/* OpenBSD S/Key (skeysubr.c)
 *
 * Authors:
 *          Neil M. Haller <nmh@thumper.bellcore.com>
 *          Philip R. Karn <karn@chicago.qualcomm.com>
 *          John S. Walden <jsw@thumper.bellcore.com>
 *          Scott Chasin <chasin@crimelab.com>
 *          Todd C. Miller <millert@openbsd.org>
 *
 * S/Key misc routines.
 *
 * $OpenBSD: skeysubr.c,v 1.36 2023/03/08 04:43:05 guenther Exp $
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <signal.h>
#include <termios.h>
#include <unistd.h>
#include <md5.h>
#include <sha1.h>
#include <rmd160.h>

#include "skey.h"

/* Default hash function to use (index into skey_algorithm_table array) */
#ifndef SKEY_HASH_DEFAULT
#define SKEY_HASH_DEFAULT       0       /* md5 */
#endif

static void keycrunch_md5(char *, char *, size_t);
static void keycrunch_sha1(char *, char *, size_t);
static void keycrunch_rmd160(char *, char *, size_t);
static void skey_echo(int);
static void trapped(int);

/* Current hash type (index into skey_algorithm_table array) */
static int skey_hash_type = SKEY_HASH_DEFAULT;

/*
 * Hash types we support.
 * Each has an associated keycrunch() and f() function.
 */
struct skey_algorithm_table {
        const char *name;
        void (*keycrunch)(char *, char *, size_t);
};
static struct skey_algorithm_table skey_algorithm_table[] = {
        { "md5", keycrunch_md5 },
        { "sha1", keycrunch_sha1 },
        { "rmd160", keycrunch_rmd160 },
        { NULL }
};


/*
 * Crunch a key:
 *  Concatenate the seed and the password, run through hash function and
 *  collapse to 64 bits.  This is defined as the user's starting key.
 *  The result pointer must have at least SKEY_BINKEY_SIZE bytes of storage.
 *  The seed and password may be of any length.
 */
int
keycrunch(char *result, char *seed, char *passwd)
{
        char *buf, *p;
        size_t buflen;

        buflen = strlen(seed) + strlen(passwd);
        if ((buf = malloc(buflen + 1)) == NULL)
                return(-1);

        (void)strlcpy(buf, seed, buflen + 1);
        for (p = buf; *p; p++)
                *p = (char)tolower((unsigned char)*p);

        (void)strlcat(buf, passwd, buflen + 1);
        sevenbit(buf);

        skey_algorithm_table[skey_hash_type].keycrunch(result, buf, buflen);

        (void)free(buf);
        return(0);
}

static void
keycrunch_md5(char *result, char *buf, size_t buflen)
{
        MD5_CTX md;
        u_int32_t results[4];

        /* Crunch the key through MD5 */
        MD5Init(&md);
        MD5Update(&md, (unsigned char *)buf, buflen);
        MD5Final((unsigned char *)results, &md);

        /* Fold result from 128 to 64 bits */
        results[0] ^= results[2];
        results[1] ^= results[3];

        (void)memcpy((void *)result, (void *)results, SKEY_BINKEY_SIZE);
}

static void
keycrunch_sha1(char *result, char *buf, size_t buflen)
{
        SHA1_CTX sha;
        int i, j;

        /* Crunch the key through SHA1 */
        SHA1Init(&sha);
        SHA1Update(&sha, (unsigned char *)buf, buflen);
        SHA1Pad(&sha);

        /* Fold 160 to 64 bits */
        sha.state[0] ^= sha.state[2];
        sha.state[1] ^= sha.state[3];
        sha.state[0] ^= sha.state[4];

        /*
         * SHA1 is a big endian algorithm but RFC2289 mandates that
         * the result be in little endian form, so we copy to the
         * result buffer manually.
         */
        for (i = 0, j = 0; j < 8; i++, j += 4) {
                result[j]   = (u_char)(sha.state[i] & 0xff);
                result[j+1] = (u_char)((sha.state[i] >> 8)  & 0xff);
                result[j+2] = (u_char)((sha.state[i] >> 16) & 0xff);
                result[j+3] = (u_char)((sha.state[i] >> 24) & 0xff);
        }
}

static void
keycrunch_rmd160(char *result, char *buf, size_t buflen)
{
        RMD160_CTX rmd;
        u_int32_t results[5];

        /* Crunch the key through RMD-160 */
        RMD160Init(&rmd);
        RMD160Update(&rmd, (unsigned char *)buf, buflen);
        RMD160Final((unsigned char *)results, &rmd);

        /* Fold 160 to 64 bits */
        results[0] ^= results[2];
        results[1] ^= results[3];
        results[0] ^= results[4];

        (void)memcpy((void *)result, (void *)results, SKEY_BINKEY_SIZE);
}

/*
 * The one-way hash function f().
 * Takes SKEY_BINKEY_SIZE bytes and returns SKEY_BINKEY_SIZE bytes in place.
 */
void
f(char *x)
{
        skey_algorithm_table[skey_hash_type].keycrunch(x, x, SKEY_BINKEY_SIZE);
}

/* Strip trailing cr/lf from a line of text */
void
rip(char *buf)
{
        buf += strcspn(buf, "\r\n");

        if (*buf)
                *buf = '\0';
}

/* Read in secret password (turns off echo) */
char *
readpass(char *buf, int n)
{
        void (*old_handler)(int);

        /* Turn off echoing */
        skey_echo(0);

        /* Catch SIGINT and save old signal handler */
        old_handler = signal(SIGINT, trapped);

        if (fgets(buf, n, stdin) == NULL)
                buf[0] = '\0';
        rip(buf);

        (void)putc('\n', stderr);
        (void)fflush(stderr);

        /* Restore signal handler and turn echo back on */
        if (old_handler != SIG_ERR)
                (void)signal(SIGINT, old_handler);
        skey_echo(1);

        sevenbit(buf);

        return(buf);
}

/* Read in an s/key OTP (does not turn off echo) */
char *
readskey(char *buf, int n)
{
        if (fgets(buf, n, stdin) == NULL)
                buf[0] = '\0';
        rip(buf);

        sevenbit(buf);

        return(buf);
}

/* Signal handler for trapping ^C */
static void
trapped(int sig)
{
        write(STDERR_FILENO, "^C\n", 3);

        /* Turn on echo if necessary */
        skey_echo(1);

        _exit(1);
}

/*
 * Convert 16-byte hex-ascii string to 8-byte binary array
 * Returns 0 on success, -1 on error
 */
int
atob8(char *out, char *in)
{
        int i;
        int val;

        if (in == NULL || out == NULL)
                return(-1);

        for (i=0; i < 8; i++) {
                if ((in = skipspace(in)) == NULL)
                        return(-1);
                if ((val = htoi(*in++)) == -1)
                        return(-1);
                *out = val << 4;

                if ((in = skipspace(in)) == NULL)
                        return(-1);
                if ((val = htoi(*in++)) == -1)
                        return(-1);
                *out++ |= val;
        }
        return(0);
}

/* Convert 8-byte binary array to 16-byte hex-ascii string */
int
btoa8(char *out, char *in)
{
        if (in == NULL || out == NULL)
                return(-1);

        (void)snprintf(out, 17, "%02x%02x%02x%02x%02x%02x%02x%02x",
            in[0] & 0xff, in[1] & 0xff, in[2] & 0xff, in[3] & 0xff,
            in[4] & 0xff, in[5] & 0xff, in[6] & 0xff, in[7] & 0xff);

        return(0);
}

/* Convert hex digit to binary integer */
int
htoi(int c)
{
        if ('0' <= c && c <= '9')
                return(c - '0');
        if ('a' <= c && c <= 'f')
                return(10 + c - 'a');
        if ('A' <= c && c <= 'F')
                return(10 + c - 'A');
        return(-1);
}

/* Skip leading spaces from the string */
char *
skipspace(char *cp)
{
        while (*cp == ' ' || *cp == '\t')
                cp++;

        if (*cp == '\0')
                return(NULL);
        else
                return(cp);
}

/* Remove backspaced over characters from the string */
void
backspace(char *buf)
{
        char bs = 0x8;
        char *cp = buf;
        char *out = buf;

        while (*cp) {
                if (*cp == bs) {
                        if (out == buf) {
                                cp++;
                                continue;
                        } else {
                                cp++;
                                out--;
                        }
                } else {
                        *out++ = *cp++;
                }

        }
        *out = '\0';
}

/* Make sure line is all seven bits */
void
sevenbit(char *s)
{
        while (*s)
                *s++ &= 0x7f;
}

/* Set hash algorithm type */
char *
skey_set_algorithm(char *new)
{
        int i;

        for (i = 0; skey_algorithm_table[i].name; i++) {
                if (strcmp(new, skey_algorithm_table[i].name) == 0) {
                        skey_hash_type = i;
                        return(new);
                }
        }

        return(NULL);
}

/* Get current hash type */
const char *
skey_get_algorithm(void)
{
        return(skey_algorithm_table[skey_hash_type].name);
}

/* Turn echo on/off */
static void
skey_echo(int action)
{
        static struct termios term;
        static int echo = 0;

        if (action == 0) {
                /* Turn echo off */
                (void) tcgetattr(fileno(stdin), &term);
                if ((echo = (term.c_lflag & ECHO))) {
                        term.c_lflag &= ~ECHO;
                        (void) tcsetattr(fileno(stdin), TCSAFLUSH|TCSASOFT, &term);
                }
        } else if (action && echo) {
                /* Turn echo on */
                term.c_lflag |= ECHO;
                (void) tcsetattr(fileno(stdin), TCSAFLUSH|TCSASOFT, &term);
                echo = 0;
        }
}