/* $OpenBSD: authpf.c,v 1.104 2007/02/24 17:35:08 beck Exp $ */ /* $DragonFly: src/usr.sbin/authpf/authpf.c,v 1.2 2004/12/18 22:48:02 swildner Exp $ */ /* * Copyright (C) 1998 - 2007 Bob Beck (beck@openbsd.org). * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include "pathnames.h" #define __dead __dead2 static int read_config(FILE *); static void print_message(const char *); static int allowed_luser(const char *); static int check_luser(const char *, const char *); static int remove_stale_rulesets(void); static int change_filter(int, const char *, const char *); static int change_table(int, const char *); static void authpf_kill_states(void); int dev_fd; /* pf device */ char anchorname[PF_ANCHOR_NAME_SIZE] = "authpf"; char rulesetname[MAXPATHLEN - PF_ANCHOR_NAME_SIZE - 2]; char tablename[PF_TABLE_NAME_SIZE] = "authpf_users"; FILE *pidfp; char luser[MAXLOGNAME]; /* username */ char ipsrc[256]; /* ip as a string */ char pidfile[MAXPATHLEN]; /* we save pid in this file. */ struct timeval Tstart, Tend; /* start and end times of session */ volatile sig_atomic_t want_death; static void need_death(int signo); static __dead void do_death(int); /* * User shell for authenticating gateways. Sole purpose is to allow * a user to ssh to a gateway, and have the gateway modify packet * filters to allow access, then remove access when the user finishes * up. Meant to be used only from ssh(1) connections. */ int main(int argc __unused, char **argv __unused) { int lockcnt = 0, n, pidfd; FILE *config; struct in6_addr ina; struct passwd *pw; char *cp; gid_t gid; uid_t uid; char *shell; login_cap_t *lc; config = fopen(PATH_CONFFILE, "r"); if (config == NULL) { syslog(LOG_ERR, "can not open %s (%m)", PATH_CONFFILE); exit(1); } if ((cp = getenv("SSH_TTY")) == NULL) { syslog(LOG_ERR, "non-interactive session connection for authpf"); exit(1); } if ((cp = getenv("SSH_CLIENT")) == NULL) { syslog(LOG_ERR, "cannot determine connection source"); exit(1); } if (strlcpy(ipsrc, cp, sizeof(ipsrc)) >= sizeof(ipsrc)) { syslog(LOG_ERR, "SSH_CLIENT variable too long"); exit(1); } cp = strchr(ipsrc, ' '); if (!cp) { syslog(LOG_ERR, "corrupt SSH_CLIENT variable %s", ipsrc); exit(1); } *cp = '\0'; if (inet_pton(AF_INET, ipsrc, &ina) != 1 && inet_pton(AF_INET6, ipsrc, &ina) != 1) { syslog(LOG_ERR, "cannot determine IP from SSH_CLIENT %s", ipsrc); exit(1); } /* open the pf device */ dev_fd = open(PATH_DEVFILE, O_RDWR); if (dev_fd == -1) { syslog(LOG_ERR, "cannot open packet filter device (%m)"); goto die; } uid = getuid(); pw = getpwuid(uid); if (pw == NULL) { syslog(LOG_ERR, "cannot find user for uid %u", uid); goto die; } if ((lc = login_getclass(pw->pw_class)) != NULL) shell = login_getcapstr(lc, "shell", pw->pw_shell, pw->pw_shell); else shell = pw->pw_shell; login_close(lc); if (strcmp(shell, PATH_AUTHPF_SHELL)) { syslog(LOG_ERR, "wrong shell for user %s, uid %u", pw->pw_name, pw->pw_uid); if (shell != pw->pw_shell) free(shell); goto die; } if (shell != pw->pw_shell) free(shell); /* * Paranoia, but this data _does_ come from outside authpf, and * truncation would be bad. */ if (strlcpy(luser, pw->pw_name, sizeof(luser)) >= sizeof(luser)) { syslog(LOG_ERR, "username too long: %s", pw->pw_name); goto die; } if ((n = snprintf(rulesetname, sizeof(rulesetname), "%s(%ld)", luser, (long)getpid())) < 0 || n >= (int)sizeof(rulesetname)) { syslog(LOG_INFO, "%s(%ld) too large, ruleset name will be %ld", luser, (long)getpid(), (long)getpid()); if ((n = snprintf(rulesetname, sizeof(rulesetname), "%ld", (long)getpid())) < 0 || n >= (int)sizeof(rulesetname)) { syslog(LOG_ERR, "pid too large for ruleset name"); goto die; } } /* Make our entry in /var/authpf as /var/authpf/ipaddr */ n = snprintf(pidfile, sizeof(pidfile), "%s/%s", PATH_PIDFILE, ipsrc); if (n < 0 || (u_int)n >= sizeof(pidfile)) { syslog(LOG_ERR, "path to pidfile too long"); goto die; } /* * If someone else is already using this ip, then this person * wants to switch users - so kill the old process and exit * as well. * * Note, we could print a message and tell them to log out, but the * usual case of this is that someone has left themselves logged in, * with the authenticated connection iconized and someone else walks * up to use and automatically logs in before using. If this just * gets rid of the old one silently, the new user never knows they * could have used someone else's old authentication. If we * tell them to log out before switching users it is an invitation * for abuse. */ do { int save_errno, otherpid = -1; char otherluser[MAXLOGNAME]; if ((pidfd = open(pidfile, O_RDWR|O_CREAT, 0644)) == -1 || (pidfp = fdopen(pidfd, "r+")) == NULL) { if (pidfd != -1) close(pidfd); syslog(LOG_ERR, "cannot open or create %s: %s", pidfile, strerror(errno)); goto die; } if (flock(fileno(pidfp), LOCK_EX|LOCK_NB) == 0) break; save_errno = errno; /* Mark our pid, and username to our file. */ rewind(pidfp); /* 31 == MAXLOGNAME - 1 */ if (fscanf(pidfp, "%d\n%31s\n", &otherpid, otherluser) != 2) otherpid = -1; syslog(LOG_DEBUG, "tried to lock %s, in use by pid %d: %s", pidfile, otherpid, strerror(save_errno)); if (otherpid > 0) { syslog(LOG_INFO, "killing prior auth (pid %d) of %s by user %s", otherpid, ipsrc, otherluser); if (kill((pid_t) otherpid, SIGTERM) == -1) { syslog(LOG_INFO, "could not kill process %d: (%m)", otherpid); } } /* * we try to kill the previous process and acquire the lock * for 10 seconds, trying once a second. if we can't after * 10 attempts we log an error and give up */ if (++lockcnt > 10) { syslog(LOG_ERR, "cannot kill previous authpf (pid %d)", otherpid); fclose(pidfp); pidfp = NULL; goto dogdeath; } sleep(1); /* re-open, and try again. The previous authpf process * we killed above should unlink the file and release * it's lock, giving us a chance to get it now */ fclose(pidfp); pidfp = NULL; } while (1); /* whack the group list */ gid = getegid(); if (setgroups(1, &gid) == -1) { syslog(LOG_INFO, "setgroups: %s", strerror(errno)); do_death(0); } /* revoke privs */ uid = getuid(); if (setresuid(uid, uid, uid) == -1) { syslog(LOG_INFO, "setresuid: %s", strerror(errno)); do_death(0); } openlog("authpf", LOG_PID | LOG_NDELAY, LOG_DAEMON); if (!check_luser(PATH_BAN_DIR, luser) || !allowed_luser(luser)) { syslog(LOG_INFO, "user %s prohibited", luser); do_death(0); } if (read_config(config)) { syslog(LOG_ERR, "invalid config file %s", PATH_CONFFILE); do_death(0); } if (remove_stale_rulesets()) { syslog(LOG_INFO, "error removing stale rulesets"); do_death(0); } /* We appear to be making headway, so actually mark our pid */ rewind(pidfp); fprintf(pidfp, "%ld\n%s\n", (long)getpid(), luser); fflush(pidfp); ftruncate(fileno(pidfp), ftell(pidfp)); if (change_filter(1, luser, ipsrc) == -1) { printf("Unable to modify filters\r\n"); do_death(0); } if (change_table(1, ipsrc) == -1) { printf("Unable to modify table\r\n"); change_filter(0, luser, ipsrc); do_death(0); } signal(SIGTERM, need_death); signal(SIGINT, need_death); signal(SIGALRM, need_death); signal(SIGPIPE, need_death); signal(SIGHUP, need_death); signal(SIGQUIT, need_death); signal(SIGTSTP, need_death); while (1) { printf("\r\nHello %s. ", luser); printf("You are authenticated from host \"%s\"\r\n", ipsrc); setproctitle("%s@%s", luser, ipsrc); print_message(PATH_MESSAGE); while (1) { sleep(10); if (want_death) do_death(1); } } /* NOTREACHED */ dogdeath: printf("\r\n\r\nSorry, this service is currently unavailable due to "); printf("technical difficulties\r\n\r\n"); print_message(PATH_PROBLEM); printf("\r\nYour authentication process (pid %ld) was unable to run\n", (long)getpid()); sleep(180); /* them lusers read reaaaaal slow */ die: do_death(0); } /* * reads config file in PATH_CONFFILE to set optional behaviours up */ static int read_config(FILE *f) { char buf[1024]; int i = 0; do { char **ap; char *pair[4], *cp, *tp; int len; if (fgets(buf, sizeof(buf), f) == NULL) { fclose(f); return (0); } i++; len = strlen(buf); if (buf[len - 1] != '\n' && !feof(f)) { syslog(LOG_ERR, "line %d too long in %s", i, PATH_CONFFILE); return (1); } buf[len - 1] = '\0'; for (cp = buf; *cp == ' ' || *cp == '\t'; cp++) ; /* nothing */ if (!*cp || *cp == '#' || *cp == '\n') continue; for (ap = pair; ap < &pair[3] && (*ap = strsep(&cp, "=")) != NULL; ) { if (**ap != '\0') ap++; } if (ap != &pair[2]) goto parse_error; tp = pair[1] + strlen(pair[1]); while ((*tp == ' ' || *tp == '\t') && tp >= pair[1]) *tp-- = '\0'; if (strcasecmp(pair[0], "anchor") == 0) { if (!pair[1][0] || strlcpy(anchorname, pair[1], sizeof(anchorname)) >= sizeof(anchorname)) goto parse_error; } if (strcasecmp(pair[0], "table") == 0) { if (!pair[1][0] || strlcpy(tablename, pair[1], sizeof(tablename)) >= sizeof(tablename)) goto parse_error; } } while (!feof(f) && !ferror(f)); fclose(f); return (0); parse_error: fclose(f); syslog(LOG_ERR, "parse error, line %d of %s", i, PATH_CONFFILE); return (1); } /* * splatter a file to stdout - max line length of 1024, * used for spitting message files at users to tell them * they've been bad or we're unavailable. */ static void print_message(const char *filename) { char buf[1024]; FILE *f; if ((f = fopen(filename, "r")) == NULL) return; /* fail silently, we don't care if it isn't there */ do { if (fgets(buf, sizeof(buf), f) == NULL) { fflush(stdout); fclose(f); return; } } while (fputs(buf, stdout) != EOF && !feof(f)); fflush(stdout); fclose(f); } /* * allowed_luser checks to see if user "luser" is allowed to * use this gateway by virtue of being listed in an allowed * users file, namely /etc/authpf/authpf.allow . * * If /etc/authpf/authpf.allow does not exist, then we assume that * all users who are allowed in by sshd(8) are permitted to * use this gateway. If /etc/authpf/authpf.allow does exist, then a * user must be listed if the connection is to continue, else * the session terminates in the same manner as being banned. */ static int allowed_luser(const char *user) { char *buf, *lbuf; int matched; size_t len; FILE *f; if ((f = fopen(PATH_ALLOWFILE, "r")) == NULL) { if (errno == ENOENT) { /* * allowfile doesn't exist, thus this gateway * isn't restricted to certain users... */ return (1); } /* * user may in fact be allowed, but we can't open * the file even though it's there. probably a config * problem. */ syslog(LOG_ERR, "cannot open allowed users file %s (%s)", PATH_ALLOWFILE, strerror(errno)); return (0); } else { /* * /etc/authpf/authpf.allow exists, thus we do a linear * search to see if they are allowed. * also, if username "*" exists, then this is a * "public" gateway, such as it is, so let * everyone use it. */ lbuf = NULL; while ((buf = fgetln(f, &len))) { if (buf[len - 1] == '\n') buf[len - 1] = '\0'; else { if ((lbuf = (char *)malloc(len + 1)) == NULL) err(1, NULL); memcpy(lbuf, buf, len); lbuf[len] = '\0'; buf = lbuf; } matched = strcmp(user, buf) == 0 || strcmp("*", buf) == 0; if (lbuf != NULL) { free(lbuf); lbuf = NULL; } if (matched) return (1); /* matched an allowed username */ } syslog(LOG_INFO, "denied access to %s: not listed in %s", user, PATH_ALLOWFILE); fputs("\n\nSorry, you are not allowed to use this facility!\n", stdout); } fflush(stdout); return (0); } /* * check_luser checks to see if user "luser" has been banned * from using us by virtue of having an file of the same name * in the "luserdir" directory. * * If the user has been banned, we copy the contents of the file * to the user's screen. (useful for telling the user what to * do to get un-banned, or just to tell them they aren't * going to be un-banned.) */ static int check_luser(const char *userdir, const char *user) { FILE *f; int n; char tmp[MAXPATHLEN]; n = snprintf(tmp, sizeof(tmp), "%s/%s", userdir, user); if (n < 0 || (u_int)n >= sizeof(tmp)) { syslog(LOG_ERR, "provided banned directory line too long (%s)", userdir); return (0); } if ((f = fopen(tmp, "r")) == NULL) { if (errno == ENOENT) { /* * file or dir doesn't exist, so therefore * this luser isn't banned.. all is well */ return (1); } else { /* * user may in fact be banned, but we can't open the * file even though it's there. probably a config * problem. */ syslog(LOG_ERR, "cannot open banned file %s (%s)", tmp, strerror(errno)); return (0); } } else { /* * user is banned - spit the file at them to * tell what they can do and where they can go. */ syslog(LOG_INFO, "denied access to %s: %s exists", luser, tmp); /* reuse tmp */ strlcpy(tmp, "\n\n-**- Sorry, you have been banned! -**-\n\n", sizeof(tmp)); while (fputs(tmp, stdout) != EOF && !feof(f)) { if (fgets(tmp, sizeof(tmp), f) == NULL) { fflush(stdout); fclose(f); return (0); } } fclose(f); } fflush(stdout); return (0); } /* * Search for rulesets left by other authpf processes (either because they * died ungracefully or were terminated) and remove them. */ static int remove_stale_rulesets(void) { struct pfioc_ruleset prs; u_int32_t nr, mnr; memset(&prs, 0, sizeof(prs)); strlcpy(prs.path, anchorname, sizeof(prs.path)); if (ioctl(dev_fd, DIOCGETRULESETS, &prs)) { if (errno == EINVAL) return (0); else return (1); } mnr = prs.nr; nr = 0; while (nr < mnr) { char *s, *t; pid_t pid; prs.nr = nr; if (ioctl(dev_fd, DIOCGETRULESET, &prs)) return (1); errno = 0; if ((t = strchr(prs.name, '(')) == NULL) t = prs.name; else t++; pid = strtoul(t, &s, 10); if (!prs.name[0] || errno || (*s && (t == prs.name || *s != ')'))) return (1); if (kill(pid, 0) && errno != EPERM) { int i; struct pfioc_trans_e t_e[PF_RULESET_MAX+1]; struct pfioc_trans t_local; bzero(&t, sizeof(t_local)); bzero(t_e, sizeof(t_e)); t_local.size = PF_RULESET_MAX+1; t_local.esize = sizeof(t_e[0]); t_local.array = t_e; for (i = 0; i < PF_RULESET_MAX+1; ++i) { t_e[i].rs_num = i; snprintf(t_e[i].anchor, sizeof(t_e[i].anchor), "%s/%s", anchorname, prs.name); } mnr--; } else nr++; } return (0); } /* * Add/remove filter entries for user "luser" from ip "ipsrc" */ static int change_filter(int add, const char *user, const char *his_ipsrc) { const char *pargv[13] = { "pfctl", "-p", "/dev/pf", "-q", "-a", "anchor/ruleset", "-D", "user_ip=X", "-D", "user_id=X", "-f", "file", NULL }; char *fdpath = NULL, *userstr = NULL, *ipstr = NULL; char *rsn = NULL, *fn = NULL; pid_t pid; gid_t gid; int s; if (user == NULL || !user[0] || his_ipsrc == NULL || !his_ipsrc[0]) { syslog(LOG_ERR, "invalid user/ipsrc"); goto error; } if (asprintf(&rsn, "%s/%s", anchorname, rulesetname) == -1) goto no_mem; if (asprintf(&fdpath, "/dev/fd/%d", dev_fd) == -1) goto no_mem; if (asprintf(&ipstr, "user_ip=%s", his_ipsrc) == -1) goto no_mem; if (asprintf(&userstr, "user_id=%s", user) == -1) goto no_mem; if (add) { struct stat sb; if (asprintf(&fn, "%s/%s/authpf.rules", PATH_USER_DIR, user) == -1) goto no_mem; if (stat(fn, &sb) == -1) { free(fn); if ((fn = strdup(PATH_PFRULES)) == NULL) goto no_mem; } } pargv[2] = fdpath; pargv[5] = rsn; pargv[7] = userstr; pargv[9] = ipstr; if (!add) pargv[11] = "/dev/null"; else pargv[11] = fn; switch (pid = fork()) { case -1: syslog(LOG_ERR, "fork failed"); goto error; case 0: /* revoke group privs before exec */ gid = getgid(); if (setregid(gid, gid) == -1) { err(1, "setregid"); } execvp(PATH_PFCTL, __DECONST(char *const *, pargv)); warn("exec of %s failed", PATH_PFCTL); _exit(1); } /* parent */ waitpid(pid, &s, 0); if (s != 0) { syslog(LOG_ERR, "pfctl exited abnormally"); goto error; } if (add) { gettimeofday(&Tstart, NULL); syslog(LOG_INFO, "allowing %s, user %s", his_ipsrc, user); } else { gettimeofday(&Tend, NULL); syslog(LOG_INFO, "removed %s, user %s - duration %ld seconds", his_ipsrc, user, Tend.tv_sec - Tstart.tv_sec); } return (0); no_mem: syslog(LOG_ERR, "malloc failed"); error: free(fdpath); free(rsn); free(userstr); free(ipstr); free(fn); return (-1); } /* * Add/remove this IP from the "authpf_users" table. */ static int change_table(int add, const char *his_ipsrc) { struct pfioc_table io; struct pfr_addr addr; bzero(&io, sizeof(io)); strlcpy(io.pfrio_table.pfrt_name, tablename, sizeof(io.pfrio_table.pfrt_name)); io.pfrio_buffer = &addr; io.pfrio_esize = sizeof(addr); io.pfrio_size = 1; bzero(&addr, sizeof(addr)); if (his_ipsrc == NULL || !his_ipsrc[0]) return (-1); if (inet_pton(AF_INET, his_ipsrc, &addr.pfra_ip4addr) == 1) { addr.pfra_af = AF_INET; addr.pfra_net = 32; } else if (inet_pton(AF_INET6, his_ipsrc, &addr.pfra_ip6addr) == 1) { addr.pfra_af = AF_INET6; addr.pfra_net = 128; } else { syslog(LOG_ERR, "invalid his_ipsrc"); return (-1); } if (ioctl(dev_fd, add ? DIOCRADDADDRS : DIOCRDELADDRS, &io) && errno != ESRCH) { syslog(LOG_ERR, "cannot %s %s from table %s: %s", add ? "add" : "remove", his_ipsrc, tablename, strerror(errno)); return (-1); } return (0); } /* * This is to kill off states that would otherwise be left behind stateful * rules. This means we don't need to allow in more traffic than we really * want to, since we don't have to worry about any luser sessions lasting * longer than their ssh session. This function is based on * pfctl_kill_states from pfctl. */ static void authpf_kill_states(void) { struct pfioc_state_kill psk; struct pf_addr target; memset(&psk, 0, sizeof(psk)); memset(&target, 0, sizeof(target)); if (inet_pton(AF_INET, ipsrc, &target.v4) == 1) psk.psk_af = AF_INET; else if (inet_pton(AF_INET6, ipsrc, &target.v6) == 1) psk.psk_af = AF_INET6; else { syslog(LOG_ERR, "inet_pton(%s) failed", ipsrc); return; } /* Kill all states from ipsrc */ memcpy(&psk.psk_src.addr.v.a.addr, &target, sizeof(psk.psk_src.addr.v.a.addr)); memset(&psk.psk_src.addr.v.a.mask, 0xff, sizeof(psk.psk_src.addr.v.a.mask)); if (ioctl(dev_fd, DIOCKILLSTATES, &psk)) syslog(LOG_ERR, "DIOCKILLSTATES failed (%m)"); /* Kill all states to ipsrc */ memset(&psk.psk_src, 0, sizeof(psk.psk_src)); memcpy(&psk.psk_dst.addr.v.a.addr, &target, sizeof(psk.psk_dst.addr.v.a.addr)); memset(&psk.psk_dst.addr.v.a.mask, 0xff, sizeof(psk.psk_dst.addr.v.a.mask)); if (ioctl(dev_fd, DIOCKILLSTATES, &psk)) syslog(LOG_ERR, "DIOCKILLSTATES failed (%m)"); } /* signal handler that makes us go away properly */ static void need_death(int signo __unused) { want_death = 1; } /* * function that removes our stuff when we go away. */ static __dead void do_death(int active) { int ret = 0; if (active) { change_filter(0, luser, ipsrc); change_table(0, ipsrc); authpf_kill_states(); remove_stale_rulesets(); } if (pidfile[0] && (pidfp != NULL)) if (unlink(pidfile) == -1) syslog(LOG_ERR, "cannot unlink %s (%m)", pidfile); exit(ret); }