1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
|
/* setgrp.c - by Michael Haardt. Set the gid if possible
* Added a bit more error recovery/reporting - poe
* Vesa Roukonen added code for asking password */
/* 1999-02-22 Arkadiusz Miśkiewicz <misiek@pld.ORG.PL>
* - added Native Language Support
*/
#include <errno.h>
#include <getopt.h>
#include <grp.h>
#include <pwd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <termios.h>
#include <unistd.h>
#ifdef HAVE_CRYPT_H
# include <crypt.h>
#endif
#ifdef HAVE_GETSGNAM
# include <gshadow.h>
#endif
#include "c.h"
#include "closestream.h"
#include "nls.h"
#include "pathnames.h"
#include "xalloc.h"
static char *xgetpass(FILE *input, const char *prompt)
{
char *pass = NULL;
struct termios saved, no_echo;
const int fd = fileno(input);
size_t dummy = 0;
ssize_t len;
fputs(prompt, stdout);
if (isatty(fd)) {
/* disable echo */
tcgetattr(fd, &saved);
no_echo = saved;
no_echo.c_lflag &= ~ECHO;
no_echo.c_lflag |= ECHONL;
if (tcsetattr(fd, TCSANOW, &no_echo))
err(EXIT_FAILURE, _("could not set terminal attributes"));
}
len = getline(&pass, &dummy, input);
if (isatty(fd))
/* restore terminal */
if (tcsetattr(fd, TCSANOW, &saved))
err(EXIT_FAILURE, _("could not set terminal attributes"));
if (len < 0)
err(EXIT_FAILURE, _("getline() failed"));
if (0 < len && *(pass + len - 1) == '\n')
*(pass + len - 1) = '\0';
return pass;
}
#ifndef HAVE_EXPLICIT_BZERO
/* Ensure memory is set to value c without compiler optimization getting
* into way that could happen with memset(3). */
static int xmemset_s(void *v, size_t sz, const int c)
{
volatile unsigned char *p = v;
if (v == NULL)
return EINVAL;
while (sz--)
*p++ = c;
return 0;
}
#endif
/* try to read password from gshadow */
static char *get_gshadow_pwd(const char *groupname)
{
#ifdef HAVE_GETSGNAM
struct sgrp *sgrp;
sgrp = getsgnam(groupname);
return sgrp ? xstrdup(sgrp->sg_passwd) : NULL;
#else
char buf[BUFSIZ];
char *pwd = NULL;
FILE *f;
if (groupname == NULL || *groupname == '\0')
return NULL;
f = fopen(_PATH_GSHADOW, "r");
if (!f)
return NULL;
while (fgets(buf, sizeof buf, f)) {
char *cp = strchr(buf, ':');
if (!cp)
/* any junk in gshadow? */
continue;
*cp = '\0';
if (strcmp(buf, groupname) == 0) {
if (cp - buf >= BUFSIZ)
/* only group name on line */
break;
pwd = cp + 1;
if ((cp = strchr(pwd, ':')) && pwd == cp + 1)
/* empty password */
pwd = NULL;
else if (cp)
*cp = '\0';
break;
}
}
fclose(f);
return pwd ? xstrdup(pwd) : NULL;
#endif /* HAVE_GETSGNAM */
}
static int allow_setgid(const struct passwd *pe, const struct group *ge)
{
char **look;
int notfound = 1;
char *pwd, *xpwd;
if (getuid() == 0)
/* root may do anything */
return TRUE;
if (ge->gr_gid == pe->pw_gid)
/* You can switch back to your default group */
return TRUE;
look = ge->gr_mem;
while (*look && (notfound = strcmp(*look++, pe->pw_name))) ;
if (!notfound)
/* member of group => OK */
return TRUE;
/* Ask for password. Often there is no password in /etc/group, so
* contrary to login et al. we let an empty password mean the same
* as in /etc/passwd */
/* check /etc/gshadow */
if (!(pwd = get_gshadow_pwd(ge->gr_name)))
pwd = ge->gr_passwd;
if (pwd && *pwd && (xpwd = xgetpass(stdin, _("Password: ")))) {
char *cbuf = crypt(xpwd, pwd);
#ifdef HAVE_EXPLICIT_BZERO
explicit_bzero(xpwd, strlen(xpwd));
#else
xmemset_s(xpwd, strlen(xpwd), 0);
#endif
free(xpwd);
if (!cbuf)
warn(_("crypt failed"));
else if (strcmp(pwd, cbuf) == 0)
return TRUE;
}
/* default to denial */
return FALSE;
}
static void __attribute__((__noreturn__)) usage(void)
{
FILE *out = stdout;
fputs(USAGE_HEADER, out);
fprintf(out, _(" %s <group>\n"), program_invocation_short_name);
fputs(USAGE_SEPARATOR, out);
fputs(_("Log in to a new group.\n"), out);
fputs(USAGE_OPTIONS, out);
printf(USAGE_HELP_OPTIONS(16));
printf(USAGE_MAN_TAIL("newgrp(1)"));
exit(EXIT_SUCCESS);
}
int main(int argc, char *argv[])
{
struct passwd *pw_entry;
struct group *gr_entry;
char *shell;
int ch;
static const struct option longopts[] = {
{"version", no_argument, NULL, 'V'},
{"help", no_argument, NULL, 'h'},
{NULL, 0, NULL, 0}
};
setlocale(LC_ALL, "");
bindtextdomain(PACKAGE, LOCALEDIR);
textdomain(PACKAGE);
close_stdout_atexit();
while ((ch = getopt_long(argc, argv, "Vh", longopts, NULL)) != -1)
switch (ch) {
case 'V':
print_version(EXIT_SUCCESS);
case 'h':
usage();
default:
errtryhelp(EXIT_FAILURE);
}
if (!(pw_entry = getpwuid(getuid())))
err(EXIT_FAILURE, _("who are you?"));
if (argc < 2) {
if (setgid(pw_entry->pw_gid) < 0)
err(EXIT_FAILURE, _("setgid failed"));
} else {
errno = 0;
if (!(gr_entry = getgrnam(argv[1]))) {
if (errno)
err(EXIT_FAILURE, _("no such group"));
else
errx(EXIT_FAILURE, _("no such group"));
}
if (!allow_setgid(pw_entry, gr_entry))
errx(EXIT_FAILURE, _("permission denied"));
if (setgid(gr_entry->gr_gid) < 0)
err(EXIT_FAILURE, _("setgid failed"));
}
if (setuid(getuid()) < 0)
err(EXIT_FAILURE, _("setuid failed"));
fflush(NULL);
shell = (pw_entry->pw_shell && *pw_entry->pw_shell ?
pw_entry->pw_shell : _PATH_BSHELL);
execl(shell, shell, (char *)0);
errexec(shell);
}
|
