Basic sudo implementation on IBM i

README.md

Basic sudo implementation on IBM i

Uses standard Unix setuid to change the current process user id and executes the parameters passed. On other platforms, this usually requires root authority, but on IBM i we just need *USE authority to the user profile. :)

Build

gcc -o sudo sudo.c

Example

$ whoami
kadler

$ ./sudo whoami
qsecofr

$ ./sudo -u dummy
dummy

$ ./sudo -u 1234
otherdummy

sudo.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <stdarg.h>
#include <unistd.h>
#include <pwd.h>

int debug(const char* fmt, ...)
{
    va_list args;
    va_start(args, fmt);
    int rc = vprintf(fmt, args);
    printf("\n");
    return rc;
}

int fatal(const char* fmt, ...)
{
    va_list args;
    va_start(args, fmt);
    vprintf(fmt, args);
    printf("\n");
    exit(1);
}


int main(int argc, char** argv)
{
    if(argc < 2 || strcmp(argv[1], "-h") == 0)
    {
        debug("usage: %s cmd [cmd args]\n", argv[0]);
        return 1;
    }
    
    int rc;
    uid_t uid = 0;
    int argindex = 1;

    if(argc > 1 && strcmp(argv[1], "-u") == 0)
    {
      if(argc > 2)
      {
        const char* username = argv[2];
        argindex = 3;
        if(*username >= '0' && *username <= '9') {
          uid = (uid_t) atoi(username);
        }
        else {
          putenv("PASE_USRGRP_LIMITED=N");
          struct passwd* pwd = getpwnam(username);
          if(!pwd) {
            fatal("Couldn't get user");
          }
          uid = pwd->pw_uid;
        }
      }
    }

    setuid(uid);
 
    execvp(argv[argindex], &argv[argindex]);
    perror("Couldn't exec");
    return 1;
}