Annotation of src/usr.bin/ssh/canohost.c, Revision 1.6
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"
1.6 ! markus 17: RCSID("$Id: canohost.c,v 1.5 1999/11/15 00:42:01 markus Exp $");
1.1 deraadt 18:
19: #include "packet.h"
20: #include "xmalloc.h"
21: #include "ssh.h"
22:
1.6 ! markus 23: /* Return the canonical name of the host at the other end of the socket.
1.1 deraadt 24: The caller should free the returned string with xfree. */
25:
1.6 ! markus 26: char *
! 27: get_remote_hostname(int socket)
1.1 deraadt 28: {
1.6 ! markus 29: struct sockaddr_in from;
! 30: int fromlen, i;
! 31: struct hostent *hp;
! 32: char name[MAXHOSTNAMELEN];
! 33:
! 34: /* Get IP address of client. */
! 35: fromlen = sizeof(from);
! 36: memset(&from, 0, sizeof(from));
! 37: if (getpeername(socket, (struct sockaddr *) & from, &fromlen) < 0) {
! 38: debug("getpeername failed: %.100s", strerror(errno));
! 39: fatal_cleanup();
! 40: }
! 41: /* Map the IP address to a host name. */
! 42: hp = gethostbyaddr((char *) &from.sin_addr, sizeof(struct in_addr),
! 43: from.sin_family);
! 44: if (hp) {
! 45: /* Got host name, find canonic host name. */
! 46: if (strchr(hp->h_name, '.') != 0)
! 47: strlcpy(name, hp->h_name, sizeof(name));
! 48: else if (hp->h_aliases != 0
! 49: && hp->h_aliases[0] != 0
! 50: && strchr(hp->h_aliases[0], '.') != 0)
! 51: strlcpy(name, hp->h_aliases[0], sizeof(name));
! 52: else
! 53: strlcpy(name, hp->h_name, sizeof(name));
! 54:
! 55: /* Convert it to all lowercase (which is expected by the
! 56: rest of this software). */
! 57: for (i = 0; name[i]; i++)
! 58: if (isupper(name[i]))
! 59: name[i] = tolower(name[i]);
! 60:
! 61: /* Map it back to an IP address and check that the given
! 62: address actually is an address of this host. This is
! 63: necessary because anyone with access to a name server
! 64: can define arbitrary names for an IP address. Mapping
! 65: from name to IP address can be trusted better (but can
! 66: still be fooled if the intruder has access to the name
! 67: server of the domain). */
! 68: hp = gethostbyname(name);
! 69: if (!hp) {
! 70: log("reverse mapping checking gethostbyname for %.700s failed - POSSIBLE BREAKIN ATTEMPT!", name);
! 71: strlcpy(name, inet_ntoa(from.sin_addr), sizeof name);
! 72: goto check_ip_options;
! 73: }
! 74: /* Look for the address from the list of addresses. */
! 75: for (i = 0; hp->h_addr_list[i]; i++)
! 76: if (memcmp(hp->h_addr_list[i], &from.sin_addr, sizeof(from.sin_addr))
! 77: == 0)
! 78: break;
! 79: /* If we reached the end of the list, the address was not
! 80: there. */
! 81: if (!hp->h_addr_list[i]) {
! 82: /* Address not found for the host name. */
! 83: log("Address %.100s maps to %.600s, but this does not map back to the address - POSSIBLE BREAKIN ATTEMPT!",
! 84: inet_ntoa(from.sin_addr), name);
! 85: strlcpy(name, inet_ntoa(from.sin_addr), sizeof name);
! 86: goto check_ip_options;
! 87: }
! 88: /* Address was found for the host name. We accept the host name. */
! 89: } else {
! 90: /* Host name not found. Use ascii representation of the address. */
! 91: strlcpy(name, inet_ntoa(from.sin_addr), sizeof name);
! 92: log("Could not reverse map address %.100s.", name);
! 93: }
! 94:
! 95: check_ip_options:
! 96:
! 97: /* If IP options are supported, make sure there are none (log and
! 98: disconnect them if any are found). Basically we are worried
! 99: about source routing; it can be used to pretend you are
! 100: somebody (ip-address) you are not. That itself may be "almost
! 101: acceptable" under certain circumstances, but rhosts
! 102: autentication is useless if source routing is accepted. Notice
! 103: also that if we just dropped source routing here, the other
! 104: side could use IP spoofing to do rest of the interaction and
! 105: could still bypass security. So we exit here if we detect any
! 106: IP options. */
1.1 deraadt 107: {
1.6 ! markus 108: unsigned char options[200], *ucp;
! 109: char text[1024], *cp;
! 110: int option_size, ipproto;
! 111: struct protoent *ip;
! 112:
! 113: if ((ip = getprotobyname("ip")) != NULL)
! 114: ipproto = ip->p_proto;
! 115: else
! 116: ipproto = IPPROTO_IP;
! 117: option_size = sizeof(options);
! 118: if (getsockopt(0, ipproto, IP_OPTIONS, (char *) options,
! 119: &option_size) >= 0 && option_size != 0) {
! 120: cp = text;
! 121: /* Note: "text" buffer must be at least 3x as big as options. */
! 122: for (ucp = options; option_size > 0; ucp++, option_size--, cp += 3)
! 123: sprintf(cp, " %2.2x", *ucp);
! 124: log("Connection from %.100s with IP options:%.800s",
! 125: inet_ntoa(from.sin_addr), text);
! 126: packet_disconnect("Connection from %.100s with IP options:%.800s",
! 127: inet_ntoa(from.sin_addr), text);
! 128: }
! 129: }
1.1 deraadt 130:
1.6 ! markus 131: return xstrdup(name);
1.1 deraadt 132: }
133:
134: static char *canonical_host_name = NULL;
135: static char *canonical_host_ip = NULL;
136:
137: /* Return the canonical name of the host in the other side of the current
1.6 ! markus 138: connection. The host name is cached, so it is efficient to call this
1.1 deraadt 139: several times. */
140:
1.6 ! markus 141: const char *
! 142: get_canonical_hostname()
1.1 deraadt 143: {
1.6 ! markus 144: /* Check if we have previously retrieved this same name. */
! 145: if (canonical_host_name != NULL)
! 146: return canonical_host_name;
! 147:
! 148: /* Get the real hostname if socket; otherwise return UNKNOWN. */
! 149: if (packet_get_connection_in() == packet_get_connection_out())
! 150: canonical_host_name = get_remote_hostname(packet_get_connection_in());
! 151: else
! 152: canonical_host_name = xstrdup("UNKNOWN");
1.1 deraadt 153:
1.6 ! markus 154: return canonical_host_name;
1.1 deraadt 155: }
156:
157: /* Returns the IP-address of the remote host as a string. The returned
158: string need not be freed. */
159:
1.6 ! markus 160: const char *
! 161: get_remote_ipaddr()
1.1 deraadt 162: {
1.6 ! markus 163: struct sockaddr_in from;
! 164: int fromlen, socket;
1.1 deraadt 165:
1.6 ! markus 166: /* Check if we have previously retrieved this same name. */
! 167: if (canonical_host_ip != NULL)
! 168: return canonical_host_ip;
! 169:
! 170: /* If not a socket, return UNKNOWN. */
! 171: if (packet_get_connection_in() != packet_get_connection_out()) {
! 172: canonical_host_ip = xstrdup("UNKNOWN");
! 173: return canonical_host_ip;
! 174: }
! 175: /* Get client socket. */
! 176: socket = packet_get_connection_in();
1.1 deraadt 177:
1.6 ! markus 178: /* Get IP address of client. */
! 179: fromlen = sizeof(from);
! 180: memset(&from, 0, sizeof(from));
! 181: if (getpeername(socket, (struct sockaddr *) & from, &fromlen) < 0) {
! 182: debug("getpeername failed: %.100s", strerror(errno));
! 183: fatal_cleanup();
! 184: }
! 185: /* Get the IP address in ascii. */
! 186: canonical_host_ip = xstrdup(inet_ntoa(from.sin_addr));
1.1 deraadt 187:
1.6 ! markus 188: /* Return ip address string. */
! 189: return canonical_host_ip;
1.1 deraadt 190: }
191:
192: /* Returns the port of the peer of the socket. */
193:
1.6 ! markus 194: int
! 195: get_peer_port(int sock)
1.1 deraadt 196: {
1.6 ! markus 197: struct sockaddr_in from;
! 198: int fromlen;
1.1 deraadt 199:
1.6 ! markus 200: /* Get IP address of client. */
! 201: fromlen = sizeof(from);
! 202: memset(&from, 0, sizeof(from));
! 203: if (getpeername(sock, (struct sockaddr *) & from, &fromlen) < 0) {
! 204: debug("getpeername failed: %.100s", strerror(errno));
! 205: fatal_cleanup();
! 206: }
! 207: /* Return port number. */
! 208: return ntohs(from.sin_port);
1.1 deraadt 209: }
210:
211: /* Returns the port number of the remote host. */
212:
1.6 ! markus 213: int
! 214: get_remote_port()
1.1 deraadt 215: {
1.6 ! markus 216: int socket;
1.1 deraadt 217:
1.6 ! markus 218: /* If the connection is not a socket, return 65535. This is
! 219: intentionally chosen to be an unprivileged port number. */
! 220: if (packet_get_connection_in() != packet_get_connection_out())
! 221: return 65535;
1.1 deraadt 222:
1.6 ! markus 223: /* Get client socket. */
! 224: socket = packet_get_connection_in();
1.1 deraadt 225:
1.6 ! markus 226: /* Get and return the peer port number. */
! 227: return get_peer_port(socket);
1.1 deraadt 228: }
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