1 /*
2 * Pager: Routines to create a "more" running out of a particular file
3 * descriptor.
4 *
5 * Copyright 1987, 1988 by MIT Student Information Processing Board
6 *
7 * Permission to use, copy, modify, and distribute this software and
8 * its documentation for any purpose is hereby granted, provided that
9 * the names of M.I.T. and the M.I.T. S.I.P.B. not be used in
10 * advertising or publicity pertaining to distribution of the software
11 * without specific, written prior permission. M.I.T. and the
12 * M.I.T. S.I.P.B. make no representations about the suitability of
13 * this software for any purpose. It is provided "as is" without
14 * express or implied warranty.
15 */
16
17 #if HAVE_SECURE_GETENV
18 #define _GNU_SOURCE
19 #endif
20 #ifdef HAVE_UNISTD_H
21 #include <unistd.h>
22 #endif
23 #ifdef HAVE_ERRNO_H
24 #include <errno.h>
25 #else
26 extern int errno;
27 #endif
28
29 #include "ss_internal.h"
30 #include <stdio.h>
31 #include <sys/types.h>
32 #include <sys/file.h>
33 #include <signal.h>
34 #ifdef HAVE_SYS_PRCTL_H
35 #include <sys/prctl.h>
36 #else
37 #define PR_GET_DUMPABLE 3
38 #endif
39 #if (!defined(HAVE_PRCTL) && defined(linux))
40 #include <sys/syscall.h>
41 #endif
42
43 static char MORE[] = "more";
44 extern char *getenv PROTOTYPE((const char *));
45
ss_safe_getenv(const char * arg)46 char *ss_safe_getenv(const char *arg)
47 {
48 if ((getuid() != geteuid()) || (getgid() != getegid()))
49 return NULL;
50 #if HAVE_PRCTL
51 if (prctl(PR_GET_DUMPABLE, 0, 0, 0, 0) == 0)
52 return NULL;
53 #else
54 #if (defined(linux) && defined(SYS_prctl))
55 if (syscall(SYS_prctl, PR_GET_DUMPABLE, 0, 0, 0, 0) == 0)
56 return NULL;
57 #endif
58 #endif
59
60 #if defined(HAVE_SECURE_GETENV)
61 return secure_getenv(arg);
62 #elif defined(HAVE___SECURE_GETENV)
63 return __secure_getenv(arg);
64 #else
65 return getenv(arg);
66 #endif
67 }
68
69 /*
70 * this needs a *lot* of work....
71 *
72 * run in same process
73 * handle SIGINT sensibly
74 * allow finer control -- put-page-break-here
75 */
76
77 #ifndef NO_FORK
ss_pager_create(void)78 int ss_pager_create(void)
79 {
80 int filedes[2];
81
82 if (pipe(filedes) != 0)
83 return(-1);
84
85 switch(fork()) {
86 case -1:
87 return(-1);
88 case 0:
89 /*
90 * Child; dup read half to 0, close all but 0, 1, and 2
91 */
92 if (dup2(filedes[0], 0) == -1)
93 exit(1);
94 ss_page_stdin();
95 default:
96 /*
97 * Parent: close "read" side of pipe, return
98 * "write" side.
99 */
100 (void) close(filedes[0]);
101 return(filedes[1]);
102 }
103 }
104 #else /* don't fork */
ss_pager_create()105 int ss_pager_create()
106 {
107 int fd;
108 fd = open("/dev/tty", O_WRONLY, 0);
109 return fd;
110 }
111 #endif
112
write_all(int fd,char * buf,size_t count)113 static int write_all(int fd, char *buf, size_t count)
114 {
115 ssize_t ret;
116 int c = 0;
117
118 while (count > 0) {
119 ret = write(fd, buf, count);
120 if (ret < 0) {
121 if ((errno == EAGAIN) || (errno == EINTR))
122 continue;
123 return -1;
124 }
125 count -= ret;
126 buf += ret;
127 c += ret;
128 }
129 return c;
130 }
131
ss_page_stdin(void)132 void ss_page_stdin(void)
133 {
134 int i;
135 sigset_t mask;
136
137 for (i = 3; i < 32; i++)
138 (void) close(i);
139 (void) signal(SIGINT, SIG_DFL);
140 sigprocmask(SIG_BLOCK, 0, &mask);
141 sigdelset(&mask, SIGINT);
142 sigprocmask(SIG_SETMASK, &mask, 0);
143 if (_ss_pager_name == (char *)NULL) {
144 if ((_ss_pager_name = ss_safe_getenv("PAGER")) == (char *)NULL)
145 _ss_pager_name = MORE;
146 }
147 (void) execlp(_ss_pager_name, _ss_pager_name, (char *) NULL);
148 {
149 /* minimal recovery if pager program isn't found */
150 char buf[80];
151 register int n;
152 while ((n = read(0, buf, 80)) > 0)
153 write_all(1, buf, n);
154 }
155 exit(errno);
156 }
157