feat(notsecrets): SSH RSA identity and recipient (OAEP-SHA256)

crates/notsecrets/src/recipients/mod.rs

@@ -10,6 +10,9 @@ pub use ssh_ed25519::SshEd25519Recipient;
 pub mod scrypt;
 pub use scrypt::ScryptRecipient;
 
+pub mod ssh_rsa;
+pub use ssh_rsa::SshRsaRecipient;
+
 /// Domain port: a recipient that can wrap a file key into a stanza.
 pub trait Recipient {
     fn wrap_file_key(&self, file_key: &FileKey) -> Result<Stanza, AgeError>;

crates/notsecrets/src/recipients/ssh_rsa.rs

@@ -0,0 +1,38 @@
+use crate::error::AgeError;
+use crate::identities::{FileKey, Stanza};
+use crate::identities::ssh_rsa::rsa_pubkey_fingerprint;
+use crate::recipients::Recipient;
+use base64::{Engine, engine::general_purpose::STANDARD_NO_PAD};
+use rsa::{Oaep, RsaPublicKey};
+use sha2::Sha256;
+
+const TAG: &str = "ssh-rsa";
+
+pub struct SshRsaRecipient {
+    public_key: RsaPublicKey,
+}
+
+impl SshRsaRecipient {
+    pub fn from_public_key(public_key: RsaPublicKey) -> Self {
+        Self { public_key }
+    }
+}
+
+impl Recipient for SshRsaRecipient {
+    fn wrap_file_key(&self, file_key: &FileKey) -> Result<Stanza, AgeError> {
+        use rand::rngs::OsRng;
+        let padding = Oaep::new::<Sha256>();
+        let wrapped = self
+            .public_key
+            .encrypt(&mut OsRng, padding, file_key.as_bytes())
+            .map_err(|_| AgeError::CryptoError("RSA-OAEP encrypt failed".to_string()))?;
+
+        let fingerprint = rsa_pubkey_fingerprint(&self.public_key);
+
+        Ok(Stanza {
+            tag: TAG.to_string(),
+            args: vec![STANDARD_NO_PAD.encode(fingerprint)],
+            body: wrapped,
+        })
+    }
+}