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authorDamien Miller <djm@mindrot.org>1999-10-27 13:42:43 +1000
committerDamien Miller <djm@mindrot.org>1999-10-27 13:42:43 +1000
commitd4a8b7e34dd619a4debf9a206c81db26d1402ea6 (patch)
treea47d770a2f790f40d18b0982d4e55fa7cfb1fa3b /canohost.c
Initial revision
Diffstat (limited to 'canohost.c')
-rw-r--r--canohost.c234
1 files changed, 234 insertions, 0 deletions
diff --git a/canohost.c b/canohost.c
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+++ b/canohost.c
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+/*
+
+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);
+}