1 files changed, 9 insertions, 0 deletions
diff --git a/openpgp/src/crypto/aead.rs b/openpgp/src/crypto/aead.rs
index 713b320e..61cfd7f7 100644
--- a/openpgp/src/crypto/aead.rs
+++ b/openpgp/src/crypto/aead.rs
@@ -1,4 +1,5 @@
 use std::cmp;
+use std::convert::TryInto;
 use std::fmt;
 use std::io;
 
@@ -24,6 +25,14 @@ use crate::parse::Cookie;
 /// malformed AEAD-encrypted messages.
 const DANGER_DISABLE_AUTHENTICATION: bool = false;
 
+/// Converts a chunk size to a usize.
+pub(crate) fn chunk_size_usize(chunk_size: u64) -> Result<usize> {
+    chunk_size.try_into()
+        .map_err(|_| Error::InvalidOperation(
+            format!("AEAD chunk size exceeds size of \
+                     virtual memory: {}", chunk_size)).into())
+}
+
 impl AEADAlgorithm {
     /// Returns the digest size of the AEAD algorithm.
     pub fn digest_size(&self) -> Result<usize> {