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8efc0c15 | 1 | /* |
2 | ||
3 | canohost.c | |
4 | ||
5 | Author: Tatu Ylonen <ylo@cs.hut.fi> | |
6 | ||
7 | Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
8 | All rights reserved | |
9 | ||
10 | Created: Sun Jul 2 17:52:22 1995 ylo | |
11 | ||
12 | Functions for returning the canonical host name of the remote site. | |
13 | ||
14 | */ | |
15 | ||
16 | #include "includes.h" | |
17 | RCSID("$Id$"); | |
18 | ||
19 | #include "packet.h" | |
20 | #include "xmalloc.h" | |
21 | #include "ssh.h" | |
22 | ||
23 | /* Return the canonical name of the host at the other end of the socket. | |
24 | The caller should free the returned string with xfree. */ | |
25 | ||
26 | char *get_remote_hostname(int socket) | |
27 | { | |
28 | struct sockaddr_in from; | |
29 | int fromlen, i; | |
30 | struct hostent *hp; | |
31 | char name[MAXHOSTNAMELEN]; | |
32 | ||
33 | /* Get IP address of client. */ | |
34 | fromlen = sizeof(from); | |
35 | memset(&from, 0, sizeof(from)); | |
36 | if (getpeername(socket, (struct sockaddr *)&from, &fromlen) < 0) | |
37 | { | |
38 | error("getpeername failed: %.100s", strerror(errno)); | |
39 | strlcpy(name, "UNKNOWN", sizeof name); | |
40 | goto check_ip_options; | |
41 | } | |
42 | ||
43 | /* Map the IP address to a host name. */ | |
44 | hp = gethostbyaddr((char *)&from.sin_addr, sizeof(struct in_addr), | |
45 | from.sin_family); | |
46 | if (hp) | |
47 | { | |
48 | /* Got host name, find canonic host name. */ | |
49 | if (strchr(hp->h_name, '.') != 0) | |
50 | strlcpy(name, hp->h_name, sizeof(name)); | |
51 | else if (hp->h_aliases != 0 | |
52 | && hp->h_aliases[0] != 0 | |
53 | && strchr(hp->h_aliases[0], '.') != 0) | |
54 | strlcpy(name, hp->h_aliases[0], sizeof(name)); | |
55 | else | |
56 | strlcpy(name, hp->h_name, sizeof(name)); | |
57 | ||
58 | /* Convert it to all lowercase (which is expected by the rest of this | |
59 | software). */ | |
60 | for (i = 0; name[i]; i++) | |
61 | if (isupper(name[i])) | |
62 | name[i] = tolower(name[i]); | |
63 | ||
64 | /* Map it back to an IP address and check that the given address actually | |
65 | is an address of this host. This is necessary because anyone with | |
66 | access to a name server can define arbitrary names for an IP address. | |
67 | Mapping from name to IP address can be trusted better (but can still | |
68 | be fooled if the intruder has access to the name server of the | |
69 | domain). */ | |
70 | hp = gethostbyname(name); | |
71 | if (!hp) | |
72 | { | |
73 | log("reverse mapping checking gethostbyname for %.700s failed - POSSIBLE BREAKIN ATTEMPT!", name); | |
74 | strlcpy(name, inet_ntoa(from.sin_addr), sizeof name); | |
75 | goto check_ip_options; | |
76 | } | |
77 | /* Look for the address from the list of addresses. */ | |
78 | for (i = 0; hp->h_addr_list[i]; i++) | |
79 | if (memcmp(hp->h_addr_list[i], &from.sin_addr, sizeof(from.sin_addr)) | |
80 | == 0) | |
81 | break; | |
82 | /* If we reached the end of the list, the address was not there. */ | |
83 | if (!hp->h_addr_list[i]) | |
84 | { | |
85 | /* Address not found for the host name. */ | |
86 | log("Address %.100s maps to %.600s, but this does not map back to the address - POSSIBLE BREAKIN ATTEMPT!", | |
87 | inet_ntoa(from.sin_addr), name); | |
88 | strlcpy(name, inet_ntoa(from.sin_addr), sizeof name); | |
89 | goto check_ip_options; | |
90 | } | |
91 | /* Address was found for the host name. We accept the host name. */ | |
92 | } | |
93 | else | |
94 | { | |
95 | /* Host name not found. Use ascii representation of the address. */ | |
96 | strlcpy(name, inet_ntoa(from.sin_addr), sizeof name); | |
97 | log("Could not reverse map address %.100s.", name); | |
98 | } | |
99 | ||
100 | check_ip_options: | |
101 | ||
102 | /* If IP options are supported, make sure there are none (log and clear | |
103 | them if any are found). Basically we are worried about source routing; | |
104 | it can be used to pretend you are somebody (ip-address) you are not. | |
105 | That itself may be "almost acceptable" under certain circumstances, | |
106 | but rhosts autentication is useless if source routing is accepted. | |
107 | Notice also that if we just dropped source routing here, the other | |
108 | side could use IP spoofing to do rest of the interaction and could still | |
109 | bypass security. So we exit here if we detect any IP options. */ | |
110 | { | |
111 | unsigned char options[200], *ucp; | |
112 | char text[1024], *cp; | |
113 | int option_size, ipproto; | |
114 | struct protoent *ip; | |
115 | ||
116 | if ((ip = getprotobyname("ip")) != NULL) | |
117 | ipproto = ip->p_proto; | |
118 | else | |
119 | ipproto = IPPROTO_IP; | |
120 | option_size = sizeof(options); | |
121 | if (getsockopt(0, ipproto, IP_OPTIONS, (char *)options, | |
122 | &option_size) >= 0 && option_size != 0) | |
123 | { | |
124 | cp = text; | |
125 | /* Note: "text" buffer must be at least 3x as big as options. */ | |
126 | for (ucp = options; option_size > 0; ucp++, option_size--, cp += 3) | |
127 | sprintf(cp, " %2.2x", *ucp); | |
128 | log("Connection from %.100s with IP options:%.800s", | |
129 | inet_ntoa(from.sin_addr), text); | |
130 | packet_disconnect("Connection from %.100s with IP options:%.800s", | |
131 | inet_ntoa(from.sin_addr), text); | |
132 | } | |
133 | } | |
134 | ||
135 | return xstrdup(name); | |
136 | } | |
137 | ||
138 | static char *canonical_host_name = NULL; | |
139 | static char *canonical_host_ip = NULL; | |
140 | ||
141 | /* Return the canonical name of the host in the other side of the current | |
142 | connection. The host name is cached, so it is efficient to call this | |
143 | several times. */ | |
144 | ||
145 | const char *get_canonical_hostname() | |
146 | { | |
147 | /* Check if we have previously retrieved this same name. */ | |
148 | if (canonical_host_name != NULL) | |
149 | return canonical_host_name; | |
150 | ||
151 | /* Get the real hostname if socket; otherwise return UNKNOWN. */ | |
152 | if (packet_get_connection_in() == packet_get_connection_out()) | |
153 | canonical_host_name = get_remote_hostname(packet_get_connection_in()); | |
154 | else | |
155 | canonical_host_name = xstrdup("UNKNOWN"); | |
156 | ||
157 | return canonical_host_name; | |
158 | } | |
159 | ||
160 | /* Returns the IP-address of the remote host as a string. The returned | |
161 | string need not be freed. */ | |
162 | ||
163 | const char *get_remote_ipaddr() | |
164 | { | |
165 | struct sockaddr_in from; | |
166 | int fromlen, socket; | |
167 | ||
168 | /* Check if we have previously retrieved this same name. */ | |
169 | if (canonical_host_ip != NULL) | |
170 | return canonical_host_ip; | |
171 | ||
172 | /* If not a socket, return UNKNOWN. */ | |
173 | if (packet_get_connection_in() != packet_get_connection_out()) | |
174 | { | |
175 | canonical_host_ip = xstrdup("UNKNOWN"); | |
176 | return canonical_host_ip; | |
177 | } | |
178 | ||
179 | /* Get client socket. */ | |
180 | socket = packet_get_connection_in(); | |
181 | ||
182 | /* Get IP address of client. */ | |
183 | fromlen = sizeof(from); | |
184 | memset(&from, 0, sizeof(from)); | |
185 | if (getpeername(socket, (struct sockaddr *)&from, &fromlen) < 0) | |
186 | { | |
187 | error("getpeername failed: %.100s", strerror(errno)); | |
188 | return NULL; | |
189 | } | |
190 | ||
191 | /* Get the IP address in ascii. */ | |
192 | canonical_host_ip = xstrdup(inet_ntoa(from.sin_addr)); | |
193 | ||
194 | /* Return ip address string. */ | |
195 | return canonical_host_ip; | |
196 | } | |
197 | ||
198 | /* Returns the port of the peer of the socket. */ | |
199 | ||
200 | int get_peer_port(int sock) | |
201 | { | |
202 | struct sockaddr_in from; | |
203 | int fromlen; | |
204 | ||
205 | /* Get IP address of client. */ | |
206 | fromlen = sizeof(from); | |
207 | memset(&from, 0, sizeof(from)); | |
208 | if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) | |
209 | { | |
210 | error("getpeername failed: %.100s", strerror(errno)); | |
211 | return 0; | |
212 | } | |
213 | ||
214 | /* Return port number. */ | |
215 | return ntohs(from.sin_port); | |
216 | } | |
217 | ||
218 | /* Returns the port number of the remote host. */ | |
219 | ||
220 | int get_remote_port() | |
221 | { | |
222 | int socket; | |
223 | ||
224 | /* If the connection is not a socket, return 65535. This is intentionally | |
225 | chosen to be an unprivileged port number. */ | |
226 | if (packet_get_connection_in() != packet_get_connection_out()) | |
227 | return 65535; | |
228 | ||
229 | /* Get client socket. */ | |
230 | socket = packet_get_connection_in(); | |
231 | ||
232 | /* Get and return the peer port number. */ | |
233 | return get_peer_port(socket); | |
234 | } |