1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis 2 * 3 * LibTomCrypt is a library that provides various cryptographic 4 * algorithms in a highly modular and flexible manner. 5 * 6 * The library is free for all purposes without any express 7 * guarantee it works. 8 * 9 * Tom St Denis, tomstdenis (at) gmail.com, http://libtomcrypt.com 10 */ 11 #include "tomcrypt.h" 12 13 /** 14 @file rsa_decrypt_key.c 15 RSA PKCS #1 Decryption, Tom St Denis and Andreas Lange 16 */ 17 18 #ifdef MRSA 19 20 /** 21 PKCS #1 decrypt then v1.5 or OAEP depad 22 @param in The ciphertext 23 @param inlen The length of the ciphertext (octets) 24 @param out [out] The plaintext 25 @param outlen [in/out] The max size and resulting size of the plaintext (octets) 26 @param lparam The system "lparam" value 27 @param lparamlen The length of the lparam value (octets) 28 @param hash_idx The index of the hash desired 29 @param padding Type of padding (LTC_PKCS_1_OAEP or LTC_PKCS_1_V1_5) 30 @param stat [out] Result of the decryption, 1==valid, 0==invalid 31 @param key The corresponding private RSA key 32 @return CRYPT_OK if succcessul (even if invalid) 33 */ 34 int rsa_decrypt_key_ex(const unsigned char *in, unsigned long inlen, 35 unsigned char *out, unsigned long *outlen, 36 const unsigned char *lparam, unsigned long lparamlen, 37 int hash_idx, int padding, 38 int *stat, rsa_key *key) 39 { 40 unsigned long modulus_bitlen, modulus_bytelen, x; 41 int err; 42 unsigned char *tmp; 43 44 LTC_ARGCHK(out != NULL); 45 LTC_ARGCHK(outlen != NULL); 46 LTC_ARGCHK(key != NULL); 47 LTC_ARGCHK(stat != NULL); 48 49 /* default to invalid */ 50 *stat = 0; 51 52 /* valid padding? */ 53 54 if ((padding != LTC_PKCS_1_V1_5) && 55 (padding != LTC_PKCS_1_OAEP)) { 56 return CRYPT_PK_INVALID_PADDING; 57 } 58 59 if (padding == LTC_PKCS_1_OAEP) { 60 /* valid hash ? */ 61 if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) { 62 return err; 63 } 64 } 65 66 /* get modulus len in bits */ 67 modulus_bitlen = mp_count_bits( (key->N)); 68 69 /* outlen must be at least the size of the modulus */ 70 modulus_bytelen = mp_unsigned_bin_size( (key->N)); 71 if (modulus_bytelen != inlen) { 72 return CRYPT_INVALID_PACKET; 73 } 74 75 /* allocate ram */ 76 tmp = XMALLOC(inlen); 77 if (tmp == NULL) { 78 return CRYPT_MEM; 79 } 80 81 /* rsa decode the packet */ 82 x = inlen; 83 if ((err = ltc_mp.rsa_me(in, inlen, tmp, &x, PK_PRIVATE, key)) != CRYPT_OK) { 84 XFREE(tmp); 85 return err; 86 } 87 88 if (padding == LTC_PKCS_1_OAEP) { 89 /* now OAEP decode the packet */ 90 err = pkcs_1_oaep_decode(tmp, x, lparam, lparamlen, modulus_bitlen, hash_idx, 91 out, outlen, stat); 92 } else { 93 /* now PKCS #1 v1.5 depad the packet */ 94 err = pkcs_1_v1_5_decode(tmp, x, LTC_PKCS_1_EME, modulus_bitlen, out, outlen, stat); 95 } 96 97 XFREE(tmp); 98 return err; 99 } 100 101 #endif /* MRSA */ 102 103 /* $Source: /cvs/libtom/libtomcrypt/src/pk/rsa/rsa_decrypt_key.c,v $ */ 104 /* $Revision: 1.8 $ */ 105 /* $Date: 2006/11/01 09:18:22 $ */ 106
