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]))
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); }
24 static void getstring(char **data, int *datalen, char **p, int *length) {
28 *length = GET_32BIT(*data);
29 *datalen -= 4; *data += 4;
30 if (*datalen < *length)
33 *data += *length; *datalen -= *length;
35 static Bignum getmp(char **data, int *datalen) {
40 getstring(data, datalen, &p, &length);
44 return NULL; /* negative mp */
45 b = bignum_from_bytes(p, length);
49 static Bignum get160(char **data, int *datalen) {
52 b = bignum_from_bytes(*data, 20);
53 *data += 20; *datalen -= 20;
62 static void *dss_newkey(char *data, int len) {
67 dss = smalloc(sizeof(struct dss_key));
68 if (!dss) return NULL;
69 getstring(&data, &len, &p, &slen);
76 printf(" %02x", (unsigned char)(data[i]));
81 if (!p || memcmp(p, "ssh-dss", 7)) {
85 dss->p = getmp(&data, &len);
86 dss->q = getmp(&data, &len);
87 dss->g = getmp(&data, &len);
88 dss->y = getmp(&data, &len);
93 static void dss_freekey(void *key) {
94 struct dss_key *dss = (struct dss_key *)key;
102 static char *dss_fmtkey(void *key) {
103 struct dss_key *dss = (struct dss_key *)key;
105 int len, i, pos, nibbles;
106 static const char hex[] = "0123456789abcdef";
109 len = 8 + 4 + 1; /* 4 x "0x", punctuation, \0 */
110 len += 4 * (ssh1_bignum_bitcount(dss->p)+15)/16;
111 len += 4 * (ssh1_bignum_bitcount(dss->q)+15)/16;
112 len += 4 * (ssh1_bignum_bitcount(dss->g)+15)/16;
113 len += 4 * (ssh1_bignum_bitcount(dss->y)+15)/16;
118 pos += sprintf(p+pos, "0x");
119 nibbles = (3 + ssh1_bignum_bitcount(dss->p))/4; if (nibbles<1) nibbles=1;
120 for (i=nibbles; i-- ;)
121 p[pos++] = hex[(bignum_byte(dss->p, i/2) >> (4*(i%2))) & 0xF];
122 pos += sprintf(p+pos, ",0x");
123 nibbles = (3 + ssh1_bignum_bitcount(dss->q))/4; if (nibbles<1) nibbles=1;
124 for (i=nibbles; i-- ;)
125 p[pos++] = hex[(bignum_byte(dss->q, i/2) >> (4*(i%2))) & 0xF];
126 pos += sprintf(p+pos, ",0x");
127 nibbles = (3 + ssh1_bignum_bitcount(dss->g))/4; if (nibbles<1) nibbles=1;
128 for (i=nibbles; i-- ;)
129 p[pos++] = hex[(bignum_byte(dss->g, i/2) >> (4*(i%2))) & 0xF];
130 pos += sprintf(p+pos, ",0x");
131 nibbles = (3 + ssh1_bignum_bitcount(dss->y))/4; if (nibbles<1) nibbles=1;
132 for (i=nibbles; i-- ;)
133 p[pos++] = hex[(bignum_byte(dss->y, i/2) >> (4*(i%2))) & 0xF];
138 static char *dss_fingerprint(void *key) {
139 struct dss_key *dss = (struct dss_key *)key;
140 struct MD5Context md5c;
141 unsigned char digest[16], lenbuf[4];
142 char buffer[16*3+40];
147 MD5Update(&md5c, "\0\0\0\7ssh-dss", 11);
149 #define ADD_BIGNUM(bignum) \
150 numlen = (ssh1_bignum_bitcount(bignum)+8)/8; \
151 PUT_32BIT(lenbuf, numlen); MD5Update(&md5c, lenbuf, 4); \
152 for (i = numlen; i-- ;) { \
153 unsigned char c = bignum_byte(bignum, i); \
154 MD5Update(&md5c, &c, 1); \
162 MD5Final(digest, &md5c);
164 sprintf(buffer, "ssh-dss %d ", ssh1_bignum_bitcount(dss->p));
165 for (i = 0; i < 16; i++)
166 sprintf(buffer+strlen(buffer), "%s%02x", i?":":"", digest[i]);
167 ret = smalloc(strlen(buffer)+1);
173 static int dss_verifysig(void *key, char *sig, int siglen,
174 char *data, int datalen) {
175 struct dss_key *dss = (struct dss_key *)key;
179 Bignum r, s, w, gu1p, yu2p, gu1yu2p, u1, u2, sha, v;
189 for (i=0;i<siglen;i++)
190 printf(" %02x", (unsigned char)(sig[i]));
195 * Commercial SSH (2.0.13) and OpenSSH disagree over the format
196 * of a DSA signature. OpenSSH is in line with the IETF drafts:
197 * it uses a string "ssh-dss", followed by a 40-byte string
198 * containing two 160-bit integers end-to-end. Commercial SSH
199 * can't be bothered with the header bit, and considers a DSA
200 * signature blob to be _just_ the 40-byte string containing
201 * the two 160-bit integers. We tell them apart by measuring
202 * the length: length 40 means the commercial-SSH bug, anything
203 * else is assumed to be IETF-compliant.
205 if (siglen != 40) { /* bug not present; read admin fields */
206 getstring(&sig, &siglen, &p, &slen);
207 if (!p || slen != 7 || memcmp(p, "ssh-dss", 7)) {
210 sig += 4, siglen -= 4; /* skip yet another length field */
212 diagbn("p=", dss->p);
213 diagbn("q=", dss->q);
214 diagbn("g=", dss->g);
215 diagbn("y=", dss->y);
216 r = get160(&sig, &siglen);
218 s = get160(&sig, &siglen);
224 * Step 1. w <- s^-1 mod q.
226 w = modinv(s, dss->q);
230 * Step 2. u1 <- SHA(message) * w mod q.
232 SHA_Simple(data, datalen, hash);
233 p = hash; slen = 20; sha = get160(&p, &slen);
235 u1 = modmul(sha, w, dss->q);
239 * Step 3. u2 <- r * w mod q.
241 u2 = modmul(r, w, dss->q);
245 * Step 4. v <- (g^u1 * y^u2 mod p) mod q.
247 gu1p = modpow(dss->g, u1, dss->p);
248 diagbn("gu1p=", gu1p);
249 yu2p = modpow(dss->y, u2, dss->p);
250 diagbn("yu2p=", yu2p);
251 gu1yu2p = modmul(gu1p, yu2p, dss->p);
252 diagbn("gu1yu2p=", gu1yu2p);
253 v = modmul(gu1yu2p, One, dss->q);
254 diagbn("gu1yu2q=v=", v);
258 * Step 5. v should now be equal to r.
261 ret = !bignum_cmp(v, r);
275 int dss_sign(void *key, char *sig, int siglen,
276 char *data, int datalen) {
277 return 0; /* do nothing */
280 struct ssh_signkey ssh_dss = {