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GCC Code Coverage Report

Directory:	./		Exec	Total	Coverage
File:	lib/libcrypto/rsa/rsa_oaep.c	Lines:	82	98	83.7 %
Date:	2017-11-07	Branches:	39	60	65.0 %


/* $OpenBSD: rsa_oaep.c,v 1.26 2017/01/29 17:49:23 beck Exp $ */
/* 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.
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include <openssl/opensslconf.h>

#if !defined(OPENSSL_NO_SHA) && !defined(OPENSSL_NO_SHA1)

#include <openssl/bn.h>
#include <openssl/err.h>
#include <openssl/evp.h>
#include <openssl/rsa.h>
#include <openssl/sha.h>

static 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) {
		RSAerror(RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
		return 0;
	}

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

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

	if (!EVP_Digest((void *)param, plen, db, NULL, EVP_sha1(), NULL))
		return 0;
	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, flen);
	arc4random_buf(seed, SHA_DIGEST_LENGTH);

	dbmask = malloc(emlen - SHA_DIGEST_LENGTH);
	if (dbmask == NULL) {
		RSAerror(ERR_R_MALLOC_FAILURE);
		return 0;
	}

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

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

	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;
	unsigned char 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 = malloc(dblen + num);
	if (db == NULL) {
		RSAerror(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;

	if (MGF1(seed, SHA_DIGEST_LENGTH, maskeddb, dblen))
		return -1;
	for (i = 0; i < SHA_DIGEST_LENGTH; i++)
		seed[i] ^= padded_from[i];

	if (MGF1(db, dblen, seed, SHA_DIGEST_LENGTH))
		return -1;
	for (i = 0; i < dblen; i++)
		db[i] ^= maskeddb[i];

	if (!EVP_Digest((void *)param, plen, phash, NULL, EVP_sha1(), NULL))
		return -1;

	if (timingsafe_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) {
				RSAerror(RSA_R_DATA_TOO_LARGE);
				mlen = -1;
			} else
				memcpy(to, db + i, mlen);
		}
	}
	free(db);
	return mlen;

decoding_err:
	/*
	 * To avoid chosen ciphertext attacks, the error message should not
	 * reveal which kind of decoding error happened
	 */
	RSAerror(RSA_R_OAEP_DECODING_ERROR);
	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;
	int rv = -1;

	EVP_MD_CTX_init(&c);
	mdlen = EVP_MD_size(dgst);
	if (mdlen < 0)
		goto err;
	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);
		if (!EVP_DigestInit_ex(&c, dgst, NULL) ||
		    !EVP_DigestUpdate(&c, seed, seedlen) ||
		    !EVP_DigestUpdate(&c, cnt, 4))
			goto err;
		if (outlen + mdlen <= len) {
			if (!EVP_DigestFinal_ex(&c, mask + outlen, NULL))
				goto err;
			outlen += mdlen;
		} else {
			if (!EVP_DigestFinal_ex(&c, md, NULL))
				goto err;
			memcpy(mask + outlen, md, len - outlen);
			outlen = len;
		}
	}
	rv = 0;
err:
	EVP_MD_CTX_cleanup(&c);
	return rv;
}

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


Generated by: GCOVR (Version 3.3)

Line	Branch	Exec	Source
1			/* $OpenBSD: rsa_oaep.c,v 1.26 2017/01/29 17:49:23 beck Exp $ */
2			/* Written by Ulf Moeller. This software is distributed on an "AS IS"
3			basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. */
4
5			/* EME-OAEP as defined in RFC 2437 (PKCS #1 v2.0) */
6
7			/* See Victor Shoup, "OAEP reconsidered," Nov. 2000,
8			* <URL: http://www.shoup.net/papers/oaep.ps.Z>
9			* for problems with the security proof for the
10			* original OAEP scheme, which EME-OAEP is based on.
11			*
12			* A new proof can be found in E. Fujisaki, T. Okamoto,
13			* D. Pointcheval, J. Stern, "RSA-OEAP is Still Alive!",
14			* Dec. 2000, <URL: http://eprint.iacr.org/2000/061/>.
15			* The new proof has stronger requirements for the
16			* underlying permutation: "partial-one-wayness" instead
17			* of one-wayness. For the RSA function, this is
18			* an equivalent notion.
19			*/
20
21			#include <stdio.h>
22			#include <stdlib.h>
23			#include <string.h>
24
25			#include <openssl/opensslconf.h>
26
27			#if !defined(OPENSSL_NO_SHA) && !defined(OPENSSL_NO_SHA1)
28
29			#include <openssl/bn.h>
30			#include <openssl/err.h>
31			#include <openssl/evp.h>
32			#include <openssl/rsa.h>
33			#include <openssl/sha.h>
34
35			static int MGF1(unsigned char mask, long len, const unsigned char seed,
36			long seedlen);
37
38			int
39			RSA_padding_add_PKCS1_OAEP(unsigned char *to, int tlen,
40			const unsigned char from, int flen, const unsigned char param, int plen)
41			{
42		72	int i, emlen = tlen - 1;
43			unsigned char db, seed;
44		36	unsigned char *dbmask, seedmask[SHA_DIGEST_LENGTH];
45
46	✗✓	36	if (flen > emlen - 2 * SHA_DIGEST_LENGTH - 1) {
47			RSAerror(RSA_R_DATA_TOO_LARGE_FOR_KEY_SIZE);
48			return 0;
49			}
50
51	✗✓	36	if (emlen < 2 * SHA_DIGEST_LENGTH + 1) {
52			RSAerror(RSA_R_KEY_SIZE_TOO_SMALL);
53			return 0;
54			}
55
56		36	to[0] = 0;
57		36	seed = to + 1;
58		36	db = to + SHA_DIGEST_LENGTH + 1;
59
60	✗✓	36	if (!EVP_Digest((void *)param, plen, db, NULL, EVP_sha1(), NULL))
61			return 0;
62		72	memset(db + SHA_DIGEST_LENGTH, 0,
63		36	emlen - flen - 2 * SHA_DIGEST_LENGTH - 1);
64		36	db[emlen - flen - SHA_DIGEST_LENGTH - 1] = 0x01;
65		36	memcpy(db + emlen - flen - SHA_DIGEST_LENGTH, from, flen);
66		36	arc4random_buf(seed, SHA_DIGEST_LENGTH);
67
68		36	dbmask = malloc(emlen - SHA_DIGEST_LENGTH);
69	✗✓	36	if (dbmask == NULL) {
70			RSAerror(ERR_R_MALLOC_FAILURE);
71			return 0;
72			}
73
74	✗✓	72	if (MGF1(dbmask, emlen - SHA_DIGEST_LENGTH, seed,
75		36	SHA_DIGEST_LENGTH) < 0)
76			return 0;
77	✓✓	4368	for (i = 0; i < emlen - SHA_DIGEST_LENGTH; i++)
78		2148	db[i] ^= dbmask[i];
79
80	✗✓	72	if (MGF1(seedmask, SHA_DIGEST_LENGTH, db,
81		36	emlen - SHA_DIGEST_LENGTH) < 0)
82			return 0;
83	✓✓	1512	for (i = 0; i < SHA_DIGEST_LENGTH; i++)
84		720	seed[i] ^= seedmask[i];
85
86		36	free(dbmask);
87		36	return 1;
88		36	}
89
90			int
91			RSA_padding_check_PKCS1_OAEP(unsigned char *to, int tlen,
92			const unsigned char from, int flen, int num, const unsigned char param,
93			int plen)
94			{
95			int i, dblen, mlen = -1;
96			const unsigned char *maskeddb;
97			int lzero;
98			unsigned char *db = NULL;
99		11760	unsigned char seed[SHA_DIGEST_LENGTH], phash[SHA_DIGEST_LENGTH];
100			unsigned char *padded_from;
101			int bad = 0;
102
103	✓✗	5880	if (--num < 2 * SHA_DIGEST_LENGTH + 1)
104			/*
105			* 'num' is the length of the modulus, i.e. does not depend
106			* on the particular ciphertext.
107			*/
108			goto decoding_err;
109
110		5880	lzero = num - flen;
111	✓✓	5880	if (lzero < 0) {
112			/*
113			* signalling this error immediately after detection might allow
114			* for side-channel attacks (e.g. timing if 'plen' is huge
115			* -- cf. James H. Manger, "A Chosen Ciphertext Attack on RSA
116			* Optimal Asymmetric Encryption Padding (OAEP) [...]",
117			* CRYPTO 2001), so we use a 'bad' flag
118			*/
119			bad = 1;
120			lzero = 0;
121			flen = num; /* don't overflow the memcpy to padded_from */
122		5739	}
123
124		5880	dblen = num - SHA_DIGEST_LENGTH;
125		5880	db = malloc(dblen + num);
126	✗✓	5880	if (db == NULL) {
127			RSAerror(ERR_R_MALLOC_FAILURE);
128			return -1;
129			}
130
131			/*
132			* Always do this zero-padding copy (even when lzero == 0)
133			* to avoid leaking timing info about the value of lzero.
134			*/
135		5880	padded_from = db + dblen;
136		5880	memset(padded_from, 0, lzero);
137		5880	memcpy(padded_from + lzero, from, flen);
138
139		5880	maskeddb = padded_from + SHA_DIGEST_LENGTH;
140
141	✗✓	5880	if (MGF1(seed, SHA_DIGEST_LENGTH, maskeddb, dblen))
142			return -1;
143	✓✓	246960	for (i = 0; i < SHA_DIGEST_LENGTH; i++)
144		117600	seed[i] ^= padded_from[i];
145
146	✗✓	5880	if (MGF1(db, dblen, seed, SHA_DIGEST_LENGTH))
147			return -1;
148	✓✓	879456	for (i = 0; i < dblen; i++)
149		433848	db[i] ^= maskeddb[i];
150
151	✗✓	5880	if (!EVP_Digest((void *)param, plen, phash, NULL, EVP_sha1(), NULL))
152			return -1;
153
154	✓✓	5880	if (timingsafe_memcmp(db, phash, SHA_DIGEST_LENGTH) != 0 \|\| bad)
155			goto decoding_err;
156			else {
157	✓✗	4560	for (i = SHA_DIGEST_LENGTH; i < dblen; i++)
158	✓✓	2280	if (db[i] != 0x00)
159			break;
160	✓✗✓✗	144	if (i == dblen \|\| db[i] != 0x01)
161			goto decoding_err;
162			else {
163			/* everything looks OK */
164
165		72	mlen = dblen - ++i;
166	✗✓	72	if (tlen < mlen) {
167			RSAerror(RSA_R_DATA_TOO_LARGE);
168			mlen = -1;
169			} else
170		72	memcpy(to, db + i, mlen);
171			}
172			}
173		72	free(db);
174		72	return mlen;
175
176			decoding_err:
177			/*
178			* To avoid chosen ciphertext attacks, the error message should not
179			* reveal which kind of decoding error happened
180			*/
181		5808	RSAerror(RSA_R_OAEP_DECODING_ERROR);
182		5808	free(db);
183		5808	return -1;
184		5880	}
185
186			int
187			PKCS1_MGF1(unsigned char mask, long len, const unsigned char seed,
188			long seedlen, const EVP_MD *dgst)
189			{
190			long i, outlen = 0;
191		23664	unsigned char cnt[4];
192		11832	EVP_MD_CTX c;
193		11832	unsigned char md[EVP_MAX_MD_SIZE];
194			int mdlen;
195			int rv = -1;
196
197		11832	EVP_MD_CTX_init(&c);
198		11832	mdlen = EVP_MD_size(dgst);
199	✓✗	11832	if (mdlen < 0)
200			goto err;
201	✓✓	87168	for (i = 0; outlen < len; i++) {
202		31752	cnt[0] = (unsigned char)((i >> 24) & 255);
203		31752	cnt[1] = (unsigned char)((i >> 16) & 255);
204		31752	cnt[2] = (unsigned char)((i >> 8)) & 255;
205		31752	cnt[3] = (unsigned char)(i & 255);
206	✓✗✓✗	63504	if (!EVP_DigestInit_ex(&c, dgst, NULL) \|\|
207	✓✗	31752	!EVP_DigestUpdate(&c, seed, seedlen) \|\|
208		31752	!EVP_DigestUpdate(&c, cnt, 4))
209			goto err;
210	✓✓	31752	if (outlen + mdlen <= len) {
211	✓✗	25836	if (!EVP_DigestFinal_ex(&c, mask + outlen, NULL))
212			goto err;
213			outlen += mdlen;
214		25836	} else {
215	✓✗	5916	if (!EVP_DigestFinal_ex(&c, md, NULL))
216			goto err;
217		5916	memcpy(mask + outlen, md, len - outlen);
218			outlen = len;
219			}
220			}
221		11832	rv = 0;
222			err:
223		11832	EVP_MD_CTX_cleanup(&c);
224		11832	return rv;
225		11832	}
226
227			static int
228			MGF1(unsigned char mask, long len, const unsigned char seed, long seedlen)
229			{
230		23664	return PKCS1_MGF1(mask, len, seed, seedlen, EVP_sha1());
231			}
232			#endif