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1c1af145 | 1 | /* |
2 | * Diffie-Hellman implementation for PuTTY. | |
3 | */ | |
4 | ||
5 | #include "ssh.h" | |
6 | ||
7 | /* | |
8 | * The primes used in the group1 and group14 key exchange. | |
9 | */ | |
10 | static const unsigned char P1[] = { | |
11 | 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2, | |
12 | 0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1, | |
13 | 0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6, | |
14 | 0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E, 0x34, 0x04, 0xDD, | |
15 | 0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B, 0x30, 0x2B, 0x0A, 0x6D, | |
16 | 0xF2, 0x5F, 0x14, 0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2, 0x45, | |
17 | 0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4, 0x4C, 0x42, 0xE9, | |
18 | 0xA6, 0x37, 0xED, 0x6B, 0x0B, 0xFF, 0x5C, 0xB6, 0xF4, 0x06, 0xB7, 0xED, | |
19 | 0xEE, 0x38, 0x6B, 0xFB, 0x5A, 0x89, 0x9F, 0xA5, 0xAE, 0x9F, 0x24, 0x11, | |
20 | 0x7C, 0x4B, 0x1F, 0xE6, 0x49, 0x28, 0x66, 0x51, 0xEC, 0xE6, 0x53, 0x81, | |
21 | 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF | |
22 | }; | |
23 | static const unsigned char P14[] = { | |
24 | 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2, | |
25 | 0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1, | |
26 | 0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6, | |
27 | 0x3B, 0x13, 0x9B, 0x22, 0x51, 0x4A, 0x08, 0x79, 0x8E, 0x34, 0x04, 0xDD, | |
28 | 0xEF, 0x95, 0x19, 0xB3, 0xCD, 0x3A, 0x43, 0x1B, 0x30, 0x2B, 0x0A, 0x6D, | |
29 | 0xF2, 0x5F, 0x14, 0x37, 0x4F, 0xE1, 0x35, 0x6D, 0x6D, 0x51, 0xC2, 0x45, | |
30 | 0xE4, 0x85, 0xB5, 0x76, 0x62, 0x5E, 0x7E, 0xC6, 0xF4, 0x4C, 0x42, 0xE9, | |
31 | 0xA6, 0x37, 0xED, 0x6B, 0x0B, 0xFF, 0x5C, 0xB6, 0xF4, 0x06, 0xB7, 0xED, | |
32 | 0xEE, 0x38, 0x6B, 0xFB, 0x5A, 0x89, 0x9F, 0xA5, 0xAE, 0x9F, 0x24, 0x11, | |
33 | 0x7C, 0x4B, 0x1F, 0xE6, 0x49, 0x28, 0x66, 0x51, 0xEC, 0xE4, 0x5B, 0x3D, | |
34 | 0xC2, 0x00, 0x7C, 0xB8, 0xA1, 0x63, 0xBF, 0x05, 0x98, 0xDA, 0x48, 0x36, | |
35 | 0x1C, 0x55, 0xD3, 0x9A, 0x69, 0x16, 0x3F, 0xA8, 0xFD, 0x24, 0xCF, 0x5F, | |
36 | 0x83, 0x65, 0x5D, 0x23, 0xDC, 0xA3, 0xAD, 0x96, 0x1C, 0x62, 0xF3, 0x56, | |
37 | 0x20, 0x85, 0x52, 0xBB, 0x9E, 0xD5, 0x29, 0x07, 0x70, 0x96, 0x96, 0x6D, | |
38 | 0x67, 0x0C, 0x35, 0x4E, 0x4A, 0xBC, 0x98, 0x04, 0xF1, 0x74, 0x6C, 0x08, | |
39 | 0xCA, 0x18, 0x21, 0x7C, 0x32, 0x90, 0x5E, 0x46, 0x2E, 0x36, 0xCE, 0x3B, | |
40 | 0xE3, 0x9E, 0x77, 0x2C, 0x18, 0x0E, 0x86, 0x03, 0x9B, 0x27, 0x83, 0xA2, | |
41 | 0xEC, 0x07, 0xA2, 0x8F, 0xB5, 0xC5, 0x5D, 0xF0, 0x6F, 0x4C, 0x52, 0xC9, | |
42 | 0xDE, 0x2B, 0xCB, 0xF6, 0x95, 0x58, 0x17, 0x18, 0x39, 0x95, 0x49, 0x7C, | |
43 | 0xEA, 0x95, 0x6A, 0xE5, 0x15, 0xD2, 0x26, 0x18, 0x98, 0xFA, 0x05, 0x10, | |
44 | 0x15, 0x72, 0x8E, 0x5A, 0x8A, 0xAC, 0xAA, 0x68, 0xFF, 0xFF, 0xFF, 0xFF, | |
45 | 0xFF, 0xFF, 0xFF, 0xFF | |
46 | }; | |
47 | ||
48 | /* | |
49 | * The generator g = 2 (used for both group1 and group14). | |
50 | */ | |
51 | static const unsigned char G[] = { 2 }; | |
52 | ||
53 | static const struct ssh_kex ssh_diffiehellman_group1_sha1 = { | |
54 | "diffie-hellman-group1-sha1", "group1", | |
55 | KEXTYPE_DH, P1, G, lenof(P1), lenof(G), &ssh_sha1 | |
56 | }; | |
57 | ||
58 | static const struct ssh_kex *const group1_list[] = { | |
59 | &ssh_diffiehellman_group1_sha1 | |
60 | }; | |
61 | ||
62 | const struct ssh_kexes ssh_diffiehellman_group1 = { | |
63 | sizeof(group1_list) / sizeof(*group1_list), | |
64 | group1_list | |
65 | }; | |
66 | ||
67 | static const struct ssh_kex ssh_diffiehellman_group14_sha1 = { | |
68 | "diffie-hellman-group14-sha1", "group14", | |
69 | KEXTYPE_DH, P14, G, lenof(P14), lenof(G), &ssh_sha1 | |
70 | }; | |
71 | ||
72 | static const struct ssh_kex *const group14_list[] = { | |
73 | &ssh_diffiehellman_group14_sha1 | |
74 | }; | |
75 | ||
76 | const struct ssh_kexes ssh_diffiehellman_group14 = { | |
77 | sizeof(group14_list) / sizeof(*group14_list), | |
78 | group14_list | |
79 | }; | |
80 | ||
81 | static const struct ssh_kex ssh_diffiehellman_gex_sha256 = { | |
82 | "diffie-hellman-group-exchange-sha256", NULL, | |
83 | KEXTYPE_DH, NULL, NULL, 0, 0, &ssh_sha256 | |
84 | }; | |
85 | ||
86 | static const struct ssh_kex ssh_diffiehellman_gex_sha1 = { | |
87 | "diffie-hellman-group-exchange-sha1", NULL, | |
88 | KEXTYPE_DH, NULL, NULL, 0, 0, &ssh_sha1 | |
89 | }; | |
90 | ||
91 | static const struct ssh_kex *const gex_list[] = { | |
92 | &ssh_diffiehellman_gex_sha256, | |
93 | &ssh_diffiehellman_gex_sha1 | |
94 | }; | |
95 | ||
96 | const struct ssh_kexes ssh_diffiehellman_gex = { | |
97 | sizeof(gex_list) / sizeof(*gex_list), | |
98 | gex_list | |
99 | }; | |
100 | ||
101 | /* | |
102 | * Variables. | |
103 | */ | |
104 | struct dh_ctx { | |
105 | Bignum x, e, p, q, qmask, g; | |
106 | }; | |
107 | ||
108 | /* | |
109 | * Common DH initialisation. | |
110 | */ | |
111 | static void dh_init(struct dh_ctx *ctx) | |
112 | { | |
113 | ctx->q = bignum_rshift(ctx->p, 1); | |
114 | ctx->qmask = bignum_bitmask(ctx->q); | |
115 | ctx->x = ctx->e = NULL; | |
116 | } | |
117 | ||
118 | /* | |
119 | * Initialise DH for a standard group. | |
120 | */ | |
121 | void *dh_setup_group(const struct ssh_kex *kex) | |
122 | { | |
123 | struct dh_ctx *ctx = snew(struct dh_ctx); | |
124 | ctx->p = bignum_from_bytes(kex->pdata, kex->plen); | |
125 | ctx->g = bignum_from_bytes(kex->gdata, kex->glen); | |
126 | dh_init(ctx); | |
127 | return ctx; | |
128 | } | |
129 | ||
130 | /* | |
131 | * Initialise DH for a server-supplied group. | |
132 | */ | |
133 | void *dh_setup_gex(Bignum pval, Bignum gval) | |
134 | { | |
135 | struct dh_ctx *ctx = snew(struct dh_ctx); | |
136 | ctx->p = copybn(pval); | |
137 | ctx->g = copybn(gval); | |
138 | dh_init(ctx); | |
139 | return ctx; | |
140 | } | |
141 | ||
142 | /* | |
143 | * Clean up and free a context. | |
144 | */ | |
145 | void dh_cleanup(void *handle) | |
146 | { | |
147 | struct dh_ctx *ctx = (struct dh_ctx *)handle; | |
148 | freebn(ctx->x); | |
149 | freebn(ctx->e); | |
150 | freebn(ctx->p); | |
151 | freebn(ctx->g); | |
152 | freebn(ctx->q); | |
153 | freebn(ctx->qmask); | |
154 | sfree(ctx); | |
155 | } | |
156 | ||
157 | /* | |
158 | * DH stage 1: invent a number x between 1 and q, and compute e = | |
159 | * g^x mod p. Return e. | |
160 | * | |
161 | * If `nbits' is greater than zero, it is used as an upper limit | |
162 | * for the number of bits in x. This is safe provided that (a) you | |
163 | * use twice as many bits in x as the number of bits you expect to | |
164 | * use in your session key, and (b) the DH group is a safe prime | |
165 | * (which SSH demands that it must be). | |
166 | * | |
167 | * P. C. van Oorschot, M. J. Wiener | |
168 | * "On Diffie-Hellman Key Agreement with Short Exponents". | |
169 | * Advances in Cryptology: Proceedings of Eurocrypt '96 | |
170 | * Springer-Verlag, May 1996. | |
171 | */ | |
172 | Bignum dh_create_e(void *handle, int nbits) | |
173 | { | |
174 | struct dh_ctx *ctx = (struct dh_ctx *)handle; | |
175 | int i; | |
176 | ||
177 | int nbytes; | |
178 | unsigned char *buf; | |
179 | ||
180 | nbytes = ssh1_bignum_length(ctx->qmask); | |
181 | buf = snewn(nbytes, unsigned char); | |
182 | ||
183 | do { | |
184 | /* | |
185 | * Create a potential x, by ANDing a string of random bytes | |
186 | * with qmask. | |
187 | */ | |
188 | if (ctx->x) | |
189 | freebn(ctx->x); | |
190 | if (nbits == 0 || nbits > bignum_bitcount(ctx->qmask)) { | |
191 | ssh1_write_bignum(buf, ctx->qmask); | |
192 | for (i = 2; i < nbytes; i++) | |
193 | buf[i] &= random_byte(); | |
194 | ssh1_read_bignum(buf, nbytes, &ctx->x); /* can't fail */ | |
195 | } else { | |
196 | int b, nb; | |
197 | ctx->x = bn_power_2(nbits); | |
198 | b = nb = 0; | |
199 | for (i = 0; i < nbits; i++) { | |
200 | if (nb == 0) { | |
201 | nb = 8; | |
202 | b = random_byte(); | |
203 | } | |
204 | bignum_set_bit(ctx->x, i, b & 1); | |
205 | b >>= 1; | |
206 | nb--; | |
207 | } | |
208 | } | |
209 | } while (bignum_cmp(ctx->x, One) <= 0 || bignum_cmp(ctx->x, ctx->q) >= 0); | |
210 | ||
211 | sfree(buf); | |
212 | ||
213 | /* | |
214 | * Done. Now compute e = g^x mod p. | |
215 | */ | |
216 | ctx->e = modpow(ctx->g, ctx->x, ctx->p); | |
217 | ||
218 | return ctx->e; | |
219 | } | |
220 | ||
221 | /* | |
222 | * DH stage 2: given a number f, compute K = f^x mod p. | |
223 | */ | |
224 | Bignum dh_find_K(void *handle, Bignum f) | |
225 | { | |
226 | struct dh_ctx *ctx = (struct dh_ctx *)handle; | |
227 | Bignum ret; | |
228 | ret = modpow(f, ctx->x, ctx->p); | |
229 | return ret; | |
230 | } |