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Diffstat (limited to 'usr.bin/ssh/canohost.c')
-rw-r--r--usr.bin/ssh/canohost.c199
1 files changed, 105 insertions, 94 deletions
diff --git a/usr.bin/ssh/canohost.c b/usr.bin/ssh/canohost.c
index 8d5a50d5648..b61a2059e26 100644
--- a/usr.bin/ssh/canohost.c
+++ b/usr.bin/ssh/canohost.c
@@ -12,154 +12,165 @@
*/
#include "includes.h"
-RCSID("$OpenBSD: canohost.c,v 1.19 2001/01/29 19:42:33 markus Exp $");
+RCSID("$OpenBSD: canohost.c,v 1.20 2001/02/03 10:08:37 markus Exp $");
#include "packet.h"
#include "xmalloc.h"
#include "log.h"
+void check_ip_options(int socket, char *ipaddr);
+
/*
* 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)
+get_remote_hostname(int socket, int reverse_mapping_check)
{
struct sockaddr_storage from;
int i;
socklen_t fromlen;
struct addrinfo hints, *ai, *aitop;
- char name[MAXHOSTNAMELEN];
- char ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
+ char name[NI_MAXHOST], ntop[NI_MAXHOST], ntop2[NI_MAXHOST];
/* Get IP address of client. */
fromlen = sizeof(from);
memset(&from, 0, sizeof(from));
- if (getpeername(socket, (struct sockaddr *) & from, &fromlen) < 0) {
+ if (getpeername(socket, (struct sockaddr *) &from, &fromlen) < 0) {
debug("getpeername failed: %.100s", strerror(errno));
fatal_cleanup();
}
+ if (from.ss_family == AF_INET)
+ check_ip_options(socket, ntop);
+
if (getnameinfo((struct sockaddr *)&from, fromlen, ntop, sizeof(ntop),
NULL, 0, NI_NUMERICHOST) != 0)
fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
/* Map the IP address to a host name. */
if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
- NULL, 0, NI_NAMEREQD) == 0) {
- /* Got host name. */
- name[sizeof(name) - 1] = '\0';
- /*
- * 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).
- */
- memset(&hints, 0, sizeof(hints));
- hints.ai_family = from.ss_family;
- hints.ai_socktype = SOCK_STREAM;
- if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
- log("reverse mapping checking getaddrinfo for %.700s failed - POSSIBLE BREAKIN ATTEMPT!", name);
- strlcpy(name, ntop, sizeof name);
- goto check_ip_options;
- }
- /* Look for the address from the list of addresses. */
- for (ai = aitop; ai; ai = ai->ai_next) {
- if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
- sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
- (strcmp(ntop, ntop2) == 0))
- break;
- }
- freeaddrinfo(aitop);
- /* If we reached the end of the list, the address was not there. */
- if (!ai) {
- /* 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!",
- ntop, name);
- strlcpy(name, ntop, 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, ntop, sizeof name);
- log("Could not reverse map address %.100s.", name);
+ NULL, 0, NI_NAMEREQD) != 0) {
+ /* Host name not found. Use ip address. */
+ log("Could not reverse map address %.100s.", ntop);
+ return xstrdup(ntop);
}
-check_ip_options:
+ /* Got host name. */
+ name[sizeof(name) - 1] = '\0';
+ /*
+ * 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]);
+ if (!reverse_mapping_check)
+ return xstrdup(name);
/*
- * If IP options are supported, make sure there are none (log and
- * disconnect 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.
+ * 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).
*/
- /* IP options -- IPv4 only */
- if (from.ss_family == AF_INET) {
- u_char options[200], *ucp;
- char text[1024], *cp;
- socklen_t option_size;
- int ipproto;
- struct protoent *ip;
-
- if ((ip = getprotobyname("ip")) != NULL)
- ipproto = ip->p_proto;
- else
- ipproto = IPPROTO_IP;
- option_size = sizeof(options);
- if (getsockopt(socket, 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",
- ntop, text);
- packet_disconnect("Connection from %.100s with IP options:%.800s",
- ntop, text);
- }
+ memset(&hints, 0, sizeof(hints));
+ hints.ai_family = from.ss_family;
+ hints.ai_socktype = SOCK_STREAM;
+ if (getaddrinfo(name, NULL, &hints, &aitop) != 0) {
+ log("reverse mapping checking getaddrinfo for %.700s "
+ "failed - POSSIBLE BREAKIN ATTEMPT!", name);
+ return xstrdup(ntop);
+ }
+ /* Look for the address from the list of addresses. */
+ for (ai = aitop; ai; ai = ai->ai_next) {
+ if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop2,
+ sizeof(ntop2), NULL, 0, NI_NUMERICHOST) == 0 &&
+ (strcmp(ntop, ntop2) == 0))
+ break;
+ }
+ freeaddrinfo(aitop);
+ /* If we reached the end of the list, the address was not there. */
+ if (!ai) {
+ /* 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!",
+ ntop, name);
+ return xstrdup(ntop);
}
-
return xstrdup(name);
}
/*
+ * If IP options are supported, make sure there are none (log and
+ * disconnect 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.
+ */
+/* IPv4 only */
+void
+check_ip_options(int socket, char *ipaddr)
+{
+ u_char options[200], *ucp;
+ char text[1024], *cp;
+ socklen_t option_size;
+ int ipproto;
+ struct protoent *ip;
+
+ if ((ip = getprotobyname("ip")) != NULL)
+ ipproto = ip->p_proto;
+ else
+ ipproto = IPPROTO_IP;
+ option_size = sizeof(options);
+ if (getsockopt(socket, ipproto, IP_OPTIONS, (void *)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",
+ ipaddr, text);
+ packet_disconnect("Connection from %.100s with IP options:%.800s",
+ ipaddr, text);
+ }
+}
+
+/*
* 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()
+get_canonical_hostname(int reverse_mapping_check)
{
static char *canonical_host_name = NULL;
+ static int reverse_mapping_checked = 0;
- /* Check if we have previously retrieved this same name. */
- if (canonical_host_name != NULL)
- return canonical_host_name;
+ /* Check if we have previously retrieved name with same option. */
+ if (canonical_host_name != NULL) {
+ if (reverse_mapping_checked != reverse_mapping_check)
+ xfree(canonical_host_name);
+ else
+ return canonical_host_name;
+ }
/* Get the real hostname if socket; otherwise return UNKNOWN. */
if (packet_connection_is_on_socket())
- canonical_host_name = get_remote_hostname(packet_get_connection_in());
+ canonical_host_name = get_remote_hostname(
+ packet_get_connection_in(), reverse_mapping_check);
else
canonical_host_name = xstrdup("UNKNOWN");
+ reverse_mapping_checked = reverse_mapping_check;
return canonical_host_name;
}
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