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Avoid caching PEMs on disk (#213) 

* TLSBox: Use OpenSSL calls that take in-memory cert / private key

* TLSBox: Add ability to compute MD5 hash for cert in memory

* OpenVPNSession: Remove disk caching of ca, cert and key

* Add test for computing MD5 hash for cert in memory

Co-authored-by: Davide De Rosa <keeshux@gmail.com>
This commit is contained in:
Roopesh Chander 2021-10-13 14:21:14 +05:30 committed by GitHub
parent 16c00410ed
commit 00d908cc89
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GPG Key ID: 4AEE18F83AFDEB23
6 changed files with 96 additions and 83 deletions
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1
CHANGELOG.md
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@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
### Changed
- Avoid caching PEMs on disk (roop). [#213](https://github.com/passepartoutvpn/tunnelkit/pull/213)
- Upgrade OpenSSL to 1.1.1l.
## 3.4.0 (2021-08-07)

2
TunnelKit/Sources/Protocols/OpenVPN/AppExtension/OpenVPNTunnelProvider.swift
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@ -238,7 +238,7 @@ open class OpenVPNTunnelProvider: NEPacketTunnelProvider {
let session: OpenVPNSession
do {
session = try OpenVPNSession(queue: tunnelQueue, configuration: cfg.sessionConfiguration, cachesURL: cachesURL)
session = try OpenVPNSession(queue: tunnelQueue, configuration: cfg.sessionConfiguration)
refreshDataCount()
} catch let e {
completionHandler(e)

69
TunnelKit/Sources/Protocols/OpenVPN/OpenVPNSession.swift
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@ -70,14 +70,6 @@ public class OpenVPNSession: Session {
case reconnect
}
private struct Caches {
static let ca = "ca.pem"
static let clientCertificate = "cert.pem"
static let clientKey = "key.pem"
}
// MARK: Configuration
/// The session base configuration.
@ -172,22 +164,6 @@ public class OpenVPNSession: Session {
private var authenticator: OpenVPN.Authenticator?
// MARK: Caching
private let cachesURL: URL
private var caURL: URL {
return cachesURL.appendingPathComponent(Caches.ca)
}
private var clientCertificateURL: URL {
return cachesURL.appendingPathComponent(Caches.clientCertificate)
}
private var clientKeyURL: URL {
return cachesURL.appendingPathComponent(Caches.clientKey)
}
// MARK: Init
/**
@ -196,14 +172,13 @@ public class OpenVPNSession: Session {
- Parameter queue: The `DispatchQueue` where to run the session loop.
- Parameter configuration: The `Configuration` to use for this session.
*/
public init(queue: DispatchQueue, configuration: OpenVPN.Configuration, cachesURL: URL) throws {
guard let ca = configuration.ca else {
public init(queue: DispatchQueue, configuration: OpenVPN.Configuration) throws {
guard let _ = configuration.ca else {
throw ConfigurationError.missingConfiguration(option: "ca")
}
self.queue = queue
self.configuration = configuration
self.cachesURL = cachesURL
withLocalOptions = true
keys = [:]
@ -224,26 +199,11 @@ public class OpenVPNSession: Session {
} else {
controlChannel = OpenVPN.ControlChannel()
}
// cache PEMs locally (mandatory for OpenSSL)
let fm = FileManager.default
try ca.pem.write(to: caURL, atomically: true, encoding: .ascii)
if let container = configuration.clientCertificate {
try container.pem.write(to: clientCertificateURL, atomically: true, encoding: .ascii)
} else {
try? fm.removeItem(at: clientCertificateURL)
}
if let container = configuration.clientKey {
try container.pem.write(to: clientKeyURL, atomically: true, encoding: .ascii)
} else {
try? fm.removeItem(at: clientKeyURL)
}
}
/// :nodoc:
deinit {
cleanup()
cleanupCache()
}
// MARK: Session
@ -354,13 +314,6 @@ public class OpenVPNSession: Session {
stopError = nil
}
func cleanupCache() {
let fm = FileManager.default
for url in [caURL, clientCertificateURL, clientKeyURL] {
try? fm.removeItem(at: url)
}
}
// MARK: Loop
// Ruby: start
@ -622,9 +575,13 @@ public class OpenVPNSession: Session {
private func hardResetPayload() -> Data? {
guard !(configuration.usesPIAPatches ?? false) else {
guard let ca = configuration.ca else {
log.error("Configuration doesn't have a CA")
return nil
}
let caMD5: String
do {
caMD5 = try TLSBox.md5(forCertificatePath: caURL.path)
caMD5 = try TLSBox.md5(forCertificatePEM: ca.pem)
} catch {
log.error("CA MD5 could not be computed, skipping custom HARD_RESET")
return nil
@ -765,6 +722,11 @@ public class OpenVPNSession: Session {
return
}
guard let ca = configuration.ca else {
log.error("Configuration doesn't have a CA")
return
}
// start new TLS handshake
if ((packet.code == .hardResetServerV2) && (negotiationKey.state == .hardReset)) ||
((packet.code == .softResetV1) && (negotiationKey.state == .softReset)) {
@ -788,9 +750,9 @@ public class OpenVPNSession: Session {
log.debug("Start TLS handshake")
let tls = TLSBox(
caPath: caURL.path,
clientCertificatePath: (configuration.clientCertificate != nil) ? clientCertificateURL.path : nil,
clientKeyPath: (configuration.clientKey != nil) ? clientKeyURL.path : nil,
ca: ca.pem,
clientCertificate: configuration.clientCertificate?.pem,
clientKey: configuration.clientKey?.pem,
checksEKU: configuration.checksEKU ?? false,
checksSANHost: configuration.checksSANHost ?? false,
hostname: configuration.sanHost
@ -1252,7 +1214,6 @@ public class OpenVPNSession: Session {
switch method {
case .shutdown:
self?.doShutdown(error: error)
self?.cleanupCache()
case .reconnect:
self?.doReconnect(error: error)

7
TunnelKit/Sources/Protocols/OpenVPN/TLSBox.h
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@ -55,12 +55,13 @@ extern const NSInteger TLSBoxDefaultSecurityLevel;
@property (nonatomic, assign) NSInteger securityLevel; // TLSBoxDefaultSecurityLevel for default
+ (nullable NSString *)md5ForCertificatePath:(NSString *)path error:(NSError **)error;
+ (nullable NSString *)md5ForCertificatePEM:(NSString *)pem error:(NSError **)error;
+ (nullable NSString *)decryptedPrivateKeyFromPath:(NSString *)path passphrase:(NSString *)passphrase error:(NSError **)error;
+ (nullable NSString *)decryptedPrivateKeyFromPEM:(NSString *)pem passphrase:(NSString *)passphrase error:(NSError **)error;
- (instancetype)initWithCAPath:(NSString *)caPath
clientCertificatePath:(nullable NSString *)clientCertificatePath
clientKeyPath:(nullable NSString *)clientKeyPath
- (instancetype)initWithCA:(nonnull NSString *)caPEM
clientCertificate:(nullable NSString *)clientCertificatePEM
clientKey:(nullable NSString *)clientKeyPEM
checksEKU:(BOOL)checksEKU
checksSANHost:(BOOL)checksSANHost
hostname:(nullable NSString *)hostname;

73
TunnelKit/Sources/Protocols/OpenVPN/TLSBox.m
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@ -65,9 +65,9 @@ const NSInteger TLSBoxDefaultSecurityLevel = -1;
@interface TLSBox ()
@property (nonatomic, strong) NSString *caPath;
@property (nonatomic, strong) NSString *clientCertificatePath;
@property (nonatomic, strong) NSString *clientKeyPath;
@property (nonatomic, strong) NSString *caPEM;
@property (nonatomic, strong) NSString *clientCertificatePEM;
@property (nonatomic, strong) NSString *clientKeyPEM;
@property (nonatomic, assign) BOOL checksEKU;
@property (nonatomic, assign) BOOL checksSANHost;
@property (nonatomic, strong) NSString *hostname;
@ -83,6 +83,10 @@ const NSInteger TLSBoxDefaultSecurityLevel = -1;
@end
static BIO *create_BIO_from_PEM(NSString *pem) {
return BIO_new_mem_buf([pem cStringUsingEncoding:NSASCIIStringEncoding], (int)[pem length]);
}
@implementation TLSBox
+ (NSString *)md5ForCertificatePath:(NSString *)path error:(NSError * _Nullable __autoreleasing * _Nullable)error
@ -112,6 +116,31 @@ const NSInteger TLSBoxDefaultSecurityLevel = -1;
return hex;
}
+ (NSString *)md5ForCertificatePEM:(NSString *)pem error:(NSError * _Nullable __autoreleasing * _Nullable)error
{
const EVP_MD *alg = EVP_get_digestbyname("MD5");
uint8_t md[16];
unsigned int len;
BIO *bio = create_BIO_from_PEM(pem);
X509 *cert = PEM_read_bio_X509(bio, NULL, NULL, NULL);
if (!cert) {
BIO_free(bio);
return NULL;
}
X509_digest(cert, alg, md, &len);
X509_free(cert);
BIO_free(bio);
NSCAssert2(len == sizeof(md), @"Unexpected MD5 size (%d != %lu)", len, sizeof(md));
NSMutableString *hex = [[NSMutableString alloc] initWithCapacity:2 * sizeof(md)];
for (int i = 0; i < sizeof(md); ++i) {
[hex appendFormat:@"%02x", md[i]];
}
return hex;
}
+ (NSString *)decryptedPrivateKeyFromPath:(NSString *)path passphrase:(NSString *)passphrase error:(NSError * _Nullable __autoreleasing *)error
{
BIO *bio;
@ -172,17 +201,17 @@ const NSInteger TLSBoxDefaultSecurityLevel = -1;
return nil;
}
- (instancetype)initWithCAPath:(NSString *)caPath
clientCertificatePath:(NSString *)clientCertificatePath
clientKeyPath:(NSString *)clientKeyPath
- (instancetype)initWithCA:(nonnull NSString *)caPEM
clientCertificate:(nullable NSString *)clientCertificatePEM
clientKey:(nullable NSString *)clientKeyPEM
checksEKU:(BOOL)checksEKU
checksSANHost:(BOOL)checksSANHost
hostname:(nullable NSString *)hostname
{
if ((self = [super init])) {
self.caPath = caPath;
self.clientCertificatePath = clientCertificatePath;
self.clientKeyPath = clientKeyPath;
self.caPEM = caPEM;
self.clientCertificatePEM = clientCertificatePEM;
self.clientKeyPEM = clientKeyPEM;
self.checksEKU = checksEKU;
self.checksSANHost = checksSANHost;
self.bufferCipherText = allocate_safely(TLSBoxMaxBufferLength);
@ -216,31 +245,47 @@ const NSInteger TLSBoxDefaultSecurityLevel = -1;
if (self.securityLevel != TLSBoxDefaultSecurityLevel) {
SSL_CTX_set_security_level(self.ctx, (int)self.securityLevel);
}
if (!SSL_CTX_load_verify_locations(self.ctx, [self.caPath cStringUsingEncoding:NSASCIIStringEncoding], NULL)) {
if (self.caPEM) {
BIO *bio = create_BIO_from_PEM(self.caPEM);
X509 *ca = PEM_read_bio_X509(bio, NULL, NULL, NULL);
BIO_free(bio);
X509_STORE *trustedStore = SSL_CTX_get_cert_store(self.ctx);
if (!X509_STORE_add_cert(trustedStore, ca)) {
ERR_print_errors_fp(stdout);
if (error) {
*error = TunnelKitErrorWithCode(TunnelKitErrorCodeTLSCertificateAuthority);
}
return NO;
}
}
if (self.clientCertificatePath) {
if (!SSL_CTX_use_certificate_file(self.ctx, [self.clientCertificatePath cStringUsingEncoding:NSASCIIStringEncoding], SSL_FILETYPE_PEM)) {
if (self.clientCertificatePEM) {
BIO *bio = create_BIO_from_PEM(self.clientCertificatePEM);
X509 *cert = PEM_read_bio_X509(bio, NULL, NULL, NULL);
BIO_free(bio);
if (!SSL_CTX_use_certificate(self.ctx, cert)) {
ERR_print_errors_fp(stdout);
if (error) {
*error = TunnelKitErrorWithCode(TunnelKitErrorCodeTLSClientCertificate);
}
return NO;
}
X509_free(cert);
if (self.clientKeyPath) {
if (!SSL_CTX_use_PrivateKey_file(self.ctx, [self.clientKeyPath cStringUsingEncoding:NSASCIIStringEncoding], SSL_FILETYPE_PEM)) {
if (self.clientKeyPEM) {
BIO *bio = create_BIO_from_PEM(self.clientKeyPEM);
EVP_PKEY *pkey = PEM_read_bio_PrivateKey(bio, NULL, NULL, NULL);
BIO_free(bio);
if (!SSL_CTX_use_PrivateKey(self.ctx, pkey)) {
ERR_print_errors_fp(stdout);
if (error) {
*error = TunnelKitErrorWithCode(TunnelKitErrorCodeTLSClientKey);
}
return NO;
}
EVP_PKEY_free(pkey);
}
}

5
TunnelKit/Tests/OpenVPN/EncryptionTests.swift
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@ -117,6 +117,11 @@ class EncryptionTests: XCTestCase {
let exp = "e2fccccaba712ccc68449b1c56427ac1"
print(md5)
XCTAssertEqual(md5, exp)
let pem = try! String(contentsOfFile: path, encoding: .ascii)
let md5FromPEM = try! TLSBox.md5(forCertificatePEM: pem)
print(md5FromPEM)
XCTAssertEqual(md5FromPEM, exp)
}
func testPrivateKeyDecryption() {