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
|
/*
20140110
20241212 - reformated using clang-format
Jan Mojzis
Public domain.
*/
#include <pwd.h>
#include "buf.h"
#include "ssh.h"
#include "e.h"
#include "str.h"
#include "packetparser.h"
#include "subprocess.h"
#include "sshcrypto.h"
#include "bug.h"
#include "purge.h"
#include "log.h"
#include "packet.h"
int packet_auth(struct buf *b, struct buf *b2, int flagnoneauth) {
crypto_uint8 ch, flagsignature;
long long pos, i, count, sign_bytes = 0;
crypto_uint32 len;
const char *pkname;
int (*sign_open)(unsigned char *, unsigned long long *,
const unsigned char *, unsigned long long,
const unsigned char *) = 0;
int (*parsesignpk)(unsigned char *, const unsigned char *, long long) = 0;
int (*parsesignature)(unsigned char *, const unsigned char *, long long) =
0;
void (*putsignpk)(struct buf *, const unsigned char *) = 0;
void (*putsignpkbase64)(struct buf *, const unsigned char *) = 0;
unsigned char pk[sshcrypto_sign_PUBLICKEYMAX];
unsigned char sig[sshcrypto_sign_MAX];
unsigned long long smlen;
buf_purge(b);
/* parse "ssh-userauth" */
pos = 0;
if (!packet_getall(b, SSH_MSG_SERVICE_REQUEST)) return 0;
pos = packetparser_uint8(b->buf, b->len, pos,
&ch); /* SSH_MSG_SERVICE_REQUEST */
if (ch != SSH_MSG_SERVICE_REQUEST) bug_proto();
pos = packetparser_uint32(b->buf, b->len, pos, &len); /* "ssh-userauth" */
pos = packetparser_skip(b->buf, b->len, pos, len);
if (!str_equaln((char *) b->buf + pos - len, len, "ssh-userauth"))
bug_proto();
pos = packetparser_end(b->buf, b->len, pos);
/* send service accept */
b->buf[0] = SSH_MSG_SERVICE_ACCEPT;
packet_put(b);
if (!packet_sendall()) return 0;
for (count = 0; count < 32; ++count) {
/* receive userauth request */
pkname = "unknown";
pos = 0;
buf_purge(b);
if (!packet_getall(b, SSH_MSG_USERAUTH_REQUEST)) return 0;
pos = packetparser_uint8(b->buf, b->len, pos,
&ch); /* SSH_MSG_USERAUTH_REQUEST */
if (ch != SSH_MSG_USERAUTH_REQUEST) bug_proto();
pos = packetparser_uint32(b->buf, b->len, pos, &len); /* name */
if (len >= sizeof packet.name) bug_proto();
pos = packetparser_copy(b->buf, b->len, pos,
(unsigned char *) packet.name, len);
packet.name[len] = 0;
pos = packetparser_uint32(b->buf, b->len, pos,
&len); /* "ssh-connection" */
pos = packetparser_skip(b->buf, b->len, pos, len);
if (!str_equaln((char *) b->buf + pos - len, len, "ssh-connection"))
bug_proto();
pos = packetparser_uint32(b->buf, b->len, pos,
&len); /* publickey/password/hostbased/none */
pos = packetparser_skip(b->buf, b->len, pos, len);
if (str_equaln((char *) b->buf + pos - len, len, "none")) {
/*
if auth. none is enabled get the user from UID
*/
if (flagnoneauth) {
struct passwd *pw;
pkname = "none";
pw = getpwuid(geteuid());
if (!pw) bug();
str_copyn(packet.name, sizeof packet.name, pw->pw_name);
b->len = 0;
b->buf[0] = 0;
goto authorized;
}
}
if (str_equaln((char *) b->buf + pos - len, len, "password"))
pkname = "password";
if (str_equaln((char *) b->buf + pos - len, len, "hostbased"))
pkname = "hostbased";
if (str_equaln((char *) b->buf + pos - len, len, "publickey")) {
pos = packetparser_uint8(b->buf, b->len, pos, &flagsignature);
pos = packetparser_uint32(b->buf, b->len, pos,
&len); /* public key algorithm name */
pos = packetparser_skip(b->buf, b->len, pos, len);
if (b->buf[pos] != 0) bug_proto();
pkname = (char *) b->buf + pos - len; /* XXX */
sign_open = 0;
parsesignpk = 0;
putsignpk = 0;
putsignpkbase64 = 0;
parsesignature = 0;
sign_bytes = 0;
for (i = 0; sshcrypto_keys[i].name; ++i) {
if (!sshcrypto_keys[i].sign_flagclient) continue;
if (!str_equaln(pkname, len, sshcrypto_keys[i].name)) continue;
pkname = sshcrypto_keys[i].name;
sign_open = sshcrypto_keys[i].sign_open;
parsesignature = sshcrypto_keys[i].parsesignature;
parsesignpk = sshcrypto_keys[i].parsesignpk;
putsignpk = sshcrypto_keys[i].buf_putsignpk;
putsignpkbase64 = sshcrypto_keys[i].buf_putsignpkbase64;
sign_bytes = sshcrypto_keys[i].sign_bytes;
break;
}
if (sign_open && parsesignpk && putsignpk && putsignpkbase64 &&
parsesignature) {
pos = packetparser_uint32(b->buf, b->len, pos,
&len); /* public key blob */
pos = packetparser_skip(b->buf, b->len, pos, len);
if (!parsesignpk(pk, b->buf + pos - len, len)) bug_proto();
if (!flagsignature) {
/* 'publickey' ... without signature */
buf_purge(b);
buf_putnum8(b, SSH_MSG_USERAUTH_PK_OK);
buf_putstring(b, pkname);
putsignpk(b, pk);
packet_put(b);
if (!packet_sendall()) return 0;
continue;
}
/* 'publickey' ... with signature */
pos = packetparser_uint32(b->buf, b->len, pos,
&len); /* signature blob */
pos = packetparser_skip(b->buf, b->len, pos, len);
if (!parsesignature(sig, b->buf + pos - len, len)) bug_proto();
pos = packetparser_end(b->buf, b->len, pos);
purge(b->buf + b->len - len - 4, len + 4);
b->len -= len + 4;
/* authenticate user - verify signature */
buf_purge(b2);
buf_put(b2, sig, sign_bytes);
buf_putstringlen(b2, packet.sessionid, sshcrypto_hash_bytes);
buf_put(b2, b->buf, b->len);
buf_purge(b);
if (b->alloc <= b2->len) bug_nomem();
if (sign_open(b->buf, &smlen, b2->buf, b2->len, pk) != 0) {
errno = EAUTH;
bug();
}
b->len = smlen;
buf_purge(b);
/* authorize user - using authorized_keys */
buf_purge(b);
putsignpkbase64(b, pk);
buf_putnum8(b, 0);
if (subprocess_auth(packet.name, pkname, (char *) b->buf) == 0)
goto authorized;
}
}
/* reject */
log_d5("auth: ", packet.name, ": ", pkname, " rejected");
buf_purge(b);
buf_putnum8(b, SSH_MSG_USERAUTH_FAILURE);
buf_putstring(b, "publickey");
buf_putnum8(b, 0);
packet_put(b);
if (!packet_sendall()) return 0;
}
log_w1("auth: too many authentication tries");
return 0;
authorized:
/* authenticated + authorized */
log_i7("auth: ", packet.name, ": ", pkname, " ", (char *) b->buf,
" accepted");
buf_purge(b);
buf_putnum8(b, SSH_MSG_USERAUTH_SUCCESS);
packet_put(b);
if (!packet_sendall()) return 0;
purge(pk, sizeof pk);
purge(sig, sizeof sig);
return 1;
}
|
