workarounds.c revision 44744 
1 /*
2  * Workarounds for known system software bugs. This module provides wrappers
3  * around library functions and system calls that are known to have problems
4  * on some systems. Most of these workarounds won't do any harm on regular
5  * systems.
6  *
7  * Author: Wietse Venema, Eindhoven University of Technology, The Netherlands.
8  */
9
10#ifndef lint
11char    sccsid[] = "@(#) workarounds.c 1.6 96/03/19 16:22:25";
12#endif
13
14#include <sys/types.h>
15#include <sys/param.h>
16#include <sys/socket.h>
17#include <netinet/in.h>
18#include <arpa/inet.h>
19#include <netdb.h>
20#include <errno.h>
21#include <stdio.h>
22#include <syslog.h>
23#include <string.h>
24
25extern int errno;
26
27#include "tcpd.h"
28
29 /*
30  * Some AIX versions advertise a too small MAXHOSTNAMELEN value (32).
31  * Result: long hostnames would be truncated, and connections would be
32  * dropped because of host name verification failures. Adrian van Bloois
33  * (A.vanBloois@info.nic.surfnet.nl) figured out what was the problem.
34  */
35
36#if (MAXHOSTNAMELEN < 64)
37#undef MAXHOSTNAMELEN
38#endif
39
40/* In case not defined in <sys/param.h>. */
41
42#ifndef MAXHOSTNAMELEN
43#define MAXHOSTNAMELEN  256             /* storage for host name */
44#endif
45
46 /*
47  * Some DG/UX inet_addr() versions return a struct/union instead of a long.
48  * You have this problem when the compiler complains about illegal lvalues
49  * or something like that. The following code fixes this mutant behaviour.
50  * It should not be enabled on "normal" systems.
51  *
52  * Bug reported by ben@piglet.cr.usgs.gov (Rev. Ben A. Mesander).
53  */
54
55#ifdef INET_ADDR_BUG
56
57#undef inet_addr
58
59long    fix_inet_addr(string)
60char   *string;
61{
62    return (inet_addr(string).s_addr);
63}
64
65#endif /* INET_ADDR_BUG */
66
67 /*
68  * With some System-V versions, the fgets() library function does not
69  * account for partial reads from e.g. sockets. The result is that fgets()
70  * gives up too soon, causing username lookups to fail. Problem first
71  * reported for IRIX 4.0.5, by Steve Kotsopoulos <steve@ecf.toronto.edu>.
72  * The following code works around the problem. It does no harm on "normal"
73  * systems.
74  */
75
76#ifdef BROKEN_FGETS
77
78#undef fgets
79
80char   *fix_fgets(buf, len, fp)
81char   *buf;
82int     len;
83FILE   *fp;
84{
85    char   *cp = buf;
86    int     c;
87
88    /*
89     * Copy until the buffer fills up, until EOF, or until a newline is
90     * found.
91     */
92    while (len > 1 && (c = getc(fp)) != EOF) {
93	len--;
94	*cp++ = c;
95	if (c == '\n')
96	    break;
97    }
98
99    /*
100     * Return 0 if nothing was read. This is correct even when a silly buffer
101     * length was specified.
102     */
103    if (cp > buf) {
104	*cp = 0;
105	return (buf);
106    } else {
107	return (0);
108    }
109}
110
111#endif /* BROKEN_FGETS */
112
113 /*
114  * With early SunOS 5 versions, recvfrom() does not completely fill in the
115  * source address structure when doing a non-destructive read. The following
116  * code works around the problem. It does no harm on "normal" systems.
117  */
118
119#ifdef RECVFROM_BUG
120
121#undef recvfrom
122
123int     fix_recvfrom(sock, buf, buflen, flags, from, fromlen)
124int     sock;
125char   *buf;
126int     buflen;
127int     flags;
128struct sockaddr *from;
129int    *fromlen;
130{
131    int     ret;
132
133    /* Assume that both ends of a socket belong to the same address family. */
134
135    if ((ret = recvfrom(sock, buf, buflen, flags, from, fromlen)) >= 0) {
136	if (from->sa_family == 0) {
137	    struct sockaddr my_addr;
138	    int     my_addr_len = sizeof(my_addr);
139
140	    if (getsockname(0, &my_addr, &my_addr_len)) {
141		tcpd_warn("getsockname: %m");
142	    } else {
143		from->sa_family = my_addr.sa_family;
144	    }
145	}
146    }
147    return (ret);
148}
149
150#endif /* RECVFROM_BUG */
151
152 /*
153  * The Apollo SR10.3 and some SYSV4 getpeername(2) versions do not return an
154  * error in case of a datagram-oriented socket. Instead, they claim that all
155  * UDP requests come from address 0.0.0.0. The following code works around
156  * the problem. It does no harm on "normal" systems.
157  */
158
159#ifdef GETPEERNAME_BUG
160
161#undef getpeername
162
163int     fix_getpeername(sock, sa, len)
164int     sock;
165struct sockaddr *sa;
166int    *len;
167{
168    int     ret;
169    struct sockaddr_in *sin = (struct sockaddr_in *) sa;
170
171    if ((ret = getpeername(sock, sa, len)) >= 0
172	&& sa->sa_family == AF_INET
173	&& sin->sin_addr.s_addr == 0) {
174	errno = ENOTCONN;
175	return (-1);
176    } else {
177	return (ret);
178    }
179}
180
181#endif /* GETPEERNAME_BUG */
182
183 /*
184  * According to Karl Vogel (vogelke@c-17igp.wpafb.af.mil) some Pyramid
185  * versions have no yp_default_domain() function. We use getdomainname()
186  * instead.
187  */
188
189#ifdef USE_GETDOMAIN
190
191int     yp_get_default_domain(ptr)
192char  **ptr;
193{
194    static char mydomain[MAXHOSTNAMELEN];
195
196    *ptr = mydomain;
197    return (getdomainname(mydomain, MAXHOSTNAMELEN));
198}
199
200#endif /* USE_GETDOMAIN */
201
202#ifndef INADDR_NONE
203#define INADDR_NONE 0xffffffff
204#endif
205
206 /*
207  * Solaris 2.4 gethostbyname() has problems with multihomed hosts. When
208  * doing DNS through NIS, only one host address ends up in the address list.
209  * All other addresses end up in the hostname alias list, interspersed with
210  * copies of the official host name. This would wreak havoc with tcpd's
211  * hostname double checks. Below is a workaround that should do no harm when
212  * accidentally left in. A side effect of the workaround is that address
213  * list members are no longer properly aligned for structure access.
214  */
215
216#ifdef SOLARIS_24_GETHOSTBYNAME_BUG
217
218#undef gethostbyname
219
220struct hostent *fix_gethostbyname(name)
221char   *name;
222{
223    struct hostent *hp;
224    struct in_addr addr;
225    char  **o_addr_list;
226    char  **o_aliases;
227    char  **n_addr_list;
228    int     broken_gethostbyname = 0;
229
230    if ((hp = gethostbyname(name)) && !hp->h_addr_list[1] && hp->h_aliases[1]) {
231	for (o_aliases = n_addr_list = hp->h_aliases; *o_aliases; o_aliases++) {
232	    if ((addr.s_addr = inet_addr(*o_aliases)) != INADDR_NONE) {
233		memcpy(*n_addr_list++, (char *) &addr, hp->h_length);
234		broken_gethostbyname = 1;
235	    }
236	}
237	if (broken_gethostbyname) {
238	    o_addr_list = hp->h_addr_list;
239	    memcpy(*n_addr_list++, *o_addr_list, hp->h_length);
240	    *n_addr_list = 0;
241	    hp->h_addr_list = hp->h_aliases;
242	    hp->h_aliases = o_addr_list + 1;
243	}
244    }
245    return (hp);
246}
247
248#endif /* SOLARIS_24_GETHOSTBYNAME_BUG */
249
250 /*
251  * Horror! Some FreeBSD 2.0 libc routines call strtok(). Since tcpd depends
252  * heavily on strtok(), strange things may happen. Workaround: use our
253  * private strtok(). This has been fixed in the meantime.
254  */
255
256#ifdef USE_STRSEP
257
258char   *fix_strtok(buf, sep)
259char   *buf;
260char   *sep;
261{
262    static char *state;
263    char   *result;
264
265    if (buf)
266	state = buf;
267    while ((result = strsep(&state, sep)) && result[0] == 0)
268	 /* void */ ;
269    return (result);
270}
271
272#endif /* USE_STRSEP */
273
274 /*
275  * IRIX 5.3 (and possibly earlier versions, too) library routines call the
276  * non-reentrant strtok() library routine, causing hosts to slip through
277  * allow/deny filters. Workaround: don't rely on the vendor and use our own
278  * strtok() function. FreeBSD 2.0 has a similar problem (fixed in 2.0.5).
279  */
280
281#ifdef LIBC_CALLS_STRTOK
282
283char   *my_strtok(buf, sep)
284char   *buf;
285char   *sep;
286{
287    static char *state;
288    char   *result;
289
290    if (buf)
291	state = buf;
292
293    /*
294     * Skip over separator characters and detect end of string.
295     */
296    if (*(state += strspn(state, sep)) == 0)
297	return (0);
298
299    /*
300     * Skip over non-separator characters and terminate result.
301     */
302    result = state;
303    if (*(state += strcspn(state, sep)) != 0)
304	*state++ = 0;
305    return (result);
306}
307
308#endif /* LIBC_CALLS_STRTOK */
309