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
|
/*
canohost.c
Author: Tatu Ylonen <ylo@cs.hut.fi>
Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
All rights reserved
Created: Sun Jul 2 17:52:22 1995 ylo
Functions for returning the canonical host name of the remote site.
*/
#include "includes.h"
RCSID("$Id: canohost.c,v 1.3 1999/09/30 05:53:04 deraadt Exp $");
#include "packet.h"
#include "xmalloc.h"
#include "ssh.h"
/* Return the canonical name of the host at the other end of the socket.
The caller should free the returned string with xfree. */
char *get_remote_hostname(int socket)
{
struct sockaddr_in from;
int fromlen, i;
struct hostent *hp;
char name[MAXHOSTNAMELEN];
/* Get IP address of client. */
fromlen = sizeof(from);
memset(&from, 0, sizeof(from));
if (getpeername(socket, (struct sockaddr *)&from, &fromlen) < 0)
{
error("getpeername failed: %.100s", strerror(errno));
strlcpy(name, "UNKNOWN", sizeof name);
goto check_ip_options;
}
/* Map the IP address to a host name. */
hp = gethostbyaddr((char *)&from.sin_addr, sizeof(struct in_addr),
from.sin_family);
if (hp)
{
/* Got host name, find canonic host name. */
if (strchr(hp->h_name, '.') != 0)
strlcpy(name, hp->h_name, sizeof(name));
else if (hp->h_aliases != 0
&& hp->h_aliases[0] != 0
&& strchr(hp->h_aliases[0], '.') != 0)
strlcpy(name, hp->h_aliases[0], sizeof(name));
else
strlcpy(name, hp->h_name, sizeof(name));
/* Convert it to all lowercase (which is expected by the rest of this
software). */
for (i = 0; name[i]; i++)
if (isupper(name[i]))
name[i] = tolower(name[i]);
/* Map it back to an IP address and check that the given address actually
is an address of this host. This is necessary because anyone with
access to a name server can define arbitrary names for an IP address.
Mapping from name to IP address can be trusted better (but can still
be fooled if the intruder has access to the name server of the
domain). */
hp = gethostbyname(name);
if (!hp)
{
log("reverse mapping checking gethostbyname for %.700s failed - POSSIBLE BREAKIN ATTEMPT!", name);
strlcpy(name, inet_ntoa(from.sin_addr), sizeof name);
goto check_ip_options;
}
/* Look for the address from the list of addresses. */
for (i = 0; hp->h_addr_list[i]; i++)
if (memcmp(hp->h_addr_list[i], &from.sin_addr, sizeof(from.sin_addr))
== 0)
break;
/* If we reached the end of the list, the address was not there. */
if (!hp->h_addr_list[i])
{
/* Address not found for the host name. */
log("Address %.100s maps to %.600s, but this does not map back to the address - POSSIBLE BREAKIN ATTEMPT!",
inet_ntoa(from.sin_addr), name);
strlcpy(name, inet_ntoa(from.sin_addr), sizeof name);
goto check_ip_options;
}
/* Address was found for the host name. We accept the host name. */
}
else
{
/* Host name not found. Use ascii representation of the address. */
strlcpy(name, inet_ntoa(from.sin_addr), sizeof name);
log("Could not reverse map address %.100s.", name);
}
check_ip_options:
/* If IP options are supported, make sure there are none (log and clear
them if any are found). Basically we are worried about source routing;
it can be used to pretend you are somebody (ip-address) you are not.
That itself may be "almost acceptable" under certain circumstances,
but rhosts autentication is useless if source routing is accepted.
Notice also that if we just dropped source routing here, the other
side could use IP spoofing to do rest of the interaction and could still
bypass security. So we exit here if we detect any IP options. */
{
unsigned char options[200], *ucp;
char text[1024], *cp;
int option_size, ipproto;
struct protoent *ip;
if ((ip = getprotobyname("ip")) != NULL)
ipproto = ip->p_proto;
else
ipproto = IPPROTO_IP;
option_size = sizeof(options);
if (getsockopt(0, ipproto, IP_OPTIONS, (char *)options,
&option_size) >= 0 && option_size != 0)
{
cp = text;
/* Note: "text" buffer must be at least 3x as big as options. */
for (ucp = options; option_size > 0; ucp++, option_size--, cp += 3)
sprintf(cp, " %2.2x", *ucp);
log("Connection from %.100s with IP options:%.800s",
inet_ntoa(from.sin_addr), text);
packet_disconnect("Connection from %.100s with IP options:%.800s",
inet_ntoa(from.sin_addr), text);
}
}
return xstrdup(name);
}
static char *canonical_host_name = NULL;
static char *canonical_host_ip = NULL;
/* Return the canonical name of the host in the other side of the current
connection. The host name is cached, so it is efficient to call this
several times. */
const char *get_canonical_hostname()
{
/* Check if we have previously retrieved this same name. */
if (canonical_host_name != NULL)
return canonical_host_name;
/* Get the real hostname if socket; otherwise return UNKNOWN. */
if (packet_get_connection_in() == packet_get_connection_out())
canonical_host_name = get_remote_hostname(packet_get_connection_in());
else
canonical_host_name = xstrdup("UNKNOWN");
return canonical_host_name;
}
/* Returns the IP-address of the remote host as a string. The returned
string need not be freed. */
const char *get_remote_ipaddr()
{
struct sockaddr_in from;
int fromlen, socket;
/* Check if we have previously retrieved this same name. */
if (canonical_host_ip != NULL)
return canonical_host_ip;
/* If not a socket, return UNKNOWN. */
if (packet_get_connection_in() != packet_get_connection_out())
{
canonical_host_ip = xstrdup("UNKNOWN");
return canonical_host_ip;
}
/* Get client socket. */
socket = packet_get_connection_in();
/* Get IP address of client. */
fromlen = sizeof(from);
memset(&from, 0, sizeof(from));
if (getpeername(socket, (struct sockaddr *)&from, &fromlen) < 0)
{
error("getpeername failed: %.100s", strerror(errno));
return NULL;
}
/* Get the IP address in ascii. */
canonical_host_ip = xstrdup(inet_ntoa(from.sin_addr));
/* Return ip address string. */
return canonical_host_ip;
}
/* Returns the port of the peer of the socket. */
int get_peer_port(int sock)
{
struct sockaddr_in from;
int fromlen;
/* Get IP address of client. */
fromlen = sizeof(from);
memset(&from, 0, sizeof(from));
if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0)
{
error("getpeername failed: %.100s", strerror(errno));
return 0;
}
/* Return port number. */
return ntohs(from.sin_port);
}
/* Returns the port number of the remote host. */
int get_remote_port()
{
int socket;
/* If the connection is not a socket, return 65535. This is intentionally
chosen to be an unprivileged port number. */
if (packet_get_connection_in() != packet_get_connection_out())
return 65535;
/* Get client socket. */
socket = packet_get_connection_in();
/* Get and return the peer port number. */
return get_peer_port(socket);
}
|
