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Tree: 717c285b311db5d809356597b2df5270360f1751

Files: 717c285b311db5d809356597b2df5270360f1751 / common.c

18553 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 "common.h"
12#include "probe.h"
13
14/* Added to make the code compilable under CYGWIN 
15 * */
16#ifndef SA_NOCLDWAIT
17#define SA_NOCLDWAIT 0
18#endif
19
20/* 
21 * Settings that depend on the command line.  They're set in main(), but also
22 * used in other places in common.c, and it'd be heavy-handed to pass it all as
23 * parameters
24 */
25int verbose = 0;
26int probing_timeout = 2;
27int inetd = 0;
28int foreground = 0;
29int background = 0;
30int transparent = 0;
31int numeric = 0;
32const char *user_name, *pid_file;
33
34struct addrinfo *addr_listen = NULL; /* what addresses do we listen to? */
35
36#ifdef LIBWRAP
37#include <tcpd.h>
38int allow_severity =0, deny_severity = 0;
39#endif
40
41/* check result and die, printing the offending address and error */
42void check_res_dumpdie(int res, struct addrinfo *addr, char* syscall)
43{
44    char buf[NI_MAXHOST];
45
46    if (res == -1) {
47        fprintf(stderr, "%s:%s: %s\n", 
48                sprintaddr(buf, sizeof(buf), addr), 
49                syscall, 
50                strerror(errno));
51        exit(1);
52    }
53}
54
55/* Starts listening sockets on specified addresses.
56 * IN: addr[], num_addr
57 * OUT: *sockfd[]  pointer to newly-allocated array of file descriptors
58 * Returns number of addresses bound
59 * Bound file descriptors are returned in newly-allocated *sockfd pointer
60   */
61int start_listen_sockets(int *sockfd[], struct addrinfo *addr_list)
62{
63   struct sockaddr_storage *saddr;
64   struct addrinfo *addr;
65   int i, res, one;
66   int num_addr = 0;
67
68   for (addr = addr_list; addr; addr = addr->ai_next)
69       num_addr++;
70
71   if (verbose)
72       fprintf(stderr, "listening to %d addresses\n", num_addr);
73
74   *sockfd = malloc(num_addr * sizeof(*sockfd[0]));
75
76   for (i = 0, addr = addr_list; i < num_addr && addr; i++, addr = addr->ai_next) {
77       if (!addr) {
78           fprintf(stderr, "FATAL: Inconsistent listen number. This should not happen.\n");
79           exit(1);
80       }
81       saddr = (struct sockaddr_storage*)addr->ai_addr;
82
83       (*sockfd)[i] = socket(saddr->ss_family, SOCK_STREAM, 0);
84       check_res_dumpdie((*sockfd)[i], addr, "socket");
85
86       one = 1;
87       res = setsockopt((*sockfd)[i], SOL_SOCKET, SO_REUSEADDR, (char*)&one, sizeof(one));
88       check_res_dumpdie(res, addr, "setsockopt(SO_REUSEADDR)");
89
90       if (IP_FREEBIND) {
91           res = setsockopt((*sockfd)[i], IPPROTO_IP, IP_FREEBIND, (char*)&one, sizeof(one));
92           check_res_dumpdie(res, addr, "setsockopt(IP_FREEBIND)");
93       }
94
95       res = bind((*sockfd)[i], addr->ai_addr, addr->ai_addrlen);
96       check_res_dumpdie(res, addr, "bind");
97
98       res = listen ((*sockfd)[i], 50);
99       check_res_dumpdie(res, addr, "listen");
100
101   }
102
103   return num_addr;
104}
105
106/* Transparent proxying: bind the peer address of fd to the peer address of
107 * fd_from */
108#define IP_TRANSPARENT 19
109int bind_peer(int fd, int fd_from)
110{
111    struct addrinfo from;
112    struct sockaddr_storage ss;
113    int res, trans = 1;
114
115    memset(&from, 0, sizeof(from));
116    from.ai_addr = (struct sockaddr*)&ss;
117    from.ai_addrlen = sizeof(ss);
118
119    /* getpeername can fail with ENOTCONN if connection was dropped before we
120     * got here */
121    res = getpeername(fd_from, from.ai_addr, &from.ai_addrlen);
122    CHECK_RES_RETURN(res, "getpeername");
123#ifndef IP_BINDANY /* use IP_TRANSPARENT */
124    res = setsockopt(fd, IPPROTO_IP, IP_TRANSPARENT, &trans, sizeof(trans));
125    CHECK_RES_DIE(res, "setsockopt");
126#else
127    if (from.ai_addr->sa_family==AF_INET) { /* IPv4 */
128        res = setsockopt(fd, IPPROTO_IP, IP_BINDANY, &trans, sizeof(trans));
129        CHECK_RES_RETURN(res, "setsockopt IP_BINDANY");
130#ifdef IPV6_BINDANY
131    } else { /* IPv6 */
132        res = setsockopt(fd, IPPROTO_IPV6, IPV6_BINDANY, &trans, sizeof(trans));
133        CHECK_RES_RETURN(res, "setsockopt IPV6_BINDANY");
134#endif /* IPV6_BINDANY */
135    }
136#endif /* IP_TRANSPARENT / IP_BINDANY */
137    res = bind(fd, from.ai_addr, from.ai_addrlen);
138    CHECK_RES_RETURN(res, "bind");
139
140    return 0;
141}
142
143/* Connect to first address that works and returns a file descriptor, or -1 if
144 * none work. 
145 * If transparent proxying is on, use fd_from peer address on external address
146 * of new file descriptor. */
147int connect_addr(struct connection *cnx, int fd_from)
148{
149    struct addrinfo *a, from;
150    struct sockaddr_storage ss;
151    char buf[NI_MAXHOST];
152    int fd, res;
153
154    memset(&from, 0, sizeof(from));
155    from.ai_addr = (struct sockaddr*)&ss;
156    from.ai_addrlen = sizeof(ss);
157
158    res = getpeername(fd_from, from.ai_addr, &from.ai_addrlen);
159    CHECK_RES_RETURN(res, "getpeername");
160
161    for (a = cnx->proto->saddr; a; a = a->ai_next) {
162        /* When transparent, make sure both connections use the same address family */
163        if (transparent && a->ai_family != from.ai_addr->sa_family)
164            continue;
165        if (verbose) 
166            fprintf(stderr, "connecting to %s family %d len %d\n", 
167                    sprintaddr(buf, sizeof(buf), a),
168                    a->ai_addr->sa_family, a->ai_addrlen);
169
170        /* XXX Needs to match ai_family from fd_from when being transparent! */
171        fd = socket(a->ai_family, SOCK_STREAM, 0);
172        if (fd == -1) {
173            log_message(LOG_ERR, "forward to %s failed:socket: %s\n",
174                        cnx->proto->description, strerror(errno));
175        } else {
176            if (transparent) {
177                res = bind_peer(fd, fd_from);
178                CHECK_RES_RETURN(res, "bind_peer");
179            }
180            res = connect(fd, a->ai_addr, a->ai_addrlen);
181            if (res == -1) {
182                log_message(LOG_ERR, "forward to %s failed:connect: %s\n", 
183                            cnx->proto->description, strerror(errno));
184                close(fd);
185            } else {
186                return fd;
187            }
188        }
189    }
190    return -1;
191}
192
193/* Store some data to write to the queue later */
194int defer_write(struct queue *q, void* data, int data_size) 
195{
196    char *p;
197    if (verbose) 
198        fprintf(stderr, "**** writing deferred on fd %d\n", q->fd);
199
200    p = realloc(q->begin_deferred_data, q->deferred_data_size + data_size);
201    if (!p) {
202        perror("realloc");
203        exit(1);
204    }
205
206    q->deferred_data = q->begin_deferred_data = p;
207    p += q->deferred_data_size;
208    q->deferred_data_size += data_size;
209    memcpy(p, data, data_size);
210
211    return 0;
212}
213
214/* tries to flush some of the data for specified queue
215 * Upon success, the number of bytes written is returned.
216 * Upon failure, -1 returned (e.g. connexion closed)
217 * */
218int flush_deferred(struct queue *q)
219{
220    int n;
221
222    if (verbose)
223        fprintf(stderr, "flushing deferred data to fd %d\n", q->fd);
224
225    n = write(q->fd, q->deferred_data, q->deferred_data_size);
226    if (n == -1)
227        return n;
228
229    if (n == q->deferred_data_size) {
230        /* All has been written -- release the memory */
231        free(q->begin_deferred_data);
232        q->begin_deferred_data = NULL;
233        q->deferred_data = NULL;
234        q->deferred_data_size = 0;
235    } else {
236        /* There is data left */
237        q->deferred_data += n;
238        q->deferred_data_size -= n;
239    }
240
241    return n;
242}
243
244
245void init_cnx(struct connection *cnx)
246{
247    memset(cnx, 0, sizeof(*cnx));
248    cnx->q[0].fd = -1;
249    cnx->q[1].fd = -1;
250    cnx->proto = get_first_protocol();
251}
252
253void dump_connection(struct connection *cnx)
254{
255    printf("state: %d\n", cnx->state);
256    printf("fd %d, %d deferred\n", cnx->q[0].fd, cnx->q[0].deferred_data_size);
257    printf("fd %d, %d deferred\n", cnx->q[1].fd, cnx->q[1].deferred_data_size);
258}
259
260
261/* 
262 * moves data from one fd to other
263 *
264 * returns number of bytes copied if success
265 * returns 0 (FD_CNXCLOSED) if incoming socket closed
266 * returns FD_NODATA if no data was available
267 * returns FD_STALLED if data was read, could not be written, and has been
268 * stored in temporary buffer.
269 */
270int fd2fd(struct queue *target_q, struct queue *from_q)
271{
272   char buffer[BUFSIZ];
273   int target, from, size_r, size_w;
274
275   target = target_q->fd;
276   from = from_q->fd;
277
278   size_r = read(from, buffer, sizeof(buffer));
279   if (size_r == -1) {
280       switch (errno) {
281       case EAGAIN:
282           if (verbose)
283               fprintf(stderr, "reading 0 from %d\n", from);
284           return FD_NODATA;
285
286       case ECONNRESET:
287       case EPIPE:
288           return FD_CNXCLOSED;
289       }
290   }
291
292   CHECK_RES_RETURN(size_r, "read");
293
294   if (size_r == 0)
295      return FD_CNXCLOSED;
296
297   size_w = write(target, buffer, size_r);
298   /* process -1 when we know how to deal with it */
299   if (size_w == -1) {
300       switch (errno) {
301       case EAGAIN:
302           /* write blocked: Defer data */
303           defer_write(target_q, buffer, size_r);
304           return FD_STALLED;
305
306       case ECONNRESET:
307       case EPIPE:
308           /* remove end closed -- drop the connection */
309           return FD_CNXCLOSED;
310       }
311   } else if (size_w < size_r) {
312       /* incomplete write -- defer the rest of the data */
313       defer_write(target_q, buffer + size_w, size_r - size_w);
314       return FD_STALLED;
315   }
316
317   CHECK_RES_RETURN(size_w, "write");
318
319   return size_w;
320}
321
322/* returns a string that prints the IP and port of the sockaddr */
323char* sprintaddr(char* buf, size_t size, struct addrinfo *a)
324{
325   char host[NI_MAXHOST], serv[NI_MAXSERV];
326   int res;
327
328   res = getnameinfo(a->ai_addr, a->ai_addrlen,
329               host, sizeof(host), 
330               serv, sizeof(serv), 
331               numeric ? NI_NUMERICHOST | NI_NUMERICSERV : 0 );
332
333   if (res) {
334       log_message(LOG_ERR, "sprintaddr:getnameinfo: %s\n", gai_strerror(res));
335       /* Name resolution failed: do it numerically instead */
336       res = getnameinfo(a->ai_addr, a->ai_addrlen,
337                         host, sizeof(host), 
338                         serv, sizeof(serv), 
339                         NI_NUMERICHOST | NI_NUMERICSERV);
340       /* should not fail but... */
341       if (res) {
342           log_message(LOG_ERR, "sprintaddr:getnameinfo(NUM): %s\n", gai_strerror(res));
343           strcpy(host, "?");
344           strcpy(serv, "?");
345       }
346   }
347
348   snprintf(buf, size, "%s:%s", host, serv);
349
350   return buf;
351}
352
353/* Turns a hostname and port (or service) into a list of struct addrinfo 
354 * returns 0 on success, -1 otherwise and logs error
355 **/
356int resolve_split_name(struct addrinfo **out, const char* host, const char* serv)
357{
358   struct addrinfo hint;
359   int res;
360
361   memset(&hint, 0, sizeof(hint));
362   hint.ai_family = PF_UNSPEC;
363   hint.ai_socktype = SOCK_STREAM;
364
365   res = getaddrinfo(host, serv, &hint, out);
366   if (res)
367      log_message(LOG_ERR, "%s `%s:%s'\n", gai_strerror(res), host, serv);
368   return res;
369}
370
371/* turns a "hostname:port" string into a list of struct addrinfo;
372out: list of newly allocated addrinfo (see getaddrinfo(3)); freeaddrinfo(3) when done
373fullname: input string -- it gets clobbered
374*/
375void resolve_name(struct addrinfo **out, char* fullname)
376{
377   char *serv, *host, *end;
378   int res;
379
380   /* Find port */
381   char *sep = strrchr(fullname, ':');
382   if (!sep) { /* No separator: parameter is just a port */
383      fprintf(stderr, "%s: names must be fully specified as hostname:port\n", fullname);
384      exit(1);
385   }
386   serv = sep+1;
387   *sep = 0;
388
389   host = fullname;
390
391   /* If it is a RFC-Compliant IPv6 address ("[1234::12]:443"), remove brackets
392    * around IP address */
393   if (host[0] == '[') {
394       end = strrchr(host, ']');
395       if (!end) {
396           fprintf(stderr, "%s: no closing bracket in IPv6 address?\n", host);
397       }
398       host++; /* skip first bracket */
399       *end = 0; /* remove last bracket */
400   }
401
402   res = resolve_split_name(out, host, serv);
403   if (res) {
404      fprintf(stderr, "%s `%s'\n", gai_strerror(res), fullname);
405      if (res == EAI_SERVICE)
406         fprintf(stderr, "(Check you have specified all ports)\n");
407      exit(4);
408   }
409}
410
411/* Log to syslog or stderr if foreground */
412void log_message(int type, char* msg, ...)
413{
414    va_list ap;
415
416    va_start(ap, msg);
417    if (foreground)
418        vfprintf(stderr, msg, ap);
419    else
420        vsyslog(type, msg, ap);
421    va_end(ap);
422}
423
424/* syslogs who connected to where */
425void log_connection(struct connection *cnx)
426{
427    struct addrinfo addr;
428    struct sockaddr_storage ss;
429#define MAX_NAMELENGTH (NI_MAXHOST + NI_MAXSERV + 1)
430    char peer[MAX_NAMELENGTH], service[MAX_NAMELENGTH],
431        local[MAX_NAMELENGTH], target[MAX_NAMELENGTH];
432    int res;
433
434    addr.ai_addr = (struct sockaddr*)&ss;
435    addr.ai_addrlen = sizeof(ss);
436
437    res = getpeername(cnx->q[0].fd, addr.ai_addr, &addr.ai_addrlen);
438    if (res == -1) return; /* Can happen if connection drops before we get here. 
439                               In that case, don't log anything (there is no connection) */
440    sprintaddr(peer, sizeof(peer), &addr);
441
442    addr.ai_addrlen = sizeof(ss);
443    res = getsockname(cnx->q[0].fd, addr.ai_addr, &addr.ai_addrlen);
444    if (res == -1) return;
445    sprintaddr(service, sizeof(service), &addr);
446
447    addr.ai_addrlen = sizeof(ss);
448    res = getpeername(cnx->q[1].fd, addr.ai_addr, &addr.ai_addrlen);
449    if (res == -1) return;
450    sprintaddr(target, sizeof(target), &addr);
451
452    addr.ai_addrlen = sizeof(ss);
453    res = getsockname(cnx->q[1].fd, addr.ai_addr, &addr.ai_addrlen);
454    if (res == -1) return;
455    sprintaddr(local, sizeof(local), &addr);
456
457    log_message(LOG_INFO, "connection from %s to %s forwarded from %s to %s\n",
458                peer,
459                service,
460                local,
461                target);
462}
463
464
465/* libwrap (tcpd): check the connection is legal. This is necessary because
466 * the actual server will only see a connection coming from localhost and can't
467 * apply the rules itself.
468 *
469 * Returns -1 if access is denied, 0 otherwise
470 */
471int check_access_rights(int in_socket, const char* service)
472{
473#ifdef LIBWRAP
474    union {
475        struct sockaddr saddr;
476        struct sockaddr_storage ss;
477    } peer;
478    socklen_t size = sizeof(peer);
479    char addr_str[NI_MAXHOST], host[NI_MAXHOST];
480    int res;
481
482    res = getpeername(in_socket, &peer.saddr, &size);
483    CHECK_RES_RETURN(res, "getpeername");
484
485    /* extract peer address */
486    res = getnameinfo(&peer.saddr, size, addr_str, sizeof(addr_str), NULL, 0, NI_NUMERICHOST);
487    if (res) {
488        if (verbose)
489            fprintf(stderr, "getnameinfo(NI_NUMERICHOST):%s\n", gai_strerror(res));
490        strcpy(addr_str, STRING_UNKNOWN);
491    }
492    /* extract peer name */
493    strcpy(host, STRING_UNKNOWN);
494    if (!numeric) {
495        res = getnameinfo(&peer.saddr, size, host, sizeof(host), NULL, 0, NI_NAMEREQD);
496        if (res) {
497            if (verbose)
498                fprintf(stderr, "getnameinfo(NI_NAMEREQD):%s\n", gai_strerror(res));
499        }
500    }
501
502    if (!hosts_ctl(service, host, addr_str, STRING_UNKNOWN)) {
503        if (verbose)
504            fprintf(stderr, "access denied\n");
505        log_message(LOG_INFO, "connection from %s(%s): access denied", host, addr_str);
506        close(in_socket);
507        return -1;
508    }
509#endif
510    return 0;
511}
512
513void setup_signals(void)
514{
515    int res;
516    struct sigaction action;
517
518    /* Request no SIGCHLD is sent upon termination of
519     * the children */
520    memset(&action, 0, sizeof(action));
521    action.sa_handler = NULL;
522    action.sa_flags = SA_NOCLDWAIT;
523    res = sigaction(SIGCHLD, &action, NULL);
524    CHECK_RES_DIE(res, "sigaction");
525
526    /* Set SIGTERM to exit. For some reason if it's not set explicitly,
527     * coverage information is lost when killing the process */
528    memset(&action, 0, sizeof(action));
529    action.sa_handler = exit;
530    res = sigaction(SIGTERM, &action, NULL);
531    CHECK_RES_DIE(res, "sigaction");
532
533    /* Ignore SIGPIPE . */
534    action.sa_handler = SIG_IGN;
535    res = sigaction(SIGPIPE, &action, NULL);
536    CHECK_RES_DIE(res, "sigaction");
537
538}
539
540/* Open syslog connection with appropriate banner; 
541 * banner is made up of basename(bin_name)+"[pid]" */
542void setup_syslog(const char* bin_name) {
543    char *name1, *name2;
544    int res;
545
546    name1 = strdup(bin_name);
547    res = asprintf(&name2, "%s[%d]", basename(name1), getpid());
548    CHECK_RES_DIE(res, "asprintf");
549    openlog(name2, LOG_CONS, LOG_AUTH);
550    free(name1); 
551    /* Don't free name2, as openlog(3) uses it (at least in glibc) */
552
553    log_message(LOG_INFO, "%s %s started\n", server_type, VERSION);
554}
555
556/* Ask OS to keep capabilities over a setuid(nonzero) */
557void set_keepcaps(int val) {
558#ifdef LIBCAP
559    int res;
560    res = prctl(PR_SET_KEEPCAPS, val, 0, 0, 0);
561    if (res) {
562        perror("prctl");
563        exit(1);
564    }
565#endif
566}
567
568/* set needed capabilities for effective and permitted, clear rest */
569void set_capabilities(void) {
570#ifdef LIBCAP
571    int res;
572    cap_t caps;
573    cap_value_t cap_list[10];
574    int ncap = 0;
575
576    if (transparent)
577        cap_list[ncap++] = CAP_NET_ADMIN;
578
579    caps = cap_init();
580
581#define _cap_set_flag(flag) do { \
582        res = cap_clear_flag(caps, flag); \
583        CHECK_RES_DIE(res, "cap_clear_flag(" #flag ")"); \
584        if (ncap > 0) { \
585            res = cap_set_flag(caps, flag, ncap, cap_list, CAP_SET); \
586            CHECK_RES_DIE(res, "cap_set_flag(" #flag ")"); \
587        } \
588    } while(0)
589
590    _cap_set_flag(CAP_EFFECTIVE);
591    _cap_set_flag(CAP_PERMITTED);
592
593#undef _cap_set_flag
594
595    res = cap_set_proc(caps);
596    CHECK_RES_DIE(res, "cap_set_proc");
597
598    res = cap_free(caps);
599    if (res) {
600        perror("cap_free");
601        exit(1);
602    }
603#endif
604}
605
606/* We don't want to run as root -- drop privileges if required */
607void drop_privileges(const char* user_name)
608{
609    int res;
610    struct passwd *pw = getpwnam(user_name);
611    if (!pw) {
612        fprintf(stderr, "%s: not found\n", user_name);
613        exit(2);
614    }
615    if (verbose)
616        fprintf(stderr, "turning into %s\n", user_name);
617
618    set_keepcaps(1);
619
620    /* remove extraneous groups in case we belong to several extra groups that
621     * may have unwanted rights. If non-root when calling setgroups(), it
622     * fails, which is fine because... we have no unwanted rights 
623     * (see POS36-C for security context)
624     * */
625    setgroups(0, NULL);
626
627    res = setgid(pw->pw_gid);
628    CHECK_RES_DIE(res, "setgid");
629    res = setuid(pw->pw_uid);
630    CHECK_RES_DIE(res, "setuid");
631
632    set_capabilities();
633    set_keepcaps(0);
634}
635
636/* Writes my PID */
637void write_pid_file(const char* pidfile)
638{
639    FILE *f;
640
641    f = fopen(pidfile, "w");
642    if (!f) {
643        perror(pidfile);
644        exit(3);
645    }
646
647    fprintf(f, "%d\n", getpid());
648    fclose(f);
649}
650
651

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