 
587  p += hlen;
588  md_free_ctx( &md_ctx );
589 
590  // Check validity
591  //
592  if( memcmp( lhash, p, hlen ) != 0 )
594 
595  p += hlen;
596 
597  while( *p == 0 && p < buf + ilen )
598  p++;
599 
600  if( p == buf + ilen )
602 
603  if( *p++ != 0x01 )
605 
606  break;
607 #endif
608 
609  default:
610 
612  }
613 
614  if (ilen - (p - buf) > output_max_len)
616 
617  *olen = ilen - (p - buf);
618  memcpy( output, p, *olen );
619 
620  return( 0 );
621 }
622 
623 /*
624  * Do an RSA operation to sign the message digest
625  */
626 int rsa_pkcs1_sign( rsa_context *ctx,
627  int (*f_rng)(void *, unsigned char *, size_t),
628  void *p_rng,
629  int mode,
630  int hash_id,
631  unsigned int hashlen,
632  const unsigned char *hash,
633  unsigned char *sig )
634 {
635  size_t nb_pad, olen;
636  unsigned char *p = sig;
637 #if defined(POLARSSL_PKCS1_V21)
638  unsigned char salt[POLARSSL_MD_MAX_SIZE];
639  unsigned int slen, hlen, offset = 0;
640  int ret;
641  size_t msb;
642  const md_info_t *md_info;
643  md_context_t md_ctx;
644 #else
645  (void) f_rng;
646  (void) p_rng;
647 #endif
648 
649  olen = ctx->len;
650 
651  switch( ctx->padding )
652  {
653  case RSA_PKCS_V15:
654 
655  switch( hash_id )
656  {
657  case SIG_RSA_RAW:
658  nb_pad = olen - 3 - hashlen;
659  break;
660 
661  case SIG_RSA_MD2:
662  case SIG_RSA_MD4:
663  case SIG_RSA_MD5:
664  nb_pad = olen - 3 - 34;
665  break;
666 
667  case SIG_RSA_SHA1:
668  nb_pad = olen - 3 - 35;
669  break;
670 
671  case SIG_RSA_SHA224:
672  nb_pad = olen - 3 - 47;
673  break;
674 
675  case SIG_RSA_SHA256:
676  nb_pad = olen - 3 - 51;
677  break;
678 
679  case SIG_RSA_SHA384:
680  nb_pad = olen - 3 - 67;
681  break;
682 
683  case SIG_RSA_SHA512:
684  nb_pad = olen - 3 - 83;
685  break;
686 
687 
688  default:
690  }
691 
692  if( ( nb_pad < 8 ) || ( nb_pad > olen ) )
694 
695  *p++ = 0;
696  *p++ = RSA_SIGN;
697  memset( p, 0xFF, nb_pad );
698  p += nb_pad;
699  *p++ = 0;
700 
701  switch( hash_id )
702  {
703  case SIG_RSA_RAW:
704  memcpy( p, hash, hashlen );
705  break;
706 
707  case SIG_RSA_MD2:
708  memcpy( p, ASN1_HASH_MDX, 18 );
709  memcpy( p + 18, hash, 16 );
710  p[13] = 2; break;
711 
712  case SIG_RSA_MD4:
713  memcpy( p, ASN1_HASH_MDX, 18 );
714  memcpy( p + 18, hash, 16 );
715  p[13] = 4; break;
716 
717  case SIG_RSA_MD5:
718  memcpy( p, ASN1_HASH_MDX, 18 );
719  memcpy( p + 18, hash, 16 );
720  p[13] = 5; break;
721 
722  case SIG_RSA_SHA1:
723  memcpy( p, ASN1_HASH_SHA1, 15 );
724  memcpy( p + 15, hash, 20 );
725  break;
726 
727  case SIG_RSA_SHA224:
728  memcpy( p, ASN1_HASH_SHA2X, 19 );
729  memcpy( p + 19, hash, 28 );
730  p[1] += 28; p[14] = 4; p[18] += 28; break;
731 
732  case SIG_RSA_SHA256:
733  memcpy( p, ASN1_HASH_SHA2X, 19 );
734  memcpy( p + 19, hash, 32 );
735  p[1] += 32; p[14] = 1; p[18] += 32; break;
736 
737  case SIG_RSA_SHA384:
738  memcpy( p, ASN1_HASH_SHA2X, 19 );
739  memcpy( p + 19, hash, 48 );
740  p[1] += 48; p[14] = 2; p[18] += 48; break;
741 
742  case SIG_RSA_SHA512:
743  memcpy( p, ASN1_HASH_SHA2X, 19 );
744  memcpy( p + 19, hash, 64 );
745  p[1] += 64; p[14] = 3; p[18] += 64; break;
746 
747  default:
749  }
750 
751  break;
752 
753 #if defined(POLARSSL_PKCS1_V21)
754  case RSA_PKCS_V21:
755 
756  if( f_rng == NULL )
758 
759  switch( hash_id )
760  {
761  case SIG_RSA_MD2:
762  case SIG_RSA_MD4:
763  case SIG_RSA_MD5:
764  hashlen = 16;
765  break;
766 
767  case SIG_RSA_SHA1:
768  hashlen = 20;
769  break;
770 
771  case SIG_RSA_SHA224:
772  hashlen = 28;
773  break;
774 
775  case SIG_RSA_SHA256:
776  hashlen = 32;
777  break;
778 
779  case SIG_RSA_SHA384:
780  hashlen = 48;
781  break;
782 
783  case SIG_RSA_SHA512:
784  hashlen = 64;
785  break;
786 
787  default:
789  }
790 
791  md_info = md_info_from_type( ctx->hash_id );
792  if( md_info == NULL )
794 
795  hlen = md_get_size( md_info );
796  slen = hlen;
797 
798  if( olen < hlen + slen + 2 )
800 
801  memset( sig, 0, olen );
802 
803  msb = mpi_msb( &ctx->N ) - 1;
804 
805  // Generate salt of length slen
806  //
807  if( ( ret = f_rng( p_rng, salt, slen ) ) != 0 )
808  return( POLARSSL_ERR_RSA_RNG_FAILED + ret );
809 
810  // Note: EMSA-PSS encoding is over the length of N - 1 bits
811  //
812  msb = mpi_msb( &ctx->N ) - 1;
813  p += olen - hlen * 2 - 2;
814  *p++ = 0x01;
815  memcpy( p, salt, slen );
816  p += slen;
817 
818  md_init_ctx( &md_ctx, md_info );
819 
820  // Generate H = Hash( M' )
821  //
822  md_starts( &md_ctx );
823  md_update( &md_ctx, p, 8 );
824  md_update( &md_ctx, hash, hashlen );
825  md_update( &md_ctx, salt, slen );
826  md_finish( &md_ctx, p );
827 
828  // Compensate for boundary condition when applying mask
829  //
830  if( msb % 8 == 0 )
831  offset = 1;
832 
833  // maskedDB: Apply dbMask to DB
834  //
835  mgf_mask( sig + offset, olen - hlen - 1 - offset, p, hlen, &md_ctx );
836 
837  md_free_ctx( &md_ctx );
838 
839  msb = mpi_msb( &ctx->N ) - 1;
840  sig[0] &= 0xFF >> ( olen * 8 - msb );
841 
842  p += hlen;
843  *p++ = 0xBC;
844  break;
845 #endif
846 
847  default:
848 
850  }
851 
852  return( ( mode == RSA_PUBLIC )
853  ? rsa_public( ctx, sig, sig )
854  : rsa_private( ctx, sig, sig ) );
855 }
856 
857 /*
858  * Do an RSA operation and check the message digest
859  */
860 int rsa_pkcs1_verify( rsa_context *ctx,
861  int mode,
862  int hash_id,
863  unsigned int hashlen,
864  const unsigned char *hash,
865  unsigned char *sig )
866 {
867  int ret;
868  size_t len, siglen;
869  unsigned char *p, c;
870  unsigned char buf[POLARSSL_MPI_MAX_SIZE];
871 #if defined(POLARSSL_PKCS1_V21)
872  unsigned char result[POLARSSL_MD_MAX_SIZE];
873  unsigned char zeros[8];
874  unsigned int hlen;
875  size_t slen, msb;
876  const md_info_t *md_info;
877  md_context_t md_ctx;
878 #endif
879  siglen = ctx->len;
880 
881  if( siglen < 16 || siglen > sizeof( buf ) )
883 
884  ret = ( mode == RSA_PUBLIC )
885  ? rsa_public( ctx, sig, buf )
886  : rsa_private( ctx, sig, buf );
887 
888  if( ret != 0 )
889  return( ret );
890 
891  p = buf;
892 
893  switch( ctx->padding )
894  {
895  case RSA_PKCS_V15:
896 
897  if( *p++ != 0 || *p++ != RSA_SIGN )
899 
900  while( *p != 0 )
901  {
902  if( p >= buf + siglen - 1 || *p != 0xFF )
904  p++;
905  }
906  p++;
907 
908  len = siglen - ( p - buf );
909 
910  if( len == 33 && hash_id == SIG_RSA_SHA1 )
911  {
912  if( memcmp( p, ASN1_HASH_SHA1_ALT, 13 ) == 0 &&
913  memcmp( p + 13, hash, 20 ) == 0 )
914  return( 0 );
915  else
917  }
918  if( len == 34 )
919  {
920  c = p[13];
921  p[13] = 0;
922 
923  if( memcmp( p, ASN1_HASH_MDX, 18 ) != 0 )
925 
926  if( ( c == 2 && hash_id == SIG_RSA_MD2 ) ||
927  ( c == 4 && hash_id == SIG_RSA_MD4 ) ||
928  ( c == 5 && hash_id == SIG_RSA_MD5 ) )
929  {
930  if( memcmp( p + 18, hash, 16 ) == 0 )
931  return( 0 );
932  else
934  }
935  }
936 
937  if( len == 35 && hash_id == SIG_RSA_SHA1 )
938  {
939  if( memcmp( p, ASN1_HASH_SHA1, 15 ) == 0 &&
940  memcmp( p + 15, hash, 20 ) == 0 )
941  return( 0 );
942  else
944  }
945  if( ( len == 19 + 28 && p[14] == 4 && hash_id == SIG_RSA_SHA224 ) ||
946  ( len == 19 + 32 && p[14] == 1 && hash_id == SIG_RSA_SHA256 ) ||
947  ( len == 19 + 48 && p[14] == 2 && hash_id == SIG_RSA_SHA384 ) ||
948  ( len == 19 + 64 && p[14] == 3 && hash_id == SIG_RSA_SHA512 ) )
949  {
950  c = p[1] - 17;
951  p[1] = 17;
952  p[14] = 0;
953 
954  if( p[18] == c &&
955  memcmp( p, ASN1_HASH_SHA2X, 18 ) == 0 &&
956  memcmp( p + 19, hash, c ) == 0 )
957  return( 0 );
958  else
960  }
961 
962  if( len == hashlen && hash_id == SIG_RSA_RAW )
963  {
964  if( memcmp( p, hash, hashlen ) == 0 )
965  return( 0 );
966  else
968  }
969 
970  break;
971 
972 #if defined(POLARSSL_PKCS1_V21)
973  case RSA_PKCS_V21:
974 
975  if( buf[siglen - 1] != 0xBC )
977 
978  switch( hash_id )
979  {
980  case SIG_RSA_MD2:
981  case SIG_RSA_MD4:
982  case SIG_RSA_MD5:
983  hashlen = 16;
984  break;
985 
986  case SIG_RSA_SHA1:
987  hashlen = 20;
988  break;
989 
990  case SIG_RSA_SHA224:
991  hashlen = 28;
992  break;
993 
994  case SIG_RSA_SHA256:
995  hashlen = 32;
996  break;
997 
998  case SIG_RSA_SHA384:
999  hashlen = 48;
1000  break;
1001 
1002  case SIG_RSA_SHA512:
1003  hashlen = 64;
1004  break;
1005 
1006  default:
1008  }
1009 
1010  md_info = md_info_from_type( ctx->hash_id );
1011  if( md_info == NULL )
1013 
1014  hlen = md_get_size( md_info );
1015  slen = siglen - hlen - 1;
1016 
1017  memset( zeros, 0, 8 );
1018 
1019  // Note: EMSA-PSS verification is over the length of N - 1 bits
1020  //
1021  msb = mpi_msb( &ctx->N ) - 1;
1022 
1023  // Compensate for boundary condition when applying mask
1024  //
1025  if( msb % 8 == 0 )
1026  {
1027  p++;
1028  siglen -= 1;
1029  }
1030  if( buf[0] >> ( 8 - siglen * 8 + msb ) )
1032 
1033  md_init_ctx( &md_ctx, md_info );
1034 
1035  mgf_mask( p, siglen - hlen - 1, p + siglen - hlen - 1, hlen, &md_ctx );
1036 
1037  buf[0] &= 0xFF >> ( siglen * 8 - msb );
1038 
1039  while( *p == 0 && p < buf + siglen )
1040  p++;
1041 
1042  if( p == buf + siglen ||
1043  *p++ != 0x01 )
1044  {
1045  md_free_ctx( &md_ctx );
1047  }
1048 
1049  slen -= p - buf;
1050 
1051  // Generate H = Hash( M' )
1052  //
1053  md_starts( &md_ctx );
1054  md_update( &md_ctx, zeros, 8 );
1055  md_update( &md_ctx, hash, hashlen );
1056  md_update( &md_ctx, p, slen );
1057  md_finish( &md_ctx, result );
1058 
1059  md_free_ctx( &md_ctx );
1060 
1061  if( memcmp( p + slen, result, hlen ) == 0 )
1062  return( 0 );
1063  else
1065 #endif
1066 
1067  default:
1068 
1070  }
1071 
1073 }
1074 
1075 /*
1076  * Free the components of an RSA key
1077  */
1078 void rsa_free( rsa_context *ctx )
1079 {
1080  mpi_free( &ctx->RQ ); mpi_free( &ctx->RP ); mpi_free( &ctx->RN );
1081  mpi_free( &ctx->QP ); mpi_free( &ctx->DQ ); mpi_free( &ctx->DP );
1082  mpi_free( &ctx->Q ); mpi_free( &ctx->P ); mpi_free( &ctx->D );
1083  mpi_free( &ctx->E ); mpi_free( &ctx->N );
1084 }
1085 
1086 #if defined(POLARSSL_SELF_TEST)
1087 
1088 #include "polarssl/sha1.h"
1089 
1090 /*
1091  * Example RSA-1024 keypair, for test purposes
1092  */
1093 #define KEY_LEN 128
1094 
1095 #define RSA_N "9292758453063D803DD603D5E777D788" \
1096  "8ED1D5BF35786190FA2F23EBC0848AEA" \
1097  "DDA92CA6C3D80B32C4D109BE0F36D6AE" \
1098  "7130B9CED7ACDF54CFC7555AC14EEBAB" \
1099  "93A89813FBF3C4F8066D2D800F7C38A8" \
1100  "1AE31942917403FF4946B0A83D3D3E05" \
1101  "EE57C6F5F5606FB5D4BC6CD34EE0801A" \
1102  "5E94BB77B07507233A0BC7BAC8F90F79"
1103 
1104 #define RSA_E "10001"
1105 
1106 #define RSA_D "24BF6185468786FDD303083D25E64EFC" \
1107  "66CA472BC44D253102F8B4A9D3BFA750" \
1108  "91386C0077937FE33FA3252D28855837" \
1109  "AE1B484A8A9A45F7EE8C0C634F99E8CD" \
1110  "DF79C5CE07EE72C7F123142198164234" \
1111  "CABB724CF78B8173B9F880FC86322407" \
1112  "AF1FEDFDDE2BEB674CA15F3E81A1521E" \
1113  "071513A1E85B5DFA031F21ECAE91A34D"
1114 
1115 #define RSA_P "C36D0EB7FCD285223CFB5AABA5BDA3D8" \
1116  "2C01CAD19EA484A87EA4377637E75500" \
1117  "FCB2005C5C7DD6EC4AC023CDA285D796" \
1118  "C3D9E75E1EFC42488BB4F1D13AC30A57"
1119 
1120 #define RSA_Q "C000DF51A7C77AE8D7C7370C1FF55B69" \
1121  "E211C2B9E5DB1ED0BF61D0D9899620F4" \
1122  "910E4168387E3C30AA1E00C339A79508" \
1123  "8452DD96A9A5EA5D9DCA68DA636032AF"
1124 
1125 #define RSA_DP "C1ACF567564274FB07A0BBAD5D26E298" \
1126  "3C94D22288ACD763FD8E5600ED4A702D" \
1127  "F84198A5F06C2E72236AE490C93F07F8" \
1128  "3CC559CD27BC2D1CA488811730BB5725"
1129 
1130 #define RSA_DQ "4959CBF6F8FEF750AEE6977C155579C7" \
1131  "D8AAEA56749EA28623272E4F7D0592AF" \
1132  "7C1F1313CAC9471B5C523BFE592F517B" \
1133  "407A1BD76C164B93DA2D32A383E58357"
1134 
1135 #define RSA_QP "9AE7FBC99546432DF71896FC239EADAE" \
1136  "F38D18D2B2F0E2DD275AA977E2BF4411" \
1137  "F5A3B2A5D33605AEBBCCBA7FEB9F2D2F" \
1138  "A74206CEC169D74BF5A8C50D6F48EA08"
1139 
1140 #define PT_LEN 24
1141 #define RSA_PT "\xAA\xBB\xCC\x03\x02\x01\x00\xFF\xFF\xFF\xFF\xFF" \
1142  "\x11\x22\x33\x0A\x0B\x0C\xCC\xDD\xDD\xDD\xDD\xDD"
1143 
1144 static int myrand( void *rng_state, unsigned char *output, size_t len )
1145 {
1146  size_t i;
1147 
1148  if( rng_state != NULL )
1149  rng_state = NULL;
1150 
1151  for( i = 0; i < len; ++i )
1152  output[i] = rand();
1153 
1154  return( 0 );
1155 }
1156 
1157 /*
1158  * Checkup routine
1159  */
1160 int rsa_self_test( int verbose )
1161 {
1162  size_t len;
1163  rsa_context rsa;
1164  unsigned char rsa_plaintext[PT_LEN];
1165  unsigned char rsa_decrypted[PT_LEN];
1166  unsigned char rsa_ciphertext[KEY_LEN];
1167 #if defined(POLARSSL_SHA1_C)
1168  unsigned char sha1sum[20];
1169 #endif
1170 
1171  rsa_init( &rsa, RSA_PKCS_V15, 0 );
1172 
1173  rsa.len = KEY_LEN;
1174  mpi_read_string( &rsa.N , 16, RSA_N );
1175  mpi_read_string( &rsa.E , 16, RSA_E );
1176  mpi_read_string( &rsa.D , 16, RSA_D );
1177  mpi_read_string( &rsa.P , 16, RSA_P );
1178  mpi_read_string( &rsa.Q , 16, RSA_Q );
1179  mpi_read_string( &rsa.DP, 16, RSA_DP );
1180  mpi_read_string( &rsa.DQ, 16, RSA_DQ );
1181  mpi_read_string( &rsa.QP, 16, RSA_QP );
1182 
1183  if( verbose != 0 )
1184  printf( " RSA key validation: " );
1185 
1186  if( rsa_check_pubkey( &rsa ) != 0 ||
1187  rsa_check_privkey( &rsa ) != 0 )
1188  {
1189  if( verbose != 0 )
1190  printf( "failed\n" );
1191 
1192  return( 1 );
1193  }
1194 
1195  if( verbose != 0 )
1196  printf( "passed\n PKCS#1 encryption : " );
1197 
1198  memcpy( rsa_plaintext, RSA_PT, PT_LEN );
1199 
1200  if( rsa_pkcs1_encrypt( &rsa, &myrand, NULL, RSA_PUBLIC, PT_LEN,
1201  rsa_plaintext, rsa_ciphertext ) != 0 )
1202  {
1203  if( verbose != 0 )
1204  printf( "failed\n" );
1205 
1206  return( 1 );
1207  }
1208 
1209  if( verbose != 0 )
1210  printf( "passed\n PKCS#1 decryption : " );
1211 
1212  if( rsa_pkcs1_decrypt( &rsa, RSA_PRIVATE, &len,
1213  rsa_ciphertext, rsa_decrypted,
1214  sizeof(rsa_decrypted) ) != 0 )
1215  {
1216  if( verbose != 0 )
1217  printf( "failed\n" );
1218 
1219  return( 1 );
1220  }
1221 
1222  if( memcmp( rsa_decrypted, rsa_plaintext, len ) != 0 )
1223  {
1224  if( verbose != 0 )
1225  printf( "failed\n" );
1226 
1227  return( 1 );
1228  }
1229 
1230 #if defined(POLARSSL_SHA1_C)
1231  if( verbose != 0 )
1232  printf( "passed\n PKCS#1 data sign : " );
1233 
1234  sha1( rsa_plaintext, PT_LEN, sha1sum );
1235 
1236  if( rsa_pkcs1_sign( &rsa, NULL, NULL, RSA_PRIVATE, SIG_RSA_SHA1, 20,
1237  sha1sum, rsa_ciphertext ) != 0 )
1238  {
1239  if( verbose != 0 )
1240  printf( "failed\n" );
1241 
1242  return( 1 );
1243  }
1244 
1245  if( verbose != 0 )
1246  printf( "passed\n PKCS#1 sig. verify: " );
1247 
1248  if( rsa_pkcs1_verify( &rsa, RSA_PUBLIC, SIG_RSA_SHA1, 20,
1249  sha1sum, rsa_ciphertext ) != 0 )
1250  {
1251  if( verbose != 0 )
1252  printf( "failed\n" );
1253 
1254  return( 1 );
1255  }
1256 
1257  if( verbose != 0 )
1258  printf( "passed\n\n" );
1259 #endif /* POLARSSL_SHA1_C */
1260 
1261  rsa_free( &rsa );
1262 
1263  return( 0 );
1264 }
1265 
1266 #endif
1267 
1268 #endif