1 files changed, 46 insertions, 0 deletions
diff --git a/third_party/rust/nss/src/ecdh.rs b/third_party/rust/nss/src/ecdh.rs
new file mode 100644
index 0000000000..9e91b0dc0d
--- /dev/null
+++ b/third_party/rust/nss/src/ecdh.rs
@@ -0,0 +1,46 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use crate::{
+    ec::{PrivateKey, PublicKey},
+    error::*,
+    pk11::types::SymKey,
+    util::{ensure_nss_initialized, map_nss_secstatus, sec_item_as_slice, ScopedPtr},
+};
+
+pub fn ecdh_agreement(priv_key: &PrivateKey, pub_key: &PublicKey) -> Result<Vec<u8>> {
+    ensure_nss_initialized();
+    if priv_key.curve() != pub_key.curve() {
+        return Err(ErrorKind::InternalError.into());
+    }
+    // The following code is adapted from:
+    // https://searchfox.org/mozilla-central/rev/444ee13e14fe30451651c0f62b3979c76766ada4/dom/crypto/WebCryptoTask.cpp#2835
+
+    // CKM_SHA512_HMAC and CKA_SIGN are key type and usage attributes of the
+    // derived symmetric key and don't matter because we ignore them anyway.
+    let sym_key = unsafe {
+        SymKey::from_ptr(nss_sys::PK11_PubDeriveWithKDF(
+            priv_key.as_mut_ptr(),
+            pub_key.as_mut_ptr(),
+            nss_sys::PR_FALSE,
+            std::ptr::null_mut(),
+            std::ptr::null_mut(),
+            nss_sys::CKM_ECDH1_DERIVE.into(),
+            nss_sys::CKM_SHA512_HMAC.into(),
+            nss_sys::CKA_SIGN.into(),
+            0,
+            nss_sys::CKD_NULL.into(),
+            std::ptr::null_mut(),
+            std::ptr::null_mut(),
+        ))?
+    };
+
+    map_nss_secstatus(|| unsafe { nss_sys::PK11_ExtractKeyValue(sym_key.as_mut_ptr()) })?;
+
+    // This doesn't leak, because the SECItem* returned by PK11_GetKeyData
+    // just refers to a buffer managed by `sym_key` which we copy into `buf`.
+    let mut key_data = unsafe { *nss_sys::PK11_GetKeyData(sym_key.as_mut_ptr()) };
+    let buf = unsafe { sec_item_as_slice(&mut key_data)? };
+    Ok(buf.to_vec())
+}