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Use memmem for searching byte patterns

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topjohnwu
2021-02-28 14:36:48 -08:00
parent 0d42f937dd
commit 55fdee4d65
3 changed files with 80 additions and 71 deletions
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51
native/jni/magiskboot/hexpatch.cpp
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@@ -1,43 +1,44 @@
#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) {
using namespace std;
static void hex2byte(const char *hex, uint8_t *buf) {
char high, low;
for (int i = 0, length = strlen((char *) hex); i < length; i += 2) {
for (int i = 0, length = strlen(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);
buf[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;
}
uint8_t *buf;
size_t sz;
mmap_rw(image, buf, sz);
run_finally f([=]{ munmap(buf, sz); });
vector<uint8_t> pattern(strlen(from) / 2);
vector<uint8_t> patch(strlen(to) / 2);
hex2byte(from, pattern.data());
hex2byte(to, patch.data());
uint8_t * const end = buf + sz;
for (uint8_t *curr = buf; curr < end; curr += pattern.size()) {
curr = static_cast<uint8_t*>(memmem(curr, end - curr, pattern.data(), pattern.size()));
if (curr == nullptr)
return patched;
fprintf(stderr, "Patch @ %08X [%s] -> [%s]\n", curr - buf, from, to);
memset(curr, 0, pattern.size());
memcpy(curr, patch.data(), patch.size());
patched = 0;
}
munmap(file, filesize);
free(pattern);
free(patch);
return patched;
}