rust-openssl · alex · May 3, 2026 · May 2, 2026 · May 2, 2026 · May 2, 2026
diff --git a/openssl/src/pkey_ctx.rs b/openssl/src/pkey_ctx.rs
@@ -959,6 +959,22 @@ impl<T> PkeyCtxRef<T> {
         }
         Ok(NonceType(nonce_type))
     }
+
+    /// Sets the context string for an ML-DSA signing or verification
+    /// operation, as defined in FIPS 204 §5.
+    ///
+    /// Requires OpenSSL 3.5.0 or newer.
+    #[cfg(ossl350)]
+    #[corresponds(EVP_PKEY_CTX_set_params)]
+    pub fn set_context_string(&mut self, context: &[u8]) -> Result<(), ErrorStack> {
+        let mut builder = crate::ossl_param::OsslParamBuilder::new()?;
+        builder.add_octet_string(c"context-string", context)?;
+        let params = builder.to_param()?;
+        unsafe {
+            cvt(ffi::EVP_PKEY_CTX_set_params(self.as_ptr(), params.as_ptr()))?;
+        }
+        Ok(())
+    }
 }
 
 #[cfg(test)]
@@ -970,7 +986,11 @@ mod test {
     use crate::ec::{EcGroup, EcKey};
     use crate::hash::{hash, MessageDigest};
     use crate::md::Md;
+    #[cfg(ossl350)]
+    use crate::md_ctx::MdCtx;
     use crate::nid::Nid;
+    #[cfg(ossl350)]
+    use crate::pkey::KeyType;
     use crate::pkey::PKey;
     use crate::rsa::Rsa;
     use crate::sign::Verifier;
@@ -1368,4 +1388,38 @@ mxJ7imIrEg9nIQ==
         assert_eq!(output, expected_output);
         assert!(ErrorStack::get().errors().is_empty());
     }
+
+    #[test]
+    #[cfg(ossl350)]
+    fn set_context_string_mldsa() {
+        // ML-DSA-65 KAT vector 0 from
+        // https://github.com/post-quantum-cryptography/KAT/blob/main/MLDSA/kat_MLDSA_65_det_pure.rsp
+        let xi = hex::decode("f696484048ec21f96cf50a56d0759c448f3779752f0383d37449690694cf7a68")
+            .unwrap();
+        let msg = hex::decode("6dbbc4375136df3b07f7c70e639e223e").unwrap();
+        let ctx = hex::decode("480c658c0cb3e040bde084345cef0df7").unwrap();
+        let expected_sig = hex::decode("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").unwrap();
+
+        let key = PKey::private_key_from_seed(None, KeyType::ML_DSA_65, None, &xi).unwrap();
+
+        // Verify the KAT signature against the matching context string.
+        let mut md_ctx = MdCtx::new().unwrap();
+        let pkey_ctx = md_ctx.digest_verify_init(None, &key).unwrap();
+        pkey_ctx.set_context_string(&ctx).unwrap();
+        assert!(md_ctx.digest_verify(&msg, &expected_sig).unwrap());
+
+        // Sign and verify roundtrip with the same context string.
+        let mut md_ctx = MdCtx::new().unwrap();
+        let pkey_ctx = md_ctx.digest_sign_init(None, &key).unwrap();
+        pkey_ctx.set_context_string(&ctx).unwrap();
+        let mut sig = vec![];
+        md_ctx.digest_sign_to_vec(&msg, &mut sig).unwrap();
+
+        let mut md_ctx = MdCtx::new().unwrap();
+        let pkey_ctx = md_ctx.digest_verify_init(None, &key).unwrap();
+        pkey_ctx.set_context_string(&ctx).unwrap();
+        assert!(md_ctx.digest_verify(&msg, &sig).unwrap());
+
+        assert!(ErrorStack::get().errors().is_empty());
+    }
 }