Annotation of src/usr.bin/ssh/canohost.c, Revision 1.5
1.1 deraadt 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"
1.5 ! markus 17: RCSID("$Id: canohost.c,v 1.4 1999/11/14 22:30:58 markus Exp $");
1.1 deraadt 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;
1.2 deraadt 31: char name[MAXHOSTNAMELEN];
1.1 deraadt 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: {
1.5 ! markus 38: debug("getpeername failed: %.100s", strerror(errno));
! 39: fatal_cleanup();
1.1 deraadt 40: }
41:
42: /* Map the IP address to a host name. */
43: hp = gethostbyaddr((char *)&from.sin_addr, sizeof(struct in_addr),
44: from.sin_family);
45: if (hp)
46: {
47: /* Got host name, find canonic host name. */
48: if (strchr(hp->h_name, '.') != 0)
1.2 deraadt 49: strlcpy(name, hp->h_name, sizeof(name));
1.1 deraadt 50: else if (hp->h_aliases != 0
51: && hp->h_aliases[0] != 0
52: && strchr(hp->h_aliases[0], '.') != 0)
1.2 deraadt 53: strlcpy(name, hp->h_aliases[0], sizeof(name));
1.1 deraadt 54: else
1.2 deraadt 55: strlcpy(name, hp->h_name, sizeof(name));
1.1 deraadt 56:
57: /* Convert it to all lowercase (which is expected by the rest of this
58: software). */
59: for (i = 0; name[i]; i++)
60: if (isupper(name[i]))
61: name[i] = tolower(name[i]);
62:
63: /* Map it back to an IP address and check that the given address actually
64: is an address of this host. This is necessary because anyone with
65: access to a name server can define arbitrary names for an IP address.
66: Mapping from name to IP address can be trusted better (but can still
67: be fooled if the intruder has access to the name server of the
68: domain). */
69: hp = gethostbyname(name);
70: if (!hp)
71: {
72: log("reverse mapping checking gethostbyname for %.700s failed - POSSIBLE BREAKIN ATTEMPT!", name);
1.2 deraadt 73: strlcpy(name, inet_ntoa(from.sin_addr), sizeof name);
1.1 deraadt 74: goto check_ip_options;
75: }
76: /* Look for the address from the list of addresses. */
77: for (i = 0; hp->h_addr_list[i]; i++)
78: if (memcmp(hp->h_addr_list[i], &from.sin_addr, sizeof(from.sin_addr))
79: == 0)
80: break;
81: /* If we reached the end of the list, the address was not there. */
82: if (!hp->h_addr_list[i])
83: {
84: /* Address not found for the host name. */
85: log("Address %.100s maps to %.600s, but this does not map back to the address - POSSIBLE BREAKIN ATTEMPT!",
86: inet_ntoa(from.sin_addr), name);
1.2 deraadt 87: strlcpy(name, inet_ntoa(from.sin_addr), sizeof name);
1.1 deraadt 88: goto check_ip_options;
89: }
90: /* Address was found for the host name. We accept the host name. */
91: }
92: else
93: {
94: /* Host name not found. Use ascii representation of the address. */
1.2 deraadt 95: strlcpy(name, inet_ntoa(from.sin_addr), sizeof name);
1.1 deraadt 96: log("Could not reverse map address %.100s.", name);
97: }
98:
99: check_ip_options:
100:
1.4 markus 101: /* If IP options are supported, make sure there are none (log and disconnect
1.1 deraadt 102: them if any are found). Basically we are worried about source routing;
103: it can be used to pretend you are somebody (ip-address) you are not.
104: That itself may be "almost acceptable" under certain circumstances,
105: but rhosts autentication is useless if source routing is accepted.
106: Notice also that if we just dropped source routing here, the other
107: side could use IP spoofing to do rest of the interaction and could still
108: bypass security. So we exit here if we detect any IP options. */
109: {
110: unsigned char options[200], *ucp;
111: char text[1024], *cp;
112: int option_size, ipproto;
113: struct protoent *ip;
114:
115: if ((ip = getprotobyname("ip")) != NULL)
116: ipproto = ip->p_proto;
117: else
118: ipproto = IPPROTO_IP;
119: option_size = sizeof(options);
120: if (getsockopt(0, ipproto, IP_OPTIONS, (char *)options,
121: &option_size) >= 0 && option_size != 0)
122: {
123: cp = text;
124: /* Note: "text" buffer must be at least 3x as big as options. */
125: for (ucp = options; option_size > 0; ucp++, option_size--, cp += 3)
126: sprintf(cp, " %2.2x", *ucp);
127: log("Connection from %.100s with IP options:%.800s",
128: inet_ntoa(from.sin_addr), text);
129: packet_disconnect("Connection from %.100s with IP options:%.800s",
130: inet_ntoa(from.sin_addr), text);
131: }
132: }
133:
134: return xstrdup(name);
135: }
136:
137: static char *canonical_host_name = NULL;
138: static char *canonical_host_ip = NULL;
139:
140: /* Return the canonical name of the host in the other side of the current
141: connection. The host name is cached, so it is efficient to call this
142: several times. */
143:
144: const char *get_canonical_hostname()
145: {
146: /* Check if we have previously retrieved this same name. */
147: if (canonical_host_name != NULL)
148: return canonical_host_name;
149:
150: /* Get the real hostname if socket; otherwise return UNKNOWN. */
151: if (packet_get_connection_in() == packet_get_connection_out())
152: canonical_host_name = get_remote_hostname(packet_get_connection_in());
153: else
154: canonical_host_name = xstrdup("UNKNOWN");
155:
156: return canonical_host_name;
157: }
158:
159: /* Returns the IP-address of the remote host as a string. The returned
160: string need not be freed. */
161:
162: const char *get_remote_ipaddr()
163: {
164: struct sockaddr_in from;
165: int fromlen, socket;
166:
167: /* Check if we have previously retrieved this same name. */
168: if (canonical_host_ip != NULL)
169: return canonical_host_ip;
170:
171: /* If not a socket, return UNKNOWN. */
172: if (packet_get_connection_in() != packet_get_connection_out())
173: {
174: canonical_host_ip = xstrdup("UNKNOWN");
175: return canonical_host_ip;
176: }
177:
178: /* Get client socket. */
179: socket = packet_get_connection_in();
180:
181: /* Get IP address of client. */
182: fromlen = sizeof(from);
183: memset(&from, 0, sizeof(from));
184: if (getpeername(socket, (struct sockaddr *)&from, &fromlen) < 0)
185: {
1.5 ! markus 186: debug("getpeername failed: %.100s", strerror(errno));
! 187: fatal_cleanup();
1.1 deraadt 188: }
189:
190: /* Get the IP address in ascii. */
191: canonical_host_ip = xstrdup(inet_ntoa(from.sin_addr));
192:
193: /* Return ip address string. */
194: return canonical_host_ip;
195: }
196:
197: /* Returns the port of the peer of the socket. */
198:
199: int get_peer_port(int sock)
200: {
201: struct sockaddr_in from;
202: int fromlen;
203:
204: /* Get IP address of client. */
205: fromlen = sizeof(from);
206: memset(&from, 0, sizeof(from));
207: if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0)
208: {
1.5 ! markus 209: debug("getpeername failed: %.100s", strerror(errno));
! 210: fatal_cleanup();
1.1 deraadt 211: }
212:
213: /* Return port number. */
214: return ntohs(from.sin_port);
215: }
216:
217: /* Returns the port number of the remote host. */
218:
219: int get_remote_port()
220: {
221: int socket;
222:
223: /* If the connection is not a socket, return 65535. This is intentionally
224: chosen to be an unprivileged port number. */
225: if (packet_get_connection_in() != packet_get_connection_out())
226: return 65535;
227:
228: /* Get client socket. */
229: socket = packet_get_connection_in();
230:
231: /* Get and return the peer port number. */
232: return get_peer_port(socket);
233: }
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