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wx-cli/decrypt_images.c

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/*
* decrypt_images.c — WeChat V2 image batch decryptor (multi-key)
*
* Decrypts all V2 encrypted .dat files in the WeChat image cache.
* Supports multiple keys via image_keys.json (CT block → AES key mapping).
*
* V2 format:
* [15B header] [AES-128-ECB ciphertext] [XOR encrypted tail]
* Header: \x07\x08V2\x08\x07 (6B) + aes_size:u32LE + xor_size:u32LE + 1B pad
* AES region: ceil(aes_size/16)*16 bytes of AES-128-ECB ciphertext
* XOR tail: xor_size bytes, each XOR'd with a single-byte key
*
* Build:
* cc -O3 -o decrypt_images decrypt_images.c -framework Security
*
* Usage:
* ./decrypt_images # auto from config + image_keys.json
* ./decrypt_images <key_hex> <image_dir> <out_dir> # single-key manual
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <dirent.h>
#include <sys/stat.h>
#include <errno.h>
#include <CommonCrypto/CommonCryptor.h>
#define MAX_PATH 4096
#define V2_MAGIC "\x07\x08V2\x08\x07"
#define V2_MAGIC_LEN 6
#define HEADER_SIZE 15
#define MAX_KEYS 4096
/* ---- Key mapping: CT block hex → AES key ---- */
typedef struct {
unsigned char ct[16]; /* CT block 0 pattern */
unsigned char key[16]; /* AES key for this pattern */
} key_map_t;
static key_map_t key_map[MAX_KEYS];
static int n_keys = 0;
/* ---- Utility ---- */
static int hex2bytes(const char *hex, unsigned char *out, int maxlen) {
int len = 0;
while (*hex && *(hex + 1) && len < maxlen) {
unsigned int b;
if (sscanf(hex, "%2x", &b) != 1) break;
out[len++] = (unsigned char)b;
hex += 2;
}
return len;
}
/* Minimal JSON string extractor (for simple unescaped string values only). */
static int json_get_string(const char *json, const char *key,
char *value, int maxlen) {
char pattern[256];
snprintf(pattern, sizeof(pattern), "\"%s\"", key);
const char *p = strstr(json, pattern);
if (!p) return 0;
p = strchr(p + strlen(pattern), '"');
if (!p) return 0;
p++;
const char *end = strchr(p, '"');
if (!end) return 0;
int len = (int)(end - p);
if (len >= maxlen) len = maxlen - 1;
memcpy(value, p, len);
value[len] = '\0';
return 1;
}
/* Load image_keys.json: { "ct_hex": "key_hex", ... } */
static int load_key_map(const char *path) {
FILE *f = fopen(path, "r");
if (!f) return 0;
fseek(f, 0, SEEK_END);
long sz = ftell(f);
if (sz <= 0) { fclose(f); return 0; }
fseek(f, 0, SEEK_SET);
char *json = malloc((size_t)sz + 1);
if (!json) { fclose(f); return 0; }
size_t rd = fread(json, 1, (size_t)sz, f);
if (rd != (size_t)sz) {
fclose(f);
free(json);
return 0;
}
json[rd] = '\0';
fclose(f);
/* Simple parser: find all "32hex": "32hex" pairs */
const char *p = json;
int warned_capacity = 0;
while ((p = strchr(p, '"')) != NULL) {
if (n_keys >= MAX_KEYS) {
if (!warned_capacity) {
fprintf(stderr, "Warning: image_keys.json exceeds MAX_KEYS=%d, extra keys ignored\n",
MAX_KEYS);
warned_capacity = 1;
}
break;
}
p++;
const char *end = strchr(p, '"');
if (!end) break;
int klen = (int)(end - p);
if (klen != 32) { p = end + 1; continue; }
char ct_hex[33];
memcpy(ct_hex, p, 32);
ct_hex[32] = '\0';
const char *colon = end + 1;
while (*colon == ' ' || *colon == '\t' || *colon == '\r' || *colon == '\n')
colon++;
if (*colon != ':') { p = end + 1; continue; }
p = colon + 1;
/* Find next quoted string (the value) */
p = strchr(p, '"');
if (!p) break;
p++;
end = strchr(p, '"');
if (!end) break;
int vlen = (int)(end - p);
if (vlen != 32) { p = end + 1; continue; }
char key_hex[33];
memcpy(key_hex, p, 32);
key_hex[32] = '\0';
p = end + 1;
if (hex2bytes(ct_hex, key_map[n_keys].ct, 16) != 16 ||
hex2bytes(key_hex, key_map[n_keys].key, 16) != 16) {
continue;
}
n_keys++;
}
free(json);
return n_keys;
}
/* Find AES key for a given CT block */
static const unsigned char *find_key_for_ct(const unsigned char *ct) {
for (int i = 0; i < n_keys; i++)
if (memcmp(key_map[i].ct, ct, 16) == 0) return key_map[i].key;
return NULL;
}
/* Create directory and parents */
static void mkdirs(const char *path) {
char tmp[MAX_PATH];
snprintf(tmp, sizeof(tmp), "%s", path);
for (char *p = tmp + 1; *p; p++) {
if (*p == '/') {
*p = '\0';
mkdir(tmp, 0755);
*p = '/';
}
}
mkdir(tmp, 0755);
}
static int has_parent_segment(const char *path) {
if (!path || !path[0]) return 1;
if (path[0] == '/' || path[0] == '\\') return 1;
const char *p = path;
while (*p) {
while (*p == '/' || *p == '\\') p++;
if (!*p) break;
const char *seg = p;
while (*p && *p != '/' && *p != '\\') p++;
if ((p - seg) == 2 && seg[0] == '.' && seg[1] == '.') return 1;
}
return 0;
}
/* Detect image type from magic bytes */
static const char *detect_ext(const unsigned char *data, size_t len) {
if (len < 4) return ".bin";
if (data[0] == 0xFF && data[1] == 0xD8) return ".jpg";
if (data[0] == 0x89 && data[1] == 0x50 &&
data[2] == 0x4E && data[3] == 0x47) return ".png";
if (data[0] == 'G' && data[1] == 'I' &&
data[2] == 'F' && data[3] == '8') return ".gif";
if (data[0] == 'R' && data[1] == 'I' &&
data[2] == 'F' && data[3] == 'F') return ".webp";
if (data[0] == 0x00 && data[1] == 0x00 &&
data[2] == 0x00 && (data[3] == 0x18 || data[3] == 0x1C ||
data[3] == 0x20 || data[3] == 0x14)) return ".mp4";
return ".bin";
}
/* Auto-detect XOR key */
static unsigned char detect_xor_key(const unsigned char *xor_data, size_t xor_size) {
if (xor_size == 0) return 0;
unsigned char candidates[] = {0x80, 0xDC, 0x00};
for (int i = 0; i < (int)(sizeof(candidates)/sizeof(candidates[0])); i++) {
/* We want a candidate that doesn't produce a leading NUL byte after XOR. */
unsigned char test = xor_data[0] ^ candidates[i];
if (test != 0x00 || candidates[i] == 0x00)
return candidates[i];
}
return 0x80;
}
/* ---- Decrypt one V2 file ---- */
static int decrypt_v2_file(const char *input_path, const char *output_dir,
const char *rel_path, const unsigned char *aes_key,
unsigned char xor_key, int auto_xor,
int *out_xor_detected) {
FILE *fin = fopen(input_path, "rb");
if (!fin) return -1;
unsigned char header[HEADER_SIZE];
if (fread(header, 1, HEADER_SIZE, fin) != HEADER_SIZE) {
fclose(fin); return -1;
}
if (memcmp(header, V2_MAGIC, V2_MAGIC_LEN) != 0) {
fclose(fin); return -2;
}
uint32_t aes_size, xor_size;
memcpy(&aes_size, header + 6, 4);
memcpy(&xor_size, header + 10, 4);
if ((uint64_t)aes_size > 100u * 1024u * 1024u ||
(uint64_t)xor_size > 100u * 1024u * 1024u) {
fclose(fin);
return -6;
}
/* PKCS7: when aes_size is already 16-byte aligned, an extra 16-byte
* padding block is present in the ciphertext */
size_t aes_ct_size = (aes_size % 16 == 0)
? (size_t)aes_size + 16
: ((size_t)aes_size + 15) / 16 * 16;
/* Get total file size and validate header claims fit within it */
long cur_pos = ftell(fin);
fseek(fin, 0, SEEK_END);
long file_size = ftell(fin);
fseek(fin, cur_pos, SEEK_SET);
if ((long)aes_ct_size + (long)xor_size > file_size - HEADER_SIZE) {
fclose(fin);
return -6; /* header claims more data than file contains */
}
unsigned char *aes_ct = malloc(aes_ct_size);
if (!aes_ct) { fclose(fin); return -1; }
size_t rd = fread(aes_ct, 1, aes_ct_size, fin);
if (rd != aes_ct_size) {
free(aes_ct);
fclose(fin);
return -8;
}
/* V2 may have unencrypted raw_data between AES and XOR sections */
long raw_data_size = file_size - HEADER_SIZE - (long)aes_ct_size - (long)xor_size;
if (raw_data_size < 0) raw_data_size = 0;
unsigned char *raw_data = NULL;
if (raw_data_size > 0) {
raw_data = malloc((size_t)raw_data_size);
if (!raw_data) { free(aes_ct); fclose(fin); return -1; }
rd = fread(raw_data, 1, (size_t)raw_data_size, fin);
if (rd != (size_t)raw_data_size) {
free(aes_ct); free(raw_data); fclose(fin); return -8;
}
}
unsigned char *xor_data = NULL;
if (xor_size > 0) {
xor_data = malloc(xor_size);
if (!xor_data) { free(aes_ct); free(raw_data); fclose(fin); return -1; }
rd = fread(xor_data, 1, xor_size, fin);
if (rd != xor_size) {
free(aes_ct); free(raw_data); free(xor_data);
fclose(fin); return -8;
}
}
fclose(fin);
/* Try multi-key lookup (image_keys.json) first, then fall back to provided key */
if (aes_ct_size >= 16) {
const unsigned char *mk = find_key_for_ct(aes_ct);
if (mk) aes_key = mk;
}
if (!aes_key) { free(aes_ct); free(raw_data); free(xor_data); return -5; }
unsigned char *aes_pt = malloc(aes_ct_size);
if (!aes_pt) { free(aes_ct); free(raw_data); free(xor_data); return -1; }
size_t moved = 0;
CCCryptorStatus st = CCCrypt(
kCCDecrypt, kCCAlgorithmAES128, kCCOptionECBMode,
aes_key, 16, NULL,
aes_ct, aes_ct_size, aes_pt, aes_ct_size, &moved);
free(aes_ct);
if (st != kCCSuccess) {
free(aes_pt); free(raw_data); free(xor_data); return -3;
}
if (auto_xor && xor_data && xor_size > 0) {
xor_key = detect_xor_key(xor_data, xor_size);
if (out_xor_detected) *out_xor_detected = xor_key;
}
if (xor_data && xor_size > 0) {
for (uint32_t i = 0; i < xor_size; i++)
xor_data[i] ^= xor_key;
}
const char *ext = detect_ext(aes_pt, aes_size);
/* Skip unrecognized formats — avoids writing garbage .bin files */
if (strcmp(ext, ".bin") == 0) {
free(aes_pt); free(raw_data); free(xor_data);
return -9; /* unrecognized image type */
}
char out_path[MAX_PATH];
char rel_noext[MAX_PATH];
snprintf(rel_noext, sizeof(rel_noext), "%s", rel_path);
char *dot = strrchr(rel_noext, '.');
if (dot) *dot = '\0';
if (has_parent_segment(rel_noext)) {
free(aes_pt); free(raw_data); free(xor_data);
return -7;
}
snprintf(out_path, sizeof(out_path), "%s/%s%s", output_dir, rel_noext, ext);
/* Skip if already decrypted */
struct stat st_out;
if (stat(out_path, &st_out) == 0 && st_out.st_size > 0) {
free(aes_pt); free(raw_data); free(xor_data);
return 1; /* already exists */
}
char parent[MAX_PATH];
snprintf(parent, sizeof(parent), "%s", out_path);
char *last_slash = strrchr(parent, '/');
if (last_slash) { *last_slash = '\0'; mkdirs(parent); }
FILE *fout = fopen(out_path, "wb");
if (!fout) { free(aes_pt); free(raw_data); free(xor_data); return -4; }
fwrite(aes_pt, 1, aes_size, fout);
if (raw_data && raw_data_size > 0) fwrite(raw_data, 1, (size_t)raw_data_size, fout);
if (xor_data && xor_size > 0) fwrite(xor_data, 1, xor_size, fout);
fclose(fout);
free(aes_pt);
free(raw_data);
free(xor_data);
return 0;
}
/* ---- Directory walking ---- */
typedef struct {
const unsigned char *fallback_key; /* single key from config.json (or NULL) */
int multi_key; /* 1 if using image_keys.json */
unsigned char xor_key;
int auto_xor;
const char *output_dir;
const char *base_dir;
int success;
int skipped;
int existed; /* already decrypted */
int no_key; /* V2 files with no matching key */
int failed;
} walk_ctx;
static void walk_dir(const char *dir, walk_ctx *ctx) {
DIR *d = opendir(dir);
if (!d) return;
struct dirent *ent;
while ((ent = readdir(d))) {
if (ent->d_name[0] == '.') continue;
char path[MAX_PATH];
snprintf(path, sizeof(path), "%s/%s", dir, ent->d_name);
struct stat st;
if (lstat(path, &st) != 0) continue;
if (S_ISLNK(st.st_mode)) continue;
if (S_ISDIR(st.st_mode)) {
walk_dir(path, ctx);
} else if (S_ISREG(st.st_mode)) {
size_t nlen = strlen(ent->d_name);
if (nlen < 5 || strcmp(ent->d_name + nlen - 4, ".dat") != 0)
continue;
const char *rel = path + strlen(ctx->base_dir);
if (*rel == '/') rel++;
int xor_detected = -1;
/* In multi-key mode, pass fallback_key — decrypt_v2_file tries
* image_keys.json lookup first, falls back to this key if provided */
const unsigned char *key = ctx->fallback_key;
int ret = decrypt_v2_file(path, ctx->output_dir, rel,
key, ctx->xor_key,
ctx->auto_xor, &xor_detected);
if (ret == 0) {
ctx->success++;
if (ctx->auto_xor && xor_detected >= 0) {
ctx->xor_key = (unsigned char)xor_detected;
ctx->auto_xor = 0;
printf(" Auto-detected XOR key: 0x%02X\n", ctx->xor_key);
}
if (ctx->success <= 5 || ctx->success % 1000 == 0) {
printf(" [%d] %s\n", ctx->success, rel);
}
} else if (ret == 1) {
ctx->existed++;
} else if (ret == -2) {
ctx->skipped++;
} else if (ret == -5) {
ctx->no_key++;
} else {
ctx->failed++;
if (ctx->failed <= 5)
printf(" FAIL(%d): %s\n", ret, rel);
}
}
}
closedir(d);
}
/* ---- Main ---- */
int main(int argc, char *argv[]) {
unsigned char aes_key[16];
char image_dir[MAX_PATH] = "";
char output_dir[MAX_PATH] = "";
char key_hex[64] = "";
int have_single_key = 0;
printf("=== WeChat V2 Image Decryptor ===\n\n");
/* Determine exe directory for config file lookup */
char exe_dir[MAX_PATH] = ".";
const char *last_slash = strrchr(argv[0], '/');
if (last_slash) {
int len = (int)(last_slash - argv[0]);
snprintf(exe_dir, sizeof(exe_dir), "%.*s", len, argv[0]);
}
if (argc >= 4) {
/* Manual single-key mode */
strncpy(key_hex, argv[1], sizeof(key_hex) - 1);
key_hex[sizeof(key_hex) - 1] = '\0';
strncpy(image_dir, argv[2], sizeof(image_dir) - 1);
image_dir[sizeof(image_dir) - 1] = '\0';
strncpy(output_dir, argv[3], sizeof(output_dir) - 1);
output_dir[sizeof(output_dir) - 1] = '\0';
have_single_key = (key_hex[0] != '\0');
} else {
/* Load image_keys.json first (multi-key) */
char keys_path[MAX_PATH];
snprintf(keys_path, sizeof(keys_path), "%s/image_keys.json", exe_dir);
int loaded = load_key_map(keys_path);
if (loaded > 0)
printf("Loaded %d key mappings from %s\n", loaded, keys_path);
/* Read config.json for paths (and fallback single key) */
char cfg_path[MAX_PATH];
snprintf(cfg_path, sizeof(cfg_path), "%s/config.json", exe_dir);
FILE *cf = fopen(cfg_path, "r");
if (!cf) {
fprintf(stderr, "ERROR: Cannot open %s\n", cfg_path);
return 1;
}
fseek(cf, 0, SEEK_END);
long sz = ftell(cf);
if (sz <= 0) { fclose(cf); return 1; }
fseek(cf, 0, SEEK_SET);
char *json = malloc((size_t)sz + 1);
if (!json) { fclose(cf); return 1; }
size_t rd = fread(json, 1, (size_t)sz, cf);
if (rd != (size_t)sz) {
free(json);
fclose(cf);
return 1;
}
json[sz] = '\0';
fclose(cf);
if (json_get_string(json, "image_key", key_hex, sizeof(key_hex)) &&
key_hex[0] != '\0')
have_single_key = 1;
else
have_single_key = 0;
char db_dir[MAX_PATH] = "";
json_get_string(json, "db_dir", db_dir, sizeof(db_dir));
char out_rel[MAX_PATH] = "decrypted_images";
json_get_string(json, "decrypted_images_dir", out_rel, sizeof(out_rel));
if (out_rel[0] == '/')
strncpy(output_dir, out_rel, sizeof(output_dir) - 1);
else
snprintf(output_dir, sizeof(output_dir), "%s/%s", exe_dir, out_rel);
output_dir[sizeof(output_dir) - 1] = '\0';
if (db_dir[0]) {
char *s = strrchr(db_dir, '/');
if (!s) s = strrchr(db_dir, '\\');
if (s) {
int plen = (int)(s - db_dir);
snprintf(image_dir, sizeof(image_dir),
"%.*s/msg", plen, db_dir);
}
}
free(json);
}
/* Parse single key if available (used as fallback or sole key) */
if (have_single_key && key_hex[0]) {
if (hex2bytes(key_hex, aes_key, 16) == 16) {
/* If no image_keys.json loaded, add single key to key_map
* by discovering its CT block at runtime */
} else {
have_single_key = 0;
}
}
if (n_keys == 0 && !have_single_key) {
fprintf(stderr, "ERROR: No keys available.\n");
fprintf(stderr, "Run find_image_key first, or set image_key in config.json\n");
return 1;
}
/* Auto-detect: scan ~/Library/Containers/com.tencent.xinWeChat */
if (image_dir[0] == '\0') {
const char *home = getenv("HOME");
if (!home) home = "/Users";
char base[MAX_PATH];
snprintf(base, sizeof(base),
"%s/Library/Containers/com.tencent.xinWeChat/Data/Documents/xwechat_files",
home);
DIR *d = opendir(base);
if (d) {
struct dirent *ent;
while ((ent = readdir(d))) {
if (ent->d_name[0] == '.') continue;
char candidate[MAX_PATH];
snprintf(candidate, sizeof(candidate), "%s/%s/msg", base, ent->d_name);
struct stat st2;
if (stat(candidate, &st2) == 0 && S_ISDIR(st2.st_mode)) {
strncpy(image_dir, candidate, sizeof(image_dir) - 1);
printf("Auto-detected image directory:\n %s\n\n", image_dir);
break;
}
}
closedir(d);
}
}
if (image_dir[0] == '\0') {
fprintf(stderr, "ERROR: Cannot determine image directory.\n");
fprintf(stderr, "Tried: command line, config.json, auto-detect.\n");
fprintf(stderr, "Set db_dir in config.json or pass image_dir as argument.\n");
return 1;
}
printf("Mode: %s\n", n_keys > 0 ? "multi-key" : "single-key");
if (n_keys > 0) printf("Keys: %d pattern→key mappings\n", n_keys);
if (have_single_key) printf("Fallback: %s\n", key_hex);
printf("Image dir: %s\n", image_dir);
printf("Output: %s\n\n", output_dir);
mkdirs(output_dir);
walk_ctx ctx = {
.fallback_key = have_single_key ? aes_key : NULL,
.multi_key = (n_keys > 0),
.xor_key = 0,
.auto_xor = 1,
.output_dir = output_dir,
.base_dir = image_dir,
.success = 0,
.skipped = 0,
.existed = 0,
.no_key = 0,
.failed = 0,
};
walk_dir(image_dir, &ctx);
printf("\n==================================================\n");
printf("Results:\n");
printf(" Decrypted: %d\n", ctx.success);
printf(" Existed: %d (already decrypted, skipped)\n", ctx.existed);
printf(" No key: %d (run find_image_key to discover more keys)\n", ctx.no_key);
printf(" Skipped: %d (non-V2)\n", ctx.skipped);
printf(" Failed: %d\n", ctx.failed);
printf("Output: %s\n", output_dir);
printf("==================================================\n");
return (ctx.success > 0) ? 0 : 1;
}
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