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| #include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>
#include <sys/types.h>
#include <fcntl.h>
#include <getopt.h>
struct {
FILE *debugfile;
int verbose;
int loggedin;
} globals;
#define dprintf(...) if(globals.debugfile) \
fprintf(globals.debugfile, __VA_ARGS__)
#define dvprintf(num, ...) if(globals.debugfile && globals.verbose >= num) \
fprintf(globals.debugfile, __VA_ARGS__)
#define PWFILE "/home/flag18/password"
void login(char *pw)
{
FILE *fp;
fp = fopen(PWFILE, "r");
if(fp) {
char file[64];
if(fgets(file, sizeof(file) - 1, fp) == NULL) {
dprintf("Unable to read password file %s\n", PWFILE);
return;
}
fclose(fp);
if(strcmp(pw, file) != 0) return;
}
dprintf("logged in successfully (with%s password file)\n",
fp == NULL ? "out" : "");
globals.loggedin = 1;
}
void notsupported(char *what)
{
char *buffer = NULL;
asprintf(&buffer, "--> [%s] is unsupported at this current time.\n", what);
dprintf(what);
free(buffer);
}
void setuser(char *user)
{
char msg[128];
sprintf(msg, "unable to set user to '%s' -- not supported.\n", user);
printf("%s\n", msg);
}
int main(int argc, char **argv, char **envp)
{
char c;
while((c = getopt(argc, argv, "d:v")) != -1) {
switch(c) {
case 'd':
globals.debugfile = fopen(optarg, "w+");
if(globals.debugfile == NULL) err(1, "Unable to open %s", optarg);
setvbuf(globals.debugfile, NULL, _IONBF, 0);
break;
case 'v':
globals.verbose++;
break;
}
}
dprintf("Starting up. Verbose level = %d\n", globals.verbose);
setresgid(getegid(), getegid(), getegid());
setresuid(geteuid(), geteuid(), geteuid());
while(1) {
char line[256];
char *p, *q;
q = fgets(line, sizeof(line)-1, stdin);
if(q == NULL) break;
p = strchr(line, '\n'); if(p) *p = 0;
p = strchr(line, '\r'); if(p) *p = 0;
dvprintf(2, "got [%s] as input\n", line);
if(strncmp(line, "login", 5) == 0) {
dvprintf(3, "attempting to login\n");
login(line + 6);
} else if(strncmp(line, "logout", 6) == 0) {
globals.loggedin = 0;
} else if(strncmp(line, "shell", 5) == 0) {
dvprintf(3, "attempting to start shell\n");
if(globals.loggedin) {
execve("/bin/sh", argv, envp);
err(1, "unable to execve");
}
dprintf("Permission denied\n");
} else if(strncmp(line, "logout", 4) == 0) {
globals.loggedin = 0;
} else if(strncmp(line, "closelog", 8) == 0) {
if(globals.debugfile) fclose(globals.debugfile);
globals.debugfile = NULL;
} else if(strncmp(line, "site exec", 9) == 0) {
notsupported(line + 10);
} else if(strncmp(line, "setuser", 7) == 0) {
setuser(line + 8);
}
}
return 0;
}
|