fuzz_regression_helpers.h

Go to the documentation of this file.

#pragma once
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
 
static unsigned char * b64_decode(const char * data, size_t * out_len) {
    // A standard lookup table for Base64 decoding. -1 represents an invalid character.
    // Size padded to 256 to prevent out-of-bounds access on invalid input.
    static const int b64_decode_table[] = {-1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           62,
                                           -1,
                                           -1,
                                           -1,
                                           63,
                                           52,
                                           53,
                                           54,
                                           55,
                                           56,
                                           57,
                                           58,
                                           59,
                                           60,
                                           61,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           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,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           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,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           // Padding to 256 elements
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1,
                                           -1};
 
    size_t in_len = strlen(data);
    if (in_len % 4 != 0)
        return NULL;  // Base64 strings must have a length that is a multiple of 4.
 
    // Calculate the output length, accounting for padding characters.
    *out_len = in_len / 4 * 3;
    if (data[in_len - 1] == '=')
        (*out_len)--;
    if (data[in_len - 2] == '=')
        (*out_len)--;
 
    unsigned char * out = (unsigned char *)malloc(*out_len);
    if (out == NULL)
        return NULL;
 
    // Process the input string in 4-character chunks.
    for (size_t i = 0, j = 0; i < in_len;) {
        int sextet_a = b64_decode_table[(unsigned char)data[i++]];
        int sextet_b = b64_decode_table[(unsigned char)data[i++]];
        int sextet_c = b64_decode_table[(unsigned char)data[i++]];
        int sextet_d = b64_decode_table[(unsigned char)data[i++]];
 
        // Validate the characters and handle padding.
        if (sextet_a == -1 || sextet_b == -1 || (data[i - 2] != '=' && sextet_c == -1) ||
            (data[i - 1] != '=' && sextet_d == -1)) {
            free(out);
            return NULL;
        }
 
        // Combine the four 6-bit sextets into a 24-bit triple.
        unsigned int triple = (sextet_a << 3 * 6) + (sextet_b << 2 * 6) + (sextet_c << 1 * 6) + (sextet_d << 0 * 6);
 
        // Extract the three 8-bit bytes from the triple.
        if (j < *out_len)
            out[j++] = (triple >> 2 * 8) & 0xFF;
        if (j < *out_len)
            out[j++] = (triple >> 1 * 8) & 0xFF;
        if (j < *out_len)
            out[j++] = (triple >> 0 * 8) & 0xFF;
    }
 
    return out;
}