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
= {