android-encrypted-archiver/.planning/phases/12-user-key-input/12-01-PLAN.md

---
phase: 12-user-key-input
plan: 01
type: execute
wave: 1
depends_on: []
files_modified:
  - Cargo.toml
  - src/cli.rs
  - src/key.rs
  - src/archive.rs
  - src/main.rs
  - tests/round_trip.rs
autonomous: true
requirements:
  - KEY-01
  - KEY-02
  - KEY-07

must_haves:
  truths:
    - "User must provide exactly one of --key, --key-file, or --password to pack/unpack"
    - "Running `pack --key <64-char-hex>` produces a valid archive using the hex-decoded 32-byte key"
    - "Running `pack --key-file <path>` reads exactly 32 bytes from file and uses them as the AES key"
    - "Running `unpack --key <hex>` with the same key used for pack extracts byte-identical files"
    - "Inspect works without a key argument (reads only metadata, not encrypted content)"
    - "Invalid hex (wrong length, non-hex chars) produces a clear error message"
    - "Key file that doesn't exist or has wrong size produces a clear error message"
  artifacts:
    - path: "src/cli.rs"
      provides: "CLI arg group for --key, --key-file, --password"
      contains: "key_group"
    - path: "src/key.rs"
      provides: "Key resolution from hex, file, and password"
      exports: ["resolve_key", "KeySource"]
    - path: "src/archive.rs"
      provides: "pack/unpack/inspect accept key parameter"
      contains: "key: &[u8; 32]"
    - path: "src/main.rs"
      provides: "Wiring: CLI -> key resolution -> archive functions"
  key_links:
    - from: "src/main.rs"
      to: "src/key.rs"
      via: "resolve_key() call"
      pattern: "resolve_key"
    - from: "src/main.rs"
      to: "src/archive.rs"
      via: "passing resolved key to pack/unpack/inspect"
      pattern: "pack.*&key|unpack.*&key"
    - from: "src/cli.rs"
      to: "src/main.rs"
      via: "KeySource enum extracted from parsed CLI args"
      pattern: "KeySource"
---

<objective>
Refactor the archive tool to accept user-specified encryption keys via CLI arguments (`--key` for hex, `--key-file` for raw file), threading the key through pack/unpack/inspect instead of using the hardcoded constant. This plan does NOT implement `--password` (Argon2 KDF) -- that is Plan 02.

Purpose: Remove the hardcoded key dependency so the archive tool is parameterized by user input, which is the foundation for all three key input methods.
Output: Working `--key` and `--key-file` support with all existing tests passing via explicit key args.
</objective>

<execution_context>
@/home/nick/.claude/get-shit-done/workflows/execute-plan.md
@/home/nick/.claude/get-shit-done/templates/summary.md
</execution_context>

<context>
@.planning/ROADMAP.md
@.planning/STATE.md
@.planning/REQUIREMENTS.md

<interfaces>
<!-- Key types and contracts the executor needs. Extracted from codebase. -->

From src/key.rs (CURRENT -- will be replaced):
```rust
pub const KEY: [u8; 32] = [ ... ];
```

From src/cli.rs (CURRENT -- will be extended):
```rust
#[derive(Parser)]
pub struct Cli {
    #[command(subcommand)]
    pub command: Commands,
}

#[derive(Subcommand)]
pub enum Commands {
    Pack { files: Vec<PathBuf>, output: PathBuf, no_compress: Vec<String> },
    Unpack { archive: PathBuf, output_dir: PathBuf },
    Inspect { archive: PathBuf },
}
```

From src/archive.rs (CURRENT signatures -- will add key param):
```rust
pub fn pack(files: &[PathBuf], output: &Path, no_compress: &[String]) -> anyhow::Result<()>
pub fn unpack(archive: &Path, output_dir: &Path) -> anyhow::Result<()>
pub fn inspect(archive: &Path) -> anyhow::Result<()>
```

From src/crypto.rs (unchanged -- already takes key as param):
```rust
pub fn encrypt_data(plaintext: &[u8], key: &[u8; 32], iv: &[u8; 16]) -> Vec<u8>
pub fn decrypt_data(ciphertext: &[u8], key: &[u8; 32], iv: &[u8; 16]) -> anyhow::Result<Vec<u8>>
pub fn compute_hmac(key: &[u8; 32], iv: &[u8; 16], ciphertext: &[u8]) -> [u8; 32]
pub fn verify_hmac(key: &[u8; 32], iv: &[u8; 16], ciphertext: &[u8], expected: &[u8; 32]) -> bool
```

Hardcoded KEY hex value (for test migration):
`7a35c1d94fe82b6a910df358bc74a61e428fd063e5179b2cfa8406cd3e79b550`
</interfaces>
</context>

<tasks>

<task type="auto">
  <name>Task 1: Add CLI key args and refactor key.rs + archive.rs signatures</name>
  <files>
    Cargo.toml
    src/cli.rs
    src/key.rs
    src/archive.rs
    src/main.rs
  </files>
  <action>
**IMPORTANT: Before using any library, verify current API via Context7.**

1. **Cargo.toml**: Add `hex = "0.4"` dependency (for hex decoding of --key arg). Verify version: `cargo search hex --limit 1`.

2. **src/cli.rs**: Add key source arguments as a clap arg group on the top-level `Cli` struct (NOT on each subcommand -- the key applies globally to all commands):

```rust
use clap::{Parser, Subcommand, Args};

#[derive(Args, Clone)]
#[group(required = false, multiple = false)]
pub struct KeyArgs {
    /// Raw 32-byte key as 64-character hex string
    #[arg(long, value_name = "HEX")]
    pub key: Option<String>,

    /// Path to file containing raw 32-byte key
    #[arg(long, value_name = "PATH")]
    pub key_file: Option<PathBuf>,

    /// Password for key derivation (interactive prompt if no value given)
    #[arg(long, value_name = "PASSWORD")]
    pub password: Option<Option<String>>,
}

#[derive(Parser)]
#[command(name = "encrypted_archive")]
#[command(about = "Custom encrypted archive tool")]
pub struct Cli {
    #[command(flatten)]
    pub key_args: KeyArgs,

    #[command(subcommand)]
    pub command: Commands,
}
```

Note: `password` uses `Option<Option<String>>` so that `--password` with no value gives `Some(None)` (interactive prompt) and `--password mypass` gives `Some(Some("mypass"))`. The group is `required = false` because inspect does not require a key (it only reads TOC metadata). pack and unpack will enforce key presence in main.rs.

3. **src/key.rs**: Replace the hardcoded KEY constant with key resolution functions. Keep the old KEY constant available as `LEGACY_KEY` for golden tests only:

```rust
use std::path::Path;

/// Legacy hardcoded key (used only in golden test vectors).
/// Do NOT use in production code.
#[cfg(test)]
pub const LEGACY_KEY: [u8; 32] = [
    0x7A, 0x35, 0xC1, 0xD9, 0x4F, 0xE8, 0x2B, 0x6A,
    0x91, 0x0D, 0xF3, 0x58, 0xBC, 0x74, 0xA6, 0x1E,
    0x42, 0x8F, 0xD0, 0x63, 0xE5, 0x17, 0x9B, 0x2C,
    0xFA, 0x84, 0x06, 0xCD, 0x3E, 0x79, 0xB5, 0x50,
];

/// Resolved key source for the archive operation.
pub enum KeySource {
    Hex(String),
    File(std::path::PathBuf),
    Password(Option<String>),  // None = interactive prompt
}

/// Resolve a KeySource into a 32-byte AES-256 key.
///
/// For Hex: decode 64-char hex string into [u8; 32].
/// For File: read exactly 32 bytes from file.
/// For Password: placeholder that returns error (implemented in Plan 02).
pub fn resolve_key(source: &KeySource) -> anyhow::Result<[u8; 32]> {
    match source {
        KeySource::Hex(hex_str) => {
            let bytes = hex::decode(hex_str)
                .map_err(|e| anyhow::anyhow!("Invalid hex key: {}", e))?;
            anyhow::ensure!(
                bytes.len() == 32,
                "Key must be exactly 32 bytes (64 hex chars), got {} bytes ({} hex chars)",
                bytes.len(),
                hex_str.len()
            );
            let mut key = [0u8; 32];
            key.copy_from_slice(&bytes);
            Ok(key)
        }
        KeySource::File(path) => {
            let bytes = std::fs::read(path)
                .map_err(|e| anyhow::anyhow!("Failed to read key file '{}': {}", path.display(), e))?;
            anyhow::ensure!(
                bytes.len() == 32,
                "Key file must be exactly 32 bytes, got {} bytes: {}",
                bytes.len(),
                path.display()
            );
            let mut key = [0u8; 32];
            key.copy_from_slice(&bytes);
            Ok(key)
        }
        KeySource::Password(_) => {
            anyhow::bail!("Password-based key derivation not yet implemented (coming in Plan 02)")
        }
    }
}
```

4. **src/archive.rs**: Refactor all three public functions to accept `key: &[u8; 32]` parameter:
   - `pub fn pack(files: &[PathBuf], output: &Path, no_compress: &[String], key: &[u8; 32])`
   - `pub fn unpack(archive: &Path, output_dir: &Path, key: &[u8; 32])`
   - `pub fn inspect(archive: &Path, key: Option<&[u8; 32]>)` -- key is optional for inspect
   - Remove `use crate::key::KEY;` import
   - Change `read_archive_metadata` to accept `key: &[u8; 32]` parameter
   - Update `process_file` to accept `key: &[u8; 32]` parameter
   - Replace all `&KEY` references with the passed-in `key` parameter
   - For `inspect`: when key is `None`, try to read header+TOC but skip TOC decryption if encrypted (show "TOC encrypted, provide key to inspect entries"); when key is `Some(k)`, use it for full inspection.

   Actually, inspect DOES need the key for encrypted TOC decryption. So inspect should also require a key. But the phase goal says "All three methods produce a 32-byte AES-256 key passed through pack/unpack/inspect." So inspect also requires a key. Change inspect signature to `pub fn inspect(archive: &Path, key: &[u8; 32])`.

5. **src/main.rs**: Wire CLI args to key resolution and archive functions:

```rust
use encrypted_archive::key::{KeySource, resolve_key};

fn main() -> anyhow::Result<()> {
    let cli = Cli::parse();

    // Determine key source from CLI args
    let key_source = if let Some(hex) = &cli.key_args.key {
        KeySource::Hex(hex.clone())
    } else if let Some(path) = &cli.key_args.key_file {
        KeySource::File(path.clone())
    } else if let Some(password_opt) = &cli.key_args.password {
        KeySource::Password(password_opt.clone())
    } else {
        anyhow::bail!("One of --key, --key-file, or --password is required")
    };

    let key = resolve_key(&key_source)?;

    match cli.command {
        Commands::Pack { files, output, no_compress } => {
            archive::pack(&files, &output, &no_compress, &key)?;
        }
        Commands::Unpack { archive: arch, output_dir } => {
            archive::unpack(&arch, &output_dir, &key)?;
        }
        Commands::Inspect { archive: arch } => {
            archive::inspect(&arch, &key)?;
        }
    }

    Ok(())
}
```

6. **Verify build compiles**: Run `cargo build` to confirm all wiring is correct before moving to tests.
  </action>
  <verify>
    <automated>cd /home/nick/Projects/Rust/encrypted_archive && cargo build 2>&1</automated>
  </verify>
  <done>
    - `cargo build` succeeds with no errors
    - archive.rs no longer imports KEY from key.rs
    - All three archive functions accept a key parameter
    - CLI accepts --key, --key-file, --password as mutually exclusive args
    - main.rs resolves key source and threads it to archive functions
  </done>
</task>

<task type="auto">
  <name>Task 2: Update tests and verify round-trip with explicit key</name>
  <files>
    tests/round_trip.rs
    tests/golden.rs
    src/crypto.rs
  </files>
  <action>
1. **tests/golden.rs**: Replace `use encrypted_archive::key::KEY;` with:
   ```rust
   // Use the legacy hardcoded key for golden test vectors
   const KEY: [u8; 32] = [
       0x7A, 0x35, 0xC1, 0xD9, 0x4F, 0xE8, 0x2B, 0x6A,
       0x91, 0x0D, 0xF3, 0x58, 0xBC, 0x74, 0xA6, 0x1E,
       0x42, 0x8F, 0xD0, 0x63, 0xE5, 0x17, 0x9B, 0x2C,
       0xFA, 0x84, 0x06, 0xCD, 0x3E, 0x79, 0xB5, 0x50,
   ];
   ```
   The golden tests call crypto functions directly with the KEY; they do not use CLI, so they stay unchanged except for the import.

2. **src/crypto.rs** tests: Replace `use crate::key::KEY;` with a local constant:
   ```rust
   #[cfg(test)]
   mod tests {
       use super::*;
       use hex_literal::hex;

       /// Test key matching legacy hardcoded value
       const TEST_KEY: [u8; 32] = [
           0x7A, 0x35, 0xC1, 0xD9, 0x4F, 0xE8, 0x2B, 0x6A,
           0x91, 0x0D, 0xF3, 0x58, 0xBC, 0x74, 0xA6, 0x1E,
           0x42, 0x8F, 0xD0, 0x63, 0xE5, 0x17, 0x9B, 0x2C,
           0xFA, 0x84, 0x06, 0xCD, 0x3E, 0x79, 0xB5, 0x50,
       ];
       // Replace all &KEY with &TEST_KEY in existing tests
   ```

3. **tests/round_trip.rs**: All CLI tests now need `--key <hex>` argument. Define a constant at the top:
   ```rust
   /// Hex-encoded 32-byte key for test archives (matches legacy hardcoded key)
   const TEST_KEY_HEX: &str = "7a35c1d94fe82b6a910df358bc74a61e428fd063e5179b2cfa8406cd3e79b550";
   ```

   Then update the `cmd()` helper or each test to pass `--key` before the subcommand:
   ```rust
   fn cmd_with_key() -> Command {
       let mut c = Command::new(assert_cmd::cargo::cargo_bin!("encrypted_archive"));
       c.args(["--key", TEST_KEY_HEX]);
       c
   }
   ```

   Replace all `cmd()` calls with `cmd_with_key()` in existing tests. This ensures all pack/unpack/inspect invocations pass the key.

   **IMPORTANT**: The `--key` arg is on the top-level CLI struct, so it goes BEFORE the subcommand: `encrypted_archive --key <hex> pack ...`

4. **Add new tests** in tests/round_trip.rs:
   - `test_key_file_roundtrip`: Create a 32-byte key file, pack with `--key-file`, unpack with `--key-file`, verify byte-identical.
   - `test_rejects_wrong_key`: Pack with one key, try unpack with different key, expect HMAC failure.
   - `test_rejects_bad_hex`: Run with `--key abcd` (too short), expect error.
   - `test_rejects_missing_key`: Run `pack file -o out` without any key arg, expect error.

5. Run full test suite: `cargo test` -- all tests must pass.
  </action>
  <verify>
    <automated>cd /home/nick/Projects/Rust/encrypted_archive && cargo test 2>&1</automated>
  </verify>
  <done>
    - All existing golden tests pass with local KEY constant
    - All existing round_trip tests pass with --key hex argument
    - New test: key file round-trip works
    - New test: wrong key causes HMAC failure
    - New test: bad hex rejected with clear error
    - New test: missing key arg rejected with clear error
    - `cargo test` reports 0 failures
  </done>
</task>

</tasks>

<verification>
1. `cargo build` succeeds
2. `cargo test` all pass (0 failures)
3. Manual smoke test: `cargo run -- --key 7a35c1d94fe82b6a910df358bc74a61e428fd063e5179b2cfa8406cd3e79b550 pack README.md -o /tmp/test.aea && cargo run -- --key 7a35c1d94fe82b6a910df358bc74a61e428fd063e5179b2cfa8406cd3e79b550 unpack /tmp/test.aea -o /tmp/test_out`
4. Inspect works: `cargo run -- --key 7a35c1d94fe82b6a910df358bc74a61e428fd063e5179b2cfa8406cd3e79b550 inspect /tmp/test.aea`
5. Missing key rejected: `cargo run -- pack README.md -o /tmp/test.aea` should fail
6. Bad hex rejected: `cargo run -- --key abcd pack README.md -o /tmp/test.aea` should fail
</verification>

<success_criteria>
- Hardcoded KEY constant is no longer used in production code (only in test constants)
- `--key <HEX>` and `--key-file <PATH>` work for pack/unpack/inspect
- `--password` is accepted by CLI but returns "not yet implemented" error
- All existing tests pass with explicit key arguments
- New tests verify key-file, wrong-key rejection, bad-hex rejection, missing-key rejection
</success_criteria>

<output>
After completion, create `.planning/phases/12-user-key-input/12-01-SUMMARY.md`
</output>