Magisk/native/jni/magiskboot/pattern.cpp

#include <malloc.h>
#include <string.h>

#include <utils.hpp>

#include "magiskboot.hpp"

#define MATCH(p) else if (strncmp(s + skip, p, sizeof(p) - 1) == 0) skip += (sizeof(p) - 1)

static int check_verity_pattern(const char *s) {
    int skip = s[0] == ',';

    if (0) {}
    MATCH("verifyatboot");
    MATCH("verify");
    MATCH("avb_keys");
    MATCH("avb");
    MATCH("support_scfs");
    MATCH("fsverity");
    else return -1;

    if (s[skip] == '=') {
        while (s[skip] != '\0' && s[skip] != ' ' && s[skip] != '\n' && s[skip] != ',')
            ++skip;
    }
    return skip;
}

#undef MATCH
#define MATCH(p) else if (strncmp(s, p, sizeof(p) - 1) == 0) return (sizeof(p) - 1)

static int check_encryption_pattern(const char *s) {
    if (0) {}
    MATCH("forceencrypt");
    MATCH("forcefdeorfbe");
    MATCH("fileencryption");
    else return -1;
}

static uint32_t remove_pattern(void *buf, uint32_t size, int(*pattern_skip)(const char *)) {
    auto src = static_cast<char *>(buf);
    int orig_sz = size;
    int write = 0;
    for (int read = 0; read < orig_sz;) {
        if (int skip = pattern_skip(src + read); skip > 0) {
            fprintf(stderr, "Remove pattern [%.*s]\n", skip, src + read);
            size -= skip;
            read += skip;
        } else {
            src[write++] = src[read++];
        }
    }
    memset(src + write, 0, orig_sz - write);
    return size;
}

uint32_t patch_verity(void *buf, uint32_t size) {
    return remove_pattern(buf, size, check_verity_pattern);
}

uint32_t patch_encryption(void *buf, uint32_t size) {
    return remove_pattern(buf, size, check_encryption_pattern);
}