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SSH Certificate Cleanup/Followup (#418)

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* Don't delete public cert keys corrresponding to secretive-tracked keys

* First pass

* Fix fallback for name

* Split out into dedicated handler

* Stub add identities

* .
This commit is contained in:
Max Goedjen 2022-12-21 20:18:27 -08:00 committed by GitHub
parent acdf0baf3a
commit f43571baa3
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GPG Key ID: 4AEE18F83AFDEB23
6 changed files with 158 additions and 101 deletions
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110
Sources/Packages/Sources/SecretAgentKit/Agent.swift
View File

@ -4,25 +4,6 @@ import OSLog
import SecretKit
import AppKit
enum OpenSSHCertificateError: Error {
case unsupportedType
case parsingFailed
case doesNotExist
}
extension OpenSSHCertificateError: CustomStringConvertible {
public var description: String {
switch self {
case .unsupportedType:
return "The key type was unsupported"
case .parsingFailed:
return "Failed to properly parse the SSH certificate"
case .doesNotExist:
return "Certificate does not exist"
}
}
}
/// The `Agent` is an implementation of an SSH agent. It manages coordination and access between a socket, traces requests, notifies witnesses and passes requests to stores.
public class Agent {
@ -30,7 +11,7 @@ public class Agent {
private let witness: SigningWitness?
private let writer = OpenSSHKeyWriter()
private let requestTracer = SigningRequestTracer()
private let certsPath = (NSHomeDirectory() as NSString).appendingPathComponent("PublicKeys") as String
private let certificateHandler = OpenSSHCertificateHandler()
private let logger = Logger(subsystem: "com.maxgoedjen.secretive.secretagent.agent", category: "")
/// Initializes an agent with a store list and a witness.
@ -41,6 +22,7 @@ public class Agent {
logger.debug("Agent is running")
self.storeList = storeList
self.witness = witness
certificateHandler.reloadCertificates(for: storeList.allSecrets)
}
}
@ -102,7 +84,8 @@ extension Agent {
/// Lists the identities available for signing operations
/// - Returns: An OpenSSH formatted Data payload listing the identities available for signing operations.
func identities() -> Data {
let secrets = storeList.stores.flatMap(\.secrets)
let secrets = storeList.allSecrets
certificateHandler.reloadCertificates(for: secrets)
var count = UInt32(secrets.count).bigEndian
let countData = Data(bytes: &count, count: UInt32.bitWidth/8)
var keyData = Data()
@ -111,9 +94,9 @@ extension Agent {
let keyBlob: Data
let curveData: Data
if let (certBlob, certName) = try? checkForCert(secret: secret) {
keyBlob = certBlob
curveData = certName
if let (certificateData, name) = try? certificateHandler.keyBlobAndName(for: secret) {
keyBlob = certificateData
curveData = name
} else {
keyBlob = writer.data(secret: secret)
curveData = writer.curveType(for: secret.algorithm, length: secret.keySize).data(using: .utf8)!
@ -134,11 +117,13 @@ extension Agent {
/// - Returns: An OpenSSH formatted Data payload containing the signed data response.
func sign(data: Data, provenance: SigningRequestProvenance) throws -> Data {
let reader = OpenSSHReader(data: data)
var hash = reader.readNextChunk()
let payloadHash = reader.readNextChunk()
let hash: Data
// Check if hash is actually an openssh certificate and reconstruct the public key if it is
if let certPublicKey = try? getPublicKeyFromCert(certBlob: hash) {
hash = certPublicKey
if let certificatePublicKey = certificateHandler.publicKeyHash(from: payloadHash) {
hash = certificatePublicKey
} else {
hash = payloadHash
}
guard let (store, secret) = secret(matching: hash) else {
@ -200,74 +185,6 @@ extension Agent {
return signedData
}
/// Reconstructs a public key from a ``Data`` object that contains an OpenSSH certificate. Currently only ecdsa certificates are supported
/// - Parameter certBlock: The openssh certificate to extract the public key from
/// - Returns: A ``Data`` object containing the public key in OpenSSH wire format
func getPublicKeyFromCert(certBlob: Data) throws -> Data {
let reader = OpenSSHReader(data: certBlob)
let certType = String(decoding: reader.readNextChunk(), as: UTF8.self)
switch certType {
case "ecdsa-sha2-nistp256-cert-v01@openssh.com",
"ecdsa-sha2-nistp384-cert-v01@openssh.com",
"ecdsa-sha2-nistp521-cert-v01@openssh.com":
_ = reader.readNextChunk() // nonce
let curveIdentifier = reader.readNextChunk()
let publicKey = reader.readNextChunk()
if let curveType = certType.replacingOccurrences(of: "-cert-v01@openssh.com", with: "").data(using: .utf8) {
return writer.lengthAndData(of: curveType) +
writer.lengthAndData(of: curveIdentifier) +
writer.lengthAndData(of: publicKey)
} else {
throw OpenSSHCertificateError.parsingFailed
}
default:
throw OpenSSHCertificateError.unsupportedType
}
}
/// Attempts to find an OpenSSH Certificate that corresponds to a ``Secret``
/// - Parameter secret: The secret to search for a certificate with
/// - Returns: Two ``Data`` objects containing the certificate and certificate name respectively
func checkForCert(secret: AnySecret) throws -> (Data, Data) {
let minimalHex = writer.openSSHMD5Fingerprint(secret: secret).replacingOccurrences(of: ":", with: "")
let certificatePath = certsPath.appending("/").appending("\(minimalHex)-cert.pub")
if FileManager.default.fileExists(atPath: certificatePath) {
logger.debug("Found certificate for \(secret.name)")
do {
let certContent = try String(contentsOfFile:certificatePath, encoding: .utf8)
let certElements = certContent.trimmingCharacters(in: .whitespacesAndNewlines).components(separatedBy: " ")
if certElements.count >= 2 {
if let certDecoded = Data(base64Encoded: certElements[1] as String) {
if certElements.count >= 3 {
if let certName = certElements[2].data(using: .utf8) {
return (certDecoded, certName)
} else if let certName = secret.name.data(using: .utf8) {
logger.info("Certificate for \(secret.name) does not have a name tag, using secret name instead")
return (certDecoded, certName)
} else {
throw OpenSSHCertificateError.parsingFailed
}
}
} else {
logger.warning("Certificate found for \(secret.name) but failed to decode base64 key")
throw OpenSSHCertificateError.parsingFailed
}
}
} catch {
logger.warning("Certificate found for \(secret.name) but failed to load")
throw OpenSSHCertificateError.parsingFailed
}
}
throw OpenSSHCertificateError.doesNotExist
}
}
@ -308,6 +225,7 @@ extension Agent {
case unhandledType
case noMatchingKey
case unsupportedKeyType
case notOpenSSHCertificate
}
}

9
Sources/Packages/Sources/SecretAgentKit/SSHAgentProtocol.swift
View File

@ -1,11 +1,11 @@
import Foundation
/// A namespace for the SSH Agent Protocol, as described in https://tools.ietf.org/id/draft-miller-ssh-agent-01.html
/// 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://tools.ietf.org/id/draft-miller-ssh-agent-01.html#rfc.section.5.1
/// 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 RequestType: UInt8, CustomDebugStringConvertible {
case requestIdentities = 11
@ -21,10 +21,11 @@ extension SSHAgent {
}
}
/// The type of the SSH Agent Response, as described in https://tools.ietf.org/id/draft-miller-ssh-agent-01.html#rfc.section.5.1
/// 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 ResponseType: UInt8, CustomDebugStringConvertible {
case agentFailure = 5
case agentSuccess = 6
case agentIdentitiesAnswer = 12
case agentSignResponse = 14
@ -32,6 +33,8 @@ extension SSHAgent {
switch self {
case .agentFailure:
return "AgentFailure"
case .agentSuccess:
return "AgentSuccess"
case .agentIdentitiesAnswer:
return "AgentIdentitiesAnswer"
case .agentSignResponse:

120
Sources/Packages/Sources/SecretKit/OpenSSH/OpenSSHCertificateHandler.swift Normal file
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@ -0,0 +1,120 @@
import Foundation
import OSLog
/// Manages storage and lookup for OpenSSH certificates.
public class OpenSSHCertificateHandler {
private let publicKeyFileStoreController = PublicKeyFileStoreController(homeDirectory: NSHomeDirectory())
private let logger = Logger()
private let writer = OpenSSHKeyWriter()
private var keyBlobsAndNames: [AnySecret: (Data, Data)] = [:]
/// Initializes an OpenSSHCertificateHandler.
public init() {
}
/// Reloads any certificates in the PublicKeys folder.
/// - Parameter secrets: the secrets to look up corresponding certificates for.
public func reloadCertificates(for secrets: [AnySecret]) {
guard publicKeyFileStoreController.hasAnyCertificates else {
logger.log("No certificates, short circuiting")
return
}
keyBlobsAndNames = secrets.reduce(into: [:]) { partialResult, next in
partialResult[next] = try? loadKeyblobAndName(for: next)
}
}
/// Whether or not the certificate handler has a certifiicate associated with a given secret.
/// - Parameter secret: The secret to check for a certificate.
/// - Returns: A boolean describing whether or not the certificate handler has a certifiicate associated with a given secret
public func hasCertificate<SecretType: Secret>(for secret: SecretType) -> Bool {
keyBlobsAndNames[AnySecret(secret)] != nil
}
/// Reconstructs a public key from a ``Data``, if that ``Data`` contains an OpenSSH certificate hash. Currently only ecdsa certificates are supported
/// - Parameter certBlock: The openssh certificate to extract the public key from
/// - Returns: A ``Data`` object containing the public key in OpenSSH wire format if the ``Data`` is an OpenSSH certificate hash, otherwise nil.
public func publicKeyHash(from hash: Data) -> Data? {
let reader = OpenSSHReader(data: hash)
let certType = String(decoding: reader.readNextChunk(), as: UTF8.self)
switch certType {
case "ecdsa-sha2-nistp256-cert-v01@openssh.com",
"ecdsa-sha2-nistp384-cert-v01@openssh.com",
"ecdsa-sha2-nistp521-cert-v01@openssh.com":
_ = reader.readNextChunk() // nonce
let curveIdentifier = reader.readNextChunk()
let publicKey = reader.readNextChunk()
let curveType = certType.replacingOccurrences(of: "-cert-v01@openssh.com", with: "").data(using: .utf8)!
return writer.lengthAndData(of: curveType) +
writer.lengthAndData(of: curveIdentifier) +
writer.lengthAndData(of: publicKey)
default:
return nil
}
}
/// Attempts to find an OpenSSH Certificate that corresponds to a ``Secret``
/// - Parameter secret: The secret to search for a certificate with
/// - Returns: A (``Data``, ``Data``) tuple containing the certificate and certificate name, respectively.
public func keyBlobAndName<SecretType: Secret>(for secret: SecretType) throws -> (Data, Data)? {
keyBlobsAndNames[AnySecret(secret)]
}
/// Attempts to find an OpenSSH Certificate that corresponds to a ``Secret``
/// - Parameter secret: The secret to search for a certificate with
/// - Returns: A (``Data``, ``Data``) tuple containing the certificate and certificate name, respectively.
private func loadKeyblobAndName<SecretType: Secret>(for secret: SecretType) throws -> (Data, Data)? {
let certificatePath = publicKeyFileStoreController.sshCertificatePath(for: secret)
guard FileManager.default.fileExists(atPath: certificatePath) else {
return nil
}
logger.debug("Found certificate for \(secret.name)")
let certContent = try String(contentsOfFile:certificatePath, encoding: .utf8)
let certElements = certContent.trimmingCharacters(in: .whitespacesAndNewlines).components(separatedBy: " ")
guard certElements.count >= 2 else {
logger.warning("Certificate found for \(secret.name) but failed to load")
throw OpenSSHCertificateError.parsingFailed
}
guard let certDecoded = Data(base64Encoded: certElements[1] as String) else {
logger.warning("Certificate found for \(secret.name) but failed to decode base64 key")
throw OpenSSHCertificateError.parsingFailed
}
if certElements.count >= 3, let certName = certElements[2].data(using: .utf8) {
return (certDecoded, certName)
} else if let certName = secret.name.data(using: .utf8) {
logger.info("Certificate for \(secret.name) does not have a name tag, using secret name instead")
return (certDecoded, certName)
} else {
throw OpenSSHCertificateError.parsingFailed
}
}
}
extension OpenSSHCertificateHandler {
enum OpenSSHCertificateError: LocalizedError {
case unsupportedType
case parsingFailed
case doesNotExist
public var errorDescription: String? {
switch self {
case .unsupportedType:
return "The key type was unsupported"
case .parsingFailed:
return "Failed to properly parse the SSH certificate"
case .doesNotExist:
return "Certificate does not exist"
}
}
}
}

12
Sources/Packages/Sources/SecretKit/PublicKeyStandinFileController.swift
View File

@ -45,6 +45,18 @@ public class PublicKeyFileStoreController {
return directory.appending("/").appending("\(minimalHex).pub")
}
/// Short-circuit check to ship enumerating a bunch of paths if there's nothing in the cert directory.
public var hasAnyCertificates: Bool {
do {
return try FileManager.default
.contentsOfDirectory(atPath: directory)
.filter { $0.hasSuffix("-cert.pub") }
.isEmpty == false
} catch {
return false
}
}
/// The path for a Secret's SSH Certificate public key.
/// - Parameter secret: The Secret to return the path for.
/// - Returns: The path to the SSH Certificate public key.

4
Sources/Packages/Sources/SecretKit/SecretStoreList.swift
View File

@ -31,6 +31,10 @@ public class SecretStoreList: ObservableObject {
stores.reduce(false, { $0 || $1.isAvailable })
}
public var allSecrets: [AnySecret] {
stores.flatMap(\.secrets)
}
}
extension SecretStoreList {

4
Sources/SecretAgent/AppDelegate.swift
View File

@ -34,9 +34,9 @@ class AppDelegate: NSObject, NSApplicationDelegate {
self.socketController.handler = self.agent.handle(reader:writer:)
}
NotificationCenter.default.addObserver(forName: .secretStoreReloaded, object: nil, queue: .main) { [self] _ in
try? publicKeyFileStoreController.generatePublicKeys(for: storeList.stores.flatMap({ $0.secrets }), clear: true)
try? publicKeyFileStoreController.generatePublicKeys(for: storeList.allSecrets, clear: true)
}
try? publicKeyFileStoreController.generatePublicKeys(for: storeList.stores.flatMap({ $0.secrets }), clear: true)
try? publicKeyFileStoreController.generatePublicKeys(for: storeList.allSecrets, clear: true)
notifier.prompt()
updateSink = updater.$update.sink { update in
guard let update = update else { return }