/* $OpenBSD: canohost.c,v 1.74 2019/06/28 13:35:04 deraadt Exp $ */ /* * Author: Tatu Ylonen * Copyright (c) 1995 Tatu Ylonen , Espoo, Finland * All rights reserved * Functions for returning the canonical host name of the remote site. * * As far as I am concerned, the code I have written for this software * can be used freely for any purpose. Any derived versions of this * software must be clearly marked as such, and if the derived work is * incompatible with the protocol description in the RFC file, it must be * called by a name other than "ssh" or "Secure Shell". */ #include "includes.h" #include #include #include #include #include #include #include #include #include #include #include #include #include "xmalloc.h" #include "packet.h" #include "log.h" #include "canohost.h" #include "misc.h" /* * Returns the remote DNS hostname as a string. The returned string must not * be freed. NB. this will usually trigger a DNS query the first time it is * called. * This function does additional checks on the hostname to mitigate some * attacks on legacy rhosts-style authentication. * XXX is RhostsRSAAuthentication vulnerable to these? * XXX Can we remove these checks? (or if not, remove RhostsRSAAuthentication?) */ char * remote_hostname(struct ssh *ssh) { struct sockaddr_storage from; socklen_t fromlen; struct addrinfo hints, *ai, *aitop; char name[NI_MAXHOST], ntop2[NI_MAXHOST]; const char *ntop = ssh_remote_ipaddr(ssh); /* Get IP address of client. */ fromlen = sizeof(from); memset(&from, 0, sizeof(from)); if (getpeername(ssh_packet_get_connection_in(ssh), (struct sockaddr *)&from, &fromlen) == -1) { debug("getpeername failed: %.100s", strerror(errno)); return xstrdup(ntop); } ipv64_normalise_mapped(&from, &fromlen); if (from.ss_family == AF_INET6) fromlen = sizeof(struct sockaddr_in6); debug3("Trying to reverse map address %.100s.", ntop); /* Map the IP address to a host name. */ if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name), NULL, 0, NI_NAMEREQD) != 0) { /* Host name not found. Use ip address. */ return xstrdup(ntop); } /* * if reverse lookup result looks like a numeric hostname, * someone is trying to trick us by PTR record like following: * 1.1.1.10.in-addr.arpa. IN PTR 2.3.4.5 */ memset(&hints, 0, sizeof(hints)); hints.ai_socktype = SOCK_DGRAM; /*dummy*/ hints.ai_flags = AI_NUMERICHOST; if (getaddrinfo(name, NULL, &hints, &ai) == 0) { logit("Nasty PTR record \"%s\" is set up for %s, ignoring", name, ntop); freeaddrinfo(ai); return xstrdup(ntop); } /* Names are stored in lowercase. */ lowercase(name); /* * 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) { logit("reverse mapping checking getaddrinfo for %.700s " "[%s] failed.", name, ntop); 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 == NULL) { /* Address not found for the host name. */ logit("Address %.100s maps to %.600s, but this does not " "map back to the address.", ntop, name); return xstrdup(ntop); } return xstrdup(name); } void ipv64_normalise_mapped(struct sockaddr_storage *addr, socklen_t *len) { struct sockaddr_in6 *a6 = (struct sockaddr_in6 *)addr; struct sockaddr_in *a4 = (struct sockaddr_in *)addr; struct in_addr inaddr; u_int16_t port; if (addr->ss_family != AF_INET6 || !IN6_IS_ADDR_V4MAPPED(&a6->sin6_addr)) return; debug3("Normalising mapped IPv4 in IPv6 address"); memcpy(&inaddr, ((char *)&a6->sin6_addr) + 12, sizeof(inaddr)); port = a6->sin6_port; memset(a4, 0, sizeof(*a4)); a4->sin_family = AF_INET; *len = sizeof(*a4); memcpy(&a4->sin_addr, &inaddr, sizeof(inaddr)); a4->sin_port = port; } /* * Returns the local/remote IP-address/hostname of socket as a string. * The returned string must be freed. */ static char * get_socket_address(int sock, int remote, int flags) { struct sockaddr_storage addr; socklen_t addrlen; char ntop[NI_MAXHOST]; int r; /* Get IP address of client. */ addrlen = sizeof(addr); memset(&addr, 0, sizeof(addr)); if (remote) { if (getpeername(sock, (struct sockaddr *)&addr, &addrlen) != 0) return NULL; } else { if (getsockname(sock, (struct sockaddr *)&addr, &addrlen) != 0) return NULL; } /* Work around Linux IPv6 weirdness */ if (addr.ss_family == AF_INET6) { addrlen = sizeof(struct sockaddr_in6); ipv64_normalise_mapped(&addr, &addrlen); } switch (addr.ss_family) { case AF_INET: case AF_INET6: /* Get the address in ascii. */ if ((r = getnameinfo((struct sockaddr *)&addr, addrlen, ntop, sizeof(ntop), NULL, 0, flags)) != 0) { error("%s: getnameinfo %d failed: %s", __func__, flags, ssh_gai_strerror(r)); return NULL; } return xstrdup(ntop); case AF_UNIX: /* Get the Unix domain socket path. */ return xstrdup(((struct sockaddr_un *)&addr)->sun_path); default: /* We can't look up remote Unix domain sockets. */ return NULL; } } char * get_peer_ipaddr(int sock) { char *p; if ((p = get_socket_address(sock, 1, NI_NUMERICHOST)) != NULL) return p; return xstrdup("UNKNOWN"); } char * get_local_ipaddr(int sock) { char *p; if ((p = get_socket_address(sock, 0, NI_NUMERICHOST)) != NULL) return p; return xstrdup("UNKNOWN"); } char * get_local_name(int fd) { char *host, myname[NI_MAXHOST]; /* Assume we were passed a socket */ if ((host = get_socket_address(fd, 0, NI_NAMEREQD)) != NULL) return host; /* Handle the case where we were passed a pipe */ if (gethostname(myname, sizeof(myname)) == -1) { verbose("%s: gethostname: %s", __func__, strerror(errno)); host = xstrdup("UNKNOWN"); } else { host = xstrdup(myname); } return host; } /* Returns the local/remote port for the socket. */ static int get_sock_port(int sock, int local) { struct sockaddr_storage from; socklen_t fromlen; char strport[NI_MAXSERV]; int r; /* Get IP address of client. */ fromlen = sizeof(from); memset(&from, 0, sizeof(from)); if (local) { if (getsockname(sock, (struct sockaddr *)&from, &fromlen) == -1) { error("getsockname failed: %.100s", strerror(errno)); return 0; } } else { if (getpeername(sock, (struct sockaddr *)&from, &fromlen) == -1) { debug("getpeername failed: %.100s", strerror(errno)); return -1; } } /* Work around Linux IPv6 weirdness */ if (from.ss_family == AF_INET6) fromlen = sizeof(struct sockaddr_in6); /* Non-inet sockets don't have a port number. */ if (from.ss_family != AF_INET && from.ss_family != AF_INET6) return 0; /* Return port number. */ if ((r = getnameinfo((struct sockaddr *)&from, fromlen, NULL, 0, strport, sizeof(strport), NI_NUMERICSERV)) != 0) fatal("%s: getnameinfo NI_NUMERICSERV failed: %s", __func__, ssh_gai_strerror(r)); return atoi(strport); } int get_peer_port(int sock) { return get_sock_port(sock, 0); } int get_local_port(int sock) { return get_sock_port(sock, 1); }