| blob | 8a92daf0ca7b958d290462be4c812cb679220513 |
1 /*\r
2 * Diffie-Hellman implementation for PuTTY.\r
3 */\r
4 \r
5 #include "ssh.h"\r
6 \r
7 /*\r
8 * The primes used in the group1 and group14 key exchange.\r
9 */\r
10 static const unsigned char P1[] = {\r
11 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2,\r
12 0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1,\r
13 0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6,\r
14 0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E, 0x34, 0x04, 0xDD,\r
15 0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B, 0x30, 0x2B, 0x0A, 0x6D,\r
16 0xF2, 0x5F, 0x14, 0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2, 0x45,\r
17 0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4, 0x4C, 0x42, 0xE9,\r
18 0xA6, 0x37, 0xED, 0x6B, 0x0B, 0xFF, 0x5C, 0xB6, 0xF4, 0x06, 0xB7, 0xED,\r
19 0xEE, 0x38, 0x6B, 0xFB, 0x5A, 0x89, 0x9F, 0xA5, 0xAE, 0x9F, 0x24, 0x11,\r
20 0x7C, 0x4B, 0x1F, 0xE6, 0x49, 0x28, 0x66, 0x51, 0xEC, 0xE6, 0x53, 0x81,\r
21 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF\r
22 };\r
23 static const unsigned char P14[] = {\r
24 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2,\r
25 0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1,\r
26 0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6,\r
27 0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E, 0x34, 0x04, 0xDD,\r
28 0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B, 0x30, 0x2B, 0x0A, 0x6D,\r
29 0xF2, 0x5F, 0x14, 0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2, 0x45,\r
30 0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4, 0x4C, 0x42, 0xE9,\r
31 0xA6, 0x37, 0xED, 0x6B, 0x0B, 0xFF, 0x5C, 0xB6, 0xF4, 0x06, 0xB7, 0xED,\r
32 0xEE, 0x38, 0x6B, 0xFB, 0x5A, 0x89, 0x9F, 0xA5, 0xAE, 0x9F, 0x24, 0x11,\r
33 0x7C, 0x4B, 0x1F, 0xE6, 0x49, 0x28, 0x66, 0x51, 0xEC, 0xE4, 0x5B, 0x3D,\r
34 0xC2, 0x00, 0x7C, 0xB8, 0xA1, 0x63, 0xBF, 0x05, 0x98, 0xDA, 0x48, 0x36,\r
35 0x1C, 0x55, 0xD3, 0x9A, 0x69, 0x16, 0x3F, 0xA8, 0xFD, 0x24, 0xCF, 0x5F,\r
36 0x83, 0x65, 0x5D, 0x23, 0xDC, 0xA3, 0xAD, 0x96, 0x1C, 0x62, 0xF3, 0x56,\r
37 0x20, 0x85, 0x52, 0xBB, 0x9E, 0xD5, 0x29, 0x07, 0x70, 0x96, 0x96, 0x6D,\r
38 0x67, 0x0C, 0x35, 0x4E, 0x4A, 0xBC, 0x98, 0x04, 0xF1, 0x74, 0x6C, 0x08,\r
39 0xCA, 0x18, 0x21, 0x7C, 0x32, 0x90, 0x5E, 0x46, 0x2E, 0x36, 0xCE, 0x3B,\r
40 0xE3, 0x9E, 0x77, 0x2C, 0x18, 0x0E, 0x86, 0x03, 0x9B, 0x27, 0x83, 0xA2,\r
41 0xEC, 0x07, 0xA2, 0x8F, 0xB5, 0xC5, 0x5D, 0xF0, 0x6F, 0x4C, 0x52, 0xC9,\r
42 0xDE, 0x2B, 0xCB, 0xF6, 0x95, 0x58, 0x17, 0x18, 0x39, 0x95, 0x49, 0x7C,\r
43 0xEA, 0x95, 0x6A, 0xE5, 0x15, 0xD2, 0x26, 0x18, 0x98, 0xFA, 0x05, 0x10,\r
44 0x15, 0x72, 0x8E, 0x5A, 0x8A, 0xAC, 0xAA, 0x68, 0xFF, 0xFF, 0xFF, 0xFF,\r
45 0xFF, 0xFF, 0xFF, 0xFF\r
46 };\r
47 \r
48 /*\r
49 * The generator g = 2 (used for both group1 and group14).\r
50 */\r
51 static const unsigned char G[] = { 2 };\r
52 \r
53 static const struct ssh_kex ssh_diffiehellman_group1_sha1 = {\r
54 "diffie-hellman-group1-sha1", "group1",\r
55 P1, G, lenof(P1), lenof(G), &ssh_sha1\r
56 };\r
57 \r
58 static const struct ssh_kex *const group1_list[] = {\r
59 &ssh_diffiehellman_group1_sha1\r
60 };\r
61 \r
62 const struct ssh_kexes ssh_diffiehellman_group1 = {\r
63 sizeof(group1_list) / sizeof(*group1_list),\r
64 group1_list\r
65 };\r
66 \r
67 static const struct ssh_kex ssh_diffiehellman_group14_sha1 = {\r
68 "diffie-hellman-group14-sha1", "group14",\r
69 P14, G, lenof(P14), lenof(G), &ssh_sha1\r
70 };\r
71 \r
72 static const struct ssh_kex *const group14_list[] = {\r
73 &ssh_diffiehellman_group14_sha1\r
74 };\r
75 \r
76 const struct ssh_kexes ssh_diffiehellman_group14 = {\r
77 sizeof(group14_list) / sizeof(*group14_list),\r
78 group14_list\r
79 };\r
80 \r
81 static const struct ssh_kex ssh_diffiehellman_gex_sha256 = {\r
82 "diffie-hellman-group-exchange-sha256", NULL,\r
83 NULL, NULL, 0, 0, &ssh_sha256\r
84 };\r
85 \r
86 static const struct ssh_kex ssh_diffiehellman_gex_sha1 = {\r
87 "diffie-hellman-group-exchange-sha1", NULL,\r
88 NULL, NULL, 0, 0, &ssh_sha1\r
89 };\r
90 \r
91 static const struct ssh_kex *const gex_list[] = {\r
92 &ssh_diffiehellman_gex_sha256,\r
93 &ssh_diffiehellman_gex_sha1\r
94 };\r
95 \r
96 const struct ssh_kexes ssh_diffiehellman_gex = {\r
97 sizeof(gex_list) / sizeof(*gex_list),\r
98 gex_list\r
99 };\r
100 \r
101 /*\r
102 * Variables.\r
103 */\r
104 struct dh_ctx {\r
105 Bignum x, e, p, q, qmask, g;\r
106 };\r
107 \r
108 /*\r
109 * Common DH initialisation.\r
110 */\r
111 static void dh_init(struct dh_ctx *ctx)\r
112 {\r
113 ctx->q = bignum_rshift(ctx->p, 1);\r
114 ctx->qmask = bignum_bitmask(ctx->q);\r
115 ctx->x = ctx->e = NULL;\r
116 }\r
117 \r
118 /*\r
119 * Initialise DH for a standard group.\r
120 */\r
121 void *dh_setup_group(const struct ssh_kex *kex)\r
122 {\r
123 struct dh_ctx *ctx = snew(struct dh_ctx);\r
124 ctx->p = bignum_from_bytes(kex->pdata, kex->plen);\r
125 ctx->g = bignum_from_bytes(kex->gdata, kex->glen);\r
126 dh_init(ctx);\r
127 return ctx;\r
128 }\r
129 \r
130 /*\r
131 * Initialise DH for a server-supplied group.\r
132 */\r
133 void *dh_setup_gex(Bignum pval, Bignum gval)\r
134 {\r
135 struct dh_ctx *ctx = snew(struct dh_ctx);\r
136 ctx->p = copybn(pval);\r
137 ctx->g = copybn(gval);\r
138 dh_init(ctx);\r
139 return ctx;\r
140 }\r
141 \r
142 /*\r
143 * Clean up and free a context.\r
144 */\r
145 void dh_cleanup(void *handle)\r
146 {\r
147 struct dh_ctx *ctx = (struct dh_ctx *)handle;\r
148 freebn(ctx->x);\r
149 freebn(ctx->e);\r
150 freebn(ctx->p);\r
151 freebn(ctx->g);\r
152 freebn(ctx->q);\r
153 freebn(ctx->qmask);\r
154 sfree(ctx);\r
155 }\r
156 \r
157 /*\r
158 * DH stage 1: invent a number x between 1 and q, and compute e =\r
159 * g^x mod p. Return e.\r
160 * \r
161 * If `nbits' is greater than zero, it is used as an upper limit\r
162 * for the number of bits in x. This is safe provided that (a) you\r
163 * use twice as many bits in x as the number of bits you expect to\r
164 * use in your session key, and (b) the DH group is a safe prime\r
165 * (which SSH demands that it must be).\r
166 * \r
167 * P. C. van Oorschot, M. J. Wiener\r
168 * "On Diffie-Hellman Key Agreement with Short Exponents".\r
169 * Advances in Cryptology: Proceedings of Eurocrypt '96\r
170 * Springer-Verlag, May 1996.\r
171 */\r
172 Bignum dh_create_e(void *handle, int nbits)\r
173 {\r
174 struct dh_ctx *ctx = (struct dh_ctx *)handle;\r
175 int i;\r
176 \r
177 int nbytes;\r
178 unsigned char *buf;\r
179 \r
180 nbytes = ssh1_bignum_length(ctx->qmask);\r
181 buf = snewn(nbytes, unsigned char);\r
182 \r
183 do {\r
184 /*\r
185 * Create a potential x, by ANDing a string of random bytes\r
186 * with qmask.\r
187 */\r
188 if (ctx->x)\r
189 freebn(ctx->x);\r
190 if (nbits == 0 || nbits > bignum_bitcount(ctx->qmask)) {\r
191 ssh1_write_bignum(buf, ctx->qmask);\r
192 for (i = 2; i < nbytes; i++)\r
193 buf[i] &= random_byte();\r
194 ssh1_read_bignum(buf, nbytes, &ctx->x); /* can't fail */\r
195 } else {\r
196 int b, nb;\r
197 ctx->x = bn_power_2(nbits);\r
198 b = nb = 0;\r
199 for (i = 0; i < nbits; i++) {\r
200 if (nb == 0) {\r
201 nb = 8;\r
202 b = random_byte();\r
203 }\r
204 bignum_set_bit(ctx->x, i, b & 1);\r
205 b >>= 1;\r
206 nb--;\r
207 }\r
208 }\r
209 } while (bignum_cmp(ctx->x, One) <= 0 || bignum_cmp(ctx->x, ctx->q) >= 0);\r
210 \r
211 sfree(buf);\r
212 \r
213 /*\r
214 * Done. Now compute e = g^x mod p.\r
215 */\r
216 ctx->e = modpow(ctx->g, ctx->x, ctx->p);\r
217 \r
218 return ctx->e;\r
219 }\r
220 \r
221 /*\r
222 * DH stage 2: given a number f, compute K = f^x mod p.\r
223 */\r
224 Bignum dh_find_K(void *handle, Bignum f)\r
225 {\r
226 struct dh_ctx *ctx = (struct dh_ctx *)handle;\r
227 Bignum ret;\r
228 ret = modpow(f, ctx->x, ctx->p);\r
229 return ret;\r
230 }\r