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 static void getstring(char **data, int *datalen, char **p, int *length) {
16 *length = GET_32BIT(*data);
17 *datalen -= 4; *data += 4;
18 if (*datalen < *length)
21 *data += *length; *datalen -= *length;
23 static Bignum getmp(char **data, int *datalen) {
28 getstring(data, datalen, &p, &length);
32 return NULL; /* negative mp */
33 b = newbn((length+1)/2);
34 for (i = 0; i < length; i++) {
37 b[j/2+1] |= ((unsigned char)p[i]) << 8;
39 b[j/2+1] |= ((unsigned char)p[i]);
44 static Bignum get160(char **data, int *datalen) {
50 *data += 20; *datalen -= 20;
53 while (length > 0 && !p[0])
55 b = newbn((length+1)/2);
56 for (i = 0; i < length; i++) {
59 b[j/2+1] |= ((unsigned char)p[i]) << 8;
61 b[j/2+1] |= ((unsigned char)p[i]);
66 static Bignum dss_p, dss_q, dss_g, dss_y;
68 static void dss_setkey(char *data, int len) {
71 getstring(&data, &len, &p, &slen);
72 if (!p || memcmp(p, "ssh-dss", 7)) {
76 dss_p = getmp(&data, &len);
77 dss_q = getmp(&data, &len);
78 dss_g = getmp(&data, &len);
79 dss_y = getmp(&data, &len);
82 static char *dss_fmtkey(void) {
88 len = 7 + 4 + 1; /* "ssh-dss", punctuation, \0 */
89 len += 4 * (dss_p[0] + dss_q[0] + dss_g[0] + dss_y[0]); /* digits */
92 strcpy(p, "ssh-dss:");
93 for (i = dss_p[0]; i > 0; i--) sprintf(p+strlen(p), "%04X", dss_p[i]);
95 for (i = dss_q[0]; i > 0; i--) sprintf(p+strlen(p), "%04X", dss_q[i]);
97 for (i = dss_g[0]; i > 0; i--) sprintf(p+strlen(p), "%04X", dss_g[i]);
99 for (i = dss_y[0]; i > 0; i--) sprintf(p+strlen(p), "%04X", dss_y[i]);
103 static int dss_verifysig(char *sig, int siglen, char *data, int datalen) {
107 Bignum qm2, r, s, w, i1, i2, i3, u1, u2, sha, v;
113 getstring(&sig, &siglen, &p, &slen);
114 if (!p || memcmp(p, "ssh-dss", 7)) {
117 sig += 4, siglen -= 4; /* skip yet another length field */
118 r = get160(&sig, &siglen);
119 s = get160(&sig, &siglen);
124 * Step 1. w <- s^-1 mod q.
128 decbn(qm2); decbn(qm2);
129 /* Now qm2 is q-2, and by Fermat's Little Theorem, s^qm2 == s^-1 (mod q).
130 * This is a silly way to do it; may fix it later. */
131 modpow(s, qm2, dss_q, w);
134 * Step 2. u1 <- SHA(message) * w mod q.
136 u1 = newbn(dss_q[0]);
137 SHA_Simple(data, datalen, hash);
138 p = hash; slen = 20; sha = get160(&p, &slen);
139 modmul(sha, w, dss_q, u1);
142 * Step 3. u2 <- r * w mod q.
144 u2 = newbn(dss_q[0]);
145 modmul(r, w, dss_q, u2);
148 * Step 4. v <- (g^u1 * y^u2 mod p) mod q.
150 i1 = newbn(dss_p[0]);
151 i2 = newbn(dss_p[0]);
152 i3 = newbn(dss_p[0]);
154 modpow(dss_g, u1, dss_p, i1);
155 modpow(dss_y, u2, dss_p, i2);
156 modmul(i1, i2, dss_p, i3);
157 modmul(i3, One, dss_q, v);
160 * Step 5. v should now be equal to r.
164 for (i = 1; i <= v[0] || i <= r[0]; i++) {
165 if ((i > v[0] && r[i] != 0) ||
166 (i > r[0] && v[i] != 0) ||
167 (i <= v[0] && i <= r[0] && r[i] != v[i]))
184 struct ssh_hostkey ssh_dss = {