openpgp: Implement GCM mode.

  - The Galois/Counter mode for block ciphers is a FIPS-approved AEAD
    mode.  It will be added to the upcoming OpenPGP standard so that
    we have a FIPS-compliant subset of OpenPGP.

1 files changed, 46 insertions, 0 deletions

diff --git a/openpgp/src/crypto/backend/nettle/aead.rs b/openpgp/src/crypto/backend/nettle/aead.rs
index 76303715..c44defb3 100644
--- a/openpgp/src/crypto/backend/nettle/aead.rs
+++ b/openpgp/src/crypto/backend/nettle/aead.rs
@@ -164,6 +164,52 @@ impl AEADAlgorithm {
                 _ => Err(Error::UnsupportedSymmetricAlgorithm(sym_algo).into()),
             },
 
+            AEADAlgorithm::GCM => match sym_algo {
+                SymmetricAlgorithm::AES128 => {
+                    let mut ctx =
+                        aead::Gcm::<cipher::Aes128>::with_key_and_nonce(key, nonce)?;
+                    ctx.update(aad);
+                    Ok(Box::new(ctx))
+                },
+                SymmetricAlgorithm::AES192 => {
+                    let mut ctx =
+                        aead::Gcm::<cipher::Aes192>::with_key_and_nonce(key, nonce)?;
+                    ctx.update(aad);
+                    Ok(Box::new(ctx))
+                },
+                SymmetricAlgorithm::AES256 => {
+                    let mut ctx =
+                        aead::Gcm::<cipher::Aes256>::with_key_and_nonce(key, nonce)?;
+                    ctx.update(aad);
+                    Ok(Box::new(ctx))
+                },
+                SymmetricAlgorithm::Twofish => {
+                    let mut ctx =
+                        aead::Gcm::<cipher::Twofish>::with_key_and_nonce(key, nonce)?;
+                    ctx.update(aad);
+                    Ok(Box::new(ctx))
+                },
+                SymmetricAlgorithm::Camellia128 => {
+                    let mut ctx =
+                        aead::Gcm::<cipher::Camellia128>::with_key_and_nonce(key, nonce)?;
+                    ctx.update(aad);
+                    Ok(Box::new(ctx))
+                },
+                SymmetricAlgorithm::Camellia192 => {
+                    let mut ctx =
+                        aead::Gcm::<cipher::Camellia192>::with_key_and_nonce(key, nonce)?;
+                    ctx.update(aad);
+                    Ok(Box::new(ctx))
+                },
+                SymmetricAlgorithm::Camellia256 => {
+                    let mut ctx =
+                        aead::Gcm::<cipher::Camellia256>::with_key_and_nonce(key, nonce)?;
+                    ctx.update(aad);
+                    Ok(Box::new(ctx))
+                },
+                _ => Err(Error::UnsupportedSymmetricAlgorithm(sym_algo).into()),
+            },
+
             _ => Err(Error::UnsupportedAEADAlgorithm(*self).into()),
         }
     }