NikitolProject/android-encrypted-archiver
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feat(06-01): implement full obfuscation pipeline in archive.rs

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- pack(): generate decoy padding (64-4096 random bytes per file)
- pack(): encrypt serialized TOC with AES-256-CBC using random toc_iv
- pack(): XOR header buffer before writing (8-byte cyclic key)
- pack(): set flags bits 1-3 (0x0E) for all obfuscation features
- unpack(): XOR bootstrapping via read_header_auto()
- unpack(): decrypt TOC when flags bit 1 is set
- inspect(): full de-obfuscation via shared read_archive_metadata()
- Factor out read_archive_metadata() helper for unpack/inspect reuse
- All existing tests pass (unit, golden, round-trip integration)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
NikitolProject
2026-02-25 02:19:48 +03:00
parent 8ac25125ab
commit b6fa51d9fd
1 changed files with 130 additions and 52 deletions
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182
src/archive.rs
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@@ -2,6 +2,8 @@ use std::fs;
use std::io::{Read, Seek, SeekFrom, Write};
use std::path::{Path, PathBuf};
use rand::Rng;
use crate::compression;
use crate::crypto;
use crate::format::{self, Header, TocEntry, HEADER_SIZE};
@@ -18,16 +20,46 @@ struct ProcessedFile {
sha256: [u8; 32],
compression_flag: u8,
ciphertext: Vec<u8>,
padding_after: u16,
padding_bytes: Vec<u8>,
}
/// Read and de-obfuscate archive header and TOC entries.
///
/// Handles XOR header bootstrapping (FORMAT.md Section 10 steps 1-3)
/// and TOC decryption (Section 10 step 4) automatically.
/// Used by both unpack() and inspect().
fn read_archive_metadata(file: &mut fs::File) -> anyhow::Result<(Header, Vec<TocEntry>)> {
// Step 1-3: Read header with XOR bootstrapping
let header = format::read_header_auto(file)?;
// Step 4: Read TOC (possibly encrypted)
file.seek(SeekFrom::Start(header.toc_offset as u64))?;
let mut toc_raw = vec![0u8; header.toc_size as usize];
file.read_exact(&mut toc_raw)?;
let entries = if header.flags & 0x02 != 0 {
// TOC is encrypted: decrypt with toc_iv, then parse
let toc_plaintext = crypto::decrypt_data(&toc_raw, &KEY, &header.toc_iv)?;
format::read_toc_from_buf(&toc_plaintext, header.file_count)?
} else {
// TOC is plaintext: parse directly
format::read_toc_from_buf(&toc_raw, header.file_count)?
};
Ok((header, entries))
}
/// Pack files into an encrypted archive.
///
/// Two-pass algorithm:
/// Pass 1: Read, hash, compress, encrypt each file.
/// Pass 2: Compute offsets, write header + TOC + data blocks.
/// Two-pass algorithm with full obfuscation:
/// Pass 1: Read, hash, compress, encrypt each file; generate decoy padding.
/// Pass 2: Encrypt TOC, compute offsets, XOR header, write archive.
pub fn pack(files: &[PathBuf], output: &Path, no_compress: &[String]) -> anyhow::Result<()> {
anyhow::ensure!(!files.is_empty(), "No input files specified");
let mut rng = rand::rng();
// --- Pass 1: Process all files ---
let mut processed: Vec<ProcessedFile> = Vec::with_capacity(files.len());
@@ -75,6 +107,11 @@ pub fn pack(files: &[PathBuf], output: &Path, no_compress: &[String]) -> anyhow:
// Step 5: Compute HMAC over IV || ciphertext
let hmac = crypto::compute_hmac(&KEY, &iv, &ciphertext);
// Step 6: Generate decoy padding (FORMAT.md Section 9.3)
let padding_after: u16 = rng.random_range(64..=4096);
let mut padding_bytes = vec![0u8; padding_after as usize];
rand::Fill::fill(&mut padding_bytes[..], &mut rng);
processed.push(ProcessedFile {
name,
original_size,
@@ -85,51 +122,62 @@ pub fn pack(files: &[PathBuf], output: &Path, no_compress: &[String]) -> anyhow:
sha256,
compression_flag,
ciphertext,
padding_after,
padding_bytes,
});
}
// --- Pass 2: Compute offsets and write archive ---
// Build TOC entries (without data_offset yet) to compute TOC size
let toc_size: u32 = processed
// Determine flags byte: bit 0 if any file is compressed, bits 1-3 for obfuscation
let any_compressed = processed.iter().any(|pf| pf.compression_flag == 1);
let mut flags: u8 = if any_compressed { 0x01 } else { 0x00 };
// Enable all three obfuscation features
flags |= 0x02; // bit 1: TOC encrypted
flags |= 0x04; // bit 2: XOR header
flags |= 0x08; // bit 3: decoy padding
// Build TOC entries (with placeholder data_offset=0, will be set after toc_size known)
let toc_entries: Vec<TocEntry> = processed
.iter()
.map(|pf| 101 + pf.name.len() as u32)
.sum();
.map(|pf| TocEntry {
name: pf.name.clone(),
original_size: pf.original_size,
compressed_size: pf.compressed_size,
encrypted_size: pf.encrypted_size,
data_offset: 0, // placeholder
iv: pf.iv,
hmac: pf.hmac,
sha256: pf.sha256,
compression_flag: pf.compression_flag,
padding_after: pf.padding_after,
})
.collect();
// Serialize TOC to get plaintext size, then encrypt to get final toc_size
let toc_plaintext = format::serialize_toc(&toc_entries)?;
// Generate TOC IV and encrypt
let toc_iv = crypto::generate_iv();
let encrypted_toc = crypto::encrypt_data(&toc_plaintext, &KEY, &toc_iv);
let encrypted_toc_size = encrypted_toc.len() as u32;
let toc_offset = HEADER_SIZE;
// Compute data offsets
// Compute data offsets (accounting for encrypted TOC size and padding)
let data_block_start = toc_offset + encrypted_toc_size;
let mut data_offsets: Vec<u32> = Vec::with_capacity(processed.len());
let mut current_offset = toc_offset + toc_size;
let mut current_offset = data_block_start;
for pf in &processed {
data_offsets.push(current_offset);
current_offset += pf.encrypted_size;
current_offset += pf.encrypted_size + pf.padding_after as u32;
}
// Determine flags byte: bit 0 if any file is compressed
let any_compressed = processed.iter().any(|pf| pf.compression_flag == 1);
let flags: u8 = if any_compressed { 0x01 } else { 0x00 };
// Create header
let header = Header {
version: format::VERSION,
flags,
file_count: processed.len() as u16,
toc_offset,
toc_size,
toc_iv: [0u8; 16], // TOC not encrypted in v1 Phase 2
reserved: [0u8; 8],
};
// Open output file
let mut out_file = fs::File::create(output)?;
// Write header
format::write_header(&mut out_file, &header)?;
// Write TOC entries
for (i, pf) in processed.iter().enumerate() {
let entry = TocEntry {
// Now re-serialize TOC with correct data_offsets
let final_toc_entries: Vec<TocEntry> = processed
.iter()
.enumerate()
.map(|(i, pf)| TocEntry {
name: pf.name.clone(),
original_size: pf.original_size,
compressed_size: pf.compressed_size,
@@ -139,14 +187,48 @@ pub fn pack(files: &[PathBuf], output: &Path, no_compress: &[String]) -> anyhow:
hmac: pf.hmac,
sha256: pf.sha256,
compression_flag: pf.compression_flag,
padding_after: 0, // No decoy padding in Phase 2
};
format::write_toc_entry(&mut out_file, &entry)?;
}
padding_after: pf.padding_after,
})
.collect();
// Write data blocks
let final_toc_plaintext = format::serialize_toc(&final_toc_entries)?;
let final_encrypted_toc = crypto::encrypt_data(&final_toc_plaintext, &KEY, &toc_iv);
let final_encrypted_toc_size = final_encrypted_toc.len() as u32;
// Sanity check: encrypted TOC size should not change (same plaintext length)
assert_eq!(
encrypted_toc_size, final_encrypted_toc_size,
"TOC encrypted size changed unexpectedly"
);
// Create header
let header = Header {
version: format::VERSION,
flags,
file_count: processed.len() as u16,
toc_offset,
toc_size: final_encrypted_toc_size,
toc_iv,
reserved: [0u8; 8],
};
// Serialize header to buffer and XOR
let mut header_buf = format::write_header_to_buf(&header);
format::xor_header_buf(&mut header_buf);
// Open output file
let mut out_file = fs::File::create(output)?;
// Write XOR'd header
out_file.write_all(&header_buf)?;
// Write encrypted TOC
out_file.write_all(&final_encrypted_toc)?;
// Write data blocks with interleaved decoy padding
for pf in &processed {
out_file.write_all(&pf.ciphertext)?;
out_file.write_all(&pf.padding_bytes)?;
}
let total_bytes = current_offset;
@@ -163,14 +245,12 @@ pub fn pack(files: &[PathBuf], output: &Path, no_compress: &[String]) -> anyhow:
/// Inspect archive metadata without decryption.
///
/// Reads and displays the header and all TOC entries.
/// Handles XOR header de-obfuscation and TOC decryption.
pub fn inspect(archive: &Path) -> anyhow::Result<()> {
let mut file = fs::File::open(archive)?;
// Read header
let header = format::read_header(&mut file)?;
// Read TOC entries
let entries = format::read_toc(&mut file, header.file_count)?;
// Read header and TOC with full de-obfuscation
let (header, entries) = read_archive_metadata(&mut file)?;
// Print header info
let filename = archive
@@ -201,6 +281,7 @@ pub fn inspect(archive: &Path) -> anyhow::Result<()> {
println!(" Encrypted: {} bytes", entry.encrypted_size);
println!(" Offset: {}", entry.data_offset);
println!(" Compression: {}", compression_str);
println!(" Padding after: {} bytes", entry.padding_after);
println!(
" IV: {}",
entry.iv.iter().map(|b| format!("{:02x}", b)).collect::<String>()
@@ -226,17 +307,14 @@ pub fn inspect(archive: &Path) -> anyhow::Result<()> {
/// Unpack an encrypted archive, extracting all files with HMAC and SHA-256 verification.
///
/// Follows FORMAT.md Section 10 decode order:
/// 1. Read header (validates magic, version, flags)
/// 2. Read TOC entries
/// 3. For each file: verify HMAC, decrypt, decompress, verify SHA-256, write
/// 1. Read header with XOR bootstrapping
/// 2. Read and decrypt TOC entries
/// 3. For each file: seek to data_offset, verify HMAC, decrypt, decompress, verify SHA-256, write
pub fn unpack(archive: &Path, output_dir: &Path) -> anyhow::Result<()> {
let mut file = fs::File::open(archive)?;
// Read header
let header = format::read_header(&mut file)?;
// Read TOC entries
let entries = format::read_toc(&mut file, header.file_count)?;
// Read header and TOC with full de-obfuscation
let (_header, entries) = read_archive_metadata(&mut file)?;
// Create output directory
fs::create_dir_all(output_dir)?;