Damien Miller | d4a8b7e | 1999-10-27 13:42:43 +1000 | [diff] [blame] | 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 | } |