From 25505898530a333011f4fd5cbc841ad6b26c089c Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 7 Apr 2024 16:40:04 +0200 Subject: Adding upstream version 1:9.2p1. Signed-off-by: Daniel Baumann --- auth-rhosts.c | 338 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 338 insertions(+) create mode 100644 auth-rhosts.c (limited to 'auth-rhosts.c') diff --git a/auth-rhosts.c b/auth-rhosts.c new file mode 100644 index 0000000..5672467 --- /dev/null +++ b/auth-rhosts.c @@ -0,0 +1,338 @@ +/* $OpenBSD: auth-rhosts.c,v 1.57 2022/12/09 00:17:40 dtucker Exp $ */ +/* + * Author: Tatu Ylonen + * Copyright (c) 1995 Tatu Ylonen , Espoo, Finland + * All rights reserved + * Rhosts authentication. This file contains code to check whether to admit + * the login based on rhosts authentication. This file also processes + * /etc/hosts.equiv. + * + * 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 +#ifdef HAVE_NETGROUP_H +# include +#endif +#include +#include +#include +#include +#include +#include + +#include "packet.h" +#include "uidswap.h" +#include "pathnames.h" +#include "log.h" +#include "misc.h" +#include "xmalloc.h" +#include "sshbuf.h" +#include "sshkey.h" +#include "servconf.h" +#include "canohost.h" +#include "hostfile.h" +#include "auth.h" + +/* import */ +extern ServerOptions options; +extern int use_privsep; + +/* + * This function processes an rhosts-style file (.rhosts, .shosts, or + * /etc/hosts.equiv). This returns true if authentication can be granted + * based on the file, and returns zero otherwise. + */ + +static int +check_rhosts_file(const char *filename, const char *hostname, + const char *ipaddr, const char *client_user, + const char *server_user) +{ + FILE *f; +#define RBUFLN 1024 + char buf[RBUFLN];/* Must not be larger than host, user, dummy below. */ + int fd; + struct stat st; + + /* Open the .rhosts file, deny if unreadable */ + if ((fd = open(filename, O_RDONLY|O_NONBLOCK)) == -1) + return 0; + if (fstat(fd, &st) == -1) { + close(fd); + return 0; + } + if (!S_ISREG(st.st_mode)) { + logit("User %s hosts file %s is not a regular file", + server_user, filename); + close(fd); + return 0; + } + unset_nonblock(fd); + if ((f = fdopen(fd, "r")) == NULL) { + close(fd); + return 0; + } + while (fgets(buf, sizeof(buf), f)) { + /* All three must have length >= buf to avoid overflows. */ + char hostbuf[RBUFLN], userbuf[RBUFLN], dummy[RBUFLN]; + char *host, *user, *cp; + int negated; + + for (cp = buf; *cp == ' ' || *cp == '\t'; cp++) + ; + if (*cp == '#' || *cp == '\n' || !*cp) + continue; + + /* + * NO_PLUS is supported at least on OSF/1. We skip it (we + * don't ever support the plus syntax). + */ + if (strncmp(cp, "NO_PLUS", 7) == 0) + continue; + + /* + * This should be safe because each buffer is as big as the + * whole string, and thus cannot be overwritten. + */ + switch (sscanf(buf, "%1023s %1023s %1023s", hostbuf, userbuf, + dummy)) { + case 0: + auth_debug_add("Found empty line in %.100s.", filename); + continue; + case 1: + /* Host name only. */ + strlcpy(userbuf, server_user, sizeof(userbuf)); + break; + case 2: + /* Got both host and user name. */ + break; + case 3: + auth_debug_add("Found garbage in %.100s.", filename); + continue; + default: + /* Weird... */ + continue; + } + + host = hostbuf; + user = userbuf; + negated = 0; + + /* Process negated host names, or positive netgroups. */ + if (host[0] == '-') { + negated = 1; + host++; + } else if (host[0] == '+') + host++; + + if (user[0] == '-') { + negated = 1; + user++; + } else if (user[0] == '+') + user++; + + /* Check for empty host/user names (particularly '+'). */ + if (!host[0] || !user[0]) { + /* We come here if either was '+' or '-'. */ + auth_debug_add("Ignoring wild host/user names " + "in %.100s.", filename); + continue; + } + /* Verify that host name matches. */ + if (host[0] == '@') { + if (!innetgr(host + 1, hostname, NULL, NULL) && + !innetgr(host + 1, ipaddr, NULL, NULL)) + continue; + } else if (strcasecmp(host, hostname) && + strcmp(host, ipaddr) != 0) + continue; /* Different hostname. */ + + /* Verify that user name matches. */ + if (user[0] == '@') { + if (!innetgr(user + 1, NULL, client_user, NULL)) + continue; + } else if (strcmp(user, client_user) != 0) + continue; /* Different username. */ + + /* Found the user and host. */ + fclose(f); + + /* If the entry was negated, deny access. */ + if (negated) { + auth_debug_add("Matched negative entry in %.100s.", + filename); + return 0; + } + /* Accept authentication. */ + return 1; + } + + /* Authentication using this file denied. */ + fclose(f); + return 0; +} + +/* + * Tries to authenticate the user using the .shosts or .rhosts file. Returns + * true if authentication succeeds. If ignore_rhosts is true, only + * /etc/hosts.equiv will be considered (.rhosts and .shosts are ignored). + */ +int +auth_rhosts2(struct passwd *pw, const char *client_user, const char *hostname, + const char *ipaddr) +{ + char *path = NULL; + struct stat st; + static const char * const rhosts_files[] = {".shosts", ".rhosts", NULL}; + u_int rhosts_file_index; + int r; + + debug2_f("clientuser %s hostname %s ipaddr %s", + client_user, hostname, ipaddr); + + /* Switch to the user's uid. */ + temporarily_use_uid(pw); + /* + * Quick check: if the user has no .shosts or .rhosts files and + * no system hosts.equiv/shosts.equiv files exist then return + * failure immediately without doing costly lookups from name + * servers. + */ + for (rhosts_file_index = 0; rhosts_files[rhosts_file_index]; + rhosts_file_index++) { + /* Check users .rhosts or .shosts. */ + xasprintf(&path, "%s/%s", + pw->pw_dir, rhosts_files[rhosts_file_index]); + r = stat(path, &st); + free(path); + if (r >= 0) + break; + } + /* Switch back to privileged uid. */ + restore_uid(); + + /* + * Deny if The user has no .shosts or .rhosts file and there + * are no system-wide files. + */ + if (!rhosts_files[rhosts_file_index] && + stat(_PATH_RHOSTS_EQUIV, &st) == -1 && + stat(_PATH_SSH_HOSTS_EQUIV, &st) == -1) { + debug3_f("no hosts access files exist"); + return 0; + } + + /* + * If not logging in as superuser, try /etc/hosts.equiv and + * shosts.equiv. + */ + if (pw->pw_uid == 0) + debug3_f("root user, ignoring system hosts files"); + else { + if (check_rhosts_file(_PATH_RHOSTS_EQUIV, hostname, ipaddr, + client_user, pw->pw_name)) { + auth_debug_add("Accepted for %.100s [%.100s] by " + "/etc/hosts.equiv.", hostname, ipaddr); + return 1; + } + if (check_rhosts_file(_PATH_SSH_HOSTS_EQUIV, hostname, ipaddr, + client_user, pw->pw_name)) { + auth_debug_add("Accepted for %.100s [%.100s] by " + "%.100s.", hostname, ipaddr, _PATH_SSH_HOSTS_EQUIV); + return 1; + } + } + + /* + * Check that the home directory is owned by root or the user, and is + * not group or world writable. + */ + if (stat(pw->pw_dir, &st) == -1) { + logit("Rhosts authentication refused for %.100s: " + "no home directory %.200s", pw->pw_name, pw->pw_dir); + auth_debug_add("Rhosts authentication refused for %.100s: " + "no home directory %.200s", pw->pw_name, pw->pw_dir); + return 0; + } + if (options.strict_modes && + ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || + (st.st_mode & 022) != 0)) { + logit("Rhosts authentication refused for %.100s: " + "bad ownership or modes for home directory.", pw->pw_name); + auth_debug_add("Rhosts authentication refused for %.100s: " + "bad ownership or modes for home directory.", pw->pw_name); + return 0; + } + /* Temporarily use the user's uid. */ + temporarily_use_uid(pw); + + /* Check all .rhosts files (currently .shosts and .rhosts). */ + for (rhosts_file_index = 0; rhosts_files[rhosts_file_index]; + rhosts_file_index++) { + /* Check users .rhosts or .shosts. */ + xasprintf(&path, "%s/%s", + pw->pw_dir, rhosts_files[rhosts_file_index]); + if (stat(path, &st) == -1) { + debug3_f("stat %s: %s", path, strerror(errno)); + free(path); + continue; + } + + /* + * Make sure that the file is either owned by the user or by + * root, and make sure it is not writable by anyone but the + * owner. This is to help avoid novices accidentally + * allowing access to their account by anyone. + */ + if (options.strict_modes && + ((st.st_uid != 0 && st.st_uid != pw->pw_uid) || + (st.st_mode & 022) != 0)) { + logit("Rhosts authentication refused for %.100s: " + "bad modes for %.200s", pw->pw_name, path); + auth_debug_add("Bad file modes for %.200s", path); + free(path); + continue; + } + /* + * Check if we have been configured to ignore .rhosts + * and .shosts files. + */ + if (options.ignore_rhosts == IGNORE_RHOSTS_YES || + (options.ignore_rhosts == IGNORE_RHOSTS_SHOSTS && + strcmp(rhosts_files[rhosts_file_index], ".shosts") != 0)) { + auth_debug_add("Server has been configured to " + "ignore %.100s.", rhosts_files[rhosts_file_index]); + free(path); + continue; + } + /* Check if authentication is permitted by the file. */ + if (check_rhosts_file(path, hostname, ipaddr, + client_user, pw->pw_name)) { + auth_debug_add("Accepted by %.100s.", + rhosts_files[rhosts_file_index]); + /* Restore the privileged uid. */ + restore_uid(); + auth_debug_add("Accepted host %s ip %s client_user " + "%s server_user %s", hostname, ipaddr, + client_user, pw->pw_name); + free(path); + return 1; + } + free(path); + } + + /* Restore the privileged uid. */ + restore_uid(); + return 0; +} -- cgit v1.2.3