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Tree: 718fe0e2e9f339a022d9bc13285017fdd76a32e1

Files: 718fe0e2e9f339a022d9bc13285017fdd76a32e1 / common.c

21133 bytesRaw
1/* Code and variables that is common to both fork and select-based
2 * servers.
3 *
4 * No code here should assume whether sockets are blocking or not.
5 **/
6
7#define _GNU_SOURCE
8#include <stdarg.h>
9#include <grp.h>
10
11#include <sys/types.h>
12#include <ifaddrs.h>
13#include <netinet/in.h>
14
15#include "common.h"
16#include "probe.h"
17
18/* Added to make the code compilable under CYGWIN
19 * */
20#ifndef SA_NOCLDWAIT
21#define SA_NOCLDWAIT 0
22#endif
23
24/* Make use of systemd socket activation
25 * */
26#ifdef SYSTEMD
27#include <systemd/sd-daemon.h>
28#endif
29
30/*
31 * Settings that depend on the command line.  They're set in main(), but also
32 * used in other places in common.c, and it'd be heavy-handed to pass it all as
33 * parameters
34 */
35int verbose = 0;
36int probing_timeout = 2;
37int inetd = 0;
38int foreground = 0;
39int background = 0;
40int numeric = 0;
41const char *user_name, *pid_file;
42
43struct addrinfo *addr_listen = NULL; /* what addresses do we listen to? */
44
45#ifdef LIBWRAP
46#include <tcpd.h>
47int allow_severity =0, deny_severity = 0;
48#endif
49
50/* check result and die, printing the offending address and error */
51void check_res_dumpdie(int res, struct addrinfo *addr, char* syscall)
52{
53    char buf[NI_MAXHOST];
54
55    if (res == -1) {
56        fprintf(stderr, "%s:%s: %s\n",
57                sprintaddr(buf, sizeof(buf), addr),
58                syscall,
59                strerror(errno));
60        exit(1);
61    }
62}
63
64int get_fd_sockets(int *sockfd[])
65{
66    int sd = 0;
67
68#ifdef SYSTEMD
69    sd = sd_listen_fds(0);
70    if (sd < 0) {
71      fprintf(stderr, "sd_listen_fds(): %s\n", strerror(-sd));
72      exit(1);
73    }
74    if (sd > 0) {
75      *sockfd = malloc(sd * sizeof(*sockfd[0]));
76      for (int i = 0; i < sd; i++) {
77        (*sockfd)[i] = SD_LISTEN_FDS_START + i;
78      }
79    }
80#endif
81
82    return sd;
83}
84
85/* Starts listening sockets on specified addresses.
86 * IN: addr[], num_addr
87 * OUT: *sockfd[]  pointer to newly-allocated array of file descriptors
88 * Returns number of addresses bound
89 * Bound file descriptors are returned in newly-allocated *sockfd pointer
90   */
91int start_listen_sockets(int *sockfd[], struct addrinfo *addr_list)
92{
93   struct sockaddr_storage *saddr;
94   struct addrinfo *addr;
95   int i, res, one;
96   int num_addr = 0;
97   int sd_socks = 0;
98
99   sd_socks = get_fd_sockets(sockfd);
100
101   if (sd_socks > 0) {
102       return sd_socks;
103   }
104
105   for (addr = addr_list; addr; addr = addr->ai_next)
106       num_addr++;
107
108   if (verbose)
109       fprintf(stderr, "listening to %d addresses\n", num_addr);
110
111   *sockfd = malloc(num_addr * sizeof(*sockfd[0]));
112
113   for (i = 0, addr = addr_list; i < num_addr && addr; i++, addr = addr->ai_next) {
114       if (!addr) {
115           fprintf(stderr, "FATAL: Inconsistent listen number. This should not happen.\n");
116           exit(1);
117       }
118       saddr = (struct sockaddr_storage*)addr->ai_addr;
119
120       (*sockfd)[i] = socket(saddr->ss_family, SOCK_STREAM, 0);
121       check_res_dumpdie((*sockfd)[i], addr, "socket");
122
123       one = 1;
124       res = setsockopt((*sockfd)[i], SOL_SOCKET, SO_REUSEADDR, (char*)&one, sizeof(one));
125       check_res_dumpdie(res, addr, "setsockopt(SO_REUSEADDR)");
126
127       if (addr->ai_flags & SO_KEEPALIVE) {
128           res = setsockopt((*sockfd)[i], SOL_SOCKET, SO_KEEPALIVE, (char*)&one, sizeof(one));
129           check_res_dumpdie(res, addr, "setsockopt(SO_KEEPALIVE)");
130           printf("set up keepalive\n");
131       }
132
133       if (IP_FREEBIND) {
134           res = setsockopt((*sockfd)[i], IPPROTO_IP, IP_FREEBIND, (char*)&one, sizeof(one));
135           check_res_dumpdie(res, addr, "setsockopt(IP_FREEBIND)");
136       }
137
138       res = bind((*sockfd)[i], addr->ai_addr, addr->ai_addrlen);
139       check_res_dumpdie(res, addr, "bind");
140
141       res = listen ((*sockfd)[i], 50);
142       check_res_dumpdie(res, addr, "listen");
143
144   }
145
146   return num_addr;
147}
148
149/* Transparent proxying: bind the peer address of fd to the peer address of
150 * fd_from */
151#define IP_TRANSPARENT 19
152int bind_peer(int fd, int fd_from)
153{
154    struct addrinfo from;
155    struct sockaddr_storage ss;
156    int res, trans = 1;
157
158    memset(&from, 0, sizeof(from));
159    from.ai_addr = (struct sockaddr*)&ss;
160    from.ai_addrlen = sizeof(ss);
161
162    /* getpeername can fail with ENOTCONN if connection was dropped before we
163     * got here */
164    res = getpeername(fd_from, from.ai_addr, &from.ai_addrlen);
165    CHECK_RES_RETURN(res, "getpeername");
166    
167    // if the destination is the same machine, there's no need to do bind
168    struct ifaddrs *ifaddrs_p = NULL, *ifa;
169
170    getifaddrs(&ifaddrs_p);
171
172    for (ifa = ifaddrs_p; ifa != NULL; ifa = ifa->ifa_next)
173    {
174        if (!ifa->ifa_addr)
175            continue;
176        int match = 0;
177        if (from.ai_addr->sa_family == ifa->ifa_addr->sa_family)
178        {
179            int family = ifa->ifa_addr->sa_family;
180            if (family == AF_INET)
181            {
182                struct sockaddr_in *from_addr = (struct sockaddr_in*)from.ai_addr;
183                struct sockaddr_in *ifa_addr = (struct sockaddr_in*)ifa->ifa_addr;
184                if (from_addr->sin_addr.s_addr == ifa_addr->sin_addr.s_addr)
185                    match = 1;
186            }
187            else if (family == AF_INET6)
188            {
189                struct sockaddr_in6 *from_addr = (struct sockaddr_in6*)from.ai_addr;
190                struct sockaddr_in6 *ifa_addr = (struct sockaddr_in6*)ifa->ifa_addr;
191                if (!memcmp(from_addr->sin6_addr.s6_addr, ifa_addr->sin6_addr.s6_addr, 16))
192                    match = 1;
193            }
194        }
195        if (match)  // the destination is the same as the source, should not create a transparent bind
196            return 0;
197    }
198
199#ifndef IP_BINDANY /* use IP_TRANSPARENT */
200    res = setsockopt(fd, IPPROTO_IP, IP_TRANSPARENT, &trans, sizeof(trans));
201    CHECK_RES_DIE(res, "setsockopt");
202#else
203    if (from.ai_addr->sa_family==AF_INET) { /* IPv4 */
204        res = setsockopt(fd, IPPROTO_IP, IP_BINDANY, &trans, sizeof(trans));
205        CHECK_RES_RETURN(res, "setsockopt IP_BINDANY");
206#ifdef IPV6_BINDANY
207    } else { /* IPv6 */
208        res = setsockopt(fd, IPPROTO_IPV6, IPV6_BINDANY, &trans, sizeof(trans));
209        CHECK_RES_RETURN(res, "setsockopt IPV6_BINDANY");
210#endif /* IPV6_BINDANY */
211    }
212#endif /* IP_TRANSPARENT / IP_BINDANY */
213    res = bind(fd, from.ai_addr, from.ai_addrlen);
214    CHECK_RES_RETURN(res, "bind");
215
216    return 0;
217}
218
219/* Connect to first address that works and returns a file descriptor, or -1 if
220 * none work.
221 * If transparent proxying is on, use fd_from peer address on external address
222 * of new file descriptor. */
223int connect_addr(struct connection *cnx, int fd_from)
224{
225    struct addrinfo *a, from;
226    struct sockaddr_storage ss;
227    char buf[NI_MAXHOST];
228    int fd, res, one;
229
230    memset(&from, 0, sizeof(from));
231    from.ai_addr = (struct sockaddr*)&ss;
232    from.ai_addrlen = sizeof(ss);
233
234    res = getpeername(fd_from, from.ai_addr, &from.ai_addrlen);
235    CHECK_RES_RETURN(res, "getpeername");
236
237    for (a = cnx->proto->saddr; a; a = a->ai_next) {
238        /* When transparent, make sure both connections use the same address family */
239        if (cnx->proto->transparent && a->ai_family != from.ai_addr->sa_family)
240            continue;
241        if (verbose)
242            fprintf(stderr, "connecting to %s family %d len %d\n",
243                    sprintaddr(buf, sizeof(buf), a),
244                    a->ai_addr->sa_family, a->ai_addrlen);
245
246        /* XXX Needs to match ai_family from fd_from when being transparent! */
247        fd = socket(a->ai_family, SOCK_STREAM, 0);
248        if (fd == -1) {
249            log_message(LOG_ERR, "forward to %s failed:socket: %s\n",
250                        cnx->proto->description, strerror(errno));
251        } else {
252            if (cnx->proto->transparent) {
253                res = bind_peer(fd, fd_from);
254                CHECK_RES_RETURN(res, "bind_peer");
255            }
256            res = connect(fd, a->ai_addr, a->ai_addrlen);
257            if (res == -1) {
258                log_message(LOG_ERR, "forward to %s failed:connect: %s\n",
259                            cnx->proto->description, strerror(errno));
260                close(fd);
261            } else {
262                if (cnx->proto->keepalive) {
263                    one = 1;
264                    res = setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, (char*)&one, sizeof(one));
265                    CHECK_RES_RETURN(res, "setsockopt(SO_KEEPALIVE)");
266                    printf("set up keepalive\n");
267                }
268                return fd;
269            }
270        }
271    }
272    return -1;
273}
274
275/* Store some data to write to the queue later */
276int defer_write(struct queue *q, void* data, int data_size)
277{
278    char *p;
279    if (verbose)
280        fprintf(stderr, "**** writing deferred on fd %d\n", q->fd);
281
282    p = realloc(q->begin_deferred_data, q->deferred_data_size + data_size);
283    if (!p) {
284        perror("realloc");
285        exit(1);
286    }
287
288    q->deferred_data = q->begin_deferred_data = p;
289    p += q->deferred_data_size;
290    q->deferred_data_size += data_size;
291    memcpy(p, data, data_size);
292
293    return 0;
294}
295
296/* tries to flush some of the data for specified queue
297 * Upon success, the number of bytes written is returned.
298 * Upon failure, -1 returned (e.g. connexion closed)
299 * */
300int flush_deferred(struct queue *q)
301{
302    int n;
303
304    if (verbose)
305        fprintf(stderr, "flushing deferred data to fd %d\n", q->fd);
306
307    n = write(q->fd, q->deferred_data, q->deferred_data_size);
308    if (n == -1)
309        return n;
310
311    if (n == q->deferred_data_size) {
312        /* All has been written -- release the memory */
313        free(q->begin_deferred_data);
314        q->begin_deferred_data = NULL;
315        q->deferred_data = NULL;
316        q->deferred_data_size = 0;
317    } else {
318        /* There is data left */
319        q->deferred_data += n;
320        q->deferred_data_size -= n;
321    }
322
323    return n;
324}
325
326
327void init_cnx(struct connection *cnx)
328{
329    memset(cnx, 0, sizeof(*cnx));
330    cnx->q[0].fd = -1;
331    cnx->q[1].fd = -1;
332    cnx->proto = get_first_protocol();
333}
334
335void dump_connection(struct connection *cnx)
336{
337    printf("state: %d\n", cnx->state);
338    printf("fd %d, %d deferred\n", cnx->q[0].fd, cnx->q[0].deferred_data_size);
339    printf("fd %d, %d deferred\n", cnx->q[1].fd, cnx->q[1].deferred_data_size);
340}
341
342
343/*
344 * moves data from one fd to other
345 *
346 * returns number of bytes copied if success
347 * returns 0 (FD_CNXCLOSED) if incoming socket closed
348 * returns FD_NODATA if no data was available
349 * returns FD_STALLED if data was read, could not be written, and has been
350 * stored in temporary buffer.
351 */
352int fd2fd(struct queue *target_q, struct queue *from_q)
353{
354   char buffer[BUFSIZ];
355   int target, from, size_r, size_w;
356
357   target = target_q->fd;
358   from = from_q->fd;
359
360   size_r = read(from, buffer, sizeof(buffer));
361   if (size_r == -1) {
362       switch (errno) {
363       case EAGAIN:
364           if (verbose)
365               fprintf(stderr, "reading 0 from %d\n", from);
366           return FD_NODATA;
367
368       case ECONNRESET:
369       case EPIPE:
370           return FD_CNXCLOSED;
371       }
372   }
373
374   CHECK_RES_RETURN(size_r, "read");
375
376   if (size_r == 0)
377      return FD_CNXCLOSED;
378
379   size_w = write(target, buffer, size_r);
380   /* process -1 when we know how to deal with it */
381   if (size_w == -1) {
382       switch (errno) {
383       case EAGAIN:
384           /* write blocked: Defer data */
385           defer_write(target_q, buffer, size_r);
386           return FD_STALLED;
387
388       case ECONNRESET:
389       case EPIPE:
390           /* remove end closed -- drop the connection */
391           return FD_CNXCLOSED;
392       }
393   } else if (size_w < size_r) {
394       /* incomplete write -- defer the rest of the data */
395       defer_write(target_q, buffer + size_w, size_r - size_w);
396       return FD_STALLED;
397   }
398
399   CHECK_RES_RETURN(size_w, "write");
400
401   return size_w;
402}
403
404/* returns a string that prints the IP and port of the sockaddr */
405char* sprintaddr(char* buf, size_t size, struct addrinfo *a)
406{
407   char host[NI_MAXHOST], serv[NI_MAXSERV];
408   int res;
409
410   res = getnameinfo(a->ai_addr, a->ai_addrlen,
411               host, sizeof(host),
412               serv, sizeof(serv),
413               numeric ? NI_NUMERICHOST | NI_NUMERICSERV : 0 );
414
415   if (res) {
416       log_message(LOG_ERR, "sprintaddr:getnameinfo: %s\n", gai_strerror(res));
417       /* Name resolution failed: do it numerically instead */
418       res = getnameinfo(a->ai_addr, a->ai_addrlen,
419                         host, sizeof(host),
420                         serv, sizeof(serv),
421                         NI_NUMERICHOST | NI_NUMERICSERV);
422       /* should not fail but... */
423       if (res) {
424           log_message(LOG_ERR, "sprintaddr:getnameinfo(NUM): %s\n", gai_strerror(res));
425           strcpy(host, "?");
426           strcpy(serv, "?");
427       }
428   }
429
430   snprintf(buf, size, "%s:%s", host, serv);
431
432   return buf;
433}
434
435/* Turns a hostname and port (or service) into a list of struct addrinfo
436 * returns 0 on success, -1 otherwise and logs error
437 **/
438int resolve_split_name(struct addrinfo **out, const char* host, const char* serv)
439{
440   struct addrinfo hint;
441   int res;
442
443   memset(&hint, 0, sizeof(hint));
444   hint.ai_family = PF_UNSPEC;
445   hint.ai_socktype = SOCK_STREAM;
446
447   res = getaddrinfo(host, serv, &hint, out);
448   if (res)
449      log_message(LOG_ERR, "%s `%s:%s'\n", gai_strerror(res), host, serv);
450   return res;
451}
452
453/* turns a "hostname:port" string into a list of struct addrinfo;
454out: list of newly allocated addrinfo (see getaddrinfo(3)); freeaddrinfo(3) when done
455fullname: input string -- it gets clobbered
456*/
457void resolve_name(struct addrinfo **out, char* fullname)
458{
459   char *serv, *host, *end;
460   int res;
461
462   /* Find port */
463   char *sep = strrchr(fullname, ':');
464   if (!sep) { /* No separator: parameter is just a port */
465      fprintf(stderr, "%s: names must be fully specified as hostname:port\n", fullname);
466      exit(1);
467   }
468   serv = sep+1;
469   *sep = 0;
470
471   host = fullname;
472
473   /* If it is a RFC-Compliant IPv6 address ("[1234::12]:443"), remove brackets
474    * around IP address */
475   if (host[0] == '[') {
476       end = strrchr(host, ']');
477       if (!end) {
478           fprintf(stderr, "%s: no closing bracket in IPv6 address?\n", host);
479       }
480       host++; /* skip first bracket */
481       *end = 0; /* remove last bracket */
482   }
483
484   res = resolve_split_name(out, host, serv);
485   if (res) {
486      fprintf(stderr, "%s `%s'\n", gai_strerror(res), fullname);
487      if (res == EAI_SERVICE)
488         fprintf(stderr, "(Check you have specified all ports)\n");
489      exit(4);
490   }
491}
492
493/* Log to syslog or stderr if foreground */
494void log_message(int type, char* msg, ...)
495{
496    va_list ap;
497
498    va_start(ap, msg);
499    if (foreground)
500        vfprintf(stderr, msg, ap);
501    else
502        vsyslog(type, msg, ap);
503    va_end(ap);
504}
505
506/* syslogs who connected to where */
507void log_connection(struct connection *cnx)
508{
509    struct addrinfo addr;
510    struct sockaddr_storage ss;
511#define MAX_NAMELENGTH (NI_MAXHOST + NI_MAXSERV + 1)
512    char peer[MAX_NAMELENGTH], service[MAX_NAMELENGTH],
513        local[MAX_NAMELENGTH], target[MAX_NAMELENGTH];
514    int res;
515
516    if (cnx->proto->log_level < 1)
517        return;
518
519    addr.ai_addr = (struct sockaddr*)&ss;
520    addr.ai_addrlen = sizeof(ss);
521
522    res = getpeername(cnx->q[0].fd, addr.ai_addr, &addr.ai_addrlen);
523    if (res == -1) return; /* Can happen if connection drops before we get here.
524                               In that case, don't log anything (there is no connection) */
525    sprintaddr(peer, sizeof(peer), &addr);
526
527    addr.ai_addrlen = sizeof(ss);
528    res = getsockname(cnx->q[0].fd, addr.ai_addr, &addr.ai_addrlen);
529    if (res == -1) return;
530    sprintaddr(service, sizeof(service), &addr);
531
532    addr.ai_addrlen = sizeof(ss);
533    res = getpeername(cnx->q[1].fd, addr.ai_addr, &addr.ai_addrlen);
534    if (res == -1) return;
535    sprintaddr(target, sizeof(target), &addr);
536
537    addr.ai_addrlen = sizeof(ss);
538    res = getsockname(cnx->q[1].fd, addr.ai_addr, &addr.ai_addrlen);
539    if (res == -1) return;
540    sprintaddr(local, sizeof(local), &addr);
541
542    log_message(LOG_INFO, "%s:connection from %s to %s forwarded from %s to %s\n",
543                cnx->proto->description,
544                peer,
545                service,
546                local,
547                target);
548}
549
550
551/* libwrap (tcpd): check the connection is legal. This is necessary because
552 * the actual server will only see a connection coming from localhost and can't
553 * apply the rules itself.
554 *
555 * Returns -1 if access is denied, 0 otherwise
556 */
557int check_access_rights(int in_socket, const char* service)
558{
559#ifdef LIBWRAP
560    union {
561        struct sockaddr saddr;
562        struct sockaddr_storage ss;
563    } peer;
564    socklen_t size = sizeof(peer);
565    char addr_str[NI_MAXHOST], host[NI_MAXHOST];
566    int res;
567
568    res = getpeername(in_socket, &peer.saddr, &size);
569    CHECK_RES_RETURN(res, "getpeername");
570
571    /* extract peer address */
572    res = getnameinfo(&peer.saddr, size, addr_str, sizeof(addr_str), NULL, 0, NI_NUMERICHOST);
573    if (res) {
574        if (verbose)
575            fprintf(stderr, "getnameinfo(NI_NUMERICHOST):%s\n", gai_strerror(res));
576        strcpy(addr_str, STRING_UNKNOWN);
577    }
578    /* extract peer name */
579    strcpy(host, STRING_UNKNOWN);
580    if (!numeric) {
581        res = getnameinfo(&peer.saddr, size, host, sizeof(host), NULL, 0, NI_NAMEREQD);
582        if (res) {
583            if (verbose)
584                fprintf(stderr, "getnameinfo(NI_NAMEREQD):%s\n", gai_strerror(res));
585        }
586    }
587
588    if (!hosts_ctl(service, host, addr_str, STRING_UNKNOWN)) {
589        if (verbose)
590            fprintf(stderr, "access denied\n");
591        log_message(LOG_INFO, "connection from %s(%s): access denied", host, addr_str);
592        close(in_socket);
593        return -1;
594    }
595#endif
596    return 0;
597}
598
599void setup_signals(void)
600{
601    int res;
602    struct sigaction action;
603
604    /* Request no SIGCHLD is sent upon termination of
605     * the children */
606    memset(&action, 0, sizeof(action));
607    action.sa_handler = NULL;
608    action.sa_flags = SA_NOCLDWAIT;
609    res = sigaction(SIGCHLD, &action, NULL);
610    CHECK_RES_DIE(res, "sigaction");
611
612    /* Set SIGTERM to exit. For some reason if it's not set explicitly,
613     * coverage information is lost when killing the process */
614    memset(&action, 0, sizeof(action));
615    action.sa_handler = exit;
616    res = sigaction(SIGTERM, &action, NULL);
617    CHECK_RES_DIE(res, "sigaction");
618
619    /* Ignore SIGPIPE . */
620    action.sa_handler = SIG_IGN;
621    res = sigaction(SIGPIPE, &action, NULL);
622    CHECK_RES_DIE(res, "sigaction");
623
624}
625
626/* Open syslog connection with appropriate banner;
627 * banner is made up of basename(bin_name)+"[pid]" */
628void setup_syslog(const char* bin_name) {
629    char *name1, *name2;
630    int res;
631
632    name1 = strdup(bin_name);
633    res = asprintf(&name2, "%s[%d]", basename(name1), getpid());
634    CHECK_RES_DIE(res, "asprintf");
635    openlog(name2, LOG_CONS, LOG_AUTH);
636    free(name1);
637    /* Don't free name2, as openlog(3) uses it (at least in glibc) */
638
639    log_message(LOG_INFO, "%s %s started\n", server_type, VERSION);
640}
641
642/* Ask OS to keep capabilities over a setuid(nonzero) */
643void set_keepcaps(int val) {
644#ifdef LIBCAP
645    int res;
646    res = prctl(PR_SET_KEEPCAPS, val, 0, 0, 0);
647    if (res) {
648        perror("prctl");
649        exit(1);
650    }
651#endif
652}
653
654/* set needed capabilities for effective and permitted, clear rest */
655void set_capabilities(void) {
656#ifdef LIBCAP
657    int res;
658    cap_t caps;
659    cap_value_t cap_list[10];
660    int ncap = 0;
661
662    if (transparent)
663        cap_list[ncap++] = CAP_NET_ADMIN;
664
665    caps = cap_init();
666
667#define _cap_set_flag(flag) do { \
668        res = cap_clear_flag(caps, flag); \
669        CHECK_RES_DIE(res, "cap_clear_flag(" #flag ")"); \
670        if (ncap > 0) { \
671            res = cap_set_flag(caps, flag, ncap, cap_list, CAP_SET); \
672            CHECK_RES_DIE(res, "cap_set_flag(" #flag ")"); \
673        } \
674    } while(0)
675
676    _cap_set_flag(CAP_EFFECTIVE);
677    _cap_set_flag(CAP_PERMITTED);
678
679#undef _cap_set_flag
680
681    res = cap_set_proc(caps);
682    CHECK_RES_DIE(res, "cap_set_proc");
683
684    res = cap_free(caps);
685    if (res) {
686        perror("cap_free");
687        exit(1);
688    }
689#endif
690}
691
692/* We don't want to run as root -- drop privileges if required */
693void drop_privileges(const char* user_name)
694{
695    int res;
696    struct passwd *pw = getpwnam(user_name);
697    if (!pw) {
698        fprintf(stderr, "%s: not found\n", user_name);
699        exit(2);
700    }
701    if (verbose)
702        fprintf(stderr, "turning into %s\n", user_name);
703
704    set_keepcaps(1);
705
706    /* remove extraneous groups in case we belong to several extra groups that
707     * may have unwanted rights. If non-root when calling setgroups(), it
708     * fails, which is fine because... we have no unwanted rights
709     * (see POS36-C for security context)
710     * */
711    setgroups(0, NULL);
712
713    res = setgid(pw->pw_gid);
714    CHECK_RES_DIE(res, "setgid");
715    res = setuid(pw->pw_uid);
716    CHECK_RES_DIE(res, "setuid");
717
718    set_capabilities();
719    set_keepcaps(0);
720}
721
722/* Writes my PID */
723void write_pid_file(const char* pidfile)
724{
725    FILE *f;
726
727    f = fopen(pidfile, "w");
728    if (!f) {
729        perror(pidfile);
730        exit(3);
731    }
732
733    fprintf(f, "%d\n", getpid());
734    fclose(f);
735}
736
737

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