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Stop using commonName to validate certificates. #238

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27 changes: 15 additions & 12 deletions Sources/NIOSSL/IdentityVerification.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -87,23 +87,27 @@ extension UInt8 {
/// follow along at home.
internal func validIdentityForService(serverHostname: String?,
socketAddress: SocketAddress,
leafCertificate: NIOSSLCertificate) throws -> Bool {
leafCertificate: NIOSSLCertificate,
includeCommonName: Bool) throws -> Bool {
if let serverHostname = serverHostname {
return try serverHostname.withLowercaseASCIIBuffer {
try validIdentityForService(serverHostname: $0,
socketAddress: socketAddress,
leafCertificate: leafCertificate)
leafCertificate: leafCertificate,
includeCommonName: includeCommonName)
}
} else {
return try validIdentityForService(serverHostname: nil as Array<UInt8>?,
socketAddress: socketAddress,
leafCertificate: leafCertificate)
leafCertificate: leafCertificate,
includeCommonName: includeCommonName)
}
}

private func validIdentityForService(serverHostname: Array<UInt8>?,
socketAddress: SocketAddress,
leafCertificate: NIOSSLCertificate) throws -> Bool {
leafCertificate: NIOSSLCertificate,
includeCommonName: Bool) throws -> Bool {
// Before we begin, we want to locate the first period in our own domain name. We need to do
// this because we may need to match a wildcard label.
var serverHostnameSlice: ArraySlice<UInt8>? = nil
Expand Down Expand Up @@ -150,16 +154,15 @@ private func validIdentityForService(serverHostname: Array<UInt8>?,
}

// In the absence of any matchable subjectAlternativeNames, we can fall back to checking
// the common name. This is a deprecated practice, and in a future release we should
// stop doing this.
guard let commonName = leafCertificate.commonName() else {
// No CN, no match.
// the common name. We only do this if the user has configured a system that trusts the commonName field.
if includeCommonName, let commonName = leafCertificate.commonName() {
// We have a common name. Let's check it against the provided hostname. We never check
// the common name against the IP address.
return matchHostname(ourHostname: serverHostnameSlice, firstPeriodIndex: firstPeriodIndex, dnsName: commonName)
} else {
// We don't trust the common name, or we do but don't have one to look at.
return false
}

// We have a common name. Let's check it against the provided hostname. We never check
// the common name against the IP address.
return matchHostname(ourHostname: serverHostnameSlice, firstPeriodIndex: firstPeriodIndex, dnsName: commonName)
}


Expand Down
3 changes: 2 additions & 1 deletion Sources/NIOSSL/SSLConnection.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -213,7 +213,8 @@ internal final class SSLConnection {

guard try validIdentityForService(serverHostname: self.expectedHostname,
socketAddress: address,
leafCertificate: peerCert) else {
leafCertificate: peerCert,
includeCommonName: self.parentContext.configuration.trustCommonName) else {
throw NIOSSLExtraError.failedToValidateHostname(expectedName: self.expectedHostname ?? "<none>")
}
}
Expand Down
118 changes: 107 additions & 11 deletions Sources/NIOSSL/TLSConfiguration.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -303,6 +303,18 @@ public struct TLSConfiguration {
/// Whether renegotiation is supported.
public var renegotiationSupport: NIORenegotiationSupport

/// Whether to trust the commonName field when validating certificate hostnames.
///
/// The commonName field of certificates has been deprecated for use as a validation source
/// for nearly two decades. As browsers and the WebPKI now forbid the usage of common names
/// in certificates, swift-nio-ssl defaults to this strict level of enforcement as well.
///
/// However, some older infrastructure does not issue certificates with valid subject alternative
/// name fields. For this reason, we currently allow an override for trusting the common name. This
/// is a temporary measure to allow users to work around these limitations, but we will remove this
/// functionality in future.
public var trustCommonName: Bool
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Should we (assuming it's possible) mark the setter for this as deprecated right from the start?


private init(cipherSuiteValues: [NIOTLSCipher] = [],
cipherSuites: String = defaultCipherSuites,
verifySignatureAlgorithms: [SignatureAlgorithm]?,
Expand All @@ -317,7 +329,8 @@ public struct TLSConfiguration {
shutdownTimeout: TimeAmount,
keyLogCallback: NIOSSLKeyLogCallback?,
renegotiationSupport: NIORenegotiationSupport,
additionalTrustRoots: [NIOSSLAdditionalTrustRoots]) {
additionalTrustRoots: [NIOSSLAdditionalTrustRoots],
trustCommonName: Bool) {
self.cipherSuites = cipherSuites
self.verifySignatureAlgorithms = verifySignatureAlgorithms
self.signingSignatureAlgorithms = signingSignatureAlgorithms
Expand All @@ -331,6 +344,7 @@ public struct TLSConfiguration {
self.encodedApplicationProtocols = []
self.shutdownTimeout = shutdownTimeout
self.renegotiationSupport = renegotiationSupport
self.trustCommonName = trustCommonName
self.applicationProtocols = applicationProtocols
self.keyLogCallback = keyLogCallback
if !cipherSuiteValues.isEmpty {
Expand Down Expand Up @@ -368,7 +382,8 @@ public struct TLSConfiguration {
shutdownTimeout: shutdownTimeout,
keyLogCallback: keyLogCallback,
renegotiationSupport: .none, // Servers never support renegotiation: there's no point.
additionalTrustRoots: additionalTrustRoots)
additionalTrustRoots: additionalTrustRoots,
trustCommonName: false)
}

/// Create a TLS configuration for use with server-side contexts.
Expand Down Expand Up @@ -398,7 +413,8 @@ public struct TLSConfiguration {
shutdownTimeout: shutdownTimeout,
keyLogCallback: keyLogCallback,
renegotiationSupport: .none, // Servers never support renegotiation: there's no point.
additionalTrustRoots: [])
additionalTrustRoots: [],
trustCommonName: false)
}

/// Create a TLS configuration for use with server-side contexts.
Expand Down Expand Up @@ -430,7 +446,8 @@ public struct TLSConfiguration {
shutdownTimeout: shutdownTimeout,
keyLogCallback: keyLogCallback,
renegotiationSupport: .none, // Servers never support renegotiation: there's no point.
additionalTrustRoots: [])
additionalTrustRoots: [],
trustCommonName: false)
}

/// Create a TLS configuration for use with server-side contexts.
Expand Down Expand Up @@ -463,7 +480,43 @@ public struct TLSConfiguration {
shutdownTimeout: shutdownTimeout,
keyLogCallback: keyLogCallback,
renegotiationSupport: .none, // Servers never support renegotiation: there's no point.
additionalTrustRoots: additionalTrustRoots)
additionalTrustRoots: additionalTrustRoots,
trustCommonName: false)
}

/// Create a TLS configuration for use with server-side contexts.
///
/// This provides sensible defaults while requiring that you provide any data that is necessary
/// for server-side function. For client use, try `forClient` instead.
public static func forServer(certificateChain: [NIOSSLCertificateSource],
privateKey: NIOSSLPrivateKeySource,
cipherSuites: String = defaultCipherSuites,
verifySignatureAlgorithms: [SignatureAlgorithm]? = nil,
signingSignatureAlgorithms: [SignatureAlgorithm]? = nil,
minimumTLSVersion: TLSVersion = .tlsv1,
maximumTLSVersion: TLSVersion? = nil,
certificateVerification: CertificateVerification = .none,
trustRoots: NIOSSLTrustRoots = .default,
applicationProtocols: [String] = [],
shutdownTimeout: TimeAmount = .seconds(5),
keyLogCallback: NIOSSLKeyLogCallback? = nil,
additionalTrustRoots: [NIOSSLAdditionalTrustRoots] = [],
trustCommonName: Bool) -> TLSConfiguration {
return TLSConfiguration(cipherSuites: cipherSuites,
verifySignatureAlgorithms: verifySignatureAlgorithms,
signingSignatureAlgorithms: signingSignatureAlgorithms,
minimumTLSVersion: minimumTLSVersion,
maximumTLSVersion: maximumTLSVersion,
certificateVerification: certificateVerification,
trustRoots: trustRoots,
certificateChain: certificateChain,
privateKey: privateKey,
applicationProtocols: applicationProtocols,
shutdownTimeout: shutdownTimeout,
keyLogCallback: keyLogCallback,
renegotiationSupport: .none, // Servers never support renegotiation: there's no point.
additionalTrustRoots: additionalTrustRoots,
trustCommonName: trustCommonName)
}

/// Creates a TLS configuration for use with client-side contexts. This allows setting the `NIOTLSCipher` property specifically.
Expand Down Expand Up @@ -497,7 +550,8 @@ public struct TLSConfiguration {
shutdownTimeout: shutdownTimeout,
keyLogCallback: keyLogCallback,
renegotiationSupport: renegotiationSupport,
additionalTrustRoots: additionalTrustRoots)
additionalTrustRoots: additionalTrustRoots,
trustCommonName: false)
}

/// Creates a TLS configuration for use with client-side contexts.
Expand Down Expand Up @@ -527,7 +581,8 @@ public struct TLSConfiguration {
shutdownTimeout: shutdownTimeout,
keyLogCallback: keyLogCallback,
renegotiationSupport: .none, // Default value is here for backward-compatibility.
additionalTrustRoots: [])
additionalTrustRoots: [],
trustCommonName: false)
}


Expand Down Expand Up @@ -559,7 +614,8 @@ public struct TLSConfiguration {
shutdownTimeout: shutdownTimeout,
keyLogCallback: keyLogCallback,
renegotiationSupport: renegotiationSupport,
additionalTrustRoots: [])
additionalTrustRoots: [],
trustCommonName: false)
}

/// Creates a TLS configuration for use with client-side contexts.
Expand Down Expand Up @@ -592,7 +648,8 @@ public struct TLSConfiguration {
shutdownTimeout: shutdownTimeout,
keyLogCallback: keyLogCallback,
renegotiationSupport: renegotiationSupport,
additionalTrustRoots: [])
additionalTrustRoots: [],
trustCommonName: false)
}

/// Creates a TLS configuration for use with client-side contexts.
Expand Down Expand Up @@ -626,7 +683,44 @@ public struct TLSConfiguration {
shutdownTimeout: shutdownTimeout,
keyLogCallback: keyLogCallback,
renegotiationSupport: renegotiationSupport,
additionalTrustRoots: additionalTrustRoots)
additionalTrustRoots: additionalTrustRoots,
trustCommonName: false)
}

/// Creates a TLS configuration for use with client-side contexts. This allows setting the `NIOTLSCipher` property specifically.
///
/// This provides sensible defaults, and can be used without customisation. For server-side
/// contexts, you should use `forServer` instead.
public static func forClient(cipherSuites: String = defaultCipherSuites,
verifySignatureAlgorithms: [SignatureAlgorithm]? = nil,
signingSignatureAlgorithms: [SignatureAlgorithm]? = nil,
minimumTLSVersion: TLSVersion = .tlsv1,
maximumTLSVersion: TLSVersion? = nil,
certificateVerification: CertificateVerification = .fullVerification,
trustRoots: NIOSSLTrustRoots = .default,
certificateChain: [NIOSSLCertificateSource] = [],
privateKey: NIOSSLPrivateKeySource? = nil,
applicationProtocols: [String] = [],
shutdownTimeout: TimeAmount = .seconds(5),
keyLogCallback: NIOSSLKeyLogCallback? = nil,
renegotiationSupport: NIORenegotiationSupport = .none,
additionalTrustRoots: [NIOSSLAdditionalTrustRoots] = [],
trustCommonName: Bool) -> TLSConfiguration {
return TLSConfiguration(cipherSuites: cipherSuites,
verifySignatureAlgorithms: verifySignatureAlgorithms,
signingSignatureAlgorithms: signingSignatureAlgorithms,
minimumTLSVersion: minimumTLSVersion,
maximumTLSVersion: maximumTLSVersion,
certificateVerification: certificateVerification,
trustRoots: trustRoots,
certificateChain: certificateChain,
privateKey: privateKey,
applicationProtocols: applicationProtocols,
shutdownTimeout: shutdownTimeout,
keyLogCallback: keyLogCallback,
renegotiationSupport: renegotiationSupport,
additionalTrustRoots: additionalTrustRoots,
trustCommonName: trustCommonName)
}
}

Expand Down Expand Up @@ -657,7 +751,8 @@ extension TLSConfiguration {
self.encodedApplicationProtocols == comparing.encodedApplicationProtocols &&
self.shutdownTimeout == comparing.shutdownTimeout &&
isKeyLoggerCallbacksEqual &&
self.renegotiationSupport == comparing.renegotiationSupport
self.renegotiationSupport == comparing.renegotiationSupport &&
self.trustCommonName == comparing.trustCommonName
}

/// Returns a best effort hash of this TLS configuration.
Expand All @@ -682,5 +777,6 @@ extension TLSConfiguration {
hasher.combine(bytes: closureBits)
}
hasher.combine(renegotiationSupport)
hasher.combine(trustCommonName)
}
}
2 changes: 2 additions & 0 deletions Tests/NIOSSLTests/IdentityVerificationTest+XCTest.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -51,6 +51,8 @@ extension IdentityVerificationTest {
("testDoesNotMatchSANWithEmbeddedNULL", testDoesNotMatchSANWithEmbeddedNULL),
("testFallsBackToCommonName", testFallsBackToCommonName),
("testLowercasesForCommonName", testLowercasesForCommonName),
("testDoesNotFallBackToCommonName", testDoesNotFallBackToCommonName),
("testNoLowercasesForCommonName", testNoLowercasesForCommonName),
("testRejectsUnicodeCommonNameWithUnencodedIDNALabel", testRejectsUnicodeCommonNameWithUnencodedIDNALabel),
("testRejectsUnicodeCommonNameWithEncodedIDNALabel", testRejectsUnicodeCommonNameWithEncodedIDNALabel),
("testHandlesMissingCommonName", testHandlesMissingCommonName),
Expand Down
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