Magisk/native/jni/magiskboot/hexpatch.cpp

#include <stdlib.h>
#include <ctype.h>
#include <string.h>
#include <sys/mman.h>

#include <utils.hpp>

#include "magiskboot.hpp"

static void hex2byte(uint8_t *hex, uint8_t *str) {
    char high, low;
    for (int i = 0, length = strlen((char *) hex); i < length; i += 2) {
        high = toupper(hex[i]) - '0';
        low = toupper(hex[i + 1]) - '0';
        str[i / 2] = ((high > 9 ? high - 7 : high) << 4) + (low > 9 ? low - 7 : low);
    }
}

int hexpatch(const char *image, const char *from, const char *to) {
    int patternsize = strlen(from) / 2, patchsize = strlen(to) / 2;
    int patched = 1;
    size_t filesize;
    uint8_t *file, *pattern, *patch;
    mmap_rw(image, file, filesize);
    pattern = (uint8_t *) xmalloc(patternsize);
    patch = (uint8_t *) xmalloc(patchsize);
    hex2byte((uint8_t *) from, pattern);
    hex2byte((uint8_t *) to, patch);
    for (size_t i = 0; filesize > 0 && i < filesize - patternsize; ++i) {
        if (memcmp(file + i, pattern, patternsize) == 0) {
            fprintf(stderr, "Patch @ %08X [%s]->[%s]\n", (unsigned) i, from, to);
            memset(file + i, 0, patternsize);
            memcpy(file + i, patch, patchsize);
            i += patternsize - 1;
            patched = 0;
        }
    }
    munmap(file, filesize);
    free(pattern);
    free(patch);

    return patched;
}