/*

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

 *

 * 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 <config.h>

#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[] =

	"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

/*@}*/

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);

}