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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis |
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2 * |
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3 * LibTomCrypt is a library that provides various cryptographic |
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4 * algorithms in a highly modular and flexible manner. |
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5 * |
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6 * The library is free for all purposes without any express |
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7 * guarantee it works. |
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8 * |
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9 * Tom St Denis, [email protected], http://libtomcrypt.org |
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10 */ |
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11 |
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12 #include "mycrypt.h" |
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13 |
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14 #ifdef MRSA |
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15 |
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16 /* decrypt then PKCS #1 v1.5 depad */ |
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17 int rsa_v15_decrypt_key(const unsigned char *in, unsigned long inlen, |
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18 unsigned char *outkey, unsigned long keylen, |
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19 prng_state *prng, int prng_idx, |
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20 int *res, rsa_key *key) |
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21 { |
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22 unsigned long modulus_bitlen, modulus_bytelen, x; |
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23 int err; |
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24 unsigned char *tmp; |
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25 |
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26 _ARGCHK(outkey != NULL); |
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27 _ARGCHK(key != NULL); |
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28 _ARGCHK(res != NULL); |
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29 |
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30 /* default to invalid */ |
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31 *res = 0; |
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32 |
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33 /* valid prng ? */ |
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34 if ((err = prng_is_valid(prng_idx)) != CRYPT_OK) { |
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35 return err; |
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36 } |
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37 |
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38 /* get modulus len in bits */ |
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39 modulus_bitlen = mp_count_bits(&(key->N)); |
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40 |
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41 /* outlen must be at least the size of the modulus */ |
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42 modulus_bytelen = mp_unsigned_bin_size(&(key->N)); |
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43 if (modulus_bytelen != inlen) { |
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44 return CRYPT_INVALID_PACKET; |
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45 } |
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46 |
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47 /* allocate ram */ |
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48 tmp = XMALLOC(inlen); |
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49 if (tmp == NULL) { |
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50 return CRYPT_MEM; |
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51 } |
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52 |
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53 /* rsa decode the packet */ |
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54 x = inlen; |
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55 if ((err = rsa_exptmod(in, inlen, tmp, &x, PK_PRIVATE, prng, prng_idx, key)) != CRYPT_OK) { |
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56 XFREE(tmp); |
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57 return err; |
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58 } |
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59 |
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60 /* PKCS #1 v1.5 depad */ |
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61 err = pkcs_1_v15_es_decode(tmp, x, modulus_bitlen, outkey, keylen, res); |
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62 XFREE(tmp); |
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63 return err; |
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64 } |
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65 |
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66 #endif |
