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#include <alloca.h>
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>
/* this will be running setuid root, so be careful! */
void usage(void) {
fprintf(stderr, "usage: usernetctl <interface-config> <up|down>\n");
exit(1);
}
static char * safeEnviron[] = {
"PATH=/bin:/sbin:/usr/bin:/usr/sbin",
"HOME=/root",
NULL
};
int userCtl(char * file, int size) {
char * contents;
char * chptr;
char * end;
int fd;
contents = alloca(size + 2);
if ((fd = open(file, O_RDONLY)) < 0) {
fprintf(stderr, "failed to open %s: %s\n", file, strerror(errno));
exit(1);
}
if (read(fd, contents, size) != size) {
perror("error reading device configuration");
exit(1);
}
close(fd);
contents[size] = '\n';
contents[size + 1] = '\0';
/* each pass parses a single line (until an answer is found), contents
itself points to the beginning of the current line */
while (*contents) {
chptr = contents;
while (*chptr != '\n') chptr++;
end = chptr + 1;
while (chptr > contents && isspace(*chptr)) chptr--;
*(++chptr) = '\0';
if (!strcmp(contents, "USERCTL=yes")) return 1;
contents = end;
}
return 0;
}
int main(int argc, char ** argv) {
char * ifaceConfig;
char * chptr;
struct stat sb;
char * cmd;
if (argc != 3) usage();
if (!strcmp(argv[2], "up")) {
cmd = "./ifup";
} else if (!strcmp(argv[2], "down")) {
cmd = "./ifdown";
} else {
usage();
}
if (chdir("/etc/sysconfig/network-scripts")) {
fprintf(stderr, "error switching to /etc/sysconfig/network-scripts: "
"%s\n", strerror(errno));
exit(1);
}
/* force the interface configuration to be in the current directory */
chptr = ifaceConfig = argv[1];
while (*chptr) {
if (*chptr == '/')
ifaceConfig = chptr + 1;
chptr++;
}
/* these shouldn't be symbolic links -- anal, but that's fine w/ me */
if (lstat(ifaceConfig, &sb)) {
fprintf(stderr, "failed to stat %s: %s\n", ifaceConfig,
strerror(errno));
exit(1);
}
/* safety checks */
if (!S_ISREG(sb.st_mode)) {
fprintf(stderr, "%s is not a normal file\n", ifaceConfig);
exit(1);
}
if (sb.st_uid) {
fprintf(stderr, "%s should be owned by root\n", ifaceConfig);
exit(1);
}
if (sb.st_mode & S_IWOTH) {
fprintf(stderr, "%s should not be world writeable\n", ifaceConfig);
exit(1);
}
if (!userCtl(ifaceConfig, sb.st_size)) {
fprintf(stderr, "Users are not allowed to control this interface.\n");
exit(1);
}
/* looks good to me -- let's go for it */
/* pppd wants the real uid to be the same as the effective (god only
knows why when it works fine setuid out of the box) */
setuid(geteuid());
execle(cmd, cmd, ifaceConfig, NULL, safeEnviron);
fprintf(stderr, "exec of %s failed: %s\n", cmd, strerror(errno));
exit(1);
}
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