encoding.c

/*
 * Copyright 2010-2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 *
 * Licensed under the Apache License, Version 2.0 (the "License").
 * You may not use this file except in compliance with the License.
 * A copy of the License is located at
 *
 *  http://aws.amazon.com/apache2.0
 *
 * or in the "license" file accompanying this file. This file is distributed
 * on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either
 * express or implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

#include <aws/common/encoding.h>

#include <assert.h>
#include <ctype.h>

static const uint8_t *HEX_CHARS = (const uint8_t *)"0123456789abcdef";

static const uint8_t BASE64_SENTIANAL_VALUE = 0xff;
static const uint8_t BASE64_ENCODING_TABLE[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

/* in this table, 0xDD is an invalid decoded value, if you have to do byte counting for any reason, there's 16 bytes
 * per row. */
static const uint8_t BASE64_DECODING_TABLE[256] = {
    64,   0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD,
    0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD,
    0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 62,   0xDD, 0xDD, 0xDD, 63,   52,   53,   54,   55,   56,   57,   58,   59,   60,
    61,   0xDD, 0xDD, 0xDD, 255,  0xDD, 0xDD, 0xDD, 0,    1,    2,    3,    4,    5,    6,    7,    8,    9,    10,
    11,   12,   13,   14,   15,   16,   17,   18,   19,   20,   21,   22,   23,   24,   25,   0xDD, 0xDD, 0xDD, 0xDD,
    0xDD, 0xDD, 26,   27,   28,   29,   30,   31,   32,   33,   34,   35,   36,   37,   38,   39,   40,   41,   42,
    43,   44,   45,   46,   47,   48,   49,   50,   51,   0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD,
    0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD,
    0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD,
    0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD,
    0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD,
    0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD,
    0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD,
    0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD, 0xDD};

int aws_hex_compute_encoded_len(size_t to_encode_len, size_t *encoded_length) {
    assert(encoded_length);

    size_t temp = (to_encode_len << 1) + 1;

    if (AWS_UNLIKELY(temp < to_encode_len)) {
        return aws_raise_error(AWS_ERROR_OVERFLOW_DETECTED);
    }

    *encoded_length = temp;

    return AWS_OP_SUCCESS;
}

int aws_hex_encode(const struct aws_byte_buf *AWS_RESTRICT to_encode, struct aws_byte_buf *AWS_RESTRICT output) {
    assert(to_encode->buffer);
    assert(output->buffer);

    size_t encoded_len = 0;

    if (AWS_UNLIKELY(aws_hex_compute_encoded_len(to_encode->len, &encoded_len))) {
        return AWS_OP_ERR;
    }

    if (AWS_UNLIKELY(output->capacity < encoded_len)) {
        return aws_raise_error(AWS_ERROR_SHORT_BUFFER);
    }

    size_t written = 0;
    for (size_t i = 0; i < to_encode->len; ++i) {

        output->buffer[written++] = HEX_CHARS[to_encode->buffer[i] >> 4 & 0x0f];
        output->buffer[written++] = HEX_CHARS[to_encode->buffer[i] & 0x0f];
    }

    output->buffer[written] = '\0';
    output->len = encoded_len;

    return AWS_OP_SUCCESS;
}

static int s_hex_decode_char_to_int(char character, uint8_t *int_val) {
    if (character >= 'a' && character <= 'f') {
        *int_val = (uint8_t)(10 + (character - 'a'));
        return 0;
    }

    if (character >= 'A' && character <= 'F') {
        *int_val = (uint8_t)(10 + (character - 'A'));
        return 0;
    }

    if (character >= '0' && character <= '9') {
        *int_val = (uint8_t)(character - '0');
        return 0;
    }

    return AWS_OP_ERR;
}

int aws_hex_compute_decoded_len(size_t to_decode_len, size_t *decoded_len) {
    assert(decoded_len);

    size_t temp = (to_decode_len + 1);

    if (AWS_UNLIKELY(temp < to_decode_len)) {
        return aws_raise_error(AWS_ERROR_OVERFLOW_DETECTED);
    }

    *decoded_len = temp >> 1;
    return AWS_OP_SUCCESS;
}

int aws_hex_decode(const struct aws_byte_buf *AWS_RESTRICT to_decode, struct aws_byte_buf *AWS_RESTRICT output) {
    assert(to_decode->buffer);
    assert(output->buffer);

    size_t decoded_length = 0;

    if (AWS_UNLIKELY(aws_hex_compute_decoded_len(to_decode->len, &decoded_length))) {
        return aws_raise_error(AWS_ERROR_OVERFLOW_DETECTED);
    }

    if (AWS_UNLIKELY(output->capacity < decoded_length)) {
        return aws_raise_error(AWS_ERROR_SHORT_BUFFER);
    }

    size_t written = 0;
    size_t i = 0;
    uint8_t high_value = 0;
    uint8_t low_value = 0;

    /* if the buffer isn't even, prepend a 0 to the buffer. */
    if (AWS_UNLIKELY(to_decode->len & 0x01)) {
        i = 1;
        if (s_hex_decode_char_to_int(to_decode->buffer[0], &low_value)) {
            return aws_raise_error(AWS_ERROR_INVALID_HEX_STR);
        }

        output->buffer[written++] = low_value;
    }

    for (; i < to_decode->len; i += 2) {
        if (AWS_UNLIKELY(
                s_hex_decode_char_to_int(to_decode->buffer[i], &high_value) ||
                s_hex_decode_char_to_int(to_decode->buffer[i + 1], &low_value))) {
            return aws_raise_error(AWS_ERROR_INVALID_HEX_STR);
        }

        uint8_t value = high_value << 4;
        value |= low_value;
        output->buffer[written++] = value;
    }

    output->len = decoded_length;

    return AWS_OP_SUCCESS;
}

int aws_base64_compute_encoded_len(size_t to_encode_len, size_t *encoded_len) {
    assert(encoded_len);

    size_t tmp = to_encode_len + 2;

    if (AWS_UNLIKELY(tmp < to_encode_len)) {
        return aws_raise_error(AWS_ERROR_OVERFLOW_DETECTED);
    }

    tmp /= 3;
    size_t overflow_check = tmp;
    tmp = 4 * tmp + 1; /* plus one for the NULL terminator */

    if (AWS_UNLIKELY(tmp < overflow_check)) {
        return aws_raise_error(AWS_ERROR_OVERFLOW_DETECTED);
    }

    *encoded_len = tmp;

    return AWS_OP_SUCCESS;
}

int aws_base64_compute_decoded_len(const char *input, size_t len, size_t *decoded_len) {
    assert(input);
    assert(decoded_len);

    if (len == 0) {
        *decoded_len = 0;
        return AWS_OP_SUCCESS;
    }

    if (AWS_UNLIKELY(len & 0x03)) {
        return aws_raise_error(AWS_ERROR_INVALID_BASE64_STR);
    }

    size_t tmp = len * 3;

    if (AWS_UNLIKELY(tmp < len)) {
        return aws_raise_error(AWS_ERROR_OVERFLOW_DETECTED);
    }

    size_t padding = 0;

    if (len >= 2 && input[len - 1] == '=' && input[len - 2] == '=') { /*last two chars are = */
        padding = 2;
    } else if (input[len - 1] == '=') { /*last char is = */
        padding = 1;
    }

    *decoded_len = (tmp / 4 - padding);
    return AWS_OP_SUCCESS;
}

int aws_base64_encode(const struct aws_byte_buf *AWS_RESTRICT to_encode, struct aws_byte_buf *AWS_RESTRICT output) {
    assert(to_encode->buffer);
    assert(output->buffer);

    size_t encoded_length = 0;
    if (AWS_UNLIKELY(aws_base64_compute_encoded_len(to_encode->len, &encoded_length))) {
        return AWS_OP_ERR;
    }

    if (AWS_UNLIKELY(output->capacity < encoded_length)) {
        return aws_raise_error(AWS_ERROR_SHORT_BUFFER);
    }

    size_t buffer_length = to_encode->len;
    size_t block_count = (buffer_length + 2) / 3;
    size_t remainder_count = (buffer_length % 3);
    size_t str_index = 0;

    for (size_t i = 0; i < to_encode->len; i += 3) {
        uint32_t block = to_encode->buffer[i];

        block <<= 8;
        if (AWS_LIKELY(i + 1 < buffer_length)) {
            block = block | to_encode->buffer[i + 1];
        }

        block <<= 8;
        if (AWS_LIKELY(i + 2 < to_encode->len)) {
            block = block | to_encode->buffer[i + 2];
        }

        output->buffer[str_index++] = BASE64_ENCODING_TABLE[(block >> 18) & 0x3F];
        output->buffer[str_index++] = BASE64_ENCODING_TABLE[(block >> 12) & 0x3F];
        output->buffer[str_index++] = BASE64_ENCODING_TABLE[(block >> 6) & 0x3F];
        output->buffer[str_index++] = BASE64_ENCODING_TABLE[block & 0x3F];
    }

    if (remainder_count > 0) {
        output->buffer[block_count * 4 - 1] = '=';
        if (remainder_count == 1) {
            output->buffer[block_count * 4 - 2] = '=';
        }
    }

    /* it's a string add the null terminator. */
    output->buffer[encoded_length - 1] = 0;

    output->len = encoded_length;
    return AWS_OP_SUCCESS;
}

static inline int s_base64_get_decoded_value(unsigned char to_decode, uint8_t *value, int8_t allow_sentinal) {

    uint8_t decode_value = BASE64_DECODING_TABLE[(size_t)to_decode];
    if (decode_value != 0xDD && (decode_value != BASE64_SENTIANAL_VALUE || allow_sentinal)) {
        *value = decode_value;
        return AWS_OP_SUCCESS;
    }

    return AWS_OP_ERR;
}

int aws_base64_decode(const struct aws_byte_buf *AWS_RESTRICT to_decode, struct aws_byte_buf *AWS_RESTRICT output) {
    size_t decoded_length = 0;

    if (AWS_UNLIKELY(aws_base64_compute_decoded_len((char *)to_decode->buffer, to_decode->len, &decoded_length))) {
        return AWS_OP_ERR;
    }

    if (output->capacity < decoded_length) {
        return aws_raise_error(AWS_ERROR_SHORT_BUFFER);
    }

    int64_t block_count = (int)to_decode->len / 4;
    size_t string_index = 0;
    uint8_t value1 = 0, value2 = 0, value3 = 0, value4 = 0;
    int64_t buffer_index = 0;

    for (int32_t i = 0; i < block_count - 1; ++i) {
        if (AWS_UNLIKELY(
                s_base64_get_decoded_value(to_decode->buffer[string_index++], &value1, 0) ||
                s_base64_get_decoded_value(to_decode->buffer[string_index++], &value2, 0) ||
                s_base64_get_decoded_value(to_decode->buffer[string_index++], &value3, 0) ||
                s_base64_get_decoded_value(to_decode->buffer[string_index++], &value4, 0))) {
            return aws_raise_error(AWS_ERROR_INVALID_BASE64_STR);
        }

        buffer_index = i * 3;
        output->buffer[buffer_index++] = (uint8_t)((value1 << 2) | ((value2 >> 4) & 0x03));
        output->buffer[buffer_index++] = (uint8_t)(((value2 << 4) & 0xF0) | ((value3 >> 2) & 0x0F));
        output->buffer[buffer_index] = (uint8_t)((value3 & 0x03) << 6 | value4);
    }

    buffer_index = (block_count - 1) * 3;

    if (buffer_index >= 0) {
        if (s_base64_get_decoded_value(to_decode->buffer[string_index++], &value1, 0) ||
            s_base64_get_decoded_value(to_decode->buffer[string_index++], &value2, 0) ||
            s_base64_get_decoded_value(to_decode->buffer[string_index++], &value3, 1) ||
            s_base64_get_decoded_value(to_decode->buffer[string_index], &value4, 1)) {
            return aws_raise_error(AWS_ERROR_INVALID_BASE64_STR);
        }

        output->buffer[buffer_index++] = (uint8_t)((value1 << 2) | ((value2 >> 4) & 0x03));

        if (value3 != BASE64_SENTIANAL_VALUE) {
            output->buffer[buffer_index++] = (uint8_t)(((value2 << 4) & 0xF0) | ((value3 >> 2) & 0x0F));
            if (value4 != BASE64_SENTIANAL_VALUE) {
                output->buffer[buffer_index] = (uint8_t)((value3 & 0x03) << 6 | value4);
            }
        }
    }
    output->len = decoded_length;
    return AWS_OP_SUCCESS;
}