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Enforce use of non-preset CA certificates

This commit is contained in:
Davide De Rosa 2018-08-23 11:32:38 +02:00
parent dfac465c1d
commit 897e824340
9 changed files with 79 additions and 111 deletions
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1
.jazzy.yaml
View File

@ -23,4 +23,5 @@ custom_categories:
- SessionError
- name: AppExtension
children:
- Certificate
- TunnelKitProvider

6
TunnelKit.xcodeproj/project.pbxproj
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@ -62,6 +62,8 @@
0EC1BBA620D712DE007C4C7B /* DNSResolver.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0EC1BBA420D71190007C4C7B /* DNSResolver.swift */; };
0EC1BBA820D7D803007C4C7B /* ConnectionStrategy.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0EC1BBA720D7D803007C4C7B /* ConnectionStrategy.swift */; };
0EC1BBA920D7D803007C4C7B /* ConnectionStrategy.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0EC1BBA720D7D803007C4C7B /* ConnectionStrategy.swift */; };
0ECE3528212EB7770040F253 /* Certificate.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0ECE3527212EB7770040F253 /* Certificate.swift */; };
0ECE352A212EB88E0040F253 /* Certificate.swift in Sources */ = {isa = PBXBuildFile; fileRef = 0ECE3527212EB7770040F253 /* Certificate.swift */; };
0EE7A79520F61EDC00B42E6A /* PacketMacros.h in Sources */ = {isa = PBXBuildFile; fileRef = 0EE7A79420F61EDC00B42E6A /* PacketMacros.h */; };
0EE7A79620F61EDC00B42E6A /* PacketMacros.h in Sources */ = {isa = PBXBuildFile; fileRef = 0EE7A79420F61EDC00B42E6A /* PacketMacros.h */; };
0EE7A79820F6296F00B42E6A /* PacketMacros.m in Sources */ = {isa = PBXBuildFile; fileRef = 0EE7A79720F6296F00B42E6A /* PacketMacros.m */; };
@ -213,6 +215,7 @@
0EBBF2FF2085196000E36B40 /* NWTCPConnectionState+Description.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "NWTCPConnectionState+Description.swift"; sourceTree = "<group>"; };
0EC1BBA420D71190007C4C7B /* DNSResolver.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = DNSResolver.swift; sourceTree = "<group>"; };
0EC1BBA720D7D803007C4C7B /* ConnectionStrategy.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ConnectionStrategy.swift; sourceTree = "<group>"; };
0ECE3527212EB7770040F253 /* Certificate.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Certificate.swift; sourceTree = "<group>"; };
0EE7A79420F61EDC00B42E6A /* PacketMacros.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = PacketMacros.h; sourceTree = "<group>"; };
0EE7A79720F6296F00B42E6A /* PacketMacros.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = PacketMacros.m; sourceTree = "<group>"; };
0EE7A79D20F6488400B42E6A /* DataPathEncryption.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = DataPathEncryption.h; sourceTree = "<group>"; };
@ -459,6 +462,7 @@
isa = PBXGroup;
children = (
0EBBF2E32084FDF400E36B40 /* Transport */,
0ECE3527212EB7770040F253 /* Certificate.swift */,
0EC1BBA720D7D803007C4C7B /* ConnectionStrategy.swift */,
0EC1BBA420D71190007C4C7B /* DNSResolver.swift */,
0EBBF2E42084FE6F00E36B40 /* GenericSocket.swift */,
@ -887,6 +891,7 @@
0EFEB4AC200760EC00F81029 /* InterfaceObserver.swift in Sources */,
0EFEB46D2006D3C800F81029 /* Data+Manipulation.swift in Sources */,
0EFEB47B2006D3C800F81029 /* TunnelKitProvider.swift in Sources */,
0ECE3528212EB7770040F253 /* Certificate.swift in Sources */,
0EFEB4742006D3C800F81029 /* CoreConfiguration.swift in Sources */,
0E07595F20EF6D1400F38FD8 /* CryptoCBC.m in Sources */,
0EC1BBA820D7D803007C4C7B /* ConnectionStrategy.swift in Sources */,
@ -935,6 +940,7 @@
0EFEB4A22006D7F300F81029 /* CoreConfiguration.swift in Sources */,
0EFEB4952006D7F300F81029 /* SecureRandom.swift in Sources */,
0EFEB49A2006D7F300F81029 /* MSS.m in Sources */,
0ECE352A212EB88E0040F253 /* Certificate.swift in Sources */,
0EFEB48D2006D7F300F81029 /* EncryptionProxy.swift in Sources */,
0EFEB4922006D7F300F81029 /* ZeroingData.m in Sources */,
0E07596020EF6D1400F38FD8 /* CryptoCBC.m in Sources */,

32
TunnelKit/Sources/AppExtension/Certificate.swift Normal file
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@ -0,0 +1,32 @@
//
// Certificate.swift
// TunnelKit
//
// Created by Davide De Rosa on 22/08/2018.
// Copyright © 2018 Davide De Rosa. All rights reserved.
//
import Foundation
/// Represents a TLS certificate in PEM format.
public struct Certificate: Equatable {
/// The content of the certificates in PEM format (ASCII).
public let pem: String
/// :nodoc:
public init(pem: String) {
self.pem = pem
}
func write(to url: URL) throws {
try pem.write(to: url, atomically: true, encoding: .ascii)
}
// MARK: Equatable
/// :nodoc:
public static func ==(lhs: Certificate, rhs: Certificate) -> Bool {
return lhs.pem == rhs.pem
}
}

110
TunnelKit/Sources/AppExtension/TunnelKitProvider+Configuration.swift
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@ -45,64 +45,6 @@ extension TunnelKitProvider {
/// SHA256 message digest.
case sha256 = "SHA256"
}
/// The available certificates for handshake.
public enum Handshake: String {
/// Certificate with RSA 2048-bit key.
case rsa2048 = "RSA-2048"
/// Certificate with RSA 3072-bit key.
case rsa3072 = "RSA-3072"
/// Certificate with RSA 4096-bit key.
case rsa4096 = "RSA-4096"
/// Certificate with ECC based on secp256r1 curve.
case ecc256r1 = "ECC-256r1"
/// Certificate with ECC based on secp256k1 curve.
case ecc256k1 = "ECC-256k1"
/// Certificate with ECC based on secp521r1 curve.
case ecc521r1 = "ECC-521r1"
/// Custom certificate.
///
/// - Seealso:
case custom = "Custom"
private static let allDigests: [Handshake: String] = [
.rsa2048: "e2fccccaba712ccc68449b1c56427ac1",
.rsa3072: "2fcdb65712df9db7dae34a1f4a84e32d",
.rsa4096: "ec085790314aa0ad4b01dda7b756a932",
.ecc256r1: "6f0f23a616479329ce54614f76b52254",
.ecc256k1: "80c3b0f34001e4101e34fde9eb1dfa87",
.ecc521r1: "82446e0c80706e33e6e793cebf1b0c59"
]
var digest: String? {
return Handshake.allDigests[self]
}
func write(to url: URL, custom: String? = nil) throws {
precondition((self != .custom) || (custom != nil))
// custom certificate?
if self == .custom, let content = custom {
try content.write(to: url, atomically: true, encoding: .ascii)
return
}
let bundle = Bundle(for: TunnelKitProvider.self)
let certName = "PIA-\(rawValue)"
guard let certUrl = bundle.url(forResource: certName, withExtension: "pem") else {
fatalError("Could not find \(certName) TLS certificate")
}
let content = try String(contentsOf: certUrl)
try content.write(to: url, atomically: true, encoding: .ascii)
}
}
}
extension TunnelKitProvider {
@ -215,16 +157,13 @@ extension TunnelKitProvider {
/// The message digest algorithm.
public var digest: Digest
/// The handshake certificate.
public var handshake: Handshake
/// The custom CA certificate in PEM format in case `handshake == .custom`. Ignored otherwise.
public var ca: String?
/// The optional CA certificate to validate server against. Set to `nil` to disable CA validation (default).
public var ca: Certificate?
/// The MTU of the tunnel.
public var mtu: NSNumber
/// The number of seconds after which a renegotiation is started. Set to `nil` to disable renegotiation.
/// The number of seconds after which a renegotiation is started. Set to `nil` to disable renegotiation (default).
public var renegotiatesAfterSeconds: Int?
// MARK: Debugging
@ -252,7 +191,6 @@ extension TunnelKitProvider {
endpointProtocols = [EndpointProtocol(.udp, 1194)]
cipher = .aes128cbc
digest = .sha1
handshake = .rsa2048
ca = nil
mtu = 1500
renegotiatesAfterSeconds = nil
@ -274,20 +212,12 @@ extension TunnelKitProvider {
throw ProviderError.configuration(field: "protocolConfiguration.providerConfiguration[\(S.digestAlgorithm)]")
}
// fallback to .rsa2048 in < 0.7 configurations (ca/caDigest)
let fallbackHandshake: Handshake = .rsa2048
var handshake: Handshake = fallbackHandshake
if let handshakeCertificate = providerConfiguration[S.handshakeCertificate] as? String {
handshake = Handshake(rawValue: handshakeCertificate) ?? fallbackHandshake
let ca: Certificate?
if let caPEM = providerConfiguration[S.ca] as? String {
ca = Certificate(pem: caPEM)
} else {
ca = nil
}
if handshake == .custom {
guard let ca = providerConfiguration[S.ca] as? String else {
throw ProviderError.configuration(field: "protocolConfiguration.providerConfiguration[\(S.ca)]")
}
self.ca = ca
}
self.appGroup = appGroup
prefersResolvedAddresses = providerConfiguration[S.prefersResolvedAddresses] as? Bool ?? false
resolvedAddresses = providerConfiguration[S.resolvedAddresses] as? [String]
@ -310,9 +240,10 @@ extension TunnelKitProvider {
return EndpointProtocol(socketType, port)
}
self.appGroup = appGroup
self.cipher = cipher
self.digest = digest
self.handshake = handshake
self.ca = ca
mtu = providerConfiguration[S.mtu] as? NSNumber ?? 1500
renegotiatesAfterSeconds = providerConfiguration[S.renegotiatesAfter] as? Int
@ -345,7 +276,6 @@ extension TunnelKitProvider {
endpointProtocols: endpointProtocols,
cipher: cipher,
digest: digest,
handshake: handshake,
ca: ca,
mtu: mtu,
renegotiatesAfterSeconds: renegotiatesAfterSeconds,
@ -371,8 +301,6 @@ extension TunnelKitProvider {
static let digestAlgorithm = "DigestAlgorithm"
static let handshakeCertificate = "HandshakeCertificate"
static let ca = "CA"
static let mtu = "MTU"
@ -404,11 +332,8 @@ extension TunnelKitProvider {
/// - Seealso: `TunnelKitProvider.ConfigurationBuilder.digest`
public let digest: Digest
/// - Seealso: `TunnelKitProvider.ConfigurationBuilder.handshake`
public let handshake: Handshake
/// - Seealso: `TunnelKitProvider.ConfigurationBuilder.ca`
public let ca: String?
public let ca: Certificate?
/// - Seealso: `TunnelKitProvider.ConfigurationBuilder.mtu`
public let mtu: NSNumber
@ -468,12 +393,11 @@ extension TunnelKitProvider {
},
S.cipherAlgorithm: cipher.rawValue,
S.digestAlgorithm: digest.rawValue,
S.handshakeCertificate: handshake.rawValue,
S.mtu: mtu,
S.debug: shouldDebug
]
if let ca = ca {
dict[S.ca] = ca
dict[S.ca] = ca.pem
}
if let resolvedAddresses = resolvedAddresses {
dict[S.resolvedAddresses] = resolvedAddresses
@ -526,7 +450,11 @@ extension TunnelKitProvider {
log.info("Protocols: \(endpointProtocols)")
log.info("Cipher: \(cipher.rawValue)")
log.info("Digest: \(digest.rawValue)")
log.info("Handshake: \(handshake.rawValue)")
if let _ = ca {
log.info("CA verification: enabled")
} else {
log.info("CA verification: disabled")
}
log.info("MTU: \(mtu)")
if let renegotiatesAfterSeconds = renegotiatesAfterSeconds {
log.info("Renegotiation: \(renegotiatesAfterSeconds) seconds")
@ -552,7 +480,7 @@ extension TunnelKitProvider.Configuration: Equatable {
builder.endpointProtocols = endpointProtocols
builder.cipher = cipher
builder.digest = digest
builder.handshake = handshake
builder.ca = ca
builder.mtu = mtu
builder.renegotiatesAfterSeconds = renegotiatesAfterSeconds
builder.shouldDebug = shouldDebug
@ -566,7 +494,7 @@ extension TunnelKitProvider.Configuration: Equatable {
(lhs.endpointProtocols == rhs.endpointProtocols) &&
(lhs.cipher == rhs.cipher) &&
(lhs.digest == rhs.digest) &&
(lhs.handshake == rhs.handshake) &&
(lhs.ca == rhs.ca) &&
(lhs.mtu == rhs.mtu) &&
(lhs.renegotiatesAfterSeconds == rhs.renegotiatesAfterSeconds)
)

19
TunnelKit/Sources/AppExtension/TunnelKitProvider.swift
View File

@ -139,18 +139,23 @@ open class TunnelKitProvider: NEPacketTunnelProvider {
return
}
do {
try cfg.handshake.write(to: tmpCaURL, custom: cfg.ca)
} catch {
completionHandler(ProviderError.certificateSerialization)
return
let caPath: String?
if let ca = cfg.ca {
do {
try ca.write(to: tmpCaURL)
caPath = tmpCaURL.path
} catch {
completionHandler(ProviderError.certificateSerialization)
return
}
} else {
caPath = nil
}
cfg.print(appVersion: appVersion)
let caPath = tmpCaURL.path
// log.info("Temporary CA is stored to: \(caPath)")
let encryption = SessionProxy.EncryptionParameters(cfg.cipher.rawValue, cfg.digest.rawValue, caPath, cfg.handshake.digest)
let encryption = SessionProxy.EncryptionParameters(cfg.cipher.rawValue, cfg.digest.rawValue, caPath)
let credentials = SessionProxy.Credentials(endpoint.username, endpoint.password)
let proxy: SessionProxy

10
TunnelKit/Sources/Core/SessionProxy.swift
View File

@ -91,17 +91,13 @@ public class SessionProxy {
public let digestName: String
/// The path to the CA for TLS negotiation (PEM format).
public let caPath: String
/// The MD5 digest of the CA (computed from DER format).
public let caDigest: String?
public let caPath: String?
/// :nodoc:
public init(_ cipherName: String, _ digestName: String, _ caPath: String, _ caDigest: String?) {
public init(_ cipherName: String, _ digestName: String, _ caPath: String?) {
self.cipherName = cipherName
self.digestName = digestName
self.caPath = caPath
self.caDigest = caDigest
}
}
@ -834,7 +830,7 @@ public class SessionProxy {
negotiationKey.tlsOptional = TLSBox(caPath: encryption.caPath)
do {
try negotiationKey.tls.start(withPeerVerification: true)
try negotiationKey.tls.start()
} catch let e {
deferStop(.shutdown, e)
return

4
TunnelKit/Sources/Core/TLSBox.h
View File

@ -20,9 +20,9 @@ extern NSString *const TLSBoxPeerVerificationErrorNotification;
//
@interface TLSBox : NSObject
- (nonnull instancetype)initWithCAPath:(NSString *)caPath;
- (nonnull instancetype)initWithCAPath:(nullable NSString *)caPath;
- (BOOL)startWithPeerVerification:(BOOL)peerVerification error:(NSError **)error;
- (BOOL)startWithError:(NSError **)error;
- (NSData *)pullCipherTextWithError:(NSError **)error;
// WARNING: text must be able to hold plain text output

4
TunnelKit/Sources/Core/TLSBox.m
View File

@ -74,7 +74,7 @@ int TLSBoxVerifyPeer(int ok, X509_STORE_CTX *ctx) {
free(self.bufferCipherText);
}
- (BOOL)startWithPeerVerification:(BOOL)peerVerification error:(NSError *__autoreleasing *)error
- (BOOL)startWithError:(NSError *__autoreleasing *)error
{
if (!TLSBoxIsOpenSSLLoaded) {
// OPENSSL_init_ssl(0, NULL);
@ -84,7 +84,7 @@ int TLSBoxVerifyPeer(int ok, X509_STORE_CTX *ctx) {
self.ctx = SSL_CTX_new(TLS_client_method());
SSL_CTX_set_options(self.ctx, SSL_OP_NO_SSLv2|SSL_OP_NO_SSLv3|SSL_OP_NO_COMPRESSION);
if (peerVerification && self.caPath) {
if (self.caPath) {
SSL_CTX_set_verify(self.ctx, SSL_VERIFY_PEER, TLSBoxVerifyPeer);
if (!SSL_CTX_load_verify_locations(self.ctx, [self.caPath cStringUsingEncoding:NSASCIIStringEncoding], NULL)) {
ERR_print_errors_fp(stdout);

4
TunnelKitTests/AppExtensionTests.swift
View File

@ -39,7 +39,7 @@ class AppExtensionTests: XCTestCase {
builder.cipher = .aes128cbc
builder.digest = .sha256
builder.handshake = .rsa3072
builder.ca = Certificate(pem: "abcdef")
cfg = builder.build()
let proto = try? cfg.generatedTunnelProtocol(withBundleIdentifier: identifier, endpoint: endpoint)
@ -58,7 +58,7 @@ class AppExtensionTests: XCTestCase {
XCTAssertEqual(proto?.providerConfiguration?[K.appGroup] as? String, cfg.appGroup)
XCTAssertEqual(proto?.providerConfiguration?[K.cipherAlgorithm] as? String, cfg.cipher.rawValue)
XCTAssertEqual(proto?.providerConfiguration?[K.digestAlgorithm] as? String, cfg.digest.rawValue)
XCTAssertEqual(proto?.providerConfiguration?[K.handshakeCertificate] as? String, cfg.handshake.rawValue)
XCTAssertEqual(proto?.providerConfiguration?[K.ca] as? String, cfg.ca?.pem)
XCTAssertEqual(proto?.providerConfiguration?[K.mtu] as? NSNumber, cfg.mtu)
XCTAssertEqual(proto?.providerConfiguration?[K.renegotiatesAfter] as? Int, cfg.renegotiatesAfterSeconds)
XCTAssertEqual(proto?.providerConfiguration?[K.debug] as? Bool, cfg.shouldDebug)