Annotation of src/usr.bin/ssh/canohost.c, Revision 1.20
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"
1.20 ! markus 15: RCSID("$OpenBSD: canohost.c,v 1.19 2001/01/29 19:42:33 markus Exp $");
1.1 deraadt 16:
17: #include "packet.h"
18: #include "xmalloc.h"
1.18 markus 19: #include "log.h"
1.1 deraadt 20:
1.20 ! markus 21: void check_ip_options(int socket, char *ipaddr);
! 22:
1.8 markus 23: /*
24: * Return the canonical name of the host at the other end of the socket. The
25: * caller should free the returned string with xfree.
26: */
1.1 deraadt 27:
1.6 markus 28: char *
1.20 ! markus 29: get_remote_hostname(int socket, int reverse_mapping_check)
1.1 deraadt 30: {
1.10 markus 31: struct sockaddr_storage from;
32: int i;
33: socklen_t fromlen;
34: struct addrinfo hints, *ai, *aitop;
1.20 ! markus 35: char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
1.6 markus 36:
37: /* Get IP address of client. */
38: fromlen = sizeof(from);
39: memset(&from, 0, sizeof(from));
1.20 ! markus 40: if (getpeername(socket, (struct sockaddr *) &from, &fromlen) < 0) {
1.6 markus 41: debug("getpeername failed: %.100s", strerror(errno));
42: fatal_cleanup();
43: }
1.20 ! markus 44: if (from.ss_family == AF_INET)
! 45: check_ip_options(socket, ntop);
! 46:
1.10 markus 47: if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
48: NULL, 0, NI_NUMERICHOST) != 0)
49: fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
50:
1.6 markus 51: /* Map the IP address to a host name. */
1.10 markus 52: if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
1.20 ! markus 53: NULL, 0, NI_NAMEREQD) != 0) {
! 54: /* Host name not found. Use ip address. */
! 55: log("Could not reverse map address %.100s.", ntop);
! 56: return xstrdup(ntop);
1.6 markus 57: }
58:
1.20 ! markus 59: /* Got host name. */
! 60: name[sizeof(name) - 1] = '\0';
! 61: /*
! 62: * Convert it to all lowercase (which is expected by the rest
! 63: * of this software).
! 64: */
! 65: for (i = 0; name[i]; i++)
! 66: if (isupper(name[i]))
! 67: name[i] = tolower(name[i]);
1.6 markus 68:
1.20 ! markus 69: if (!reverse_mapping_check)
! 70: return xstrdup(name);
1.8 markus 71: /*
1.20 ! markus 72: * Map it back to an IP address and check that the given
! 73: * address actually is an address of this host. This is
! 74: * necessary because anyone with access to a name server can
! 75: * define arbitrary names for an IP address. Mapping from
! 76: * name to IP address can be trusted better (but can still be
! 77: * fooled if the intruder has access to the name server of
! 78: * the domain).
1.8 markus 79: */
1.20 ! markus 80: memset(&hints, 0, sizeof(hints));
! 81: hints.ai_family = from.ss_family;
! 82: hints.ai_socktype = SOCK_STREAM;
! 83: if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
! 84: log("reverse mapping checking getaddrinfo for %.700s "
! 85: "failed - POSSIBLE BREAKIN ATTEMPT!", name);
! 86: return xstrdup(ntop);
! 87: }
! 88: /* Look for the address from the list of addresses. */
! 89: for (ai = aitop; ai; ai = ai->ai_next) {
! 90: if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
! 91: sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
! 92: (strcmp(ntop, ntop2) == 0))
! 93: break;
! 94: }
! 95: freeaddrinfo(aitop);
! 96: /* If we reached the end of the list, the address was not there. */
! 97: if (!ai) {
! 98: /* Address not found for the host name. */
! 99: log("Address %.100s maps to %.600s, but this does not "
! 100: "map back to the address - POSSIBLE BREAKIN ATTEMPT!",
! 101: ntop, name);
! 102: return xstrdup(ntop);
! 103: }
! 104: return xstrdup(name);
! 105: }
1.6 markus 106:
1.20 ! markus 107: /*
! 108: * If IP options are supported, make sure there are none (log and
! 109: * disconnect them if any are found). Basically we are worried about
! 110: * source routing; it can be used to pretend you are somebody
! 111: * (ip-address) you are not. That itself may be "almost acceptable"
! 112: * under certain circumstances, but rhosts autentication is useless
! 113: * if source routing is accepted. Notice also that if we just dropped
! 114: * source routing here, the other side could use IP spoofing to do
! 115: * rest of the interaction and could still bypass security. So we
! 116: * exit here if we detect any IP options.
! 117: */
! 118: /* IPv4 only */
! 119: void
! 120: check_ip_options(int socket, char *ipaddr)
! 121: {
! 122: u_char options[200], *ucp;
! 123: char text[1024], *cp;
! 124: socklen_t option_size;
! 125: int ipproto;
! 126: struct protoent *ip;
! 127:
! 128: if ((ip = getprotobyname("ip")) != NULL)
! 129: ipproto = ip->p_proto;
! 130: else
! 131: ipproto = IPPROTO_IP;
! 132: option_size = sizeof(options);
! 133: if (getsockopt(socket, ipproto, IP_OPTIONS, (void *)options,
! 134: &option_size) >= 0 && option_size != 0) {
! 135: cp = text;
! 136: /* Note: "text" buffer must be at least 3x as big as options. */
! 137: for (ucp = options; option_size > 0; ucp++, option_size--, cp += 3)
! 138: sprintf(cp, " %2.2x", *ucp);
! 139: log("Connection from %.100s with IP options:%.800s",
! 140: ipaddr, text);
! 141: packet_disconnect("Connection from %.100s with IP options:%.800s",
! 142: ipaddr, text);
1.6 markus 143: }
1.1 deraadt 144: }
145:
1.8 markus 146: /*
147: * Return the canonical name of the host in the other side of the current
148: * connection. The host name is cached, so it is efficient to call this
149: * several times.
150: */
1.1 deraadt 151:
1.6 markus 152: const char *
1.20 ! markus 153: get_canonical_hostname(int reverse_mapping_check)
1.1 deraadt 154: {
1.10 markus 155: static char *canonical_host_name = NULL;
1.20 ! markus 156: static int reverse_mapping_checked = 0;
1.10 markus 157:
1.20 ! markus 158: /* Check if we have previously retrieved name with same option. */
! 159: if (canonical_host_name != NULL) {
! 160: if (reverse_mapping_checked != reverse_mapping_check)
! 161: xfree(canonical_host_name);
! 162: else
! 163: return canonical_host_name;
! 164: }
1.6 markus 165:
166: /* Get the real hostname if socket; otherwise return UNKNOWN. */
1.10 markus 167: if (packet_connection_is_on_socket())
1.20 ! markus 168: canonical_host_name = get_remote_hostname(
! 169: packet_get_connection_in(), reverse_mapping_check);
1.6 markus 170: else
171: canonical_host_name = xstrdup("UNKNOWN");
1.1 deraadt 172:
1.20 ! markus 173: reverse_mapping_checked = reverse_mapping_check;
1.6 markus 174: return canonical_host_name;
1.1 deraadt 175: }
176:
1.8 markus 177: /*
1.19 markus 178: * Returns the remote IP-address of socket as a string. The returned
179: * string must be freed.
1.8 markus 180: */
1.1 deraadt 181:
1.19 markus 182: char *
183: get_peer_ipaddr(int socket)
1.1 deraadt 184: {
1.10 markus 185: struct sockaddr_storage from;
186: socklen_t fromlen;
187: char ntop[NI_MAXHOST];
1.1 deraadt 188:
1.6 markus 189: /* Get IP address of client. */
190: fromlen = sizeof(from);
191: memset(&from, 0, sizeof(from));
192: if (getpeername(socket, (struct sockaddr *) & from, &fromlen) < 0) {
1.19 markus 193: debug("get_peer_ipaddr: getpeername failed: %.100s", strerror(errno));
194: return NULL;
1.6 markus 195: }
196: /* Get the IP address in ascii. */
1.10 markus 197: if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
1.19 markus 198: NULL, 0, NI_NUMERICHOST) != 0) {
199: error("get_peer_ipaddr: getnameinfo NI_NUMERICHOST failed");
200: return NULL;
201: }
202: return xstrdup(ntop);
203: }
204:
205: /*
206: * Returns the IP-address of the remote host as a string. The returned
207: * string must not be freed.
208: */
1.10 markus 209:
1.19 markus 210: const char *
211: get_remote_ipaddr()
212: {
213: static char *canonical_host_ip = NULL;
1.1 deraadt 214:
1.19 markus 215: /* Check whether we have cached the ipaddr. */
216: if (canonical_host_ip == NULL) {
217: if (packet_connection_is_on_socket()) {
218: canonical_host_ip =
219: get_peer_ipaddr(packet_get_connection_in());
220: if (canonical_host_ip == NULL)
221: fatal_cleanup();
222: } else {
223: /* If not on socket, return UNKNOWN. */
224: canonical_host_ip = xstrdup("UNKNOWN");
225: }
226: }
1.6 markus 227: return canonical_host_ip;
1.1 deraadt 228: }
229:
1.10 markus 230: /* Returns the local/remote port for the socket. */
1.1 deraadt 231:
1.10 markus 232: int
233: get_sock_port(int sock, int local)
1.1 deraadt 234: {
1.10 markus 235: struct sockaddr_storage from;
236: socklen_t fromlen;
237: char strport[NI_MAXSERV];
1.1 deraadt 238:
1.6 markus 239: /* Get IP address of client. */
240: fromlen = sizeof(from);
241: memset(&from, 0, sizeof(from));
1.10 markus 242: if (local) {
243: if (getsockname(sock, (struct sockaddr *)&from, &fromlen) < 0) {
244: error("getsockname failed: %.100s", strerror(errno));
245: return 0;
246: }
247: } else {
248: if (getpeername(sock, (struct sockaddr *) & from, &fromlen) < 0) {
249: debug("getpeername failed: %.100s", strerror(errno));
250: fatal_cleanup();
251: }
1.6 markus 252: }
253: /* Return port number. */
1.10 markus 254: if (getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0,
255: strport, sizeof(strport), NI_NUMERICSERV) != 0)
256: fatal("get_sock_port: getnameinfo NI_NUMERICSERV failed");
257: return atoi(strport);
1.1 deraadt 258: }
259:
1.10 markus 260: /* Returns remote/local port number for the current connection. */
1.1 deraadt 261:
1.12 markus 262: int
1.10 markus 263: get_port(int local)
1.1 deraadt 264: {
1.8 markus 265: /*
266: * If the connection is not a socket, return 65535. This is
267: * intentionally chosen to be an unprivileged port number.
268: */
1.10 markus 269: if (!packet_connection_is_on_socket())
1.6 markus 270: return 65535;
1.1 deraadt 271:
1.10 markus 272: /* Get socket and return the port number. */
273: return get_sock_port(packet_get_connection_in(), local);
274: }
275:
1.12 markus 276: int
1.10 markus 277: get_peer_port(int sock)
278: {
279: return get_sock_port(sock, 0);
280: }
281:
1.12 markus 282: int
1.10 markus 283: get_remote_port()
284: {
285: return get_port(0);
286: }
1.1 deraadt 287:
1.10 markus 288: int
289: get_local_port()
290: {
291: return get_port(1);
1.1 deraadt 292: }
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