1 /*
2 * Copyright 2004-2021 The OpenSSL Project Authors. All Rights Reserved.
3 * Copyright (c) 2004, EdelKey Project. All Rights Reserved.
4 *
5 * Licensed under the OpenSSL license (the "License"). You may not use
6 * this file except in compliance with the License. You can obtain a copy
7 * in the file LICENSE in the source distribution or at
8 * https://www.openssl.org/source/license.html
9 *
10 * Originally written by Christophe Renou and Peter Sylvester,
11 * for the EdelKey project.
12 */
13
14 #ifndef OPENSSL_NO_SRP
15 # include "internal/cryptlib.h"
16 # include <openssl/sha.h>
17 # include <openssl/srp.h>
18 # include <openssl/evp.h>
19 # include "crypto/bn_srp.h"
20
21 /* calculate = SHA1(PAD(x) || PAD(y)) */
22
srp_Calc_xy(const BIGNUM * x,const BIGNUM * y,const BIGNUM * N)23 static BIGNUM *srp_Calc_xy(const BIGNUM *x, const BIGNUM *y, const BIGNUM *N)
24 {
25 unsigned char digest[SHA_DIGEST_LENGTH];
26 unsigned char *tmp = NULL;
27 int numN = BN_num_bytes(N);
28 BIGNUM *res = NULL;
29
30 if (x != N && BN_ucmp(x, N) >= 0)
31 return NULL;
32 if (y != N && BN_ucmp(y, N) >= 0)
33 return NULL;
34 if ((tmp = OPENSSL_malloc(numN * 2)) == NULL)
35 goto err;
36 if (BN_bn2binpad(x, tmp, numN) < 0
37 || BN_bn2binpad(y, tmp + numN, numN) < 0
38 || !EVP_Digest(tmp, numN * 2, digest, NULL, EVP_sha1(), NULL))
39 goto err;
40 res = BN_bin2bn(digest, sizeof(digest), NULL);
41 err:
42 OPENSSL_free(tmp);
43 return res;
44 }
45
srp_Calc_k(const BIGNUM * N,const BIGNUM * g)46 static BIGNUM *srp_Calc_k(const BIGNUM *N, const BIGNUM *g)
47 {
48 /* k = SHA1(N | PAD(g)) -- tls-srp draft 8 */
49 return srp_Calc_xy(N, g, N);
50 }
51
SRP_Calc_u(const BIGNUM * A,const BIGNUM * B,const BIGNUM * N)52 BIGNUM *SRP_Calc_u(const BIGNUM *A, const BIGNUM *B, const BIGNUM *N)
53 {
54 /* k = SHA1(PAD(A) || PAD(B) ) -- tls-srp draft 8 */
55 return srp_Calc_xy(A, B, N);
56 }
57
SRP_Calc_server_key(const BIGNUM * A,const BIGNUM * v,const BIGNUM * u,const BIGNUM * b,const BIGNUM * N)58 BIGNUM *SRP_Calc_server_key(const BIGNUM *A, const BIGNUM *v, const BIGNUM *u,
59 const BIGNUM *b, const BIGNUM *N)
60 {
61 BIGNUM *tmp = NULL, *S = NULL;
62 BN_CTX *bn_ctx;
63
64 if (u == NULL || A == NULL || v == NULL || b == NULL || N == NULL)
65 return NULL;
66
67 if ((bn_ctx = BN_CTX_new()) == NULL || (tmp = BN_new()) == NULL)
68 goto err;
69
70 /* S = (A*v**u) ** b */
71
72 if (!BN_mod_exp(tmp, v, u, N, bn_ctx))
73 goto err;
74 if (!BN_mod_mul(tmp, A, tmp, N, bn_ctx))
75 goto err;
76
77 S = BN_new();
78 if (S != NULL && !BN_mod_exp(S, tmp, b, N, bn_ctx)) {
79 BN_free(S);
80 S = NULL;
81 }
82 err:
83 BN_CTX_free(bn_ctx);
84 BN_clear_free(tmp);
85 return S;
86 }
87
SRP_Calc_B(const BIGNUM * b,const BIGNUM * N,const BIGNUM * g,const BIGNUM * v)88 BIGNUM *SRP_Calc_B(const BIGNUM *b, const BIGNUM *N, const BIGNUM *g,
89 const BIGNUM *v)
90 {
91 BIGNUM *kv = NULL, *gb = NULL;
92 BIGNUM *B = NULL, *k = NULL;
93 BN_CTX *bn_ctx;
94
95 if (b == NULL || N == NULL || g == NULL || v == NULL ||
96 (bn_ctx = BN_CTX_new()) == NULL)
97 return NULL;
98
99 if ((kv = BN_new()) == NULL ||
100 (gb = BN_new()) == NULL || (B = BN_new()) == NULL)
101 goto err;
102
103 /* B = g**b + k*v */
104
105 if (!BN_mod_exp(gb, g, b, N, bn_ctx)
106 || (k = srp_Calc_k(N, g)) == NULL
107 || !BN_mod_mul(kv, v, k, N, bn_ctx)
108 || !BN_mod_add(B, gb, kv, N, bn_ctx)) {
109 BN_free(B);
110 B = NULL;
111 }
112 err:
113 BN_CTX_free(bn_ctx);
114 BN_clear_free(kv);
115 BN_clear_free(gb);
116 BN_free(k);
117 return B;
118 }
119
SRP_Calc_x(const BIGNUM * s,const char * user,const char * pass)120 BIGNUM *SRP_Calc_x(const BIGNUM *s, const char *user, const char *pass)
121 {
122 unsigned char dig[SHA_DIGEST_LENGTH];
123 EVP_MD_CTX *ctxt;
124 unsigned char *cs = NULL;
125 BIGNUM *res = NULL;
126
127 if ((s == NULL) || (user == NULL) || (pass == NULL))
128 return NULL;
129
130 ctxt = EVP_MD_CTX_new();
131 if (ctxt == NULL)
132 return NULL;
133 if ((cs = OPENSSL_malloc(BN_num_bytes(s))) == NULL)
134 goto err;
135
136 if (!EVP_DigestInit_ex(ctxt, EVP_sha1(), NULL)
137 || !EVP_DigestUpdate(ctxt, user, strlen(user))
138 || !EVP_DigestUpdate(ctxt, ":", 1)
139 || !EVP_DigestUpdate(ctxt, pass, strlen(pass))
140 || !EVP_DigestFinal_ex(ctxt, dig, NULL)
141 || !EVP_DigestInit_ex(ctxt, EVP_sha1(), NULL))
142 goto err;
143 if (BN_bn2bin(s, cs) < 0)
144 goto err;
145 if (!EVP_DigestUpdate(ctxt, cs, BN_num_bytes(s)))
146 goto err;
147
148 if (!EVP_DigestUpdate(ctxt, dig, sizeof(dig))
149 || !EVP_DigestFinal_ex(ctxt, dig, NULL))
150 goto err;
151
152 res = BN_bin2bn(dig, sizeof(dig), NULL);
153
154 err:
155 OPENSSL_free(cs);
156 EVP_MD_CTX_free(ctxt);
157 return res;
158 }
159
SRP_Calc_A(const BIGNUM * a,const BIGNUM * N,const BIGNUM * g)160 BIGNUM *SRP_Calc_A(const BIGNUM *a, const BIGNUM *N, const BIGNUM *g)
161 {
162 BN_CTX *bn_ctx;
163 BIGNUM *A = NULL;
164
165 if (a == NULL || N == NULL || g == NULL || (bn_ctx = BN_CTX_new()) == NULL)
166 return NULL;
167
168 if ((A = BN_new()) != NULL && !BN_mod_exp(A, g, a, N, bn_ctx)) {
169 BN_free(A);
170 A = NULL;
171 }
172 BN_CTX_free(bn_ctx);
173 return A;
174 }
175
SRP_Calc_client_key(const BIGNUM * N,const BIGNUM * B,const BIGNUM * g,const BIGNUM * x,const BIGNUM * a,const BIGNUM * u)176 BIGNUM *SRP_Calc_client_key(const BIGNUM *N, const BIGNUM *B, const BIGNUM *g,
177 const BIGNUM *x, const BIGNUM *a, const BIGNUM *u)
178 {
179 BIGNUM *tmp = NULL, *tmp2 = NULL, *tmp3 = NULL, *k = NULL, *K = NULL;
180 BIGNUM *xtmp = NULL;
181 BN_CTX *bn_ctx;
182
183 if (u == NULL || B == NULL || N == NULL || g == NULL || x == NULL
184 || a == NULL || (bn_ctx = BN_CTX_new()) == NULL)
185 return NULL;
186
187 if ((tmp = BN_new()) == NULL ||
188 (tmp2 = BN_new()) == NULL ||
189 (tmp3 = BN_new()) == NULL ||
190 (xtmp = BN_new()) == NULL)
191 goto err;
192
193 BN_with_flags(xtmp, x, BN_FLG_CONSTTIME);
194 BN_set_flags(tmp, BN_FLG_CONSTTIME);
195 if (!BN_mod_exp(tmp, g, xtmp, N, bn_ctx))
196 goto err;
197 if ((k = srp_Calc_k(N, g)) == NULL)
198 goto err;
199 if (!BN_mod_mul(tmp2, tmp, k, N, bn_ctx))
200 goto err;
201 if (!BN_mod_sub(tmp, B, tmp2, N, bn_ctx))
202 goto err;
203 if (!BN_mul(tmp3, u, xtmp, bn_ctx))
204 goto err;
205 if (!BN_add(tmp2, a, tmp3))
206 goto err;
207 K = BN_new();
208 if (K != NULL && !BN_mod_exp(K, tmp, tmp2, N, bn_ctx)) {
209 BN_free(K);
210 K = NULL;
211 }
212
213 err:
214 BN_CTX_free(bn_ctx);
215 BN_free(xtmp);
216 BN_clear_free(tmp);
217 BN_clear_free(tmp2);
218 BN_clear_free(tmp3);
219 BN_free(k);
220 return K;
221 }
222
SRP_Verify_B_mod_N(const BIGNUM * B,const BIGNUM * N)223 int SRP_Verify_B_mod_N(const BIGNUM *B, const BIGNUM *N)
224 {
225 BIGNUM *r;
226 BN_CTX *bn_ctx;
227 int ret = 0;
228
229 if (B == NULL || N == NULL || (bn_ctx = BN_CTX_new()) == NULL)
230 return 0;
231
232 if ((r = BN_new()) == NULL)
233 goto err;
234 /* Checks if B % N == 0 */
235 if (!BN_nnmod(r, B, N, bn_ctx))
236 goto err;
237 ret = !BN_is_zero(r);
238 err:
239 BN_CTX_free(bn_ctx);
240 BN_free(r);
241 return ret;
242 }
243
SRP_Verify_A_mod_N(const BIGNUM * A,const BIGNUM * N)244 int SRP_Verify_A_mod_N(const BIGNUM *A, const BIGNUM *N)
245 {
246 /* Checks if A % N == 0 */
247 return SRP_Verify_B_mod_N(A, N);
248 }
249
250 static SRP_gN knowngN[] = {
251 {"8192", &bn_generator_19, &bn_group_8192},
252 {"6144", &bn_generator_5, &bn_group_6144},
253 {"4096", &bn_generator_5, &bn_group_4096},
254 {"3072", &bn_generator_5, &bn_group_3072},
255 {"2048", &bn_generator_2, &bn_group_2048},
256 {"1536", &bn_generator_2, &bn_group_1536},
257 {"1024", &bn_generator_2, &bn_group_1024},
258 };
259
260 # define KNOWN_GN_NUMBER sizeof(knowngN) / sizeof(SRP_gN)
261
262 /*
263 * Check if G and N are known parameters. The values have been generated
264 * from the ietf-tls-srp draft version 8
265 */
SRP_check_known_gN_param(const BIGNUM * g,const BIGNUM * N)266 char *SRP_check_known_gN_param(const BIGNUM *g, const BIGNUM *N)
267 {
268 size_t i;
269 if ((g == NULL) || (N == NULL))
270 return 0;
271
272 for (i = 0; i < KNOWN_GN_NUMBER; i++) {
273 if (BN_cmp(knowngN[i].g, g) == 0 && BN_cmp(knowngN[i].N, N) == 0)
274 return knowngN[i].id;
275 }
276 return NULL;
277 }
278
SRP_get_default_gN(const char * id)279 SRP_gN *SRP_get_default_gN(const char *id)
280 {
281 size_t i;
282
283 if (id == NULL)
284 return knowngN;
285 for (i = 0; i < KNOWN_GN_NUMBER; i++) {
286 if (strcmp(knowngN[i].id, id) == 0)
287 return knowngN + i;
288 }
289 return NULL;
290 }
291 #endif
292