aboutsummaryrefslogtreecommitdiffstats
path: root/crypto/openssl/crypto/rsa/rsa_oaep.c
blob: b8e3edc000f2a82cb6eb16fbd257ae5d519d6bf9 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
/* crypto/rsa/rsa_oaep.c */
/* Written by Ulf Moeller. This software is distributed on an "AS IS"
   basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. */

/* EME-OAEP as defined in RFC 2437 (PKCS #1 v2.0) */

/* See Victor Shoup, "OAEP reconsidered," Nov. 2000,
 * <URL: http://www.shoup.net/papers/oaep.ps.Z>
 * for problems with the security proof for the
 * original OAEP scheme, which EME-OAEP is based on.
 * 
 * A new proof can be found in E. Fujisaki, T. Okamoto,
 * D. Pointcheval, J. Stern, "RSA-OEAP is Still Alive!",
 * Dec. 2000, <URL: http://eprint.iacr.org/2000/061/>.
 * The new proof has stronger requirements for the
 * underlying permutation: "partial-one-wayness" instead
 * of one-wayness.  For the RSA function, this is
 * an equivalent notion.
 */


#if !defined(OPENSSL_NO_SHA) && !defined(OPENSSL_NO_SHA1)
#include <stdio.h>
#include "cryptlib.h"
#include <openssl/bn.h>
#include <openssl/rsa.h>
#include <openssl/evp.h>
#include <openssl/rand.h>
#include <openssl/sha.h>

int MGF1(unsigned char *mask, long len,
	const unsigned char *seed, long seedlen);

int RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
	const unsigned char *from, int flen,
	const unsigned char *param, int plen)
	{
	int i, emlen = tlen - 1;
	unsigned char *db, *seed;
	unsigned char *dbmask, seedmask[SHA_DIGEST_LENGTH];

	if (flen > emlen - 2 * SHA_DIGEST_LENGTH - 1)
		{
		RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP,
		   RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
		return 0;
		}

	if (emlen < 2 * SHA_DIGEST_LENGTH + 1)
		{
		RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, RSA_R_KEY_SIZE_TOO_SMALL);
		return 0;
		}

	to[0] = 0;
	seed = to + 1;
	db = to + SHA_DIGEST_LENGTH + 1;

	EVP_Digest((void *)param, plen, db, NULL, EVP_sha1(), NULL);
	memset(db + SHA_DIGEST_LENGTH, 0,
		emlen - flen - 2 * SHA_DIGEST_LENGTH - 1);
	db[emlen - flen - SHA_DIGEST_LENGTH - 1] = 0x01;
	memcpy(db + emlen - flen - SHA_DIGEST_LENGTH, from, (unsigned int) flen);
	if (RAND_bytes(seed, SHA_DIGEST_LENGTH) <= 0)
		return 0;
#ifdef PKCS_TESTVECT
	memcpy(seed,
	   "\xaa\xfd\x12\xf6\x59\xca\xe6\x34\x89\xb4\x79\xe5\x07\x6d\xde\xc2\xf0\x6c\xb5\x8f",
	   20);
#endif

	dbmask = OPENSSL_malloc(emlen - SHA_DIGEST_LENGTH);
	if (dbmask == NULL)
		{
		RSAerr(RSA_F_RSA_PADDING_ADD_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
		return 0;
		}

	MGF1(dbmask, emlen - SHA_DIGEST_LENGTH, seed, SHA_DIGEST_LENGTH);
	for (i = 0; i < emlen - SHA_DIGEST_LENGTH; i++)
		db[i] ^= dbmask[i];

	MGF1(seedmask, SHA_DIGEST_LENGTH, db, emlen - SHA_DIGEST_LENGTH);
	for (i = 0; i < SHA_DIGEST_LENGTH; i++)
		seed[i] ^= seedmask[i];

	OPENSSL_free(dbmask);
	return 1;
	}

int RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
	const unsigned char *from, int flen, int num,
	const unsigned char *param, int plen)
	{
	int i, dblen, mlen = -1;
	const unsigned char *maskeddb;
	int lzero;
	unsigned char *db = NULL, seed[SHA_DIGEST_LENGTH], phash[SHA_DIGEST_LENGTH];
	unsigned char *padded_from;
	int bad = 0;

	if (--num < 2 * SHA_DIGEST_LENGTH + 1)
		/* 'num' is the length of the modulus, i.e. does not depend on the
		 * particular ciphertext. */
		goto decoding_err;

	lzero = num - flen;
	if (lzero < 0)
		{
		/* signalling this error immediately after detection might allow
		 * for side-channel attacks (e.g. timing if 'plen' is huge
		 * -- cf. James H. Manger, "A Chosen Ciphertext Attack on RSA Optimal
		 * Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001),
		 * so we use a 'bad' flag */
		bad = 1;
		lzero = 0;
		flen = num; /* don't overflow the memcpy to padded_from */
		}

	dblen = num - SHA_DIGEST_LENGTH;
	db = OPENSSL_malloc(dblen + num);
	if (db == NULL)
		{
		RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, ERR_R_MALLOC_FAILURE);
		return -1;
		}

	/* Always do this zero-padding copy (even when lzero == 0)
	 * to avoid leaking timing info about the value of lzero. */
	padded_from = db + dblen;
	memset(padded_from, 0, lzero);
	memcpy(padded_from + lzero, from, flen);

	maskeddb = padded_from + SHA_DIGEST_LENGTH;

	MGF1(seed, SHA_DIGEST_LENGTH, maskeddb, dblen);
	for (i = 0; i < SHA_DIGEST_LENGTH; i++)
		seed[i] ^= padded_from[i];
  
	MGF1(db, dblen, seed, SHA_DIGEST_LENGTH);
	for (i = 0; i < dblen; i++)
		db[i] ^= maskeddb[i];

	EVP_Digest((void *)param, plen, phash, NULL, EVP_sha1(), NULL);

	if (CRYPTO_memcmp(db, phash, SHA_DIGEST_LENGTH) != 0 || bad)
		goto decoding_err;
	else
		{
		for (i = SHA_DIGEST_LENGTH; i < dblen; i++)
			if (db[i] != 0x00)
				break;
		if (i == dblen || db[i] != 0x01)
			goto decoding_err;
		else
			{
			/* everything looks OK */

			mlen = dblen - ++i;
			if (tlen < mlen)
				{
				RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_DATA_TOO_LARGE);
				mlen = -1;
				}
			else
				memcpy(to, db + i, mlen);
			}
		}
	OPENSSL_free(db);
	return mlen;

decoding_err:
	/* to avoid chosen ciphertext attacks, the error message should not reveal
	 * which kind of decoding error happened */
	RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_OAEP, RSA_R_OAEP_DECODING_ERROR);
	if (db != NULL) OPENSSL_free(db);
	return -1;
	}

int PKCS1_MGF1(unsigned char *mask, long len,
	const unsigned char *seed, long seedlen, const EVP_MD *dgst)
	{
	long i, outlen = 0;
	unsigned char cnt[4];
	EVP_MD_CTX c;
	unsigned char md[EVP_MAX_MD_SIZE];
	int mdlen;

	EVP_MD_CTX_init(&c);
	mdlen = M_EVP_MD_size(dgst);
	for (i = 0; outlen < len; i++)
		{
		cnt[0] = (unsigned char)((i >> 24) & 255);
		cnt[1] = (unsigned char)((i >> 16) & 255);
		cnt[2] = (unsigned char)((i >> 8)) & 255;
		cnt[3] = (unsigned char)(i & 255);
		EVP_DigestInit_ex(&c,dgst, NULL);
		EVP_DigestUpdate(&c, seed, seedlen);
		EVP_DigestUpdate(&c, cnt, 4);
		if (outlen + mdlen <= len)
			{
			EVP_DigestFinal_ex(&c, mask + outlen, NULL);
			outlen += mdlen;
			}
		else
			{
			EVP_DigestFinal_ex(&c, md, NULL);
			memcpy(mask + outlen, md, len - outlen);
			outlen = len;
			}
		}
	EVP_MD_CTX_cleanup(&c);
	return 0;
	}

int MGF1(unsigned char *mask, long len, const unsigned char *seed, long seedlen)
	{
	return PKCS1_MGF1(mask, len, seed, seedlen, EVP_sha1());
	}
#endif