2 * The RSA public-key cryptosystem
4 * Copyright (C) 2006-2010, Brainspark B.V.
6 * This file is part of PolarSSL (http://www.polarssl.org)
7 * Lead Maintainer: Paul Bakker <polarssl_maintainer at polarssl.org>
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.
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.
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.
26 * RSA was designed by Ron Rivest, Adi Shamir and Len Adleman.
28 * http://theory.lcs.mit.edu/~rivest/rsapaper.pdf
29 * http://www.cacr.math.uwaterloo.ca/hac/about/chap8.pdf
32 /* $Cambridge: exim/src/src/pdkim/rsa.c,v 1.3 2009/12/07 13:05:07 tom Exp $ */
43 /* *************** begin copy from x509parse.c ********************/
45 * ASN.1 DER decoding routines
47 static int asn1_get_len( unsigned char **p,
48 const unsigned char *end,
51 if( ( end - *p ) < 1 )
52 return( POLARSSL_ERR_ASN1_OUT_OF_DATA );
54 if( ( **p & 0x80 ) == 0 )
61 if( ( end - *p ) < 2 )
62 return( POLARSSL_ERR_ASN1_OUT_OF_DATA );
69 if( ( end - *p ) < 3 )
70 return( POLARSSL_ERR_ASN1_OUT_OF_DATA );
72 *len = ( (*p)[1] << 8 ) | (*p)[2];
77 return( POLARSSL_ERR_ASN1_INVALID_LENGTH );
82 if( *len > (int) ( end - *p ) )
83 return( POLARSSL_ERR_ASN1_OUT_OF_DATA );
88 static int asn1_get_tag( unsigned char **p,
89 const unsigned char *end,
92 if( ( end - *p ) < 1 )
93 return( POLARSSL_ERR_ASN1_OUT_OF_DATA );
96 return( POLARSSL_ERR_ASN1_UNEXPECTED_TAG );
100 return( asn1_get_len( p, end, len ) );
103 static int asn1_get_int( unsigned char **p,
104 const unsigned char *end,
109 if( ( ret = asn1_get_tag( p, end, &len, ASN1_INTEGER ) ) != 0 )
112 if( len > (int) sizeof( int ) || ( **p & 0x80 ) != 0 )
113 return( POLARSSL_ERR_ASN1_INVALID_LENGTH );
119 *val = ( *val << 8 ) | **p;
126 static int asn1_get_mpi( unsigned char **p,
127 const unsigned char *end,
132 if( ( ret = asn1_get_tag( p, end, &len, ASN1_INTEGER ) ) != 0 )
135 ret = mpi_read_binary( X, *p, len );
141 /* *************** end copy from x509parse.c ********************/
147 * Initialize an RSA context
149 void rsa_init( rsa_context *ctx,
153 memset( ctx, 0, sizeof( rsa_context ) );
155 ctx->padding = padding;
156 ctx->hash_id = hash_id;
159 #if defined(POLARSSL_GENPRIME)
162 * Generate an RSA keypair
164 int rsa_gen_key( rsa_context *ctx,
165 int (*f_rng)(void *),
167 int nbits, int exponent )
172 if( f_rng == NULL || nbits < 128 || exponent < 3 )
173 return( POLARSSL_ERR_RSA_BAD_INPUT_DATA );
175 mpi_init( &P1, &Q1, &H, &G, NULL );
178 * find primes P and Q with Q < P so that:
179 * GCD( E, (P-1)*(Q-1) ) == 1
181 MPI_CHK( mpi_lset( &ctx->E, exponent ) );
185 MPI_CHK( mpi_gen_prime( &ctx->P, ( nbits + 1 ) >> 1, 0,
188 MPI_CHK( mpi_gen_prime( &ctx->Q, ( nbits + 1 ) >> 1, 0,
191 if( mpi_cmp_mpi( &ctx->P, &ctx->Q ) < 0 )
192 mpi_swap( &ctx->P, &ctx->Q );
194 if( mpi_cmp_mpi( &ctx->P, &ctx->Q ) == 0 )
197 MPI_CHK( mpi_mul_mpi( &ctx->N, &ctx->P, &ctx->Q ) );
198 if( mpi_msb( &ctx->N ) != nbits )
201 MPI_CHK( mpi_sub_int( &P1, &ctx->P, 1 ) );
202 MPI_CHK( mpi_sub_int( &Q1, &ctx->Q, 1 ) );
203 MPI_CHK( mpi_mul_mpi( &H, &P1, &Q1 ) );
204 MPI_CHK( mpi_gcd( &G, &ctx->E, &H ) );
206 while( mpi_cmp_int( &G, 1 ) != 0 );
209 * D = E^-1 mod ((P-1)*(Q-1))
214 MPI_CHK( mpi_inv_mod( &ctx->D , &ctx->E, &H ) );
215 MPI_CHK( mpi_mod_mpi( &ctx->DP, &ctx->D, &P1 ) );
216 MPI_CHK( mpi_mod_mpi( &ctx->DQ, &ctx->D, &Q1 ) );
217 MPI_CHK( mpi_inv_mod( &ctx->QP, &ctx->Q, &ctx->P ) );
219 ctx->len = ( mpi_msb( &ctx->N ) + 7 ) >> 3;
223 mpi_free( &G, &H, &Q1, &P1, NULL );
228 return( POLARSSL_ERR_RSA_KEY_GEN_FAILED | ret );
237 * Check a public RSA key
239 int rsa_check_pubkey( const rsa_context *ctx )
241 if( !ctx->N.p || !ctx->E.p )
242 return( POLARSSL_ERR_RSA_KEY_CHECK_FAILED );
244 if( ( ctx->N.p[0] & 1 ) == 0 ||
245 ( ctx->E.p[0] & 1 ) == 0 )
246 return( POLARSSL_ERR_RSA_KEY_CHECK_FAILED );
248 if( mpi_msb( &ctx->N ) < 128 ||
249 mpi_msb( &ctx->N ) > 4096 )
250 return( POLARSSL_ERR_RSA_KEY_CHECK_FAILED );
252 if( mpi_msb( &ctx->E ) < 2 ||
253 mpi_msb( &ctx->E ) > 64 )
254 return( POLARSSL_ERR_RSA_KEY_CHECK_FAILED );
260 * Check a private RSA key
262 int rsa_check_privkey( const rsa_context *ctx )
265 mpi PQ, DE, P1, Q1, H, I, G, G2, L1, L2;
267 if( ( ret = rsa_check_pubkey( ctx ) ) != 0 )
270 if( !ctx->P.p || !ctx->Q.p || !ctx->D.p )
271 return( POLARSSL_ERR_RSA_KEY_CHECK_FAILED );
273 mpi_init( &PQ, &DE, &P1, &Q1, &H, &I, &G, &G2, &L1, &L2, NULL );
275 MPI_CHK( mpi_mul_mpi( &PQ, &ctx->P, &ctx->Q ) );
276 MPI_CHK( mpi_mul_mpi( &DE, &ctx->D, &ctx->E ) );
277 MPI_CHK( mpi_sub_int( &P1, &ctx->P, 1 ) );
278 MPI_CHK( mpi_sub_int( &Q1, &ctx->Q, 1 ) );
279 MPI_CHK( mpi_mul_mpi( &H, &P1, &Q1 ) );
280 MPI_CHK( mpi_gcd( &G, &ctx->E, &H ) );
282 MPI_CHK( mpi_gcd( &G2, &P1, &Q1 ) );
283 MPI_CHK( mpi_div_mpi( &L1, &L2, &H, &G2 ) );
284 MPI_CHK( mpi_mod_mpi( &I, &DE, &L1 ) );
287 * Check for a valid PKCS1v2 private key
289 if( mpi_cmp_mpi( &PQ, &ctx->N ) == 0 &&
290 mpi_cmp_int( &L2, 0 ) == 0 &&
291 mpi_cmp_int( &I, 1 ) == 0 &&
292 mpi_cmp_int( &G, 1 ) == 0 )
294 mpi_free( &G, &I, &H, &Q1, &P1, &DE, &PQ, &G2, &L1, &L2, NULL );
301 mpi_free( &G, &I, &H, &Q1, &P1, &DE, &PQ, &G2, &L1, &L2, NULL );
302 return( POLARSSL_ERR_RSA_KEY_CHECK_FAILED | ret );
306 * Do an RSA public key operation
308 int rsa_public( rsa_context *ctx,
309 const unsigned char *input,
310 unsigned char *output )
315 mpi_init( &T, NULL );
317 MPI_CHK( mpi_read_binary( &T, input, ctx->len ) );
319 if( mpi_cmp_mpi( &T, &ctx->N ) >= 0 )
321 mpi_free( &T, NULL );
322 return( POLARSSL_ERR_RSA_BAD_INPUT_DATA );
326 MPI_CHK( mpi_exp_mod( &T, &T, &ctx->E, &ctx->N, &ctx->RN ) );
327 MPI_CHK( mpi_write_binary( &T, output, olen ) );
331 mpi_free( &T, NULL );
334 return( POLARSSL_ERR_RSA_PUBLIC_FAILED | ret );
340 * Do an RSA private key operation
342 int rsa_private( rsa_context *ctx,
343 const unsigned char *input,
344 unsigned char *output )
349 mpi_init( &T, &T1, &T2, NULL );
351 MPI_CHK( mpi_read_binary( &T, input, ctx->len ) );
353 if( mpi_cmp_mpi( &T, &ctx->N ) >= 0 )
355 mpi_free( &T, NULL );
356 return( POLARSSL_ERR_RSA_BAD_INPUT_DATA );
360 MPI_CHK( mpi_exp_mod( &T, &T, &ctx->D, &ctx->N, &ctx->RN ) );
363 * faster decryption using the CRT
365 * T1 = input ^ dP mod P
366 * T2 = input ^ dQ mod Q
368 MPI_CHK( mpi_exp_mod( &T1, &T, &ctx->DP, &ctx->P, &ctx->RP ) );
369 MPI_CHK( mpi_exp_mod( &T2, &T, &ctx->DQ, &ctx->Q, &ctx->RQ ) );
372 * T = (T1 - T2) * (Q^-1 mod P) mod P
374 MPI_CHK( mpi_sub_mpi( &T, &T1, &T2 ) );
375 MPI_CHK( mpi_mul_mpi( &T1, &T, &ctx->QP ) );
376 MPI_CHK( mpi_mod_mpi( &T, &T1, &ctx->P ) );
379 * output = T2 + T * Q
381 MPI_CHK( mpi_mul_mpi( &T1, &T, &ctx->Q ) );
382 MPI_CHK( mpi_add_mpi( &T, &T2, &T1 ) );
386 MPI_CHK( mpi_write_binary( &T, output, olen ) );
390 mpi_free( &T, &T1, &T2, NULL );
393 return( POLARSSL_ERR_RSA_PRIVATE_FAILED | ret );
399 * Add the message padding, then do an RSA operation
401 int rsa_pkcs1_encrypt( rsa_context *ctx,
402 int (*f_rng)(void *),
405 const unsigned char *input,
406 unsigned char *output )
409 unsigned char *p = output;
413 switch( ctx->padding )
417 if( ilen < 0 || olen < ilen + 11 || f_rng == NULL )
418 return( POLARSSL_ERR_RSA_BAD_INPUT_DATA );
420 nb_pad = olen - 3 - ilen;
425 while( nb_pad-- > 0 )
430 *p = (unsigned char) f_rng( p_rng );
431 } while( *p == 0 && --rng_dl );
433 // Check if RNG failed to generate data
436 return POLARSSL_ERR_RSA_RNG_FAILED;
441 memcpy( p, input, ilen );
446 return( POLARSSL_ERR_RSA_INVALID_PADDING );
449 return( ( mode == RSA_PUBLIC )
450 ? rsa_public( ctx, output, output )
451 : rsa_private( ctx, output, output ) );
455 * Do an RSA operation, then remove the message padding
457 int rsa_pkcs1_decrypt( rsa_context *ctx,
459 const unsigned char *input,
460 unsigned char *output,
465 unsigned char buf[1024];
469 if( ilen < 16 || ilen > (int) sizeof( buf ) )
470 return( POLARSSL_ERR_RSA_BAD_INPUT_DATA );
472 ret = ( mode == RSA_PUBLIC )
473 ? rsa_public( ctx, input, buf )
474 : rsa_private( ctx, input, buf );
481 switch( ctx->padding )
485 if( *p++ != 0 || *p++ != RSA_CRYPT )
486 return( POLARSSL_ERR_RSA_INVALID_PADDING );
490 if( p >= buf + ilen - 1 )
491 return( POLARSSL_ERR_RSA_INVALID_PADDING );
499 return( POLARSSL_ERR_RSA_INVALID_PADDING );
502 if (ilen - (int)(p - buf) > output_max_len)
503 return( POLARSSL_ERR_RSA_OUTPUT_TOO_LARGE );
505 *olen = ilen - (int)(p - buf);
506 memcpy( output, p, *olen );
512 * Do an RSA operation to sign the message digest
514 int rsa_pkcs1_sign( rsa_context *ctx,
518 const unsigned char *hash,
522 unsigned char *p = sig;
526 switch( ctx->padding )
533 nb_pad = olen - 3 - hashlen;
539 nb_pad = olen - 3 - 34;
543 nb_pad = olen - 3 - 35;
547 nb_pad = olen - 3 - 47;
551 nb_pad = olen - 3 - 51;
555 nb_pad = olen - 3 - 67;
559 nb_pad = olen - 3 - 83;
564 return( POLARSSL_ERR_RSA_BAD_INPUT_DATA );
568 return( POLARSSL_ERR_RSA_BAD_INPUT_DATA );
572 memset( p, 0xFF, nb_pad );
579 return( POLARSSL_ERR_RSA_INVALID_PADDING );
585 memcpy( p, hash, hashlen );
589 memcpy( p, ASN1_HASH_MDX, 18 );
590 memcpy( p + 18, hash, 16 );
594 memcpy( p, ASN1_HASH_MDX, 18 );
595 memcpy( p + 18, hash, 16 );
599 memcpy( p, ASN1_HASH_MDX, 18 );
600 memcpy( p + 18, hash, 16 );
604 memcpy( p, ASN1_HASH_SHA1, 15 );
605 memcpy( p + 15, hash, 20 );
609 memcpy( p, ASN1_HASH_SHA2X, 19 );
610 memcpy( p + 19, hash, 28 );
611 p[1] += 28; p[14] = 4; p[18] += 28; break;
614 memcpy( p, ASN1_HASH_SHA2X, 19 );
615 memcpy( p + 19, hash, 32 );
616 p[1] += 32; p[14] = 1; p[18] += 32; break;
619 memcpy( p, ASN1_HASH_SHA2X, 19 );
620 memcpy( p + 19, hash, 48 );
621 p[1] += 48; p[14] = 2; p[18] += 48; break;
624 memcpy( p, ASN1_HASH_SHA2X, 19 );
625 memcpy( p + 19, hash, 64 );
626 p[1] += 64; p[14] = 3; p[18] += 64; break;
629 return( POLARSSL_ERR_RSA_BAD_INPUT_DATA );
632 return( ( mode == RSA_PUBLIC )
633 ? rsa_public( ctx, sig, sig )
634 : rsa_private( ctx, sig, sig ) );
638 * Do an RSA operation and check the message digest
640 int rsa_pkcs1_verify( rsa_context *ctx,
644 const unsigned char *hash,
647 int ret, len, siglen;
649 unsigned char buf[1024];
653 if( siglen < 16 || siglen > (int) sizeof( buf ) )
654 return( POLARSSL_ERR_RSA_BAD_INPUT_DATA );
656 ret = ( mode == RSA_PUBLIC )
657 ? rsa_public( ctx, sig, buf )
658 : rsa_private( ctx, sig, buf );
665 switch( ctx->padding )
669 if( *p++ != 0 || *p++ != RSA_SIGN )
670 return( POLARSSL_ERR_RSA_INVALID_PADDING );
674 if( p >= buf + siglen - 1 || *p != 0xFF )
675 return( POLARSSL_ERR_RSA_INVALID_PADDING );
683 return( POLARSSL_ERR_RSA_INVALID_PADDING );
686 len = siglen - (int)( p - buf );
693 if( memcmp( p, ASN1_HASH_MDX, 18 ) != 0 )
694 return( POLARSSL_ERR_RSA_VERIFY_FAILED );
696 if( ( c == 2 && hash_id == SIG_RSA_MD2 ) ||
697 ( c == 4 && hash_id == SIG_RSA_MD4 ) ||
698 ( c == 5 && hash_id == SIG_RSA_MD5 ) )
700 if( memcmp( p + 18, hash, 16 ) == 0 )
703 return( POLARSSL_ERR_RSA_VERIFY_FAILED );
707 if( len == 35 && hash_id == SIG_RSA_SHA1 )
709 if( memcmp( p, ASN1_HASH_SHA1, 15 ) == 0 &&
710 memcmp( p + 15, hash, 20 ) == 0 )
713 return( POLARSSL_ERR_RSA_VERIFY_FAILED );
715 if( ( len == 19 + 28 && p[14] == 4 && hash_id == SIG_RSA_SHA224 ) ||
716 ( len == 19 + 32 && p[14] == 1 && hash_id == SIG_RSA_SHA256 ) ||
717 ( len == 19 + 48 && p[14] == 2 && hash_id == SIG_RSA_SHA384 ) ||
718 ( len == 19 + 64 && p[14] == 3 && hash_id == SIG_RSA_SHA512 ) )
725 memcmp( p, ASN1_HASH_SHA2X, 18 ) == 0 &&
726 memcmp( p + 19, hash, c ) == 0 )
729 return( POLARSSL_ERR_RSA_VERIFY_FAILED );
732 if( len == hashlen && hash_id == SIG_RSA_RAW )
734 if( memcmp( p, hash, hashlen ) == 0 )
737 return( POLARSSL_ERR_RSA_VERIFY_FAILED );
740 return( POLARSSL_ERR_RSA_INVALID_PADDING );
744 * Free the components of an RSA key
746 void rsa_free( rsa_context *ctx )
748 mpi_free( &ctx->RQ, &ctx->RP, &ctx->RN,
749 &ctx->QP, &ctx->DQ, &ctx->DP,
750 &ctx->Q, &ctx->P, &ctx->D,
751 &ctx->E, &ctx->N, NULL );
755 /* PDKIM code (not copied from polarssl) */
757 * Parse a public RSA key
759 OpenSSL RSA public key ASN1 container
760 0:d=0 hl=3 l= 159 cons: SEQUENCE
761 3:d=1 hl=2 l= 13 cons: SEQUENCE
762 5:d=2 hl=2 l= 9 prim: OBJECT:rsaEncryption
763 16:d=2 hl=2 l= 0 prim: NULL
764 18:d=1 hl=3 l= 141 prim: BIT STRING:RSAPublicKey (below)
766 RSAPublicKey ASN1 container
767 0:d=0 hl=3 l= 137 cons: SEQUENCE
768 3:d=1 hl=3 l= 129 prim: INTEGER:Public modulus
769 135:d=1 hl=2 l= 3 prim: INTEGER:Public exponent
772 int rsa_parse_public_key( rsa_context *rsa, unsigned char *buf, int buflen )
774 unsigned char *p, *end;
780 if( ( ret = asn1_get_tag( &p, end, &len,
781 ASN1_CONSTRUCTED | ASN1_SEQUENCE ) ) != 0 ) {
782 return( POLARSSL_ERR_X509_KEY_INVALID_FORMAT | ret );
785 if( ( ret = asn1_get_tag( &p, end, &len,
786 ASN1_CONSTRUCTED | ASN1_SEQUENCE ) ) == 0 ) {
787 /* Skip over embedded rsaEncryption Object */
790 /* The RSAPublicKey ASN1 container is wrapped in a BIT STRING */
791 if( ( ret = asn1_get_tag( &p, end, &len,
792 ASN1_BIT_STRING ) ) != 0 ) {
793 return( POLARSSL_ERR_X509_KEY_INVALID_FORMAT | ret );
796 /* Limit range to that BIT STRING */
800 if( ( ret = asn1_get_tag( &p, end, &len,
801 ASN1_CONSTRUCTED | ASN1_SEQUENCE ) ) != 0 ) {
802 return( POLARSSL_ERR_X509_KEY_INVALID_FORMAT | ret );
806 if ( ( ( ret = asn1_get_mpi( &p, end, &(rsa->N) ) ) == 0 ) &&
807 ( ( ret = asn1_get_mpi( &p, end, &(rsa->E) ) ) == 0 ) ) {
808 rsa->len = mpi_size( &rsa->N );
812 return( POLARSSL_ERR_X509_KEY_INVALID_FORMAT | ret );
816 * Parse a private RSA key
818 int rsa_parse_key( rsa_context *rsa, unsigned char *buf, int buflen,
819 unsigned char *pwd, int pwdlen )
822 unsigned char *s1, *s2;
823 unsigned char *p, *end;
825 s1 = (unsigned char *) strstr( (char *) buf,
826 "-----BEGIN RSA PRIVATE KEY-----" );
830 s2 = (unsigned char *) strstr( (char *) buf,
831 "-----END RSA PRIVATE KEY-----" );
833 if( s2 == NULL || s2 <= s1 )
834 return( POLARSSL_ERR_X509_KEY_INVALID_PEM );
837 if( *s1 == '\r' ) s1++;
838 if( *s1 == '\n' ) s1++;
839 else return( POLARSSL_ERR_X509_KEY_INVALID_PEM );
843 if( memcmp( s1, "Proc-Type: 4,ENCRYPTED", 22 ) == 0 )
845 return( POLARSSL_ERR_X509_FEATURE_UNAVAILABLE );
849 ret = base64_decode( NULL, &len, s1, s2 - s1 );
851 if( ret == POLARSSL_ERR_BASE64_INVALID_CHARACTER )
852 return( ret | POLARSSL_ERR_X509_KEY_INVALID_PEM );
854 if( ( buf = (unsigned char *) malloc( len ) ) == NULL )
857 if( ( ret = base64_decode( buf, &len, s1, s2 - s1 ) ) != 0 )
860 return( ret | POLARSSL_ERR_X509_KEY_INVALID_PEM );
867 return( POLARSSL_ERR_X509_FEATURE_UNAVAILABLE );
871 memset( rsa, 0, sizeof( rsa_context ) );
877 * RSAPrivateKey ::= SEQUENCE {
879 * modulus INTEGER, -- n
880 * publicExponent INTEGER, -- e
881 * privateExponent INTEGER, -- d
882 * prime1 INTEGER, -- p
883 * prime2 INTEGER, -- q
884 * exponent1 INTEGER, -- d mod (p-1)
885 * exponent2 INTEGER, -- d mod (q-1)
886 * coefficient INTEGER, -- (inverse of q) mod p
887 * otherPrimeInfos OtherPrimeInfos OPTIONAL
890 if( ( ret = asn1_get_tag( &p, end, &len,
891 ASN1_CONSTRUCTED | ASN1_SEQUENCE ) ) != 0 )
897 return( POLARSSL_ERR_X509_KEY_INVALID_FORMAT | ret );
902 if( ( ret = asn1_get_int( &p, end, &rsa->ver ) ) != 0 )
908 return( POLARSSL_ERR_X509_KEY_INVALID_FORMAT | ret );
917 return( ret | POLARSSL_ERR_X509_KEY_INVALID_VERSION );
920 if( ( ret = asn1_get_mpi( &p, end, &rsa->N ) ) != 0 ||
921 ( ret = asn1_get_mpi( &p, end, &rsa->E ) ) != 0 ||
922 ( ret = asn1_get_mpi( &p, end, &rsa->D ) ) != 0 ||
923 ( ret = asn1_get_mpi( &p, end, &rsa->P ) ) != 0 ||
924 ( ret = asn1_get_mpi( &p, end, &rsa->Q ) ) != 0 ||
925 ( ret = asn1_get_mpi( &p, end, &rsa->DP ) ) != 0 ||
926 ( ret = asn1_get_mpi( &p, end, &rsa->DQ ) ) != 0 ||
927 ( ret = asn1_get_mpi( &p, end, &rsa->QP ) ) != 0 )
933 return( ret | POLARSSL_ERR_X509_KEY_INVALID_FORMAT );
936 rsa->len = mpi_size( &rsa->N );
944 return( POLARSSL_ERR_X509_KEY_INVALID_FORMAT |
945 POLARSSL_ERR_ASN1_LENGTH_MISMATCH );
948 if( ( ret = rsa_check_privkey( rsa ) ) != 0 )