X-Git-Url: http://andersk.mit.edu/gitweb/openssh.git/blobdiff_plain/01ca0dfeb48f1c76b32506423c04e934668689ef..442c82934f796b15ed31fda55e7cdf933aa9e97d:/sshconnect.c diff --git a/sshconnect.c b/sshconnect.c index 651e3fcf..dfeddd39 100644 --- a/sshconnect.c +++ b/sshconnect.c @@ -13,7 +13,7 @@ */ #include "includes.h" -RCSID("$OpenBSD: sshconnect.c,v 1.123 2002/06/09 22:17:21 itojun Exp $"); +RCSID("$OpenBSD: sshconnect.c,v 1.156 2004/01/25 03:49:09 djm Exp $"); #include @@ -33,33 +33,32 @@ RCSID("$OpenBSD: sshconnect.c,v 1.123 2002/06/09 22:17:21 itojun Exp $"); #include "misc.h" #include "readpass.h" +#include "dns.h" + char *client_version_string = NULL; char *server_version_string = NULL; +int matching_host_key_dns = 0; + +/* import */ extern Options options; extern char *__progname; +extern uid_t original_real_uid; +extern uid_t original_effective_uid; +extern pid_t proxy_command_pid; #ifndef INET6_ADDRSTRLEN /* for non IPv6 machines */ #define INET6_ADDRSTRLEN 46 #endif -static const char * -sockaddr_ntop(struct sockaddr *sa, socklen_t salen) -{ - static char addrbuf[NI_MAXHOST]; - - if (getnameinfo(sa, salen, addrbuf, sizeof(addrbuf), NULL, 0, - NI_NUMERICHOST) != 0) - fatal("sockaddr_ntop: getnameinfo NI_NUMERICHOST failed"); - return addrbuf; -} +static int show_other_keys(const char *, Key *); +static void warn_changed_key(Key *); /* * Connect to the given ssh server using a proxy command. */ static int -ssh_proxy_connect(const char *host, u_short port, struct passwd *pw, - const char *proxy_command) +ssh_proxy_connect(const char *host, u_short port, const char *proxy_command) { Buffer command; const char *cp; @@ -71,9 +70,16 @@ ssh_proxy_connect(const char *host, u_short port, struct passwd *pw, /* Convert the port number into a string. */ snprintf(strport, sizeof strport, "%hu", port); - /* Build the final command string in the buffer by making the - appropriate substitutions to the given proxy command. */ + /* + * Build the final command string in the buffer by making the + * appropriate substitutions to the given proxy command. + * + * Use "exec" to avoid "sh -c" processes on some platforms + * (e.g. Solaris) + */ buffer_init(&command); + buffer_append(&command, "exec ", 5); + for (cp = proxy_command; *cp; cp++) { if (cp[0] == '%' && cp[1] == '%') { buffer_append(&command, "%", 1); @@ -109,7 +115,8 @@ ssh_proxy_connect(const char *host, u_short port, struct passwd *pw, char *argv[10]; /* Child. Permanently give up superuser privileges. */ - permanently_set_uid(pw); + seteuid(original_real_uid); + setuid(original_real_uid); /* Redirect stdin and stdout. */ close(pin[1]); @@ -140,6 +147,8 @@ ssh_proxy_connect(const char *host, u_short port, struct passwd *pw, /* Parent. */ if (pid < 0) fatal("fork failed: %.100s", strerror(errno)); + else + proxy_command_pid = pid; /* save pid to clean up later */ /* Close child side of the descriptors. */ close(pin[0]); @@ -159,7 +168,7 @@ ssh_proxy_connect(const char *host, u_short port, struct passwd *pw, * Creates a (possibly privileged) socket for use as the ssh connection. */ static int -ssh_create_socket(struct passwd *pw, int privileged, int family) +ssh_create_socket(int privileged, struct addrinfo *ai) { int sock, gaierr; struct addrinfo hints, *res; @@ -170,30 +179,28 @@ ssh_create_socket(struct passwd *pw, int privileged, int family) */ if (privileged) { int p = IPPORT_RESERVED - 1; - sock = rresvport_af(&p, family); + PRIV_START; + sock = rresvport_af(&p, ai->ai_family); + PRIV_END; if (sock < 0) - error("rresvport: af=%d %.100s", family, strerror(errno)); + error("rresvport: af=%d %.100s", ai->ai_family, + strerror(errno)); else debug("Allocated local port %d.", p); return sock; } - /* - * Just create an ordinary socket on arbitrary port. We use - * the user's uid to create the socket. - */ - temporarily_use_uid(pw); - sock = socket(family, SOCK_STREAM, 0); + sock = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol); if (sock < 0) error("socket: %.100s", strerror(errno)); - restore_uid(); /* Bind the socket to an alternative local IP address */ if (options.bind_address == NULL) return sock; memset(&hints, 0, sizeof(hints)); - hints.ai_family = family; - hints.ai_socktype = SOCK_STREAM; + hints.ai_family = ai->ai_family; + hints.ai_socktype = ai->ai_socktype; + hints.ai_protocol = ai->ai_protocol; hints.ai_flags = AI_PASSIVE; gaierr = getaddrinfo(options.bind_address, "0", &hints, &res); if (gaierr) { @@ -212,12 +219,81 @@ ssh_create_socket(struct passwd *pw, int privileged, int family) return sock; } +static int +timeout_connect(int sockfd, const struct sockaddr *serv_addr, + socklen_t addrlen, int timeout) +{ + fd_set *fdset; + struct timeval tv; + socklen_t optlen; + int fdsetsz, optval, rc, result = -1; + + if (timeout <= 0) + return (connect(sockfd, serv_addr, addrlen)); + + set_nonblock(sockfd); + rc = connect(sockfd, serv_addr, addrlen); + if (rc == 0) { + unset_nonblock(sockfd); + return (0); + } + if (errno != EINPROGRESS) + return (-1); + + fdsetsz = howmany(sockfd + 1, NFDBITS) * sizeof(fd_mask); + fdset = (fd_set *)xmalloc(fdsetsz); + + memset(fdset, 0, fdsetsz); + FD_SET(sockfd, fdset); + tv.tv_sec = timeout; + tv.tv_usec = 0; + + for(;;) { + rc = select(sockfd + 1, NULL, fdset, NULL, &tv); + if (rc != -1 || errno != EINTR) + break; + } + + switch(rc) { + case 0: + /* Timed out */ + errno = ETIMEDOUT; + break; + case -1: + /* Select error */ + debug("select: %s", strerror(errno)); + break; + case 1: + /* Completed or failed */ + optval = 0; + optlen = sizeof(optval); + if (getsockopt(sockfd, SOL_SOCKET, SO_ERROR, &optval, + &optlen) == -1) { + debug("getsockopt: %s", strerror(errno)); + break; + } + if (optval != 0) { + errno = optval; + break; + } + result = 0; + unset_nonblock(sockfd); + break; + default: + /* Should not occur */ + fatal("Bogus return (%d) from select()", rc); + } + + xfree(fdset); + return (result); +} + /* * Opens a TCP/IP connection to the remote server on the given host. * The address of the remote host will be returned in hostaddr. - * If port is 0, the default port will be used. If anonymous is zero, + * If port is 0, the default port will be used. If needpriv is true, * a privileged port will be allocated to make the connection. - * This requires super-user privileges if anonymous is false. + * This requires super-user privileges if needpriv is true. * Connection_attempts specifies the maximum number of tries (one per * second). If proxy_command is non-NULL, it specifies the command (with %h * and %p substituted for host and port, respectively) to use to contact @@ -232,14 +308,13 @@ ssh_create_socket(struct passwd *pw, int privileged, int family) int ssh_connect(const char *host, struct sockaddr_storage * hostaddr, u_short port, int family, int connection_attempts, - int anonymous, struct passwd *pw, const char *proxy_command) + int needpriv, const char *proxy_command) { int gaierr; int on = 1; int sock = -1, attempt; char ntop[NI_MAXHOST], strport[NI_MAXSERV]; struct addrinfo hints, *ai, *aitop; - struct linger linger; struct servent *sp; /* * Did we get only other errors than "Connection refused" (which @@ -248,8 +323,7 @@ ssh_connect(const char *host, struct sockaddr_storage * hostaddr, */ int full_failure = 1; - debug("ssh_connect: getuid %u geteuid %u anon %d", - (u_int) getuid(), (u_int) geteuid(), anonymous); + debug2("ssh_connect: needpriv %d", needpriv); /* Get default port if port has not been set. */ if (port == 0) { @@ -261,14 +335,14 @@ ssh_connect(const char *host, struct sockaddr_storage * hostaddr, } /* If a proxy command is given, connect using it. */ if (proxy_command != NULL) - return ssh_proxy_connect(host, port, pw, proxy_command); + return ssh_proxy_connect(host, port, proxy_command); /* No proxy command. */ memset(&hints, 0, sizeof(hints)); hints.ai_family = family; hints.ai_socktype = SOCK_STREAM; - snprintf(strport, sizeof strport, "%d", port); + snprintf(strport, sizeof strport, "%u", port); if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) fatal("%s: %.100s: %s", __progname, host, gai_strerror(gaierr)); @@ -297,34 +371,21 @@ ssh_connect(const char *host, struct sockaddr_storage * hostaddr, host, ntop, strport); /* Create a socket for connecting. */ - sock = ssh_create_socket(pw, -#ifdef HAVE_CYGWIN - !anonymous, -#else - !anonymous && geteuid() == 0, -#endif - ai->ai_family); + sock = ssh_create_socket(needpriv, ai); if (sock < 0) /* Any error is already output */ continue; - /* Connect to the host. We use the user's uid in the - * hope that it will help with tcp_wrappers showing - * the remote uid as root. - */ - temporarily_use_uid(pw); - if (connect(sock, ai->ai_addr, ai->ai_addrlen) >= 0) { + if (timeout_connect(sock, ai->ai_addr, ai->ai_addrlen, + options.connection_timeout) >= 0) { /* Successful connection. */ memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); - restore_uid(); break; } else { if (errno == ECONNREFUSED) full_failure = 0; - log("ssh: connect to address %s port %s: %s", - sockaddr_ntop(ai->ai_addr, ai->ai_addrlen), - strport, strerror(errno)); - restore_uid(); + debug("connect to address %s port %s: %s", + ntop, strport, strerror(errno)); /* * Close the failed socket; there appear to * be some problems when reusing a socket for @@ -347,22 +408,16 @@ ssh_connect(const char *host, struct sockaddr_storage * hostaddr, freeaddrinfo(aitop); /* Return failure if we didn't get a successful connection. */ - if (attempt >= connection_attempts) + if (attempt >= connection_attempts) { + logit("ssh: connect to host %s port %s: %s", + host, strport, strerror(errno)); return full_failure ? ECONNABORTED : ECONNREFUSED; + } debug("Connection established."); - /* - * Set socket options. We would like the socket to disappear as soon - * as it has been closed for whatever reason. - */ - /* setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */ - linger.l_onoff = 1; - linger.l_linger = 5; - setsockopt(sock, SOL_SOCKET, SO_LINGER, (void *)&linger, sizeof(linger)); - - /* Set keepalives if requested. */ - if (options.keepalives && + /* Set SO_KEEPALIVE if requested. */ + if (options.tcp_keep_alive && setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, sizeof(on)) < 0) error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); @@ -443,7 +498,7 @@ ssh_exchange_identification(void) enable_compat13(); minor1 = 3; if (options.forward_agent) { - log("Agent forwarding disabled for protocol 1.3"); + logit("Agent forwarding disabled for protocol 1.3"); options.forward_agent = 0; } } @@ -467,7 +522,7 @@ ssh_exchange_identification(void) compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, compat20 ? PROTOCOL_MINOR_2 : minor1, SSH_VERSION); - if (atomicio(write, connection_out, buf, strlen(buf)) != strlen(buf)) + if (atomicio(vwrite, connection_out, buf, strlen(buf)) != strlen(buf)) fatal("write: %.100s", strerror(errno)); client_version_string = xstrdup(buf); chop(client_version_string); @@ -491,7 +546,7 @@ confirm(const char *prompt) (p[0] == '\0') || (p[0] == '\n') || strncasecmp(p, "no", 2) == 0) ret = 0; - if (strncasecmp(p, "yes", 3) == 0) + if (p && strncasecmp(p, "yes", 3) == 0) ret = 1; if (p) xfree(p); @@ -504,13 +559,12 @@ confirm(const char *prompt) * check whether the supplied host key is valid, return -1 if the key * is not valid. the user_hostfile will not be updated if 'readonly' is true. */ - static int check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key, int readonly, const char *user_hostfile, const char *system_hostfile) { Key *file_key; - char *type = key_type(host_key); + const char *type = key_type(host_key); char *ip = NULL; char hostline[1000], *hostp, *fp; HostStatus host_status; @@ -635,16 +689,16 @@ check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key, debug("Found key in %s:%d", host_file, host_line); if (options.check_host_ip && ip_status == HOST_NEW) { if (readonly) - log("%s host key for IP address " + logit("%s host key for IP address " "'%.128s' not in list of known hosts.", type, ip); else if (!add_host_to_hostfile(user_hostfile, ip, host_key)) - log("Failed to add the %s host key for IP " + logit("Failed to add the %s host key for IP " "address '%.128s' to the list of known " "hosts (%.30s).", type, ip, user_hostfile); else - log("Warning: Permanently added the %s host " + logit("Warning: Permanently added the %s host " "key for IP address '%.128s' to the list " "of known hosts.", type, ip); } @@ -663,14 +717,34 @@ check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key, "have requested strict checking.", type, host); goto fail; } else if (options.strict_host_key_checking == 2) { + char msg1[1024], msg2[1024]; + + if (show_other_keys(host, host_key)) + snprintf(msg1, sizeof(msg1), + "\nbut keys of different type are already" + " known for this host."); + else + snprintf(msg1, sizeof(msg1), "."); /* The default */ fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); + msg2[0] = '\0'; + if (options.verify_host_key_dns) { + if (matching_host_key_dns) + snprintf(msg2, sizeof(msg2), + "Matching host key fingerprint" + " found in DNS.\n"); + else + snprintf(msg2, sizeof(msg2), + "No matching host key fingerprint" + " found in DNS.\n"); + } snprintf(msg, sizeof(msg), "The authenticity of host '%.200s (%s)' can't be " - "established.\n" - "%s key fingerprint is %s.\n" + "established%s\n" + "%s key fingerprint is %s.\n%s" "Are you sure you want to continue connecting " - "(yes/no)? ", host, ip, type, fp); + "(yes/no)? ", + host, ip, msg1, type, fp, msg2); xfree(fp); if (!confirm(msg)) goto fail; @@ -686,10 +760,10 @@ check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key, * local known_hosts file. */ if (!add_host_to_hostfile(user_hostfile, hostp, host_key)) - log("Failed to add the host to the list of known " + logit("Failed to add the host to the list of known " "hosts (%.500s).", user_hostfile); else - log("Warning: Permanently added '%.200s' (%s) to the " + logit("Warning: Permanently added '%.200s' (%s) to the " "list of known hosts.", hostp, type); break; case HOST_CHANGED: @@ -713,20 +787,10 @@ check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key, error("Offending key for IP in %s:%d", ip_file, ip_line); } /* The host key has changed. */ - fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); - error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); - error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); - error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); - error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); - error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); - error("It is also possible that the %s host key has just been changed.", type); - error("The fingerprint for the %s key sent by the remote host is\n%s.", - type, fp); - error("Please contact your system administrator."); + warn_changed_key(host_key); error("Add correct host key in %.100s to get rid of this message.", user_hostfile); error("Offending key in %s:%d", host_file, host_line); - xfree(fp); /* * If strict host key checking is in use, the user will have @@ -740,7 +804,7 @@ check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key, /* * If strict host key checking has not been requested, allow - * the connection but without password authentication or + * the connection but without MITM-able authentication or * agent forwarding. */ if (options.password_authentication) { @@ -748,6 +812,17 @@ check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key, "man-in-the-middle attacks."); options.password_authentication = 0; } + if (options.kbd_interactive_authentication) { + error("Keyboard-interactive authentication is disabled" + " to avoid man-in-the-middle attacks."); + options.kbd_interactive_authentication = 0; + options.challenge_response_authentication = 0; + } + if (options.challenge_response_authentication) { + error("Challenge/response authentication is disabled" + " to avoid man-in-the-middle attacks."); + options.challenge_response_authentication = 0; + } if (options.forward_agent) { error("Agent forwarding is disabled to avoid " "man-in-the-middle attacks."); @@ -773,6 +848,9 @@ check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key, * accept the authentication. */ break; + case HOST_FOUND: + fatal("internal error"); + break; } if (options.check_host_ip && host_status != HOST_CHANGED && @@ -786,10 +864,10 @@ check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key, len = strlen(msg); snprintf(msg + len, sizeof(msg) - len, "\nMatching host key in %s:%d", - host_file, host_line); + host_file, host_line); } if (options.strict_host_key_checking == 1) { - log(msg); + logit("%s", msg); error("Exiting, you have requested strict checking."); goto fail; } else if (options.strict_host_key_checking == 2) { @@ -798,7 +876,7 @@ check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key, if (!confirm(msg)) goto fail; } else { - log(msg); + logit("%s", msg); } } @@ -810,10 +888,32 @@ fail: return -1; } +/* returns 0 if key verifies or -1 if key does NOT verify */ int verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) { struct stat st; + int flags = 0; + + if (options.verify_host_key_dns && + verify_host_key_dns(host, hostaddr, host_key, &flags) == 0) { + + if (flags & DNS_VERIFY_FOUND) { + + if (options.verify_host_key_dns == 1 && + flags & DNS_VERIFY_MATCH && + flags & DNS_VERIFY_SECURE) + return 0; + + if (flags & DNS_VERIFY_MATCH) { + matching_host_key_dns = 1; + } else { + warn_changed_key(host_key); + error("Update the SSHFP RR in DNS with the new " + "host key to get rid of this message."); + } + } + } /* return ok if the key can be found in an old keyfile */ if (stat(options.system_hostfile2, &st) == 0 || @@ -884,3 +984,79 @@ ssh_put_password(char *password) memset(padded, 0, size); xfree(padded); } + +static int +show_key_from_file(const char *file, const char *host, int keytype) +{ + Key *found; + char *fp; + int line, ret; + + found = key_new(keytype); + if ((ret = lookup_key_in_hostfile_by_type(file, host, + keytype, found, &line))) { + fp = key_fingerprint(found, SSH_FP_MD5, SSH_FP_HEX); + logit("WARNING: %s key found for host %s\n" + "in %s:%d\n" + "%s key fingerprint %s.", + key_type(found), host, file, line, + key_type(found), fp); + xfree(fp); + } + key_free(found); + return (ret); +} + +/* print all known host keys for a given host, but skip keys of given type */ +static int +show_other_keys(const char *host, Key *key) +{ + int type[] = { KEY_RSA1, KEY_RSA, KEY_DSA, -1}; + int i, found = 0; + + for (i = 0; type[i] != -1; i++) { + if (type[i] == key->type) + continue; + if (type[i] != KEY_RSA1 && + show_key_from_file(options.user_hostfile2, host, type[i])) { + found = 1; + continue; + } + if (type[i] != KEY_RSA1 && + show_key_from_file(options.system_hostfile2, host, type[i])) { + found = 1; + continue; + } + if (show_key_from_file(options.user_hostfile, host, type[i])) { + found = 1; + continue; + } + if (show_key_from_file(options.system_hostfile, host, type[i])) { + found = 1; + continue; + } + debug2("no key of type %d for host %s", type[i], host); + } + return (found); +} + +static void +warn_changed_key(Key *host_key) +{ + char *fp; + const char *type = key_type(host_key); + + fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); + + error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); + error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); + error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); + error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); + error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); + error("It is also possible that the %s host key has just been changed.", type); + error("The fingerprint for the %s key sent by the remote host is\n%s.", + type, fp); + error("Please contact your system administrator."); + + xfree(fp); +}