crypt.c

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/*      crypt() - one-way password encryption function  Author: Kees J. Bot
 *                                                              7 Feb 1994
 * This routine does not encrypt anything, it uses the pwdauth
 * program to do the hard work.
 */
#define nil ((void*)0)
#define pipe _pipe
#define fork _fork
#define close _close
#define dup2 _dup2
#define execl _execl
#define read _read
#define _exit __exit
#define write _write
#define waitpid _waitpid
#include <sys/types.h>
#include <unistd.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <stdarg.h>
#include <sys/wait.h>

/* Set-uid root program to read /etc/shadow or encrypt passwords. */
static char PWDAUTH[] = "/usr/lib/pwdauth";
#define LEN     1024

static void tell(const char *s0, ...)
{
        va_list ap;
        const char *s;

        va_start(ap, s0);
        s= s0;
        while (s != nil) {
                (void) write(2, s, strlen(s));
                s= va_arg(ap, const char *);
        }
        va_end(ap);
}

char *crypt(const char *key, const char *salt)
{
        pid_t pid;
        int status;
        int pfd[2];
        static char pwdata[LEN];
        char *p= pwdata;
        const char *k= key;
        const char *s= salt;
        int n;

        /* Fill pwdata[] with the key and salt. */
        while ((*p++ = *k++) != 0) if (p == pwdata+LEN-1) goto fail;
        while ((*p++ = *s++) != 0) if (p == pwdata+LEN-0) goto fail;

        if (pipe(pfd) < 0) goto fail;

        /* Prefill the pipe. */
        (void) write(pfd[1], pwdata, p - pwdata);

        switch ((pid= fork())) {
        case -1:
                close(pfd[0]);
                close(pfd[1]);
                goto fail;
        case 0:
                /* Connect both input and output to the pipe. */
                if (pfd[0] != 0) {
                        dup2(pfd[0], 0);
                        close(pfd[0]);
                }
                if (pfd[1] != 1) {
                        dup2(pfd[1], 1);
                        close(pfd[1]);
                }

                execl(PWDAUTH, PWDAUTH, (char *) nil);

                tell("crypt(): ", PWDAUTH, ": ", strerror(errno), "\r\n",
                                                                (char *) nil);
                /* No pwdauth?  Fail! */
                (void) read(0, pwdata, LEN);
                _exit(1);
        }
        close(pfd[1]);

        status= -1;
        while (waitpid(pid, &status, 0) == -1 && errno == EINTR) {}
        if (status != 0) {
                close(pfd[0]);
                goto fail;
        }

        /* Read and return the result.  Check if it contains exactly one
         * string.
         */
        n= read(pfd[0], pwdata, LEN);
        close(pfd[0]);
        if (n < 0) goto fail;
        p = pwdata + n;
        n = 0;
        while (p > pwdata) if (*--p == 0) n++;
        if (n != 1) goto fail;
        return pwdata;

fail:
        pwdata[0] = salt[0] ^ 1;                /* make result != salt */
        pwdata[1] = 0;
        return pwdata;
}

/*
 * $PchId: crypt.c,v 1.5 1996/04/11 07:46:11 philip Exp $
 */

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