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comparison libtomcrypt/src/pk/pkcs1/pkcs_1_v1_5_encode.c @ 382:0cbe8f6dbf9e

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propagate from branch 'au.asn.ucc.matt.ltc.dropbear' (head 2af22fb4e878750b88f80f90d439b316d229796f) to branch 'au.asn.ucc.matt.dropbear' (head 02c413252c90e9de8e03d91e9939dde3029f5c0a)
author Matt Johnston <matt@ucc.asn.au>
date Thu, 11 Jan 2007 02:41:05 +0000
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children f849a5ca2efc
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379:b66a00272a90 382:0cbe8f6dbf9e
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, [email protected], http://libtomcrypt.com
10 */
11 #include "tomcrypt.h"
12
13 /*! \file pkcs_1_v1_5_encode.c
14 *
15 * PKCS #1 v1.5 Padding (Andreas Lange)
16 */
17
18 #ifdef PKCS_1
19
20 /*! \brief PKCS #1 v1.5 encode.
21 *
22 * \param msg The data to encode
23 * \param msglen The length of the data to encode (octets)
24 * \param block_type Block type to use in padding (\sa ltc_pkcs_1_v1_5_blocks)
25 * \param modulus_bitlen The bit length of the RSA modulus
26 * \param prng An active PRNG state (only for LTC_PKCS_1_EME)
27 * \param prng_idx The index of the PRNG desired (only for LTC_PKCS_1_EME)
28 * \param out [out] The destination for the encoded data
29 * \param outlen [in/out] The max size and resulting size of the encoded data
30 *
31 * \return CRYPT_OK if successful
32 */
33 int pkcs_1_v1_5_encode(const unsigned char *msg,
34 unsigned long msglen,
35 int block_type,
36 unsigned long modulus_bitlen,
37 prng_state *prng,
38 int prng_idx,
39 unsigned char *out,
40 unsigned long *outlen)
41 {
42 unsigned long modulus_len, ps_len, i;
43 unsigned char *ps;
44 int result;
45
46 /* valid block_type? */
47 if ((block_type != LTC_PKCS_1_EMSA) &&
48 (block_type != LTC_PKCS_1_EME)) {
49 return CRYPT_PK_INVALID_PADDING;
50 }
51
52 if (block_type == LTC_PKCS_1_EME) { /* encryption padding, we need a valid PRNG */
53 if ((result = prng_is_valid(prng_idx)) != CRYPT_OK) {
54 return result;
55 }
56 }
57
58 modulus_len = (modulus_bitlen >> 3) + (modulus_bitlen & 7 ? 1 : 0);
59
60 /* test message size */
61 if ((msglen + 11) > modulus_len) {
62 return CRYPT_PK_INVALID_SIZE;
63 }
64
65 if (*outlen < modulus_len) {
66 *outlen = modulus_len;
67 result = CRYPT_BUFFER_OVERFLOW;
68 goto bail;
69 }
70
71 /* generate an octets string PS */
72 ps = &out[2];
73 ps_len = modulus_len - msglen - 3;
74
75 if (block_type == LTC_PKCS_1_EME) {
76 /* now choose a random ps */
77 if (prng_descriptor[prng_idx].read(ps, ps_len, prng) != ps_len) {
78 result = CRYPT_ERROR_READPRNG;
79 goto bail;
80 }
81
82 /* transform zero bytes (if any) to non-zero random bytes */
83 for (i = 0; i < ps_len; i++) {
84 while (ps[i] == 0) {
85 if (prng_descriptor[prng_idx].read(&ps[i], 1, prng) != 1) {
86 result = CRYPT_ERROR_READPRNG;
87 goto bail;
88 }
89 }
90 }
91 } else {
92 XMEMSET(ps, 0xFF, ps_len);
93 }
94
95 /* create string of length modulus_len */
96 out[0] = 0x00;
97 out[1] = (unsigned char)block_type; /* block_type 1 or 2 */
98 out[2 + ps_len] = 0x00;
99 XMEMCPY(&out[2 + ps_len + 1], msg, msglen);
100 *outlen = modulus_len;
101
102 result = CRYPT_OK;
103 bail:
104 return result;
105 } /* pkcs_1_v1_5_encode */
106
107 #endif /* #ifdef PKCS_1 */
108
109 /* $Source: /cvs/libtom/libtomcrypt/src/pk/pkcs1/pkcs_1_v1_5_encode.c,v $ */
110 /* $Revision: 1.2 $ */
111 /* $Date: 2006/11/01 09:12:06 $ */