/* $OpenBSD: authpf.c,v 1.54 2003/04/20 02:37:00 beck 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 "pathnames.h" extern int symset(const char *, const char *, int); static int read_config(FILE *); static void print_message(char *); static int allowed_luser(char *); static int check_luser(char *, char *); static int remove_stale_rulesets(void); static int change_filter(int, const char *, const char *); static void authpf_kill_states(void); int dev; /* pf device */ char anchorname[PF_ANCHOR_NAME_SIZE] = "authpf"; char rulesetname[PF_RULESET_NAME_SIZE]; FILE *pidfp; char *infile; /* file name printed by yyerror() in parse.y */ 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, char *argv[]) { int lockcnt = 0, n, pidfd; FILE *config; struct in_addr ina; struct passwd *pw; char *cp; uid_t uid; if ((n = snprintf(rulesetname, sizeof(rulesetname), "%ld", (long)getpid())) < 0 || n >= sizeof(rulesetname)) { syslog(LOG_ERR, "pid too large for ruleset name"); exit(1); } config = fopen(PATH_CONFFILE, "r"); 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) { 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, "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 (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; } /* * 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; } /* 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); 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); openlog("authpf", LOG_PID | LOG_NDELAY, LOG_DAEMON); if (config == NULL || read_config(config)) do_death(0); if (remove_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); (void) ftruncate(fileno(pidfp), ftell(pidfp)); if (change_filter(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); 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 %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; 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; } } 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, "cannot 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 are not 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) { FILE *f; int n; char tmp[MAXPATHLEN]; n = snprintf(tmp, sizeof(tmp), "%s/%s", luserdir, luser); if (n < 0 || (u_int)n >= 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, "cannot 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); } /* * Search for rulesets left by other authpf processes (either because they * died ungracefully or were terminated) and remove them. */ static int remove_stale_rulesets() { struct pfioc_ruleset prs; const int action[PF_RULESET_MAX] = { PF_SCRUB, PF_PASS, PF_NAT, PF_BINAT, PF_RDR }; u_int32_t nr, mnr; memset(&prs, 0, sizeof(prs)); strlcpy(prs.anchor, anchorname, sizeof(prs.anchor)); if (ioctl(dev, DIOCGETRULESETS, &prs)) { if (errno == EINVAL) return (0); else return (1); } mnr = prs.nr; nr = 0; while (nr < mnr) { char *s; pid_t pid; prs.nr = nr; if (ioctl(dev, DIOCGETRULESET, &prs)) return (1); errno = 0; pid = strtoul(prs.name, &s, 10); if (!prs.name[0] || errno || *s) return (1); if (kill(pid, 0)) { int i; for (i = 0; i < PF_RULESET_MAX; ++i) { struct pfioc_rule pr; memset(&pr, 0, sizeof(pr)); memcpy(pr.anchor, prs.anchor, sizeof(pr.anchor)); memcpy(pr.ruleset, prs.name, sizeof(pr.ruleset)); pr.rule.action = action[i]; if ((ioctl(dev, DIOCBEGINRULES, &pr) || ioctl(dev, DIOCCOMMITRULES, &pr)) && errno != EINVAL) return (1); } mnr--; } else nr++; } return (0); } /* * Add/remove filter entries for user "luser" from ip "ipsrc" */ static int change_filter(int add, const char *luser, const char *ipsrc) { char fn[MAXPATHLEN]; FILE *f = NULL; const int action[PF_RULESET_MAX] = { PF_SCRUB, PF_PASS, PF_NAT, PF_BINAT, PF_RDR }; struct pfctl pf; struct pfioc_rule pr[PF_RULESET_MAX]; int i; if (luser == NULL || !luser[0] || strlen(luser) >= PF_RULESET_NAME_SIZE || ipsrc == NULL || !ipsrc[0]) { syslog(LOG_ERR, "invalid luser/ipsrc"); goto error; } if (add) { if ((i = snprintf(fn, sizeof(fn), "%s/%s/authpf.rules", PATH_USER_DIR, luser)) < 0 || i >= sizeof(fn)) { syslog(LOG_ERR, "user rule path too long"); goto error; } if ((f = fopen(fn, "r")) == NULL && errno != ENOENT) { syslog(LOG_ERR, "cannot open %s (%m)", fn); goto error; } if (f == NULL) { if (strlcpy(fn, PATH_PFRULES, sizeof(fn)) >= sizeof(fn)) { syslog(LOG_ERR, "rule path too long"); goto error; } if ((f = fopen(fn, "r")) == NULL) { syslog(LOG_ERR, "cannot open %s (%m)", fn); goto error; } } } memset(&pf, 0, sizeof(pf)); for (i = 0; i < PF_RULESET_MAX; ++i) { memset(&pr[i], 0, sizeof(pr[i])); pr[i].rule.action = action[i]; strlcpy(pr[i].anchor, anchorname, sizeof(pr[i].anchor)); strlcpy(pr[i].ruleset, rulesetname, sizeof(pr[i].ruleset)); if (ioctl(dev, DIOCBEGINRULES, &pr[i])) { syslog(LOG_ERR, "DIOCBEGINRULES %m"); goto error; } pf.prule[i] = &pr[i]; } if (add) { if (symset("user_ip", ipsrc, 0) || symset("user_id", luser, 0)) { syslog(LOG_ERR, "symset"); goto error; } pf.dev = dev; infile = fn; if (parse_rules(f, &pf) < 0) { syslog(LOG_ERR, "syntax error in rule file: " "authpf rules not loaded"); goto error; } fclose(f); f = NULL; } for (i = 0; i < PF_RULESET_MAX; ++i) /* * ignore EINVAL on removal, it means the anchor was * already automatically removed by the kernel. */ if (ioctl(dev, DIOCCOMMITRULES, &pr[i]) && (add || errno != EINVAL)) { syslog(LOG_ERR, "DIOCCOMMITRULES %m"); goto error; } if (add) { gettimeofday(&Tstart, NULL); syslog(LOG_INFO, "allowing %s, user %s", ipsrc, luser); } else { gettimeofday(&Tend, NULL); syslog(LOG_INFO, "removed %s, user %s - duration %ld seconds", ipsrc, luser, Tend.tv_sec - Tstart.tv_sec); } return (0); error: if (f != NULL) fclose(f); return (-1); } /* * 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.v.a.addr.v4 = target; memset(&psk.psk_src.addr.v.a.mask, 0xff, sizeof(psk.psk_src.addr.v.a.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.v.a.addr.v4 = target; memset(&psk.psk_dst.addr.v.a.mask, 0xff, sizeof(psk.psk_dst.addr.v.a.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) { change_filter(0, luser, ipsrc); authpf_kill_states(); remove_stale_rulesets(); } if (pidfp) ftruncate(fileno(pidfp), 0); if (pidfile[0]) if (unlink(pidfile) == -1) syslog(LOG_ERR, "cannot unlink %s (%m)", pidfile); exit(ret); } /* * callbacks for parse_rules() */ int pfctl_add_rule(struct pfctl *pf, struct pf_rule *r) { struct pfioc_rule *pr; switch (r->action) { case PF_PASS: case PF_DROP: pr = pf->prule[PF_RULESET_FILTER]; break; case PF_SCRUB: pr = pf->prule[PF_RULESET_SCRUB]; break; case PF_NAT: case PF_NONAT: pr = pf->prule[PF_RULESET_NAT]; break; case PF_RDR: case PF_NORDR: pr = pf->prule[PF_RULESET_RDR]; break; case PF_BINAT: case PF_NOBINAT: pr = pf->prule[PF_RULESET_BINAT]; break; default: syslog(LOG_ERR, "invalid rule action %d", r->action); return (1); } if (pfctl_add_pool(pf, &r->rpool, r->af)) return (1); pr->pool_ticket = pf->paddr.ticket; memcpy(&pr->rule, r, sizeof(pr->rule)); if (ioctl(pf->dev, DIOCADDRULE, pr)) { syslog(LOG_ERR, "DIOCADDRULE %m"); return (1); } pfctl_clear_pool(&r->rpool); return (0); } int pfctl_add_pool(struct pfctl *pf, struct pf_pool *p, sa_family_t af) { struct pf_pooladdr *pa; if (ioctl(pf->dev, DIOCBEGINADDRS, &pf->paddr)) { syslog(LOG_ERR, "DIOCBEGINADDRS %m"); return (1); } pf->paddr.af = af; TAILQ_FOREACH(pa, &p->list, entries) { memcpy(&pf->paddr.addr, pa, sizeof(struct pf_pooladdr)); if (ioctl(pf->dev, DIOCADDADDR, &pf->paddr)) { syslog(LOG_ERR, "DIOCADDADDR %m"); return (1); } } return (0); } void pfctl_clear_pool(struct pf_pool *pool) { struct pf_pooladdr *pa; while ((pa = TAILQ_FIRST(&pool->list)) != NULL) { TAILQ_REMOVE(&pool->list, pa, entries); free(pa); } } int pfctl_add_altq(struct pfctl *pf, struct pf_altq *a) { fprintf(stderr, "altq rules not supported in authpf\n"); return (1); } int pfctl_set_optimization(struct pfctl *pf, const char *opt) { fprintf(stderr, "set optimization not supported in authpf\n"); return (1); } int pfctl_set_logif(struct pfctl *pf, char *ifname) { fprintf(stderr, "set loginterface not supported in authpf\n"); return (1); } int pfctl_set_timeout(struct pfctl *pf, const char *opt, int seconds, int quiet) { fprintf(stderr, "set timeout not supported in authpf\n"); return (1); } int pfctl_set_limit(struct pfctl *pf, const char *opt, unsigned int limit) { fprintf(stderr, "set limit not supported in authpf\n"); return (1); } void pfctl_append_addr(char *addr, int net, int neg) { /* appropriate message will be printed by following function */ } void pfctl_append_file(char *file) { /* appropriate message will be printed by following function */ } void pfctl_define_table(char *name, int flags, int addrs, int noaction) { fprintf(stderr, "table definitions not yet supported in authpf\n"); }