7cca0d81 |
1 | #include <stdio.h> |
2 | #include <stdlib.h> |
3 | |
e5574168 |
4 | #include "ssh.h" |
5 | |
7cca0d81 |
6 | #define GET_32BIT(cp) \ |
7 | (((unsigned long)(unsigned char)(cp)[0] << 24) | \ |
8 | ((unsigned long)(unsigned char)(cp)[1] << 16) | \ |
9 | ((unsigned long)(unsigned char)(cp)[2] << 8) | \ |
10 | ((unsigned long)(unsigned char)(cp)[3])) |
11 | |
d5859615 |
12 | #define PUT_32BIT(cp, value) { \ |
13 | (cp)[0] = (unsigned char)((value) >> 24); \ |
14 | (cp)[1] = (unsigned char)((value) >> 16); \ |
15 | (cp)[2] = (unsigned char)((value) >> 8); \ |
16 | (cp)[3] = (unsigned char)(value); } |
17 | |
9c621433 |
18 | #if 0 |
9c621433 |
19 | /* |
20 | * Condition this section in for debugging of DSS. |
21 | */ |
22 | static void diagbn(char *prefix, Bignum md) { |
23 | int i, nibbles, morenibbles; |
24 | static const char hex[] = "0123456789ABCDEF"; |
25 | |
26 | printf("%s0x", prefix ? prefix : ""); |
27 | |
28 | nibbles = (3 + ssh1_bignum_bitcount(md))/4; if (nibbles<1) nibbles=1; |
29 | morenibbles = 4*md[0] - nibbles; |
30 | for (i=0; i<morenibbles; i++) putchar('-'); |
31 | for (i=nibbles; i-- ;) |
32 | putchar(hex[(bignum_byte(md, i/2) >> (4*(i%2))) & 0xF]); |
33 | |
34 | if (prefix) putchar('\n'); |
35 | } |
c5fbd713 |
36 | #define DEBUG_DSS |
9c621433 |
37 | #else |
38 | #define diagbn(x,y) |
39 | #endif |
40 | |
7cca0d81 |
41 | static void getstring(char **data, int *datalen, char **p, int *length) { |
42 | *p = NULL; |
43 | if (*datalen < 4) |
44 | return; |
45 | *length = GET_32BIT(*data); |
46 | *datalen -= 4; *data += 4; |
47 | if (*datalen < *length) |
48 | return; |
49 | *p = *data; |
50 | *data += *length; *datalen -= *length; |
51 | } |
52 | static Bignum getmp(char **data, int *datalen) { |
53 | char *p; |
54 | int i, j, length; |
55 | Bignum b; |
56 | |
57 | getstring(data, datalen, &p, &length); |
58 | if (!p) |
59 | return NULL; |
60 | if (p[0] & 0x80) |
61 | return NULL; /* negative mp */ |
62 | b = newbn((length+1)/2); |
63 | for (i = 0; i < length; i++) { |
64 | j = length - 1 - i; |
65 | if (j & 1) |
66 | b[j/2+1] |= ((unsigned char)p[i]) << 8; |
67 | else |
68 | b[j/2+1] |= ((unsigned char)p[i]); |
69 | } |
9c621433 |
70 | while (b[0] > 1 && b[b[0]] == 0) b[0]--; |
7cca0d81 |
71 | return b; |
72 | } |
73 | |
74 | static Bignum get160(char **data, int *datalen) { |
75 | char *p; |
76 | int i, j, length; |
77 | Bignum b; |
78 | |
79 | p = *data; |
80 | *data += 20; *datalen -= 20; |
81 | |
82 | length = 20; |
83 | while (length > 0 && !p[0]) |
84 | p++, length--; |
85 | b = newbn((length+1)/2); |
86 | for (i = 0; i < length; i++) { |
87 | j = length - 1 - i; |
88 | if (j & 1) |
89 | b[j/2+1] |= ((unsigned char)p[i]) << 8; |
90 | else |
91 | b[j/2+1] |= ((unsigned char)p[i]); |
92 | } |
93 | return b; |
94 | } |
95 | |
e055a386 |
96 | struct dss_key { |
97 | Bignum p, q, g, y; |
98 | }; |
7cca0d81 |
99 | |
e055a386 |
100 | static void *dss_newkey(char *data, int len) { |
7cca0d81 |
101 | char *p; |
102 | int slen; |
e055a386 |
103 | struct dss_key *dss; |
104 | |
dcbde236 |
105 | dss = smalloc(sizeof(struct dss_key)); |
e055a386 |
106 | if (!dss) return NULL; |
7cca0d81 |
107 | getstring(&data, &len, &p, &slen); |
9c621433 |
108 | |
109 | #ifdef DEBUG_DSS |
110 | { |
111 | int i; |
112 | printf("key:"); |
113 | for (i=0;i<len;i++) |
114 | printf(" %02x", (unsigned char)(data[i])); |
115 | printf("\n"); |
116 | } |
117 | #endif |
118 | |
7cca0d81 |
119 | if (!p || memcmp(p, "ssh-dss", 7)) { |
dcbde236 |
120 | sfree(dss); |
e055a386 |
121 | return NULL; |
7cca0d81 |
122 | } |
e055a386 |
123 | dss->p = getmp(&data, &len); |
124 | dss->q = getmp(&data, &len); |
125 | dss->g = getmp(&data, &len); |
126 | dss->y = getmp(&data, &len); |
127 | |
128 | return dss; |
7cca0d81 |
129 | } |
130 | |
e055a386 |
131 | static void dss_freekey(void *key) { |
132 | struct dss_key *dss = (struct dss_key *)key; |
133 | freebn(dss->p); |
134 | freebn(dss->q); |
135 | freebn(dss->g); |
136 | freebn(dss->y); |
dcbde236 |
137 | sfree(dss); |
e055a386 |
138 | } |
139 | |
140 | static char *dss_fmtkey(void *key) { |
141 | struct dss_key *dss = (struct dss_key *)key; |
7cca0d81 |
142 | char *p; |
d5859615 |
143 | int len, i, pos, nibbles; |
144 | static const char hex[] = "0123456789abcdef"; |
e055a386 |
145 | if (!dss->p) |
7cca0d81 |
146 | return NULL; |
d5859615 |
147 | len = 8 + 4 + 1; /* 4 x "0x", punctuation, \0 */ |
e055a386 |
148 | len += 4 * (dss->p[0] + dss->q[0] + dss->g[0] + dss->y[0]); /* digits */ |
dcbde236 |
149 | p = smalloc(len); |
7cca0d81 |
150 | if (!p) return NULL; |
d5859615 |
151 | |
152 | pos = 0; |
153 | pos += sprintf(p+pos, "0x"); |
e055a386 |
154 | nibbles = (3 + ssh1_bignum_bitcount(dss->p))/4; if (nibbles<1) nibbles=1; |
d5859615 |
155 | for (i=nibbles; i-- ;) |
e055a386 |
156 | p[pos++] = hex[(bignum_byte(dss->p, i/2) >> (4*(i%2))) & 0xF]; |
3aa0b691 |
157 | pos += sprintf(p+pos, ",0x"); |
e055a386 |
158 | nibbles = (3 + ssh1_bignum_bitcount(dss->q))/4; if (nibbles<1) nibbles=1; |
d5859615 |
159 | for (i=nibbles; i-- ;) |
e055a386 |
160 | p[pos++] = hex[(bignum_byte(dss->q, i/2) >> (4*(i%2))) & 0xF]; |
3aa0b691 |
161 | pos += sprintf(p+pos, ",0x"); |
e055a386 |
162 | nibbles = (3 + ssh1_bignum_bitcount(dss->g))/4; if (nibbles<1) nibbles=1; |
d5859615 |
163 | for (i=nibbles; i-- ;) |
e055a386 |
164 | p[pos++] = hex[(bignum_byte(dss->g, i/2) >> (4*(i%2))) & 0xF]; |
3aa0b691 |
165 | pos += sprintf(p+pos, ",0x"); |
e055a386 |
166 | nibbles = (3 + ssh1_bignum_bitcount(dss->y))/4; if (nibbles<1) nibbles=1; |
d5859615 |
167 | for (i=nibbles; i-- ;) |
e055a386 |
168 | p[pos++] = hex[(bignum_byte(dss->y, i/2) >> (4*(i%2))) & 0xF]; |
d5859615 |
169 | p[pos] = '\0'; |
7cca0d81 |
170 | return p; |
171 | } |
172 | |
e055a386 |
173 | static char *dss_fingerprint(void *key) { |
174 | struct dss_key *dss = (struct dss_key *)key; |
d5859615 |
175 | struct MD5Context md5c; |
176 | unsigned char digest[16], lenbuf[4]; |
177 | char buffer[16*3+40]; |
178 | char *ret; |
179 | int numlen, i; |
180 | |
181 | MD5Init(&md5c); |
182 | MD5Update(&md5c, "\0\0\0\7ssh-dss", 11); |
183 | |
184 | #define ADD_BIGNUM(bignum) \ |
185 | numlen = (ssh1_bignum_bitcount(bignum)+8)/8; \ |
186 | PUT_32BIT(lenbuf, numlen); MD5Update(&md5c, lenbuf, 4); \ |
187 | for (i = numlen; i-- ;) { \ |
188 | unsigned char c = bignum_byte(bignum, i); \ |
189 | MD5Update(&md5c, &c, 1); \ |
190 | } |
e055a386 |
191 | ADD_BIGNUM(dss->p); |
192 | ADD_BIGNUM(dss->q); |
193 | ADD_BIGNUM(dss->g); |
194 | ADD_BIGNUM(dss->y); |
d5859615 |
195 | #undef ADD_BIGNUM |
196 | |
197 | MD5Final(digest, &md5c); |
198 | |
e055a386 |
199 | sprintf(buffer, "%d ", ssh1_bignum_bitcount(dss->p)); |
d5859615 |
200 | for (i = 0; i < 16; i++) |
201 | sprintf(buffer+strlen(buffer), "%s%02x", i?":":"", digest[i]); |
dcbde236 |
202 | ret = smalloc(strlen(buffer)+1); |
d5859615 |
203 | if (ret) |
204 | strcpy(ret, buffer); |
205 | return ret; |
206 | } |
207 | |
e055a386 |
208 | static int dss_verifysig(void *key, char *sig, int siglen, |
209 | char *data, int datalen) { |
210 | struct dss_key *dss = (struct dss_key *)key; |
7cca0d81 |
211 | char *p; |
c5fbd713 |
212 | int slen; |
7cca0d81 |
213 | char hash[20]; |
59600f67 |
214 | Bignum r, s, w, gu1p, yu2p, gu1yu2p, u1, u2, sha, v; |
7cca0d81 |
215 | int ret; |
216 | |
e055a386 |
217 | if (!dss->p) |
7cca0d81 |
218 | return 0; |
219 | |
9c621433 |
220 | #ifdef DEBUG_DSS |
221 | { |
222 | int i; |
223 | printf("sig:"); |
224 | for (i=0;i<siglen;i++) |
225 | printf(" %02xf", (unsigned char)(sig[i])); |
226 | printf("\n"); |
227 | } |
228 | #endif |
7f7837c8 |
229 | /* |
230 | * Commercial SSH (2.0.13) and OpenSSH disagree over the format |
231 | * of a DSA signature. OpenSSH is in line with the IETF drafts: |
232 | * it uses a string "ssh-dss", followed by a 40-byte string |
233 | * containing two 160-bit integers end-to-end. Commercial SSH |
234 | * can't be bothered with the header bit, and considers a DSA |
235 | * signature blob to be _just_ the 40-byte string containing |
236 | * the two 160-bit integers. We tell them apart by measuring |
237 | * the length: length 40 means the commercial-SSH bug, anything |
238 | * else is assumed to be IETF-compliant. |
239 | */ |
240 | if (siglen != 40) { /* bug not present; read admin fields */ |
241 | getstring(&sig, &siglen, &p, &slen); |
242 | if (!p || memcmp(p, "ssh-dss", 7)) { |
243 | return 0; |
244 | } |
245 | sig += 4, siglen -= 4; /* skip yet another length field */ |
7cca0d81 |
246 | } |
e055a386 |
247 | diagbn("p=", dss->p); |
248 | diagbn("q=", dss->q); |
249 | diagbn("g=", dss->g); |
250 | diagbn("y=", dss->y); |
7cca0d81 |
251 | r = get160(&sig, &siglen); |
9c621433 |
252 | diagbn("r=", r); |
7cca0d81 |
253 | s = get160(&sig, &siglen); |
9c621433 |
254 | diagbn("s=", s); |
7cca0d81 |
255 | if (!r || !s) |
256 | return 0; |
257 | |
258 | /* |
259 | * Step 1. w <- s^-1 mod q. |
260 | */ |
e055a386 |
261 | w = modinv(s, dss->q); |
9c621433 |
262 | diagbn("w=", w); |
7cca0d81 |
263 | |
264 | /* |
265 | * Step 2. u1 <- SHA(message) * w mod q. |
266 | */ |
7cca0d81 |
267 | SHA_Simple(data, datalen, hash); |
268 | p = hash; slen = 20; sha = get160(&p, &slen); |
9c621433 |
269 | diagbn("sha=", sha); |
e055a386 |
270 | u1 = modmul(sha, w, dss->q); |
9c621433 |
271 | diagbn("u1=", u1); |
7cca0d81 |
272 | |
273 | /* |
274 | * Step 3. u2 <- r * w mod q. |
275 | */ |
e055a386 |
276 | u2 = modmul(r, w, dss->q); |
9c621433 |
277 | diagbn("u2=", u2); |
7cca0d81 |
278 | |
279 | /* |
280 | * Step 4. v <- (g^u1 * y^u2 mod p) mod q. |
281 | */ |
e055a386 |
282 | gu1p = modpow(dss->g, u1, dss->p); |
59600f67 |
283 | diagbn("gu1p=", gu1p); |
e055a386 |
284 | yu2p = modpow(dss->y, u2, dss->p); |
59600f67 |
285 | diagbn("yu2p=", yu2p); |
e055a386 |
286 | gu1yu2p = modmul(gu1p, yu2p, dss->p); |
59600f67 |
287 | diagbn("gu1yu2p=", gu1yu2p); |
e055a386 |
288 | v = modmul(gu1yu2p, One, dss->q); |
9c621433 |
289 | diagbn("gu1yu2q=v=", v); |
290 | diagbn("r=", r); |
7cca0d81 |
291 | |
292 | /* |
293 | * Step 5. v should now be equal to r. |
294 | */ |
295 | |
c5fbd713 |
296 | ret = !bignum_cmp(v, r); |
7cca0d81 |
297 | |
298 | freebn(w); |
7cca0d81 |
299 | freebn(sha); |
59600f67 |
300 | freebn(gu1p); |
301 | freebn(yu2p); |
302 | freebn(gu1yu2p); |
7cca0d81 |
303 | freebn(v); |
304 | freebn(r); |
305 | freebn(s); |
306 | |
307 | return ret; |
308 | } |
309 | |
e055a386 |
310 | int dss_sign(void *key, char *sig, int siglen, |
311 | char *data, int datalen) { |
312 | return 0; /* do nothing */ |
313 | } |
314 | |
315 | struct ssh_signkey ssh_dss = { |
316 | dss_newkey, |
317 | dss_freekey, |
7cca0d81 |
318 | dss_fmtkey, |
d5859615 |
319 | dss_fingerprint, |
7cca0d81 |
320 | dss_verifysig, |
e055a386 |
321 | dss_sign, |
d5859615 |
322 | "ssh-dss", |
323 | "dss" |
e5574168 |
324 | }; |