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#include <alloca.h>
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.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|report>\n");
exit(1);
}
static char * safeEnviron[] = {
"PATH=/bin:/sbin:/usr/bin:/usr/sbin",
"HOME=/root",
NULL
};
#define FOUND_FALSE -1
#define NOT_FOUND 0
#define FOUND_TRUE 1
int testSafe(char * ifaceConfig) {
struct stat sb;
/* 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);
}
return sb.st_size;
}
int userCtl(char * file) {
char * contents;
char * chptr;
char * end;
int fd;
int size;
size = testSafe(file);
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 (!strncmp(contents, "USERCTL=", 8)) {
if (!strcmp(contents+8, "yes")) return FOUND_TRUE;
else return FOUND_FALSE;
}
contents = end;
}
return NOT_FOUND;
}
int main(int argc, char ** argv) {
char * ifaceConfig;
char * chptr;
char * cmd;
int report = 0;
char tmp;
if (argc != 3) usage();
if (!strcmp(argv[2], "up")) {
cmd = "./ifup";
} else if (!strcmp(argv[2], "down")) {
cmd = "./ifdown";
} else if (!strcmp(argv[2], "report")) {
report = 1;
} 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++;
}
/* automatically prepend "ifcfg-" if it is not specified */
if (strncmp(ifaceConfig, "ifcfg-", 6)) {
char *temp;
temp = (char *) alloca(strlen(ifaceConfig) + 7);
strcpy(temp, "ifcfg-");
/* strcat is safe because we got the length from strlen */
strcat(temp, ifaceConfig);
ifaceConfig = temp;
}
switch (userCtl(ifaceConfig)) {
char *dash;
case NOT_FOUND:
/* a `-' will be found at least in "ifcfg-" */
dash = strrchr(ifaceConfig, '-');
if (*(dash-1) != 'g') {
/* This was a clone configuration; ask the parent config */
tmp = *dash;
*dash = '\0';
if (userCtl(ifaceConfig) == FOUND_TRUE) {
/* exit the switch; users are allowed to control */
*dash = tmp;
break;
}
*dash = tmp;
}
/* else fall through */
case FOUND_FALSE:
if (! report)
fprintf(stderr,
"Users are not allowed to control this interface.\n");
exit(1);
break;
}
/* looks good to me -- let's go for it if we are changing the interface,
* report good status to the user otherwise */
if (report)
exit(0);
/* 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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