/*

 * Copyright 2019-2023 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the Apache License 2.0 (the "License").  You may not use

 * this file except in compliance with the License.  You can obtain a copy

 * in the file LICENSE in the source distribution or at

 * https://www.openssl.org/source/license.html

 */

#include <stddef.h>

#include <stdio.h>

#include <openssl/e_os2.h>

#include "crypto/punycode.h"

#include "internal/common.h" /* for HAS_PREFIX */

#include "internal/packet.h" /* for WPACKET */

static const unsigned int base = 36;

static const unsigned int tmin = 1;

static const unsigned int tmax = 26;

static const unsigned int skew = 38;

static const unsigned int damp = 700;

static const unsigned int initial_bias = 72;

static const unsigned int initial_n = 0x80;

static const unsigned int maxint = 0xFFFFFFFF;

static const char delimiter = '-';

#define LABEL_BUF_SIZE 512

/*-

 * Pseudocode:

 *

 * function adapt(delta,numpoints,firsttime):

 *  if firsttime then let delta = delta div damp

 *  else let delta = delta div 2

 *  let delta = delta + (delta div numpoints)

 *  let k = 0

 *  while delta > ((base - tmin) * tmax) div 2 do begin

 *    let delta = delta div (base - tmin)

 *    let k = k + base

 *  end

 *  return k + (((base - tmin + 1) * delta) div (delta + skew))

 */

static int adapt(unsigned int delta, unsigned int numpoints,

                 unsigned int firsttime)

{

    unsigned int k = 0;

    delta = (firsttime) ? delta / damp : delta / 2;

    delta = delta + delta / numpoints;

    while (delta > ((base - tmin) * tmax) / 2) {

        delta = delta / (base - tmin);

        k = k + base;

    }

    return k + (((base - tmin + 1) * delta) / (delta + skew));

}

static ossl_inline int is_basic(unsigned int a)

{

    return (a < 0x80) ? 1 : 0;

}

/*-

 * code points    digit-values

 * ------------   ----------------------

 * 41..5A (A-Z) =  0 to 25, respectively

 * 61..7A (a-z) =  0 to 25, respectively

 * 30..39 (0-9) = 26 to 35, respectively

 */

static ossl_inline int digit_decoded(const unsigned char a)

{

    if (a >= 0x41 && a <= 0x5A)

        return a - 0x41;

    if (a >= 0x61 && a <= 0x7A)

        return a - 0x61;

    if (a >= 0x30 && a <= 0x39)

        return a - 0x30 + 26;

    return -1;

}

/*-

 * Pseudocode:

 *

 * function ossl_punycode_decode

 *  let n = initial_n

 *  let i = 0

 *  let bias = initial_bias

 *  let output = an empty string indexed from 0

 *  consume all code points before the last delimiter (if there is one)

 *    and copy them to output, fail on any non-basic code point

 *  if more than zero code points were consumed then consume one more

 *    (which will be the last delimiter)

 *  while the input is not exhausted do begin

 *    let oldi = i

 *    let w = 1

 *    for k = base to infinity in steps of base do begin

 *      consume a code point, or fail if there was none to consume

 *      let digit = the code point's digit-value, fail if it has none

 *      let i = i + digit * w, fail on overflow

 *      let t = tmin if k <= bias {+ tmin}, or

 *              tmax if k >= bias + tmax, or k - bias otherwise

 *      if digit < t then break

 *      let w = w * (base - t), fail on overflow

 *    end

 *    let bias = adapt(i - oldi, length(output) + 1, test oldi is 0?)

 *    let n = n + i div (length(output) + 1), fail on overflow

 *    let i = i mod (length(output) + 1)

 *    {if n is a basic code point then fail}

 *    insert n into output at position i

 *    increment i

 *  end

 */

int ossl_punycode_decode(const char *pEncoded, const size_t enc_len,

                         unsigned int *pDecoded, unsigned int *pout_length)

{

    unsigned int n = initial_n;

    unsigned int i = 0;

    unsigned int bias = initial_bias;

    size_t processed_in = 0, written_out = 0;

    unsigned int max_out = *pout_length;

    unsigned int basic_count = 0;

    unsigned int loop;

    for (loop = 0; loop < enc_len; loop++) {

        if (pEncoded[loop] == delimiter)

            basic_count = loop;

    }

    if (basic_count > 0) {

        if (basic_count > max_out)

            return 0;

        for (loop = 0; loop < basic_count; loop++) {

            if (is_basic(pEncoded[loop]) == 0)

                return 0;

            pDecoded[loop] = pEncoded[loop];

            written_out++;

        }

        processed_in = basic_count + 1;

    }

    for (loop = processed_in; loop < enc_len;) {

        unsigned int oldi = i;

        unsigned int w = 1;

        unsigned int k, t;

        int digit;

        for (k = base;; k += base) {

            if (loop >= enc_len)

                return 0;

            digit = digit_decoded(pEncoded[loop]);

            loop++;

            if (digit < 0)

                return 0;

            if ((unsigned int)digit > (maxint - i) / w)

                return 0;

            i = i + digit * w;

            t = (k <= bias) ? tmin : (k >= bias + tmax) ? tmax : k - bias;

            if ((unsigned int)digit < t)

                break;

            if (w > maxint / (base - t))

                return 0;

            w = w * (base - t);

        }

        bias = adapt(i - oldi, written_out + 1, (oldi == 0));

        if (i / (written_out + 1) > maxint - n)

            return 0;

        n = n + i / (written_out + 1);

        i %= (written_out + 1);

        if (written_out >= max_out)

            return 0;

        memmove(pDecoded + i + 1, pDecoded + i,

                (written_out - i) * sizeof(*pDecoded));

        pDecoded[i] = n;

        i++;

        written_out++;

    }

    *pout_length = written_out;

    return 1;

}

/*

 * Encode a code point using UTF-8

 * return number of bytes on success, 0 on failure

 * (also produces U+FFFD, which uses 3 bytes on failure)

 */

static int codepoint2utf8(unsigned char *out, unsigned long utf)

{

    if (utf <= 0x7F) {

        /* Plain ASCII */

        out[0] = (unsigned char)utf;

        out[1] = 0;

        return 1;

    } else if (utf <= 0x07FF) {

        /* 2-byte unicode */

        out[0] = (unsigned char)(((utf >> 6) & 0x1F) | 0xC0);

        out[1] = (unsigned char)(((utf >> 0) & 0x3F) | 0x80);

        out[2] = 0;

        return 2;

    } else if (utf <= 0xFFFF) {

        /* 3-byte unicode */

        out[0] = (unsigned char)(((utf >> 12) & 0x0F) | 0xE0);

        out[1] = (unsigned char)(((utf >> 6) & 0x3F) | 0x80);

        out[2] = (unsigned char)(((utf >> 0) & 0x3F) | 0x80);

        out[3] = 0;

        return 3;

    } else if (utf <= 0x10FFFF) {

        /* 4-byte unicode */

        out[0] = (unsigned char)(((utf >> 18) & 0x07) | 0xF0);

        out[1] = (unsigned char)(((utf >> 12) & 0x3F) | 0x80);

        out[2] = (unsigned char)(((utf >> 6) & 0x3F) | 0x80);

        out[3] = (unsigned char)(((utf >> 0) & 0x3F) | 0x80);

        out[4] = 0;

        return 4;

    } else {

        /* error - use replacement character */

        out[0] = (unsigned char)0xEF;

        out[1] = (unsigned char)0xBF;

        out[2] = (unsigned char)0xBD;

        out[3] = 0;

        return 0;

    }

}

/*-

 * Return values:

 * 1 - ok

 * 0 - ok but buf was too short

 * -1 - bad string passed or other error

 */

int ossl_a2ulabel(const char *in, char *out, size_t outlen)

{

    /*-

     * Domain name has some parts consisting of ASCII chars joined with dot.

     * If a part is shorter than 5 chars, it becomes U-label as is.

     * If it does not start with xn--,    it becomes U-label as is.

     * Otherwise we try to decode it.

     */

    const char *inptr = in;

    int result = 1;

    unsigned int i;

    unsigned int buf[LABEL_BUF_SIZE];      /* It's a hostname */

    WPACKET pkt;

    /* Internal API, so should not fail */

    if (!ossl_assert(out != NULL))

        return -1;

    if (!WPACKET_init_static_len(&pkt, (unsigned char *)out, outlen, 0))

        return -1;

    while (1) {

        char *tmpptr = strchr(inptr, '.');

        size_t delta = tmpptr != NULL ? (size_t)(tmpptr - inptr) : strlen(inptr);

        if (!HAS_PREFIX(inptr, "xn--")) {

            if (!WPACKET_memcpy(&pkt, inptr, delta))

                result = 0;

        } else {

            unsigned int bufsize = LABEL_BUF_SIZE;

            if (ossl_punycode_decode(inptr + 4, delta - 4, buf, &bufsize) <= 0) {

                result = -1;

                goto end;

            }

            for (i = 0; i < bufsize; i++) {

                unsigned char seed[6];

                size_t utfsize = codepoint2utf8(seed, buf[i]);

                if (utfsize == 0) {

                    result = -1;

                    goto end;

                }

                if (!WPACKET_memcpy(&pkt, seed, utfsize))

                    result = 0;

            }

        }

        if (tmpptr == NULL)

            break;

        if (!WPACKET_put_bytes_u8(&pkt, '.'))

            result = 0;

        inptr = tmpptr + 1;

    }

    if (!WPACKET_put_bytes_u8(&pkt, '\0'))

        result = 0;

 end:

    WPACKET_cleanup(&pkt);

    return result;

}