ddidderr
898697016a
Replace the homegrown `region::lock` + `Zeroizing` wrappers with thin
adapters over `secrets::SecretBox` and `secrets::SecretVec`. The
upstream crate already provides everything the local types were doing
by hand (mlock, zero-on-drop) and adds protections we didn't have:
guard pages around the allocation and `mprotect`-based access control
(`PROT_NONE` at rest, `PROT_READ` during a borrow, `PROT_READ|WRITE`
during a mut borrow). Net result is a security upgrade, not just a
dependency swap.
Why a local adapter still exists
--------------------------------
`secrets::SecretVec` is fixed-length — no `push`. The tty passphrase
reader needs to append bytes one at a time without ever reallocating
(a panicking partial read must not leave stale plaintext on the heap),
so `SecretVec` keeps a separate logical `len` over a fixed protected
allocation of `MAX_PASSPHRASE_LEN` bytes. Bytes past `len` stay
zero-padding and are never exposed through `with_slice`.
API shape: closure-scoped borrows
---------------------------------
The previous `as_slice` / `as_array` returned long-lived `&[u8]`
references, which would have kept the upstream pages in `PROT_READ`
for the full lifetime of the borrow. The new API uses
`with_array(|s| ...)`, `with_mut_array(|s| ...)`, `with_slice(|s| ...)`
so the unprotected window is exactly the closure body. This is uglier
at call sites (notably the nested closures in `derive_key`) but it's
the right tradeoff — minimizing the unprotected window is the whole
point of using the crate.
AEAD key copy footnote
----------------------
`XChaCha20Poly1305::new` copies the key into its own (unprotected)
state, which then lives in the `aead` binding for the entire
encrypt/decrypt loop. This is unchanged from before — the cipher
state was never protected — but it's now called out explicitly with
a comment at both call sites noting that `chacha20poly1305` zeroizes
that internal copy on drop. Future readers shouldn't have to
rediscover this by reading upstream source.
`from_vec` zeroing
------------------
`SecretVec::from_vec(v: Vec<u8>)` is used on the env-var path. It
calls `secrets::SecretVec::from(&mut [u8])`, which (verified against
secrets-1.3.0: `Box::from` -> `transfer` -> `memtransfer`) copies the
bytes into protected storage and zeroes the source slice. The
original Vec's allocation is then released through the normal
allocator — the bytes inside it are zero, but the heap block itself
isn't specially handled. The doc comment on `from_vec` reflects this
precisely. As before, the env-var path also leaves a copy in the
process `environ` table, which is a known accepted leak.
Cargo.toml
----------
Use `protected-secrets = { package = "secrets", version = "1.3" }`
with default features. The `secrets` crate has no pure-Rust backend
at v1.3 — disabling default features only switches *how* libsodium
is linked (bundled `libsodium-sys` vs. the crate's own bindings to a
system libsodium), and can break builds where the chosen path isn't
set up. Defaults are correct here. The `region` dependency is
dropped.
Test plan
---------
- `cargo build` clean.
- `cargo test` — 2 unit + 18 integration tests pass, including
`roundtrip_passphrase_argon2id` which exercises the full
passphrase -> argon2id -> AEAD key path through the new wrappers.
- `cargo clippy` (and `--tests`, `--benches`) clean.
- `cargo +nightly fmt` applied.
37 lines
750 B
TOML
37 lines
750 B
TOML
[package]
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authors = ["ddidderr <ddidderr@paul.network>"]
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edition = "2024"
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name = "fcry"
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version = "0.10.0"
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[dependencies]
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argon2 = "0.5"
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chacha20poly1305 = "0.10"
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clap = {version = "4", features = ["derive"]}
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getrandom = {version = "0.3"}
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protected-secrets = {package = "secrets", version = "1.3"}
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zeroize = {version = "1", features = ["derive"]}
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[target.'cfg(unix)'.dependencies]
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libc = "0.2"
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rlimit = "0.10"
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[target.'cfg(windows)'.dependencies]
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windows-sys = {version = "0.59", features = [
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"Win32_System_Console",
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"Win32_Foundation",
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"Win32_Storage_FileSystem",
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"Win32_Security",
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]}
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[dev-dependencies]
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assert_cmd = "2"
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tempfile = "3"
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[profile.release]
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lto = false
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debug = false
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strip = true
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panic = "unwind"
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codegen-units = 1
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