Add files via upload

__init__.py

@@ -0,0 +1,10 @@
+from .engine import (
+    encrypt_path,
+    decrypt_container,
+    list_container,
+    verify_container,
+    change_password,
+    SecureArchiveError,
+    InvalidContainerError,
+    WrongPasswordError,
+)

crypto.py

@@ -0,0 +1,36 @@
+import os
+from dataclasses import dataclass
+from typing import Tuple
+
+from cryptography.hazmat.primitives.kdf.pbkdf2 import PBKDF2HMAC
+from cryptography.hazmat.primitives import hashes
+from cryptography.hazmat.primitives.ciphers.aead import AESGCM
+from cryptography.hazmat.backends import default_backend
+
+@dataclass
+class KdfParams:
+    iterations: int
+    salt: bytes
+
+def derive_key(password: str, params: KdfParams, length: int = 32) -> bytes:
+    kdf = PBKDF2HMAC(
+        algorithm=hashes.SHA512(),
+        length=length,
+        salt=params.salt,
+        iterations=params.iterations,
+        backend=default_backend(),
+    )
+    return kdf.derive(password.encode("utf-8"))
+
+def generate_salt(size: int = 16) -> bytes:
+    return os.urandom(size)
+
+def encrypt_aes_gcm(key: bytes, plaintext: bytes, aad: bytes = b"") -> Tuple[bytes, bytes]:
+    nonce = os.urandom(12)
+    aesgcm = AESGCM(key)
+    ciphertext = aesgcm.encrypt(nonce, plaintext, aad)
+    return nonce, ciphertext
+
+def decrypt_aes_gcm(key: bytes, nonce: bytes, ciphertext: bytes, aad: bytes = b"") -> bytes:
+    aesgcm = AESGCM(key)
+    return aesgcm.decrypt(nonce, ciphertext, aad)

engine.py

@@ -0,0 +1,288 @@
+import json
+from dataclasses import dataclass
+from pathlib import Path
+from typing import Dict, Any, List, Tuple
+
+from cryptography.exceptions import InvalidTag
+
+from .crypto import (
+    KdfParams,
+    derive_key,
+    generate_salt,
+    encrypt_aes_gcm,
+    decrypt_aes_gcm,
+)
+from .fsutil import collect_entries, FileEntry
+
+MAGIC = b"SECARC01"
+VERSION = 1
+PAYLOAD_SEPARATOR = b"\n---PAYLOAD---\n"
+
+class SecureArchiveError(Exception):
+    """Base exception for all SecureArchive-related errors."""
+    pass
+
+class InvalidContainerError(SecureArchiveError):
+    """Raised when the container is corrupted, invalid or unreadable."""
+    pass
+
+class WrongPasswordError(SecureArchiveError):
+    """Raised when AES-GCM decryption fails due to an incorrect password."""
+    pass
+
+@dataclass
+class ContainerHeader:
+    version: int
+    salt: bytes
+    iterations: int
+    nonce: bytes
+
+
+def _build_header_bytes(header: ContainerHeader) -> bytes:
+    salt_len = len(header.salt)
+    nonce_len = len(header.nonce)
+    data = bytearray()
+    data.extend(MAGIC)
+    data.append(header.version & 0xFF)
+    data.append(salt_len & 0xFF)
+    data.extend(header.salt)
+    data.extend(header.iterations.to_bytes(4, "big"))
+    data.append(nonce_len & 0xFF)
+    data.extend(header.nonce)
+    return bytes(data)
+
+
+def _parse_header_bytes(data: bytes) -> Tuple[ContainerHeader, bytes]:
+    if len(data) < 8 + 1 + 1 + 4 + 1:
+        raise InvalidContainerError("Header too short")
+
+    offset = 0
+    magic = data[offset:offset + 8]
+    offset += 8
+    if magic != MAGIC:
+        raise InvalidContainerError("Magic mismatch")
+
+    version = data[offset]
+    offset += 1
+    if version != VERSION:
+        raise InvalidContainerError("Unsupported version")
+
+    salt_len = data[offset]
+    offset += 1
+    if len(data) < offset + salt_len + 4 + 1:
+        raise InvalidContainerError("Header corrupt")
+    salt = data[offset:offset + salt_len]
+    offset += salt_len
+
+    iterations = int.from_bytes(data[offset:offset + 4], "big")
+    offset += 4
+
+    nonce_len = data[offset]
+    offset += 1
+
+    if len(data) < offset + nonce_len:
+        raise InvalidContainerError("Header corrupt (nonce)")
+    nonce = data[offset:offset + nonce_len]
+    offset += nonce_len
+
+    header = ContainerHeader(
+        version=version,
+        salt=salt,
+        iterations=iterations,
+        nonce=nonce,
+    )
+    remaining = data[offset:]
+    return header, remaining
+
+
+def encrypt_path(
+    input_path: str,
+    container_path: str,
+    password: str,
+    iterations: int = 300_000,
+    overwrite: bool = False,
+) -> None:
+    src = Path(input_path)
+    if not src.exists():
+        raise FileNotFoundError(input_path)
+
+    dst = Path(container_path)
+    if dst.exists() and not overwrite:
+        raise FileExistsError(container_path)
+
+    entries: List[FileEntry] = collect_entries(src)
+    if not entries:
+        raise SecureArchiveError("Input path contains no files.")
+
+    salt = generate_salt(16)
+    kdf_params = KdfParams(iterations=iterations, salt=salt)
+    key = derive_key(password, kdf_params)
+
+    manifest: Dict[str, Any] = {
+        "version": VERSION,
+        "cipher": "AES-256-GCM",
+        "kdf": {
+            "type": "PBKDF2-SHA512",
+            "iterations": iterations,
+            "salt_hex": salt.hex(),
+        },
+        "root": str(src.resolve()),
+        "entries": [],
+    }
+
+    data_chunks = bytearray()
+    current_offset = 0
+
+    for e in entries:
+        with open(e.abs_path, "rb") as f:
+            content = f.read()
+        start = current_offset
+        data_chunks.extend(content)
+        length = len(content)
+        current_offset += length
+
+        manifest["entries"].append(
+            {
+                "path": e.rel_path,
+                "size": e.size,
+                "mtime": e.mtime,
+                "offset": start,
+                "length": length,
+            }
+        )
+
+    manifest_bytes = json.dumps(manifest, ensure_ascii=False).encode("utf-8")
+    payload = manifest_bytes + PAYLOAD_SEPARATOR + bytes(data_chunks)
+
+    nonce, ciphertext = encrypt_aes_gcm(key, payload, aad=MAGIC)
+
+    header = ContainerHeader(
+        version=VERSION,
+        salt=salt,
+        iterations=iterations,
+        nonce=nonce,
+    )
+    header_bytes = _build_header_bytes(header)
+
+    with open(dst, "wb") as out:
+        out.write(header_bytes)
+        out.write(ciphertext)
+
+
+def _load_and_decrypt(container_path: str, password: str) -> Tuple[Dict[str, Any], bytes, ContainerHeader]:
+    p = Path(container_path)
+    if not p.exists() or not p.is_file():
+        raise FileNotFoundError(container_path)
+
+    with open(p, "rb") as f:
+        file_data = f.read()
+
+    header, ciphertext = _parse_header_bytes(file_data)
+
+    kdf_params = KdfParams(iterations=header.iterations, salt=header.salt)
+    key = derive_key(password, kdf_params)
+
+    try:
+        plaintext = decrypt_aes_gcm(key, header.nonce, ciphertext, aad=MAGIC)
+    except InvalidTag as ex:
+        raise WrongPasswordError("Decryption failed") from ex
+
+    try:
+        manifest_part, data_part = plaintext.split(PAYLOAD_SEPARATOR, 1)
+    except ValueError as ex:
+        raise InvalidContainerError("Payload separator missing") from ex
+
+    try:
+        manifest = json.loads(manifest_part.decode("utf-8"))
+    except json.JSONDecodeError as ex:
+        raise InvalidContainerError("Manifest JSON invalid") from ex
+
+    return manifest, data_part, header
+
+
+def decrypt_container(container_path: str, output_path: str, password: str) -> None:
+    manifest, data_part, _header = _load_and_decrypt(container_path, password)
+
+    out_root = Path(output_path)
+    out_root.mkdir(parents=True, exist_ok=True)
+
+    for entry in manifest.get("entries", []):
+        rel_path = entry["path"]
+        offset = entry["offset"]
+        length = entry["length"]
+        chunk = data_part[offset:offset + length]
+
+        target_path = out_root / rel_path
+        target_path.parent.mkdir(parents=True, exist_ok=True)
+        with open(target_path, "wb") as f:
+            f.write(chunk)
+
+
+def list_container(container_path: str, password: str) -> List[Dict[str, Any]]:
+    manifest, _data_part, _header = _load_and_decrypt(container_path, password)
+    return manifest.get("entries", [])
+
+
+def verify_container(container_path: str, password: str) -> bool:
+    try:
+        manifest, data_part, _header = _load_and_decrypt(container_path, password)
+    except WrongPasswordError:
+        return False
+    except SecureArchiveError:
+        return False
+
+    entries = manifest.get("entries", [])
+    max_offset = 0
+    for e in entries:
+        offset = e["offset"]
+        length = e["length"]
+        if offset < 0 or length < 0:
+            return False
+        end = offset + length
+        if end > max_offset:
+            max_offset = end
+
+    if max_offset > len(data_part):
+        return False
+
+    return True
+
+
+def change_password(
+    container_path: str,
+    old_password: str,
+    new_password: str,
+    iterations: int | None = None,
+) -> None:
+    manifest, data_part, old_header = _load_and_decrypt(container_path, old_password)
+
+    if iterations is None:
+        iterations = old_header.iterations
+
+    new_salt = generate_salt(16)
+    kdf_params = KdfParams(iterations=iterations, salt=new_salt)
+    key = derive_key(new_password, kdf_params)
+
+    manifest["kdf"] = {
+        "type": "PBKDF2-SHA512",
+        "iterations": iterations,
+        "salt_hex": new_salt.hex(),
+    }
+
+    manifest_bytes = json.dumps(manifest, ensure_ascii=False).encode("utf-8")
+    payload = manifest_bytes + PAYLOAD_SEPARATOR + data_part
+
+    nonce, ciphertext = encrypt_aes_gcm(key, payload, aad=MAGIC)
+
+    new_header = ContainerHeader(
+        version=VERSION,
+        salt=new_salt,
+        iterations=iterations,
+        nonce=nonce,
+    )
+    header_bytes = _build_header_bytes(new_header)
+
+    p = Path(container_path)
+    with open(p, "wb") as out:
+        out.write(header_bytes)
+        out.write(ciphertext)

fsutil.py

@@ -0,0 +1,42 @@
+from pathlib import Path
+from dataclasses import dataclass
+from typing import List
+
+@dataclass
+class FileEntry:
+    rel_path: str
+    abs_path: Path
+    size: int
+    mtime: float
+
+def collect_entries(root: Path) -> List[FileEntry]:
+    root = root.resolve()
+    entries: List[FileEntry] = []
+
+    if not root.exists():
+        return entries
+
+    if root.is_file():
+        stat = root.stat()
+        entries.append(
+            FileEntry(
+                rel_path=root.name,
+                abs_path=root,
+                size=stat.st_size,
+                mtime=stat.st_mtime,
+            )
+        )
+        return entries
+
+    for p in root.rglob("*"):
+        if p.is_file():
+            stat = p.stat()
+            entries.append(
+                FileEntry(
+                    rel_path=str(p.relative_to(root)),
+                    abs_path=p,
+                    size=stat.st_size,
+                    mtime=stat.st_mtime,
+                )
+            )
+    return entries