diff options
Diffstat (limited to 'canohost.c')
| -rw-r--r-- | canohost.c | 234 |
1 files changed, 234 insertions, 0 deletions
diff --git a/canohost.c b/canohost.c new file mode 100644 index 00000000..85d97292 --- /dev/null +++ b/canohost.c @@ -0,0 +1,234 @@ +/* + +canohost.c + +Author: Tatu Ylonen <ylo@cs.hut.fi> + +Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland + All rights reserved + +Created: Sun Jul 2 17:52:22 1995 ylo + +Functions for returning the canonical host name of the remote site. + +*/ + +#include "includes.h" +RCSID("$Id: canohost.c,v 1.1 1999/10/27 03:42:43 damien Exp $"); + +#include "packet.h" +#include "xmalloc.h" +#include "ssh.h" + +/* Return the canonical name of the host at the other end of the socket. + The caller should free the returned string with xfree. */ + +char *get_remote_hostname(int socket) +{ + struct sockaddr_in from; + int fromlen, i; + struct hostent *hp; + char name[MAXHOSTNAMELEN]; + + /* Get IP address of client. */ + fromlen = sizeof(from); + memset(&from, 0, sizeof(from)); + if (getpeername(socket, (struct sockaddr *)&from, &fromlen) < 0) + { + error("getpeername failed: %.100s", strerror(errno)); + strlcpy(name, "UNKNOWN", sizeof name); + goto check_ip_options; + } + + /* Map the IP address to a host name. */ + hp = gethostbyaddr((char *)&from.sin_addr, sizeof(struct in_addr), + from.sin_family); + if (hp) + { + /* Got host name, find canonic host name. */ + if (strchr(hp->h_name, '.') != 0) + strlcpy(name, hp->h_name, sizeof(name)); + else if (hp->h_aliases != 0 + && hp->h_aliases[0] != 0 + && strchr(hp->h_aliases[0], '.') != 0) + strlcpy(name, hp->h_aliases[0], sizeof(name)); + else + strlcpy(name, hp->h_name, sizeof(name)); + + /* Convert it to all lowercase (which is expected by the rest of this + software). */ + for (i = 0; name[i]; i++) + if (isupper(name[i])) + name[i] = tolower(name[i]); + + /* Map it back to an IP address and check that the given address actually + is an address of this host. This is necessary because anyone with + access to a name server can define arbitrary names for an IP address. + Mapping from name to IP address can be trusted better (but can still + be fooled if the intruder has access to the name server of the + domain). */ + hp = gethostbyname(name); + if (!hp) + { + log("reverse mapping checking gethostbyname for %.700s failed - POSSIBLE BREAKIN ATTEMPT!", name); + strlcpy(name, inet_ntoa(from.sin_addr), sizeof name); + goto check_ip_options; + } + /* Look for the address from the list of addresses. */ + for (i = 0; hp->h_addr_list[i]; i++) + if (memcmp(hp->h_addr_list[i], &from.sin_addr, sizeof(from.sin_addr)) + == 0) + break; + /* If we reached the end of the list, the address was not there. */ + if (!hp->h_addr_list[i]) + { + /* Address not found for the host name. */ + log("Address %.100s maps to %.600s, but this does not map back to the address - POSSIBLE BREAKIN ATTEMPT!", + inet_ntoa(from.sin_addr), name); + strlcpy(name, inet_ntoa(from.sin_addr), sizeof name); + goto check_ip_options; + } + /* Address was found for the host name. We accept the host name. */ + } + else + { + /* Host name not found. Use ascii representation of the address. */ + strlcpy(name, inet_ntoa(from.sin_addr), sizeof name); + log("Could not reverse map address %.100s.", name); + } + + check_ip_options: + + /* If IP options are supported, make sure there are none (log and clear + them if any are found). Basically we are worried about source routing; + it can be used to pretend you are somebody (ip-address) you are not. + That itself may be "almost acceptable" under certain circumstances, + but rhosts autentication is useless if source routing is accepted. + Notice also that if we just dropped source routing here, the other + side could use IP spoofing to do rest of the interaction and could still + bypass security. So we exit here if we detect any IP options. */ + { + unsigned char options[200], *ucp; + char text[1024], *cp; + int option_size, ipproto; + struct protoent *ip; + + if ((ip = getprotobyname("ip")) != NULL) + ipproto = ip->p_proto; + else + ipproto = IPPROTO_IP; + option_size = sizeof(options); + if (getsockopt(0, ipproto, IP_OPTIONS, (char *)options, + &option_size) >= 0 && option_size != 0) + { + cp = text; + /* Note: "text" buffer must be at least 3x as big as options. */ + for (ucp = options; option_size > 0; ucp++, option_size--, cp += 3) + sprintf(cp, " %2.2x", *ucp); + log("Connection from %.100s with IP options:%.800s", + inet_ntoa(from.sin_addr), text); + packet_disconnect("Connection from %.100s with IP options:%.800s", + inet_ntoa(from.sin_addr), text); + } + } + + return xstrdup(name); +} + +static char *canonical_host_name = NULL; +static char *canonical_host_ip = NULL; + +/* Return the canonical name of the host in the other side of the current + connection. The host name is cached, so it is efficient to call this + several times. */ + +const char *get_canonical_hostname() +{ + /* Check if we have previously retrieved this same name. */ + if (canonical_host_name != NULL) + return canonical_host_name; + + /* Get the real hostname if socket; otherwise return UNKNOWN. */ + if (packet_get_connection_in() == packet_get_connection_out()) + canonical_host_name = get_remote_hostname(packet_get_connection_in()); + else + canonical_host_name = xstrdup("UNKNOWN"); + + return canonical_host_name; +} + +/* Returns the IP-address of the remote host as a string. The returned + string need not be freed. */ + +const char *get_remote_ipaddr() +{ + struct sockaddr_in from; + int fromlen, socket; + + /* Check if we have previously retrieved this same name. */ + if (canonical_host_ip != NULL) + return canonical_host_ip; + + /* If not a socket, return UNKNOWN. */ + if (packet_get_connection_in() != packet_get_connection_out()) + { + canonical_host_ip = xstrdup("UNKNOWN"); + return canonical_host_ip; + } + + /* Get client socket. */ + socket = packet_get_connection_in(); + + /* Get IP address of client. */ + fromlen = sizeof(from); + memset(&from, 0, sizeof(from)); + if (getpeername(socket, (struct sockaddr *)&from, &fromlen) < 0) + { + error("getpeername failed: %.100s", strerror(errno)); + return NULL; + } + + /* Get the IP address in ascii. */ + canonical_host_ip = xstrdup(inet_ntoa(from.sin_addr)); + + /* Return ip address string. */ + return canonical_host_ip; +} + +/* Returns the port of the peer of the socket. */ + +int get_peer_port(int sock) +{ + struct sockaddr_in from; + int fromlen; + + /* Get IP address of client. */ + fromlen = sizeof(from); + memset(&from, 0, sizeof(from)); + if (getpeername(sock, (struct sockaddr *)&from, &fromlen) < 0) + { + error("getpeername failed: %.100s", strerror(errno)); + return 0; + } + + /* Return port number. */ + return ntohs(from.sin_port); +} + +/* Returns the port number of the remote host. */ + +int get_remote_port() +{ + int socket; + + /* If the connection is not a socket, return 65535. This is intentionally + chosen to be an unprivileged port number. */ + if (packet_get_connection_in() != packet_get_connection_out()) + return 65535; + + /* Get client socket. */ + socket = packet_get_connection_in(); + + /* Get and return the peer port number. */ + return get_peer_port(socket); +} |