decode.c

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#include <ctype.h>
#include <stdlib.h>
#include <string.h>
 
#include "decode.h"
#include "log.h"
 
#ifdef LIBTMJ_ZSTD
 
uint8_t* tmj_zstd_decompress(const uint8_t* data, size_t data_size, size_t* decompressed_size) {
    logmsg(TMJ_LOG_DEBUG, "Decode (zstd): Decompressing buffer of size %zu", data_size);
 
    if (data == NULL) {
        logmsg(TMJ_LOG_ERR, "Decode (zstd): Cannot decompress NULL buffer");
 
        return NULL;
    }
 
    size_t ret_size = ZSTD_getFrameContentSize(data, data_size);
 
    if (ret_size == ZSTD_CONTENTSIZE_ERROR) {
        logmsg(TMJ_LOG_ERR, "Decode (zstd): Unable to decompress non-zstd buffer");
 
        return NULL;
    }
 
    if (ret_size == ZSTD_CONTENTSIZE_UNKNOWN) {
        logmsg(TMJ_LOG_ERR, "Decode (zstd): Unable to determine uncompressed size of compressed data");
 
        return NULL;
    }
 
    void* ret = malloc(ret_size);
 
    if (ret == NULL) {
        logmsg(TMJ_LOG_ERR, "Decode (zstd): Unable to allocate buffer for decompressed data, the system is out of memory");
 
        return NULL;
    }
 
    size_t dsize = ZSTD_decompress(ret, ret_size, data, data_size);
 
    logmsg(TMJ_LOG_DEBUG, "Decode (zstd): Decompressed byte total: %zu", dsize);
 
    if (ZSTD_isError(dsize)) {
        logmsg(TMJ_LOG_ERR, "Decode (zstd): Decompression error: %s", ZSTD_getErrorName(dsize));
 
        free(ret);
 
        return NULL;
    }
 
    *decompressed_size = ret_size;
 
    return ret;
}
 
#endif
 
#ifdef LIBTMJ_ZLIB
 
uint8_t* tmj_zlib_decompress(const uint8_t* data, size_t data_size, size_t* decompressed_size) {
    logmsg(TMJ_LOG_DEBUG, "Decode (zlib): Decompressing buffer of size %zu", data_size);
 
    if (data == NULL) {
        logmsg(TMJ_LOG_ERR, "Decode (zlib): Cannot decompress NULL buffer");
 
        return NULL;
    }
 
    const size_t INFLATE_BLOCK_SIZE = 262144;
 
    uint8_t* out = malloc(INFLATE_BLOCK_SIZE);
 
    if (out == NULL) {
        logmsg(TMJ_LOG_ERR, "Decode (zlib): Unable to allocate buffer for decompressed data, the system is out of memory");
 
        return NULL;
    }
 
    z_stream stream = {0};
 
    stream.zalloc = Z_NULL;
    stream.zfree = Z_NULL;
    stream.opaque = Z_NULL;
 
    stream.avail_in = data_size;
    stream.avail_out = INFLATE_BLOCK_SIZE;
 
    stream.next_in = data; // NOLINT(clang-diagnostic-incompatible-pointer-types-discards-qualifiers)
    stream.next_out = out;
 
    // 15 + 32 for zlib and gzip decoding with automatic header detection, according to the manual
    int ret = inflateInit2(&stream, 15 + 32);
 
    switch (ret) {
        case Z_OK:
            logmsg(TMJ_LOG_DEBUG, "Decode (zlib): inflate initialization OK");
            break;
 
        case Z_MEM_ERROR:
            logmsg(TMJ_LOG_ERR, "Decode (zlib): Unable to initialize inflate, the system is out of memory");
 
            goto fail_zlib;
 
        case Z_VERSION_ERROR:
            logmsg(TMJ_LOG_ERR, "Decode (zlib): Unable to initialize inflate, incompatible zlib library version");
 
            goto fail_zlib;
 
        case Z_STREAM_ERROR:
            logmsg(TMJ_LOG_ERR,
                    "Decode (zlib): Unable to initialize inflate, invalid parameter(s) to inflate initialization "
                    "routine");
 
            goto fail_zlib;
 
        default:
            goto fail_zlib;
    }
 
    size_t realloc_scale = 2;
 
    // Iteratively inflate, growing the output buffer by 1 block each time we run out of space
    //
    // Note from the manual: "If inflate returns Z_OK and with zero avail_out,
    // it must be called again after making room in the output buffer because
    // there might be more output pending."
    // Unsure if this is actually necessary, or if we can rely on Z_BUF_ERROR to tell us when to resize
    int stat = inflate(&stream, Z_NO_FLUSH);
 
    while (stat != Z_STREAM_END) {
        switch (stat) {
            case Z_BUF_ERROR:
                // If we hit Z_BUF_ERROR with buffer space left, something's fucked
                if (stream.avail_out != 0) {
                    logmsg(TMJ_LOG_ERR, "Decode (zlib): No progress possible");
 
                    return NULL;
                }
 
                logmsg(TMJ_LOG_DEBUG, "Decode (zlib): Z_BUF_ERROR");
            case Z_OK:
                logmsg(TMJ_LOG_DEBUG, "Decode (zlib): inflate OK");
 
                out = realloc(out, INFLATE_BLOCK_SIZE * realloc_scale);
                if (out == NULL) {
                    logmsg(TMJ_LOG_ERR, "Decode (zlib): Unable to grow inflate output buffer, the system is out memory");
 
                    return NULL;
                }
 
                stream.avail_out = INFLATE_BLOCK_SIZE;
 
                stream.next_out = out + stream.total_out;
 
                realloc_scale++;
 
                break;
 
            case Z_NEED_DICT:
                logmsg(TMJ_LOG_ERR, "Decode (zlib): Unable to complete inflate, preset dictionary required");
 
                goto fail_zlib;
 
            case Z_DATA_ERROR:
                logmsg(TMJ_LOG_ERR, "Decode (zlib): Unable to complete inflate, input data appears corrupted");
 
                goto fail_zlib;
 
            case Z_STREAM_ERROR:
                logmsg(TMJ_LOG_ERR, "Decode (zlib): Unable to complete inflate, stream structure inconsistent");
 
                goto fail_zlib;
 
            case Z_MEM_ERROR:
                logmsg(TMJ_LOG_ERR, "Decode (zlib): Unable to complete inflate, the system is out of memory");
 
                goto fail_zlib;
 
            default:
                goto fail_zlib;
        }
 
        stat = inflate(&stream, Z_NO_FLUSH);
    }
 
    logmsg(TMJ_LOG_DEBUG, "Decode (zlib): Completed inflate, %zd bytes written to output buffer", stream.total_out);
 
    if (inflateEnd(&stream) != Z_OK) {
        logmsg(TMJ_LOG_ERR, "Decode (zlib): Completed inflate, but could not clean up; stream state was inconsistent");
 
        goto fail_zlib;
    }
 
    *decompressed_size = stream.total_out;
 
    return out;
 
fail_zlib:
    free(out);
 
    if (stream.msg) {
        logmsg(TMJ_LOG_ERR, "Decode (zlib): zlib error: '%s'", stream.msg);
    }
 
    return NULL;
}
 
#endif
 
// Thanks to John's article for explaining Base64: https://nachtimwald.com/2017/11/18/base64-encode-and-decode-in-c/
 
// clang-format off
const char b64_encode_table[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
const unsigned char b64_decode_table[] = { 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 62, 255, 255, 255, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 255,
255, 255, 255, 255, 255, 255, 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, 255, 255, 255, 255, 255, 255, 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, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
255, 255, 255, 255, 255, 255, 255, 255, 255, };
// clang-format on
 
// Not used, but included here for reference, to explain how the decode table was generated
// void b64_generate_decode_table(){
//    memset(&b64_decode_table, -1, 256);
//
//    for(size_t i = 0; i < 256; i++){
//        b64_decode_table[b64_encode_table[i]] = i;
//    }
//}
 
size_t b64_decode_size(const char* data) {
    if (data == NULL) {
        return 0;
    }
 
    size_t len = strlen(data);
 
    size_t ret = len / 4 * 3;
 
    // Check to see if the last 2 characters are padding bytes
    if (data[len - 1] == '=') {
        ret--;
 
        if (data[len - 2] == '=') {
            ret--;
        }
    }
 
    return ret;
}
 
bool b64_is_valid_char(char c) {
    if (isalnum(c)) {
        return true;
    }
 
    if (c == '+' || c == '/' || c == '=') {
        return true;
    }
 
    return false;
}
 
// Don't need this yet, so it'll stay unimplemented for now
char* tmj_b64_encode(uint8_t* data) {
    return NULL;
}
 
uint8_t* tmj_b64_decode(const char* data, size_t* decoded_size) {
    if (data == NULL) {
        logmsg(TMJ_LOG_ERR, "Decode (b64): Unable to decode null input");
 
        return NULL;
    }
 
    size_t len = strlen(data);
 
    if (len % 4 != 0) {
        logmsg(TMJ_LOG_ERR, "Decode (b64): Invalid Base64 string, input length is not a multiple of 4");
 
        return NULL;
    }
 
    size_t dSize = b64_decode_size(data);
    uint8_t* out = malloc(dSize);
 
    if (out == NULL) {
        logmsg(TMJ_LOG_ERR, "Decode (b64): Unable to allocate output buffer, the system is out of memory");
 
        return NULL;
    }
 
    // Validate the input
    for (size_t i = 0; i < len; i++) {
        if (!b64_is_valid_char(data[i])) {
            logmsg(TMJ_LOG_ERR, "Decode (b64): Invalid Base64 character, '%c'", data[i]);
 
            free(out);
 
            return NULL;
        }
    }
 
    for (size_t i = 0, j = 0; i < len; i += 4, j += 3) {
        // Pack decoded 6-bit values into an integer
        uint32_t p = b64_decode_table[data[i]];
        p = (p << 6) | b64_decode_table[data[i + 1]];
        p = data[i + 2] == '=' ? p << 6 : (p << 6) | b64_decode_table[data[i + 2]];
        p = data[i + 3] == '=' ? p << 6 : (p << 6) | b64_decode_table[data[i + 3]];
 
        // Reinterpret into 8-bit bytes
        out[j] = (p >> 16) & 0xFF;
        if (data[i + 2] != '=') {
            out[j + 1] = (p >> 8) & 0xFF;
        }
        if (data[i + 3] != '=') {
            out[j + 2] = p & 0xFF;
        }
    }
 
    *decoded_size = dSize;
 
    return out;
}