Pulling out a bunch of openssh stuff to dedicated package. (#775)

2026-09-19 14:48:01 +02:00 · 2025-12-14 19:54:56 +00:00
parent 845b1ec313
commit 2b712864d6
25 changed files with 158 additions and 47 deletions
@@ -0,0 +1,76 @@
+import Foundation
+import CryptoKit
+import SecretKit
+
+/// Generates OpenSSH representations of Secrets.
+public struct OpenSSHSignatureWriter: Sendable {
+
+    /// Initializes the writer.
+    public init() {
+    }
+
+    /// Generates an OpenSSH data payload identifying the secret.
+    /// - Returns: OpenSSH data payload identifying the secret.
+    public func data<SecretType: Secret>(secret: SecretType, signature: Data) -> Data {
+        switch secret.keyType.algorithm {
+        case .ecdsa:
+            // https://datatracker.ietf.org/doc/html/rfc5656#section-3.1
+            ecdsaSignature(signature, keyType: secret.keyType)
+        case .mldsa:
+            // https://datatracker.ietf.org/doc/html/draft-sfluhrer-ssh-mldsa-00#name-public-key-algorithms
+            mldsaSignature(signature, keyType: secret.keyType)
+        case .rsa:
+            // https://datatracker.ietf.org/doc/html/rfc4253#section-6.6
+            rsaSignature(signature)
+        }
+    }
+
+}
+
+
+extension OpenSSHSignatureWriter {
+
+    func ecdsaSignature(_ rawRepresentation: Data, keyType: KeyType) -> Data {
+        let rawLength = rawRepresentation.count/2
+        // Check if we need to pad with 0x00 to prevent certain
+        // ssh servers from thinking r or s is negative
+        let paddingRange: ClosedRange<UInt8> = 0x80...0xFF
+        var r = Data(rawRepresentation[0..<rawLength])
+        if paddingRange ~= r.first! {
+            r.insert(0x00, at: 0)
+        }
+        var s = Data(rawRepresentation[rawLength...])
+        if paddingRange ~= s.first! {
+            s.insert(0x00, at: 0)
+        }
+
+        var signatureChunk = Data()
+        signatureChunk.append(r.lengthAndData)
+        signatureChunk.append(s.lengthAndData)
+        var mutSignedData = Data()
+        var sub = Data()
+        sub.append(OpenSSHPublicKeyWriter().openSSHIdentifier(for: keyType).lengthAndData)
+        sub.append(signatureChunk.lengthAndData)
+        mutSignedData.append(sub.lengthAndData)
+        return mutSignedData
+    }
+
+    func mldsaSignature(_ rawRepresentation: Data, keyType: KeyType) -> Data {
+        var mutSignedData = Data()
+        var sub = Data()
+        sub.append(OpenSSHPublicKeyWriter().openSSHIdentifier(for: keyType).lengthAndData)
+        sub.append(rawRepresentation.lengthAndData)
+        mutSignedData.append(sub.lengthAndData)
+        return mutSignedData
+    }
+
+    func rsaSignature(_ rawRepresentation: Data) -> Data {
+        var mutSignedData = Data()
+        var sub = Data()
+        sub.append("rsa-sha2-512".lengthAndData)
+        sub.append(rawRepresentation.lengthAndData)
+        mutSignedData.append(sub.lengthAndData)
+        return mutSignedData
+    }
+
+}