diff options
author | Damien Miller <djm@mindrot.org> | 1999-10-27 13:42:43 +1000 |
---|---|---|
committer | Damien Miller <djm@mindrot.org> | 1999-10-27 13:42:43 +1000 |
commit | d4a8b7e34dd619a4debf9a206c81db26d1402ea6 (patch) | |
tree | a47d770a2f790f40d18b0982d4e55fa7cfb1fa3b /canohost.c |
Initial revision
Diffstat (limited to 'canohost.c')
-rw-r--r-- | canohost.c | 234 |
1 files changed, 234 insertions, 0 deletions
diff --git a/canohost.c b/canohost.c new file mode 100644 index 000000000..85d97292b --- /dev/null +++ b/canohost.c | |||
@@ -0,0 +1,234 @@ | |||
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: canohost.c,v 1.1 1999/10/27 03:42:43 damien Exp $"); | ||
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 | } | ||