/* $OpenBSD: authpf.c,v 1.20 2002/06/11 04:45:32 kjell Exp $ */ /* * Copyright (C) 1998 - 2002 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. * 3. Neither the name of the author nor the names of contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * 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 #include #include #include #include #include #include #include #include #include "pathnames.h" int Rule_Action = PF_CHANGE_ADD_TAIL; int Nat_Action = PF_CHANGE_ADD_HEAD; int Rdr_Action = PF_CHANGE_ADD_HEAD; int dev; /* pf device */ int Delete_Rules; /* for parse_rules callbacks */ FILE *pidfp; char *infile; /* infile name needed by parse_[rules|nat] */ 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 */ int pfctl_add_rule(struct pfctl *, struct pf_rule *); int pfctl_add_nat(struct pfctl *, struct pf_nat *); int pfctl_add_rdr(struct pfctl *, struct pf_rdr *); int pfctl_add_binat(struct pfctl *, struct pf_binat *); static int read_config(FILE *); static void print_message(char *); static int allowed_luser(char *); static int check_luser(char *, char *); static int changefilter(int, char *, char *); static void authpf_kill_states(void); 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, char *argv[]) { int lockcnt = 0, pidfd; FILE *config; struct in_addr ina; struct passwd *pw; char *cp; uid_t uid; config = fopen(PATH_CONFFILE, "r"); if (config == NULL) exit(1); if ((cp = getenv("SSH_CLIENT")) == NULL) { syslog(LOG_ERR, "Can't determine connection source"); exit(1); } strlcpy(ipsrc, cp, sizeof(ipsrc)); 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) { syslog(LOG_ERR, "Cannot determine IP from SSH_CLIENT %s", ipsrc); exit(1); } /* open the pf device */ dev = open(PATH_DEVFILE, O_RDWR); if (dev == -1) { syslog(LOG_ERR, "Can't open filter device (%m)"); goto die; } uid = getuid(); pw = getpwuid(uid); if (pw == NULL) { syslog(LOG_ERR, "can't find user for uid %u", uid); goto die; } if (strcmp(pw->pw_shell, PATH_AUTHPF_SHELL)) { syslog(LOG_ERR, "wrong shell for user %s, uid %u", pw->pw_name, pw->pw_uid); goto die; } strlcpy(luser, pw->pw_name, sizeof(luser)); /* * 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[33]; if ((pidfd = open(pidfile, O_RDWR|O_CREAT, 0644)) == -1 || (pidfp = fdopen(pidfd, "r+")) == NULL) { if (pidfd == -1) close(pidfd); syslog(LOG_ERR, "can't 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); if (fscanf(pidfp, "%d\n%32s\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, "Couldn't 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, "Can't kill previous authpf (pid %d)", otherpid); 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); } while (1); /* revoke privs */ seteuid(getuid()); setuid(getuid()); if (!check_luser(PATH_BAN_DIR, luser) || !allowed_luser(luser)) do_death(0); if (read_config(config)) 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); (void) ftruncate(fileno(pidfp), ftell(pidfp)); if (changefilter(1, luser, ipsrc) == -1) { printf("Unable to modify filters\r\n"); do_death(1); } signal(SIGTERM, need_death); signal(SIGINT, need_death); signal(SIGALRM, need_death); signal(SIGPIPE, need_death); signal(SIGHUP, need_death); signal(SIGSTOP, need_death); signal(SIGTSTP, need_death); while (1) { printf("\r\nHello %s, ", luser); printf("You are authenticated from host \"%s\"\r\n", 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 %d) was unable to run\n", 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; openlog("authpf", LOG_PID | LOG_NDELAY, LOG_DAEMON); do { char **ap, *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++) ; 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], "rule_action") == 0) { if (strcasecmp(pair[1], "head") == 0) Rule_Action = PF_CHANGE_ADD_HEAD; else if (strcasecmp(pair[1], "tail") == 0) Rule_Action = PF_CHANGE_ADD_TAIL; else goto parse_error; } else if (strcasecmp(pair[0], "nat_action") == 0) { if (strcasecmp(pair[1], "head") == 0) Nat_Action = PF_CHANGE_ADD_HEAD; else if (strcasecmp(pair[1], "tail") == 0) Nat_Action = PF_CHANGE_ADD_TAIL; else goto parse_error; } else if (strcasecmp(pair[0], "rdr_action") == 0) { if (strcasecmp(pair[1], "head") == 0) Rdr_Action = PF_CHANGE_ADD_HEAD; else if (strcasecmp(pair[1], "tail") == 0) Rdr_Action = PF_CHANGE_ADD_TAIL; else 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(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.allow . * * If /etc/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.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(char *luser) { 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); } /* * luser may in fact be allowed, but we can't open * the file even though it's there. probably a config * problem. */ syslog(LOG_ERR, "Can't open allowed users file %s (%s)", PATH_ALLOWFILE, strerror(errno)); return(0); } else { /* * /etc/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(luser, 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", luser, PATH_ALLOWFILE); /* reuse buf */ buf = "\n\nSorry, you aren't allowed to use this facility!\n"; fputs(buf, 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(char *luserdir, char *luser) { char tmp[1024]; FILE *f; if (snprintf(tmp, sizeof(tmp), "%s/%s", luserdir, luser) >= sizeof(tmp)) { syslog(LOG_ERR, "Provided banned directory line too long (%s)", luserdir); 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 { /* * luser may in fact be banned, but we can't open the * file even though it's there. probably a config * problem. */ syslog(LOG_ERR, "Can't open banned file %s (%s)", tmp, strerror(errno)); return(0); } } else { /* * luser 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); return(0); } } } fflush(stdout); return(0); } /* * Add/remove filter entries for user "luser" from ip "ipsrc" */ static int changefilter(int add, char *luser, char *ipsrc) { char rulesfile[MAXPATHLEN], buf[1024]; char template[] = "/tmp/authpfrules.XXXXXXX"; int tmpfile = -1, from_fd = -1, ret = -1; struct pfioc_nat pn; struct pfioc_binat pb; struct pfioc_rdr pd; struct pfioc_rule pr; struct pfctl pf; int rcount, wcount; FILE *fin = NULL; memset(&pf, 0, sizeof(pf)); memset(&pr, 0, sizeof(pr)); syslog(LOG_DEBUG, "%s filter for ip=%s, user %s", add ? "Adding" : "Removing", ipsrc, luser); /* add filter rules */ if (add) Delete_Rules = 0; else Delete_Rules = 1; tmpfile = mkstemp(template); if (tmpfile == -1) { syslog(LOG_ERR, "Can't open temp file %s (%m)", template); goto error; } fin = fdopen(tmpfile, "r+"); if (fin == NULL) { syslog(LOG_ERR, "can't open %s (%m)", template); goto error; } /* write the variable to the start of the file */ fprintf(fin, "user_ip = \"%s\"\n", ipsrc); fflush(fin); if (snprintf(rulesfile, sizeof rulesfile, "%s/%s/authpf.rules", PATH_USER_DIR, luser) >= sizeof rulesfile) { syslog(LOG_ERR, "user path too long, exiting"); goto error; } if ((from_fd = open(rulesfile, O_RDONLY, 0)) == -1) { /* if user dir rules do not exist, we try PATH_PFRULES */ if (errno != ENOENT) { syslog(LOG_ERR, "can't open %s (%m)", rulesfile); if (unlink(template) == -1) syslog(LOG_ERR, "can't unlink %s", template); goto error; } } if (from_fd == -1) { snprintf(rulesfile, sizeof rulesfile, PATH_PFRULES); if ((from_fd = open(rulesfile, O_RDONLY, 0)) == -1) { syslog(LOG_ERR, "can't open %s (%m)", rulesfile); if (unlink(template) == -1) syslog(LOG_ERR, "can't unlink %s", template); goto error; } } while ((rcount = read(from_fd, buf, sizeof(buf))) > 0) { wcount = write(tmpfile, buf, rcount); if (rcount != wcount || wcount == -1) { syslog(LOG_ERR, "rules template copy failed"); if (unlink(template) == -1) syslog(LOG_ERR, "can't unlink %s", template); goto error; } } if (rcount == -1) { syslog(LOG_ERR, "read of rules template failed"); if (unlink(template) == -1) syslog(LOG_ERR, "can't unlink %s", template); goto error; } fclose(fin); fin = NULL; close(tmpfile); tmpfile = -1; close(from_fd); from_fd = -1; fin = fopen(template, "r"); if (fin == NULL) { syslog(LOG_ERR, "can't open %s (%m)", template); if (unlink(template) == -1) syslog(LOG_ERR, "can't unlink %s", template); goto error; } infile = template; if (unlink(template) == -1) { syslog(LOG_ERR, "can't unlink %s", template); goto error; } /* add/delete rules, using parse_rule */ memset(&pf, 0, sizeof(pf)); pf.dev = dev; pf.pnat = &pn; pf.pbinat = &pb; pf.prdr = &pd; pf.prule = ≺ if (parse_rules(fin, &pf) < 0) { syslog(LOG_ERR, "syntax error in rule file: authpf rules not loaded"); goto error; } ret = 0; goto out; error: ret = -1; out: if (fin != NULL) fclose(fin); if (tmpfile != -1) close(tmpfile); if (from_fd != -1) close(from_fd); if (add) { (void)gettimeofday(&Tstart, NULL); syslog(LOG_INFO, "Allowing %s, user %s", ipsrc, luser); } else { (void)gettimeofday(&Tend, NULL); syslog(LOG_INFO, "Removed %s, user %s - duration %ld seconds", ipsrc, luser, Tend.tv_sec - Tstart.tv_sec); } return(ret); } /* * 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() { struct pfioc_state_kill psk; struct in_addr target; memset(&psk, 0, sizeof(psk)); psk.psk_af = AF_INET; inet_pton(AF_INET, ipsrc, &target); /* Kill all states from ipsrc */ psk.psk_src.addr.addr.v4 = target; memset(&psk.psk_src.mask, 0xff, sizeof(psk.psk_src.mask)); if (ioctl(dev, DIOCKILLSTATES, &psk)) syslog(LOG_ERR, "DIOCKILLSTATES failed (%m)"); /* Kill all states to ipsrc */ memset(&psk.psk_src, 0, sizeof(psk.psk_src)); psk.psk_dst.addr.addr.v4 = target; memset(&psk.psk_dst.mask, 0xff, sizeof(psk.psk_dst.mask)); if (ioctl(dev, DIOCKILLSTATES, &psk)) syslog(LOG_ERR, "DIOCKILLSTATES failed (%m)"); } /* signal handler that makes us go away properly */ static void need_death(int signo) { want_death = 1; } /* * function that removes our stuff when we go away. */ static __dead void do_death(int active) { int ret = 0; if (active) { changefilter(0, luser, ipsrc); authpf_kill_states(); } if (pidfp) ftruncate(fileno(pidfp), 0); if (pidfile[0]) if (unlink(pidfile) == -1) syslog(LOG_ERR, "can't unlink %s (%m)", pidfile); exit(ret); } /* * callback for rule add, used by parser in parse_rules */ int pfctl_add_rule(struct pfctl *pf, struct pf_rule *r) { struct pfioc_changerule pcr; memset(&pcr, 0, sizeof(pcr)); if (Delete_Rules) { pcr.action = PF_CHANGE_REMOVE; memcpy(&pcr.oldrule, r, sizeof(pcr.oldrule)); } else { pcr.action = Rule_Action; memcpy(&pcr.newrule, r, sizeof(pcr.newrule)); } if ((pf->opts & PF_OPT_NOACTION) == 0) { if (ioctl(pf->dev, DIOCCHANGERULE, &pcr)) syslog(LOG_INFO, "DIOCCHANGERULE %m"); } return 0; } /* * callback for nat add, used by parser in parse_rules */ int pfctl_add_nat(struct pfctl *pf, struct pf_nat *n) { struct pfioc_changenat pcr; memset(&pcr, 0, sizeof(pcr)); if (Delete_Rules) { pcr.action = PF_CHANGE_REMOVE; memcpy(&pcr.oldnat, n, sizeof(pcr.oldnat)); } else { pcr.action = Nat_Action; memcpy(&pcr.newnat, n, sizeof(pcr.newnat)); } if ((pf->opts & PF_OPT_NOACTION) == 0) { if (ioctl(pf->dev, DIOCCHANGENAT, &pcr)) syslog(LOG_INFO, "DIOCCHANGENAT %m"); } return 0; } /* * callback for rdr add, used by parser in parse_rules */ int pfctl_add_rdr(struct pfctl *pf, struct pf_rdr *r) { struct pfioc_changerdr pcr; memset(&pcr, 0, sizeof(pcr)); if (Delete_Rules) { pcr.action = PF_CHANGE_REMOVE; memcpy(&pcr.oldrdr, r, sizeof(pcr.oldrdr)); } else { pcr.action = Rdr_Action; memcpy(&pcr.newrdr, r, sizeof(pcr.newrdr)); } if ((pf->opts & PF_OPT_NOACTION) == 0) { if (ioctl(pf->dev, DIOCCHANGERDR, &pcr)) syslog(LOG_INFO, "DIOCCHANGERDR %m"); } return 0; } /* * We don't support adding binat's, since pf doesn't, * and I can't for the life of me think of a sane situation where it * might be useful. This is here only because the pfctl parse * routines need this defined. */ int pfctl_add_binat(struct pfctl *pf, struct pf_binat *b) { return 0; }