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

2026-08-20 16:19:00 +02:00 · 2025-12-14 11:54:56 -08:00
parent 845b1ec313
commit 2b712864d6
25 changed files with 158 additions and 47 deletions
--- a/Sources/Packages/Sources/SSHProtocolKit/Data+Hex.swift
+++ b/Sources/Packages/Sources/SSHProtocolKit/Data+Hex.swift
@@ -0,0 +1,37 @@
+import Foundation
+import CryptoKit
+
+public struct HexDataStyle<SequenceType: Sequence>: Hashable, Codable {
+
+    let separator: String
+
+    public init(separator: String) {
+        self.separator = separator
+    }
+
+}
+
+extension HexDataStyle: FormatStyle where SequenceType.Element == UInt8 {
+
+    public func format(_ value: SequenceType) -> String {
+        value
+            .compactMap { ("0" + String($0, radix: 16, uppercase: false)).suffix(2) }
+            .joined(separator: separator)
+    }
+
+}
+
+extension FormatStyle where Self == HexDataStyle<Data> {
+
+    public static func hex(separator: String = "") -> HexDataStyle<Data> {
+        HexDataStyle(separator: separator)
+    }
+
+}
+extension FormatStyle where Self == HexDataStyle<Insecure.MD5Digest> {
+
+    public static func hex(separator: String = ":") -> HexDataStyle<Insecure.MD5Digest> {
+        HexDataStyle(separator: separator)
+    }
+
+}
--- a/Sources/Packages/Sources/SSHProtocolKit/LengthAndData.swift
+++ b/Sources/Packages/Sources/SSHProtocolKit/LengthAndData.swift
@@ -0,0 +1,23 @@
+import Foundation
+
+extension Data {
+
+    /// Creates an OpenSSH protocol style data object, which has a length header, followed by the data payload.
+    /// - Returns: OpenSSH data.
+    package var lengthAndData: Data {
+        let rawLength = UInt32(count)
+        var endian = rawLength.bigEndian
+        return unsafe Data(bytes: &endian, count: MemoryLayout<UInt32>.size) + self
+    }
+
+}
+
+extension String {
+
+    /// Creates an OpenSSH protocol style data object, which has a length header, followed by the data payload.
+    /// - Returns: OpenSSH data.
+    package var lengthAndData: Data {
+        Data(utf8).lengthAndData
+    }
+
+}
--- a/Sources/Packages/Sources/SSHProtocolKit/OpenSSHPublicKeyWriter.swift
+++ b/Sources/Packages/Sources/SSHProtocolKit/OpenSSHPublicKeyWriter.swift
@@ -0,0 +1,113 @@
+import Foundation
+import CryptoKit
+import SecretKit
+
+/// Generates OpenSSH representations of the public key sof secrets.
+public struct OpenSSHPublicKeyWriter: 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) -> Data {
+        switch secret.keyType.algorithm {
+        case .ecdsa:
+            // https://datatracker.ietf.org/doc/html/rfc5656#section-3.1
+            openSSHIdentifier(for: secret.keyType).lengthAndData +
+            ("nistp" + String(describing: secret.keyType.size)).lengthAndData +
+            secret.publicKey.lengthAndData
+        case .mldsa:
+            // https://www.ietf.org/archive/id/draft-sfluhrer-ssh-mldsa-04.txt
+            openSSHIdentifier(for: secret.keyType).lengthAndData +
+            secret.publicKey.lengthAndData
+        case .rsa:
+            // https://datatracker.ietf.org/doc/html/rfc4253#section-6.6
+            openSSHIdentifier(for: secret.keyType).lengthAndData +
+            rsaPublicKeyBlob(secret: secret)
+        }
+    }
+
+    /// Generates an OpenSSH string representation of the secret.
+    /// - Returns: OpenSSH string representation of the secret.
+    public func openSSHString<SecretType: Secret>(secret: SecretType) -> String {
+        return [openSSHIdentifier(for: secret.keyType), data(secret: secret).base64EncodedString(), comment(secret: secret)]
+            .compactMap { $0 }
+            .joined(separator: " ")
+    }
+
+    /// Generates an OpenSSH SHA256 fingerprint string.
+    /// - Returns: OpenSSH SHA256 fingerprint string.
+    public func openSSHSHA256Fingerprint<SecretType: Secret>(secret: SecretType) -> String {
+        // OpenSSL format seems to strip the padding at the end.
+        let base64 = Data(SHA256.hash(data: data(secret: secret))).base64EncodedString()
+        let paddingRange = base64.index(base64.endIndex, offsetBy: -2)..<base64.endIndex
+        let cleaned = base64.replacingOccurrences(of: "=", with: "", range: paddingRange)
+        return "SHA256:\(cleaned)"
+    }
+
+    /// Generates an OpenSSH MD5 fingerprint string.
+    /// - Returns: OpenSSH MD5 fingerprint string.
+    public func openSSHMD5Fingerprint<SecretType: Secret>(secret: SecretType) -> String {
+        Insecure.MD5.hash(data: data(secret: secret)).formatted(.hex(separator: ":"))
+    }
+
+    public func comment<SecretType: Secret>(secret: SecretType) -> String {
+        if let comment = secret.publicKeyAttribution {
+            return comment
+        } else {
+            let dashedKeyName = secret.name.replacingOccurrences(of: " ", with: "-")
+            let dashedHostName = ["secretive", Host.current().localizedName, "local"]
+                .compactMap { $0 }
+                .joined(separator: ".")
+                .replacingOccurrences(of: " ", with: "-")
+            return "\(dashedKeyName)@\(dashedHostName)"
+        }
+
+    }
+}
+
+extension OpenSSHPublicKeyWriter {
+
+    /// The fully qualified OpenSSH identifier for the algorithm.
+    /// - Parameters:
+    ///   - algorithm: The algorithm to identify.
+    ///   - length: The key length of the algorithm.
+    /// - Returns: The OpenSSH identifier for the algorithm.
+    public func openSSHIdentifier(for keyType: KeyType) -> String {
+        switch keyType {
+        case .ecdsa256:
+            "ecdsa-sha2-nistp256"
+        case .ecdsa384:
+            "ecdsa-sha2-nistp384"
+        case .mldsa65:
+            "ssh-mldsa-65"
+        case .mldsa87:
+            "ssh-mldsa-87"
+        case .rsa2048:
+            "ssh-rsa"
+        default:
+            "unknown"
+        }
+    }
+
+}
+
+extension OpenSSHPublicKeyWriter {
+
+    func rsaPublicKeyBlob<SecretType: Secret>(secret: SecretType) -> Data {
+        // Cheap way to pull out e and n as defined in https://datatracker.ietf.org/doc/html/rfc4253
+        // Keychain stores it as a thin ASN.1 wrapper with this format:
+        // [4 byte prefix][2 byte prefix][n][2 byte prefix][e]
+        // Rather than parse out the whole ASN.1 blob, we'll cheat and pull values directly since
+        // we only support one key type, and the keychain always gives it in a specific format.
+        guard secret.keyType == .rsa2048 else { fatalError() }
+        let length = secret.keyType.size/8
+        let data = secret.publicKey
+        let n = Data(data[8..<(9+length)])
+        let e = Data(data[(2+9+length)...])
+        return e.lengthAndData + n.lengthAndData
+    }
+
+}
--- a/Sources/Packages/Sources/SSHProtocolKit/OpenSSHReader.swift
+++ b/Sources/Packages/Sources/SSHProtocolKit/OpenSSHReader.swift
@@ -0,0 +1,54 @@
+import Foundation
+
+/// Reads OpenSSH protocol data.
+public final class OpenSSHReader {
+
+    var remaining: Data
+    var done = false
+
+    /// Initialize the reader with an OpenSSH data payload.
+    /// - Parameter data: The data to read.
+    public init(data: Data) {
+        remaining = Data(data)
+    }
+
+    /// Reads the next chunk of data from the playload.
+    /// - Returns: The next chunk of data.
+    public func readNextChunk(convertEndianness: Bool = true) throws(OpenSSHReaderError) -> Data {
+        let length = try readNextBytes(as: UInt32.self, convertEndianness: convertEndianness)
+        guard remaining.count >= length else { throw .beyondBounds }
+        let dataRange = 0..<Int(length)
+        let ret = Data(remaining[dataRange])
+        remaining.removeSubrange(dataRange)
+        if remaining.isEmpty {
+            done = true
+        }
+        return ret
+    }
+
+    public func readNextBytes<T: FixedWidthInteger>(as: T.Type, convertEndianness: Bool = true) throws(OpenSSHReaderError) -> T {
+        let size = MemoryLayout<T>.size
+        guard remaining.count >= size else { throw .beyondBounds }
+        let lengthRange = 0..<size
+        let lengthChunk = remaining[lengthRange]
+        remaining.removeSubrange(lengthRange)
+        if remaining.isEmpty {
+            done = true
+        }
+        let value = unsafe lengthChunk.bytes.unsafeLoad(as: T.self)
+        return convertEndianness ? T(value.bigEndian) : T(value)
+    }
+
+    public func readNextChunkAsString(convertEndianness: Bool = true) throws(OpenSSHReaderError) -> String {
+        try String(decoding: readNextChunk(convertEndianness: convertEndianness), as: UTF8.self)
+    }
+
+    public func readNextChunkAsSubReader(convertEndianness: Bool = true) throws(OpenSSHReaderError) -> OpenSSHReader {
+        OpenSSHReader(data: try readNextChunk(convertEndianness: convertEndianness))
+    }
+
+}
+
+public enum OpenSSHReaderError: Error, Codable {
+    case beyondBounds
+}
--- a/Sources/Packages/Sources/SSHProtocolKit/OpenSSHSignatureWriter.swift
+++ b/Sources/Packages/Sources/SSHProtocolKit/OpenSSHSignatureWriter.swift
@@ -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
+    }
+
+}
--- a/Sources/Packages/Sources/SSHProtocolKit/SSHAgentProtocol.swift
+++ b/Sources/Packages/Sources/SSHProtocolKit/SSHAgentProtocol.swift
@@ -0,0 +1,99 @@
+import Foundation
+
+/// A namespace for the SSH Agent Protocol, as described in https://datatracker.ietf.org/doc/html/draft-miller-ssh-agent#section-5.1
+public enum SSHAgent {}
+
+extension SSHAgent {
+
+    /// The type of the SSH Agent Request, as described in https://datatracker.ietf.org/doc/html/draft-miller-ssh-agent#section-5.1
+    public enum Request: CustomDebugStringConvertible, Codable, Sendable {
+
+        case requestIdentities
+        case signRequest(SignatureRequestContext)
+        case addIdentity
+        case removeIdentity
+        case removeAllIdentities
+        case addIDConstrained
+        case addSmartcardKey
+        case removeSmartcardKey
+        case lock
+        case unlock
+        case addSmartcardKeyConstrained
+        case protocolExtension
+        case unknown(UInt8)
+
+        public var protocolID: UInt8 {
+            switch self {
+            case .requestIdentities: 11
+            case .signRequest: 13
+            case .addIdentity: 17
+            case .removeIdentity: 18
+            case .removeAllIdentities: 19
+            case .addIDConstrained: 25
+            case .addSmartcardKey: 20
+            case .removeSmartcardKey: 21
+            case .lock: 22
+            case .unlock: 23
+            case .addSmartcardKeyConstrained: 26
+            case .protocolExtension: 27
+            case .unknown(let value): value
+            }
+        }
+
+        public var debugDescription: String {
+            switch self {
+            case .requestIdentities: "SSH_AGENTC_REQUEST_IDENTITIES"
+            case .signRequest: "SSH_AGENTC_SIGN_REQUEST"
+            case .addIdentity: "SSH_AGENTC_ADD_IDENTITY"
+            case .removeIdentity: "SSH_AGENTC_REMOVE_IDENTITY"
+            case .removeAllIdentities: "SSH_AGENTC_REMOVE_ALL_IDENTITIES"
+            case .addIDConstrained: "SSH_AGENTC_ADD_ID_CONSTRAINED"
+            case .addSmartcardKey: "SSH_AGENTC_ADD_SMARTCARD_KEY"
+            case .removeSmartcardKey: "SSH_AGENTC_REMOVE_SMARTCARD_KEY"
+            case .lock: "SSH_AGENTC_LOCK"
+            case .unlock: "SSH_AGENTC_UNLOCK"
+            case .addSmartcardKeyConstrained: "SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED"
+            case .protocolExtension: "SSH_AGENTC_EXTENSION"
+            case .unknown: "UNKNOWN_MESSAGE"
+            }
+        }
+
+        public struct SignatureRequestContext: Sendable, Codable {
+            public let keyBlob: Data
+            public let dataToSign: Data
+
+            public init(keyBlob: Data, dataToSign: Data) {
+                self.keyBlob = keyBlob
+                self.dataToSign = dataToSign
+            }
+
+            public static var empty: SignatureRequestContext {
+                SignatureRequestContext(keyBlob: Data(), dataToSign: Data())
+            }
+        }
+
+    }
+
+    /// The type of the SSH Agent Response, as described in https://datatracker.ietf.org/doc/html/draft-miller-ssh-agent#section-5.1
+    public enum Response: UInt8, CustomDebugStringConvertible {
+        
+        case agentFailure = 5
+        case agentSuccess = 6
+        case agentIdentitiesAnswer = 12
+        case agentSignResponse = 14
+        case agentExtensionFailure = 28
+        case agentExtensionResponse = 29
+
+        public var debugDescription: String {
+            switch self {
+            case .agentFailure: "SSH_AGENT_FAILURE"
+            case .agentSuccess: "SSH_AGENT_SUCCESS"
+            case .agentIdentitiesAnswer: "SSH_AGENT_IDENTITIES_ANSWER"
+            case .agentSignResponse: "SSH_AGENT_SIGN_RESPONSE"
+            case .agentExtensionFailure: "SSH_AGENT_EXTENSION_FAILURE"
+            case .agentExtensionResponse: "SSH_AGENT_EXTENSION_RESPONSE"
+            }
+        }
+    }
+    
+}