feat(stdlib): Add ML-DSA-44/65/87 signature support

Cargo.toml

@@ -56,6 +56,7 @@ base32ct = { version = "0.3.1", features = ["alloc"] }
 base64ct = { version = "1.8.3", features = ["alloc"] }
 rand = "0.10.1"
 openssl = { version = "0.10.78" }
+openssl-sys = { version = "0.9.109" }
 yubikey = "0.8"
 tempfile = "3.27.0"
 clap = { version = "4.6.1", features = ["derive"] }

README.md

@@ -139,6 +139,7 @@ Both bundle the `rite-ls` language server. For other LSP-aware editors, run `rit
     - [ ] Teardown act on abort or failure
 - [x] **Cryptographic backends**
   - [x] OpenSSL: RSA, ECDSA-P256, signing, wrapping, PKI
+    - [x] Post-quantum: ML-DSA-44/65/87 signatures and certificates (needs OpenSSL 3.5+)
     - [ ] Post-quantum: ML-KEM key encapsulation
   - [x] Hardware backends
     - [x] YubiKey PIV: key generation, signing, certificate read, on-device attestation

crates/rite-openssl/Cargo.toml

@@ -18,6 +18,11 @@ vendored = ["openssl/vendored"]
 [dependencies]
 rite-sdk = { workspace = true }
 openssl = { workspace = true }
+# Referenced by build.rs, not by the source. `openssl-sys` carries the
+# `links = "openssl"` key, and Cargo only hands `DEP_OPENSSL_*` metadata to
+# build scripts of *direct* dependents. Removing this as an "unused" dependency
+# silently drops ML-DSA support from every build.
+openssl-sys = { workspace = true }
 base16ct = { workspace = true }
 zeroize = { workspace = true }
 

crates/rite-openssl/build.rs

@@ -0,0 +1,33 @@
+//! Detects the linked OpenSSL version so ML-DSA support is compiled in only
+//! where the provider exists.
+//!
+//! ML-DSA landed in OpenSSL 3.5, and the `openssl` crate gates the
+//! corresponding bindings behind its own `ossl350` cfg. That cfg is private to
+//! that crate, so this build script re-derives it from the version number
+//! `openssl-sys` publishes through its `links` metadata.
+
+fn main() {
+    println!("cargo::rustc-check-cfg=cfg(ossl350)");
+
+    // LibreSSL and BoringSSL report an OpenSSL version number for source
+    // compatibility but do not ship the ML-DSA provider. Each signals itself
+    // through a separate variable, so bail out rather than trusting the
+    // version number alone.
+    if std::env::var_os("DEP_OPENSSL_LIBRESSL_VERSION_NUMBER").is_some()
+        || std::env::var_os("DEP_OPENSSL_BORINGSSL").is_some()
+    {
+        return;
+    }
+
+    let Ok(raw) = std::env::var("DEP_OPENSSL_VERSION_NUMBER") else {
+        return;
+    };
+    let Ok(version) = u64::from_str_radix(&raw, 16) else {
+        return;
+    };
+
+    // OPENSSL_VERSION_NUMBER is 0xMNN00PPSL, so 3.5.0 is 0x30500000.
+    if version >= 0x3050_0000 {
+        println!("cargo::rustc-cfg=ossl350");
+    }
+}