1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
|
/* This bit implements a simple API for using the SRP library over sockets. */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include "t_defines.h"
#include "t_pwd.h"
#include "t_server.h"
#include "t_client.h"
#include "tinysrp.h"
#ifndef MSG_WAITALL
#ifdef linux
#define MSG_WAITALL 0x100 /* somehow not defined on my box */
#endif
#endif
/* This is called by the client with a connected socket, username, and
passphrase. pass can be NULL in which case the user is queried. */
int tsrp_client_authenticate(int s, char *user, char *pass, TSRP_SESSION *tsrp)
{
int i, index;
unsigned char username[MAXUSERLEN + 1], sbuf[MAXSALTLEN];
unsigned char msgbuf[MAXPARAMLEN + 1], bbuf[MAXPARAMLEN];
unsigned char passbuf[128], *skey;
struct t_client *tc;
struct t_preconf *tcp; /* @@@ should go away */
struct t_num salt, *A, B;
/* Send the username. */
i = strlen(user);
if (i > MAXUSERLEN) {
i = MAXUSERLEN;
}
msgbuf[0] = i;
memcpy(msgbuf + 1, user, i);
if (send(s, msgbuf, i + 1, 0) < 0) {
return 0;
}
memcpy(username, user, i);
username[i] = '\0';
/* Get the prime index and salt. */
i = recv(s, msgbuf, 2, MSG_WAITALL);
if (i <= 0) {
return 0;
}
index = msgbuf[0];
if (index <= 0 || index > t_getprecount()) {
return 0;
}
tcp = t_getpreparam(index - 1);
salt.len = msgbuf[1];
if (salt.len > MAXSALTLEN) {
return 0;
}
salt.data = sbuf;
i = recv(s, sbuf, salt.len, MSG_WAITALL);
if (i <= 0) {
return 0;
}
/* @@@ t_clientopen() needs a variant that takes the index */
tc = t_clientopen(username, &tcp->modulus, &tcp->generator, &salt);
if (tc == NULL) {
return 0;
}
/* Calculate A and send it to the server. */
A = t_clientgenexp(tc);
msgbuf[0] = A->len - 1; /* len is max 256 */
memcpy(msgbuf + 1, A->data, A->len);
if (send(s, msgbuf, A->len + 1, 0) < 0) {
return 0;
}
/* Ask the user for the passphrase. */
if (pass == NULL) {
t_getpass(passbuf, sizeof(passbuf), "Enter password:");
pass = passbuf;
}
t_clientpasswd(tc, pass);
/* Get B from the server. */
i = recv(s, msgbuf, 1, 0);
if (i <= 0) {
return 0;
}
B.len = msgbuf[0] + 1;
B.data = bbuf;
i = recv(s, bbuf, B.len, MSG_WAITALL);
if (i <= 0) {
return 0;
}
/* Compute the session key. */
skey = t_clientgetkey(tc, &B);
if (skey == NULL) {
return 0;
}
/* Send the response. */
if (send(s, t_clientresponse(tc), RESPONSE_LEN, 0) < 0) {
return 0;
}
/* Get the server's response. */
i = recv(s, msgbuf, RESPONSE_LEN, MSG_WAITALL);
if (i <= 0) {
return 0;
}
if (t_clientverify(tc, msgbuf) != 0) {
return 0;
}
/* All done. Now copy the key and clean up. */
if (tsrp) {
memcpy(tsrp->username, username, strlen(username) + 1);
memcpy(tsrp->key, skey, SESSION_KEY_LEN);
}
t_clientclose(tc);
return 1;
}
/* This is called by the server with a connected socket. */
int tsrp_server_authenticate(int s, TSRP_SESSION *tsrp)
{
int i, j;
unsigned char username[MAXUSERLEN], *skey;
unsigned char msgbuf[MAXPARAMLEN + 1], abuf[MAXPARAMLEN];
struct t_server *ts;
struct t_num A, *B;
/* Get the username. */
i = recv(s, msgbuf, 1, 0);
if (i <= 0) {
return 0;
}
j = msgbuf[0];
i = recv(s, username, j, MSG_WAITALL);
if (i <= 0) {
return 0;
}
username[j] = '\0';
ts = t_serveropen(username);
if (ts == NULL) {
return 0;
}
/* Send the prime index and the salt. */
msgbuf[0] = ts->index; /* max 256 primes... */
i = ts->s.len;
msgbuf[1] = i;
memcpy(msgbuf + 2, ts->s.data, i);
if (send(s, msgbuf, i + 2, 0) < 0) {
return 0;
}
/* Calculate B while we're waiting. */
B = t_servergenexp(ts);
/* Get A from the client. */
i = recv(s, msgbuf, 1, 0);
if (i <= 0) {
return 0;
}
A.len = msgbuf[0] + 1;
A.data = abuf;
i = recv(s, abuf, A.len, MSG_WAITALL);
if (i <= 0) {
return 0;
}
/* Now send B. */
msgbuf[0] = B->len - 1;
memcpy(msgbuf + 1, B->data, B->len);
if (send(s, msgbuf, B->len + 1, 0) < 0) {
return 0;
}
/* Calculate the session key while we're waiting. */
skey = t_servergetkey(ts, &A);
if (skey == NULL) {
return 0;
}
/* Get the response from the client. */
i = recv(s, msgbuf, RESPONSE_LEN, MSG_WAITALL);
if (i <= 0) {
return 0;
}
if (t_serververify(ts, msgbuf) != 0) {
return 0;
}
/* Client authenticated. Now authenticate ourselves to the client. */
if (send(s, t_serverresponse(ts), RESPONSE_LEN, 0) < 0) {
return 0;
}
/* Copy the key and clean up. */
if (tsrp) {
memcpy(tsrp->username, username, strlen(username) + 1);
memcpy(tsrp->key, skey, SESSION_KEY_LEN);
}
t_serverclose(ts);
return 1;
}
|
