openpgp: Check for supported AEAD ciphersuite in tests.

  - Previously the AEAD roundtrip test checked supported symmetric
    ciphers and AEAD algorithms separately but only certain combinations
    of them are valid in some libraries.

  - See: https://openpgp-wg.gitlab.io/rfc4880bis/#name-preferred-aead-ciphersuites

3 files changed, 55 insertions, 0 deletions

diff --git a/openpgp/src/crypto/backend/cng.rs b/openpgp/src/crypto/backend/cng.rs
index b2a47e74..607b0414 100644
--- a/openpgp/src/crypto/backend/cng.rs
+++ b/openpgp/src/crypto/backend/cng.rs
@@ -67,4 +67,22 @@ impl AEADAlgorithm {
                 => false,
         }
     }
+
+    #[cfg(test)]
+    pub(crate) fn supports_symmetric_algo(&self, algo: &SymmetricAlgorithm) -> bool {
+        match &self {
+            AEADAlgorithm::EAX =>
+                match algo {
+                    SymmetricAlgorithm::AES128 |
+                    SymmetricAlgorithm::AES192 |
+                    SymmetricAlgorithm::AES256 |
+                    SymmetricAlgorithm::Twofish |
+                    SymmetricAlgorithm::Camellia128 |
+                    SymmetricAlgorithm::Camellia192 |
+                    SymmetricAlgorithm::Camellia256 => true,
+                    _ => false,
+                },
+            _ => false
+        }
+    }
 }
diff --git a/openpgp/src/crypto/backend/nettle.rs b/openpgp/src/crypto/backend/nettle.rs
index 716ec5e1..d2197493 100644
--- a/openpgp/src/crypto/backend/nettle.rs
+++ b/openpgp/src/crypto/backend/nettle.rs
@@ -66,4 +66,22 @@ impl AEADAlgorithm {
                 => false,
         }
     }
+
+    #[cfg(test)]
+    pub(crate) fn supports_symmetric_algo(&self, algo: &SymmetricAlgorithm) -> bool {
+        match &self {
+            AEADAlgorithm::EAX =>
+                match algo {
+                    SymmetricAlgorithm::AES128 |
+                    SymmetricAlgorithm::AES192 |
+                    SymmetricAlgorithm::AES256 |
+                    SymmetricAlgorithm::Twofish |
+                    SymmetricAlgorithm::Camellia128 |
+                    SymmetricAlgorithm::Camellia192 |
+                    SymmetricAlgorithm::Camellia256 => true,
+                    _ => false,
+                },
+            _ => false
+        }
+    }
 }
diff --git a/openpgp/src/crypto/backend/rust.rs b/openpgp/src/crypto/backend/rust.rs
index 61784b2c..7fe567ef 100644
--- a/openpgp/src/crypto/backend/rust.rs
+++ b/openpgp/src/crypto/backend/rust.rs
@@ -73,4 +73,23 @@ impl AEADAlgorithm {
                 => false,
         }
     }
+
+    #[cfg(test)]
+    pub(crate) fn supports_symmetric_algo(&self, algo: &SymmetricAlgorithm) -> bool {
+        match &self {
+            AEADAlgorithm::EAX =>
+                match algo {
+                    SymmetricAlgorithm::AES128 |
+                    SymmetricAlgorithm::AES192 |
+                    SymmetricAlgorithm::AES256 |
+                    // XXX: Skipping Twofish until Twofish implements Clone
+                    // SymmetricAlgorithm::Twofish |
+                    SymmetricAlgorithm::Camellia128 |
+                    SymmetricAlgorithm::Camellia192 |
+                    SymmetricAlgorithm::Camellia256 => true,
+                    _ => false,
+                },
+            _ => false
+        }
+    }
 }