/*

 * Copyright (C) Internet Systems Consortium, Inc. ("ISC")

 *

 * SPDX-License-Identifier: MPL-2.0

 *

 * This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, you can obtain one at https://mozilla.org/MPL/2.0/.

 *

 * See the COPYRIGHT file distributed with this work for additional

 * information regarding copyright ownership.

 */

/*! \file */

#include <stdbool.h>

#include <isc/base64.h>

#include <isc/buffer.h>

#include <isc/lex.h>

#include <isc/string.h>

#include <isc/util.h>

#define RETERR(x)                        \

  do {                             \

    isc_result_t _r = (x);   \

    if (_r != ISC_R_SUCCESS) \

      return ((_r));   \

  } while (0)

/*@{*/

/*!

 * These static functions are also present in lib/dns/rdata.c.  I'm not

 * sure where they should go. -- bwelling

 */

static isc_result_t

str_totext(const char *source, isc_buffer_t *target);

static isc_result_t

mem_tobuffer(isc_buffer_t *target, void *base, unsigned int length);

static const char base64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvw"

           "xyz0123456789+/=";

/*@}*/

isc_result_t

isc_base64_totext(isc_region_t *source, int wordlength, const char *wordbreak,

      isc_buffer_t *target) {

  char buf[5];

  unsigned int loops = 0;

  if (wordlength < 4) {

    wordlength = 4;

  }

  memset(buf, 0, sizeof(buf));

  while (source->length > 2) {

    buf[0] = base64[(source->base[0] >> 2) & 0x3f];

    buf[1] = base64[((source->base[0] << 4) & 0x30) |

        ((source->base[1] >> 4) & 0x0f)];

    buf[2] = base64[((source->base[1] << 2) & 0x3c) |

        ((source->base[2] >> 6) & 0x03)];

    buf[3] = base64[source->base[2] & 0x3f];

    RETERR(str_totext(buf, target));

    isc_region_consume(source, 3);

    loops++;

    if (source->length != 0 && (int)((loops + 1) * 4) >= wordlength)

    {

      loops = 0;

      RETERR(str_totext(wordbreak, target));

    }

  }

  if (source->length == 2) {

    buf[0] = base64[(source->base[0] >> 2) & 0x3f];

    buf[1] = base64[((source->base[0] << 4) & 0x30) |

        ((source->base[1] >> 4) & 0x0f)];

    buf[2] = base64[((source->base[1] << 2) & 0x3c)];

    buf[3] = '=';

    RETERR(str_totext(buf, target));

    isc_region_consume(source, 2);

  } else if (source->length == 1) {

    buf[0] = base64[(source->base[0] >> 2) & 0x3f];

    buf[1] = base64[((source->base[0] << 4) & 0x30)];

    buf[2] = buf[3] = '=';

    RETERR(str_totext(buf, target));

    isc_region_consume(source, 1);

  }

  return (ISC_R_SUCCESS);

}

/*%

 * State of a base64 decoding process in progress.

 */

typedef struct {

  int length;       /*%< Desired length of binary data or -1 */

  isc_buffer_t *target; /*%< Buffer for resulting binary data */

  int digits;       /*%< Number of buffered base64 digits */

  bool seen_end;        /*%< True if "=" end marker seen */

  int val[4];

} base64_decode_ctx_t;

static inline void

base64_decode_init(base64_decode_ctx_t *ctx, int length, isc_buffer_t *target) {

  ctx->digits = 0;

  ctx->seen_end = false;

  ctx->length = length;

  ctx->target = target;

}

static inline isc_result_t

base64_decode_char(base64_decode_ctx_t *ctx, int c) {

  const char *s;

  if (ctx->seen_end) {

    return (ISC_R_BADBASE64);

  }

  if ((s = strchr(base64, c)) == NULL) {

    return (ISC_R_BADBASE64);

  }

  ctx->val[ctx->digits++] = (int)(s - base64);

  if (ctx->digits == 4) {

    int n;

    unsigned char buf[3];

    if (ctx->val[0] == 64 || ctx->val[1] == 64) {

      return (ISC_R_BADBASE64);

    }

    if (ctx->val[2] == 64 && ctx->val[3] != 64) {

      return (ISC_R_BADBASE64);

    }

    /*

     * Check that bits that should be zero are.

     */

    if (ctx->val[2] == 64 && (ctx->val[1] & 0xf) != 0) {

      return (ISC_R_BADBASE64);

    }

    /*

     * We don't need to test for ctx->val[2] != 64 as

     * the bottom two bits of 64 are zero.

     */

    if (ctx->val[3] == 64 && (ctx->val[2] & 0x3) != 0) {

      return (ISC_R_BADBASE64);

    }

    n = (ctx->val[2] == 64) ? 1 : (ctx->val[3] == 64) ? 2 : 3;

    if (n != 3) {

      ctx->seen_end = true;

      if (ctx->val[2] == 64) {

        ctx->val[2] = 0;

      }

      if (ctx->val[3] == 64) {

        ctx->val[3] = 0;

      }

    }

    buf[0] = (ctx->val[0] << 2) | (ctx->val[1] >> 4);

    buf[1] = (ctx->val[1] << 4) | (ctx->val[2] >> 2);

    buf[2] = (ctx->val[2] << 6) | (ctx->val[3]);

    RETERR(mem_tobuffer(ctx->target, buf, n));

    if (ctx->length >= 0) {

      if (n > ctx->length) {

        return (ISC_R_BADBASE64);

      } else {

        ctx->length -= n;

      }

    }

    ctx->digits = 0;

  }

  return (ISC_R_SUCCESS);

}

static inline isc_result_t

base64_decode_finish(base64_decode_ctx_t *ctx) {

  if (ctx->length > 0) {

    return (ISC_R_UNEXPECTEDEND);

  }

  if (ctx->digits != 0) {

    return (ISC_R_BADBASE64);

  }

  return (ISC_R_SUCCESS);

}

isc_result_t

isc_base64_tobuffer(isc_lex_t *lexer, isc_buffer_t *target, int length) {

  unsigned int before, after;

  base64_decode_ctx_t ctx;

  isc_textregion_t *tr;

  isc_token_t token;

  bool eol;

  REQUIRE(length >= -2);

  base64_decode_init(&ctx, length, target);

  before = isc_buffer_usedlength(target);

  while (!ctx.seen_end && (ctx.length != 0)) {

    unsigned int i;

    if (length > 0) {

      eol = false;

    } else {

      eol = true;

    }

    RETERR(isc_lex_getmastertoken(lexer, &token,

                isc_tokentype_string, eol));

    if (token.type != isc_tokentype_string) {

      break;

    }

    tr = &token.value.as_textregion;

    for (i = 0; i < tr->length; i++) {

      RETERR(base64_decode_char(&ctx, tr->base[i]));

    }

  }

  after = isc_buffer_usedlength(target);

  if (ctx.length < 0 && !ctx.seen_end) {

    isc_lex_ungettoken(lexer, &token);

  }

  RETERR(base64_decode_finish(&ctx));

  if (length == -2 && before == after) {

    return (ISC_R_UNEXPECTEDEND);

  }

  return (ISC_R_SUCCESS);

}

isc_result_t

isc_base64_decodestring(const char *cstr, isc_buffer_t *target) {

  base64_decode_ctx_t ctx;

  base64_decode_init(&ctx, -1, target);

  for (;;) {

    int c = *cstr++;

    if (c == '\0') {

      break;

    }

    if (c == ' ' || c == '\t' || c == '\n' || c == '\r') {

      continue;

    }

    RETERR(base64_decode_char(&ctx, c));

  }

  RETERR(base64_decode_finish(&ctx));

  return (ISC_R_SUCCESS);

}

static isc_result_t

str_totext(const char *source, isc_buffer_t *target) {

  unsigned int l;

  isc_region_t region;

  isc_buffer_availableregion(target, &region);

  l = strlen(source);

  if (l > region.length) {

    return (ISC_R_NOSPACE);

  }

  memmove(region.base, source, l);

  isc_buffer_add(target, l);

  return (ISC_R_SUCCESS);

}

static isc_result_t

mem_tobuffer(isc_buffer_t *target, void *base, unsigned int length) {

  isc_region_t tr;

  isc_buffer_availableregion(target, &tr);

  if (length > tr.length) {

    return (ISC_R_NOSPACE);

  }

  memmove(tr.base, base, length);

  isc_buffer_add(target, length);

  return (ISC_R_SUCCESS);

}