Annotation of src/usr.bin/ssh/canohost.c, Revision 1.21
1.1 deraadt 1: /*
1.7 deraadt 2: * Author: Tatu Ylonen <ylo@cs.hut.fi>
3: * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4: * All rights reserved
5: * Functions for returning the canonical host name of the remote site.
1.12 markus 6: *
1.14 deraadt 7: * As far as I am concerned, the code I have written for this software
8: * can be used freely for any purpose. Any derived versions of this
9: * software must be clearly marked as such, and if the derived work is
10: * incompatible with the protocol description in the RFC file, it must be
11: * called by a name other than "ssh" or "Secure Shell".
1.7 deraadt 12: */
1.1 deraadt 13:
14: #include "includes.h"
1.21 ! itojun 15: RCSID("$OpenBSD: canohost.c,v 1.20 2001/02/03 10:08:37 markus Exp $");
1.1 deraadt 16:
17: #include "packet.h"
18: #include "xmalloc.h"
1.18 markus 19: #include "log.h"
1.21 ! itojun 20: #include "canohost.h"
1.1 deraadt 21:
1.20 markus 22: void check_ip_options(int socket, char *ipaddr);
23:
1.8 markus 24: /*
25: * Return the canonical name of the host at the other end of the socket. The
26: * caller should free the returned string with xfree.
27: */
1.1 deraadt 28:
1.6 markus 29: char *
1.20 markus 30: get_remote_hostname(int socket, int reverse_mapping_check)
1.1 deraadt 31: {
1.10 markus 32: struct sockaddr_storage from;
33: int i;
34: socklen_t fromlen;
35: struct addrinfo hints, *ai, *aitop;
1.20 markus 36: char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
1.6 markus 37:
38: /* Get IP address of client. */
39: fromlen = sizeof(from);
40: memset(&from, 0, sizeof(from));
1.20 markus 41: if (getpeername(socket, (struct sockaddr *) &from, &fromlen) < 0) {
1.6 markus 42: debug("getpeername failed: %.100s", strerror(errno));
43: fatal_cleanup();
44: }
1.20 markus 45: if (from.ss_family == AF_INET)
46: check_ip_options(socket, ntop);
47:
1.10 markus 48: if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
49: NULL, 0, NI_NUMERICHOST) != 0)
50: fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
51:
1.6 markus 52: /* Map the IP address to a host name. */
1.10 markus 53: if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
1.20 markus 54: NULL, 0, NI_NAMEREQD) != 0) {
55: /* Host name not found. Use ip address. */
56: log("Could not reverse map address %.100s.", ntop);
57: return xstrdup(ntop);
1.6 markus 58: }
59:
1.20 markus 60: /* Got host name. */
61: name[sizeof(name) - 1] = '\0';
62: /*
63: * Convert it to all lowercase (which is expected by the rest
64: * of this software).
65: */
66: for (i = 0; name[i]; i++)
67: if (isupper(name[i]))
68: name[i] = tolower(name[i]);
1.6 markus 69:
1.20 markus 70: if (!reverse_mapping_check)
71: return xstrdup(name);
1.8 markus 72: /*
1.20 markus 73: * Map it back to an IP address and check that the given
74: * address actually is an address of this host. This is
75: * necessary because anyone with access to a name server can
76: * define arbitrary names for an IP address. Mapping from
77: * name to IP address can be trusted better (but can still be
78: * fooled if the intruder has access to the name server of
79: * the domain).
1.8 markus 80: */
1.20 markus 81: memset(&hints, 0, sizeof(hints));
82: hints.ai_family = from.ss_family;
83: hints.ai_socktype = SOCK_STREAM;
84: if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
85: log("reverse mapping checking getaddrinfo for %.700s "
86: "failed - POSSIBLE BREAKIN ATTEMPT!", name);
87: return xstrdup(ntop);
88: }
89: /* Look for the address from the list of addresses. */
90: for (ai = aitop; ai; ai = ai->ai_next) {
91: if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
92: sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
93: (strcmp(ntop, ntop2) == 0))
94: break;
95: }
96: freeaddrinfo(aitop);
97: /* If we reached the end of the list, the address was not there. */
98: if (!ai) {
99: /* Address not found for the host name. */
100: log("Address %.100s maps to %.600s, but this does not "
101: "map back to the address - POSSIBLE BREAKIN ATTEMPT!",
102: ntop, name);
103: return xstrdup(ntop);
104: }
105: return xstrdup(name);
106: }
1.6 markus 107:
1.20 markus 108: /*
109: * If IP options are supported, make sure there are none (log and
110: * disconnect them if any are found). Basically we are worried about
111: * source routing; it can be used to pretend you are somebody
112: * (ip-address) you are not. That itself may be "almost acceptable"
113: * under certain circumstances, but rhosts autentication is useless
114: * if source routing is accepted. Notice also that if we just dropped
115: * source routing here, the other side could use IP spoofing to do
116: * rest of the interaction and could still bypass security. So we
117: * exit here if we detect any IP options.
118: */
119: /* IPv4 only */
120: void
121: check_ip_options(int socket, char *ipaddr)
122: {
123: u_char options[200], *ucp;
124: char text[1024], *cp;
125: socklen_t option_size;
126: int ipproto;
127: struct protoent *ip;
128:
129: if ((ip = getprotobyname("ip")) != NULL)
130: ipproto = ip->p_proto;
131: else
132: ipproto = IPPROTO_IP;
133: option_size = sizeof(options);
134: if (getsockopt(socket, ipproto, IP_OPTIONS, (void *)options,
135: &option_size) >= 0 && option_size != 0) {
136: cp = text;
137: /* Note: "text" buffer must be at least 3x as big as options. */
138: for (ucp = options; option_size > 0; ucp++, option_size--, cp += 3)
139: sprintf(cp, " %2.2x", *ucp);
140: log("Connection from %.100s with IP options:%.800s",
141: ipaddr, text);
142: packet_disconnect("Connection from %.100s with IP options:%.800s",
143: ipaddr, text);
1.6 markus 144: }
1.1 deraadt 145: }
146:
1.8 markus 147: /*
148: * Return the canonical name of the host in the other side of the current
149: * connection. The host name is cached, so it is efficient to call this
150: * several times.
151: */
1.1 deraadt 152:
1.6 markus 153: const char *
1.20 markus 154: get_canonical_hostname(int reverse_mapping_check)
1.1 deraadt 155: {
1.10 markus 156: static char *canonical_host_name = NULL;
1.20 markus 157: static int reverse_mapping_checked = 0;
1.10 markus 158:
1.20 markus 159: /* Check if we have previously retrieved name with same option. */
160: if (canonical_host_name != NULL) {
161: if (reverse_mapping_checked != reverse_mapping_check)
162: xfree(canonical_host_name);
163: else
164: return canonical_host_name;
165: }
1.6 markus 166:
167: /* Get the real hostname if socket; otherwise return UNKNOWN. */
1.10 markus 168: if (packet_connection_is_on_socket())
1.20 markus 169: canonical_host_name = get_remote_hostname(
170: packet_get_connection_in(), reverse_mapping_check);
1.6 markus 171: else
172: canonical_host_name = xstrdup("UNKNOWN");
1.1 deraadt 173:
1.20 markus 174: reverse_mapping_checked = reverse_mapping_check;
1.6 markus 175: return canonical_host_name;
1.1 deraadt 176: }
177:
1.8 markus 178: /*
1.19 markus 179: * Returns the remote IP-address of socket as a string. The returned
180: * string must be freed.
1.8 markus 181: */
1.1 deraadt 182:
1.19 markus 183: char *
184: get_peer_ipaddr(int socket)
1.1 deraadt 185: {
1.10 markus 186: struct sockaddr_storage from;
187: socklen_t fromlen;
188: char ntop[NI_MAXHOST];
1.1 deraadt 189:
1.6 markus 190: /* Get IP address of client. */
191: fromlen = sizeof(from);
192: memset(&from, 0, sizeof(from));
193: if (getpeername(socket, (struct sockaddr *) & from, &fromlen) < 0) {
1.19 markus 194: debug("get_peer_ipaddr: getpeername failed: %.100s", strerror(errno));
195: return NULL;
1.6 markus 196: }
197: /* Get the IP address in ascii. */
1.10 markus 198: if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
1.19 markus 199: NULL, 0, NI_NUMERICHOST) != 0) {
200: error("get_peer_ipaddr: getnameinfo NI_NUMERICHOST failed");
201: return NULL;
202: }
203: return xstrdup(ntop);
204: }
205:
206: /*
207: * Returns the IP-address of the remote host as a string. The returned
208: * string must not be freed.
209: */
1.10 markus 210:
1.19 markus 211: const char *
212: get_remote_ipaddr()
213: {
214: static char *canonical_host_ip = NULL;
1.1 deraadt 215:
1.19 markus 216: /* Check whether we have cached the ipaddr. */
217: if (canonical_host_ip == NULL) {
218: if (packet_connection_is_on_socket()) {
219: canonical_host_ip =
220: get_peer_ipaddr(packet_get_connection_in());
221: if (canonical_host_ip == NULL)
222: fatal_cleanup();
223: } else {
224: /* If not on socket, return UNKNOWN. */
225: canonical_host_ip = xstrdup("UNKNOWN");
226: }
227: }
1.6 markus 228: return canonical_host_ip;
1.1 deraadt 229: }
230:
1.10 markus 231: /* Returns the local/remote port for the socket. */
1.1 deraadt 232:
1.10 markus 233: int
234: get_sock_port(int sock, int local)
1.1 deraadt 235: {
1.10 markus 236: struct sockaddr_storage from;
237: socklen_t fromlen;
238: char strport[NI_MAXSERV];
1.1 deraadt 239:
1.6 markus 240: /* Get IP address of client. */
241: fromlen = sizeof(from);
242: memset(&from, 0, sizeof(from));
1.10 markus 243: if (local) {
244: if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
245: error("getsockname failed: %.100s", strerror(errno));
246: return 0;
247: }
248: } else {
249: if (getpeername(sock, (struct sockaddr *) & from, &fromlen) < 0) {
250: debug("getpeername failed: %.100s", strerror(errno));
251: fatal_cleanup();
252: }
1.6 markus 253: }
254: /* Return port number. */
1.10 markus 255: if (getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
256: strport, sizeof(strport), NI_NUMERICSERV) != 0)
257: fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed");
258: return atoi(strport);
1.1 deraadt 259: }
260:
1.10 markus 261: /* Returns remote/local port number for the current connection. */
1.1 deraadt 262:
1.12 markus 263: int
1.10 markus 264: get_port(int local)
1.1 deraadt 265: {
1.8 markus 266: /*
267: * If the connection is not a socket, return 65535. This is
268: * intentionally chosen to be an unprivileged port number.
269: */
1.10 markus 270: if (!packet_connection_is_on_socket())
1.6 markus 271: return 65535;
1.1 deraadt 272:
1.10 markus 273: /* Get socket and return the port number. */
274: return get_sock_port(packet_get_connection_in(), local);
275: }
276:
1.12 markus 277: int
1.10 markus 278: get_peer_port(int sock)
279: {
280: return get_sock_port(sock, 0);
281: }
282:
1.12 markus 283: int
1.10 markus 284: get_remote_port()
285: {
286: return get_port(0);
287: }
1.1 deraadt 288:
1.10 markus 289: int
290: get_local_port()
291: {
292: return get_port(1);
1.1 deraadt 293: }
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