openpgp: Zero secret keys on Drop.

3 files changed, 38 insertions, 0 deletions

diff --git a/openpgp/Cargo.toml b/openpgp/Cargo.toml
index 58b1aff4..e9afbdfe 100644
--- a/openpgp/Cargo.toml
+++ b/openpgp/Cargo.toml
@@ -11,6 +11,7 @@ bzip2 = { version = "0.3.2", optional = true }
 failure = "0.1.2"
 flate2 = { version = "1.0.1", optional = true }
 lalrpop-util = "0.16"
+memsec = "0.5.4"
 nettle = { git = "https://gitlab.com/sequoia-pgp/nettle-rs.git" }
 quickcheck = "0.7"
 rand = "0.5"
diff --git a/openpgp/src/lib.rs b/openpgp/src/lib.rs
index d2cabdad..690827cc 100644
--- a/openpgp/src/lib.rs
+++ b/openpgp/src/lib.rs
@@ -47,6 +47,7 @@ extern crate failure;
 
 extern crate buffered_reader;
 
+extern crate memsec;
 extern crate nettle;
 
 #[cfg(feature = "compression-deflate")]
diff --git a/openpgp/src/mpis.rs b/openpgp/src/mpis.rs
index d204ec54..2d2c82d9 100644
--- a/openpgp/src/mpis.rs
+++ b/openpgp/src/mpis.rs
@@ -50,6 +50,12 @@ impl MPI {
         hash.update(len);
         hash.update(&self.value);
     }
+
+    fn secure_memzero(&mut self) {
+        unsafe {
+            ::memsec::memzero(self.value.as_mut_ptr(), self.value.len());
+        }
+    }
 }
 
 impl fmt::Debug for MPI {
@@ -345,6 +351,36 @@ pub enum SecretKey {
     },
 }
 
+impl Drop for SecretKey {
+    fn drop(&mut self) {
+        use self::SecretKey::*;
+        match self {
+            RSA { ref mut d, ref mut p, ref mut q, ref mut u } => {
+                d.secure_memzero();
+                p.secure_memzero();
+                q.secure_memzero();
+                u.secure_memzero();
+            },
+            DSA { ref mut x } =>
+                x.secure_memzero(),
+            Elgamal { ref mut x } =>
+                x.secure_memzero(),
+            EdDSA { ref mut scalar } =>
+                scalar.secure_memzero(),
+            ECDSA { ref mut scalar } =>
+                scalar.secure_memzero(),
+            ECDH { ref mut scalar } =>
+                scalar.secure_memzero(),
+            Unknown { ref mut mpis, ref mut rest } => {
+                mpis.iter_mut().for_each(|m| m.secure_memzero());
+                unsafe {
+                    ::memsec::memzero(rest.as_mut_ptr(), rest.len());
+                }
+            },
+        }
+    }
+}
+
 impl SecretKey {
     /// Number of octets all MPIs of this instance occupy when serialized.
     pub fn serialized_len(&self) -> usize {