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fix: clear DH shared secrets after Noise handshake operations

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Added secureClear() calls for all 6 DH operations in NoiseProtocol.swift
to properly clear sensitive shared secrets from memory after use:

- writeMessage(): .es initiator/responder, .se initiator/responder
- performDHOperation(): .ee and .ss operations

This fixes a forward secrecy vulnerability where shared secrets could
persist in memory after handshake completion.

Also adds:
- TrackingMockKeychain to count secureClear calls in tests
- 3 new tests verifying secureClear is called during handshake

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
This commit is contained in:
jack
2026-01-04 13:21:01 -10:00
co-authored by Claude Opus 4.5
parent f71bd506fd
commit 84fd92ef4b
3 changed files with 268 additions and 8 deletions
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bitchat/Noise/NoiseProtocol.swift
+26 -8
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@@ -610,14 +610,20 @@ final class NoiseHandshakeState {
throw NoiseError.missingKeys
}
let shared = try localEphemeral.sharedSecretFromKeyAgreement(with: remoteStatic)
symmetricState.mixKey(shared.withUnsafeBytes { Data($0) })
var sharedData = shared.withUnsafeBytes { Data($0) }
symmetricState.mixKey(sharedData)
// Clear sensitive shared secret
keychain.secureClear(&sharedData)
} else {
guard let localStatic = localStaticPrivate,
let remoteEphemeral = remoteEphemeralPublic else {
throw NoiseError.missingKeys
}
let shared = try localStatic.sharedSecretFromKeyAgreement(with: remoteEphemeral)
symmetricState.mixKey(shared.withUnsafeBytes { Data($0) })
var sharedData = shared.withUnsafeBytes { Data($0) }
symmetricState.mixKey(sharedData)
// Clear sensitive shared secret
keychain.secureClear(&sharedData)
}
case .se:
@@ -628,14 +634,20 @@ final class NoiseHandshakeState {
throw NoiseError.missingKeys
}
let shared = try localStatic.sharedSecretFromKeyAgreement(with: remoteEphemeral)
symmetricState.mixKey(shared.withUnsafeBytes { Data($0) })
var sharedData = shared.withUnsafeBytes { Data($0) }
symmetricState.mixKey(sharedData)
// Clear sensitive shared secret
keychain.secureClear(&sharedData)
} else {
guard let localEphemeral = localEphemeralPrivate,
let remoteStatic = remoteStaticPublic else {
throw NoiseError.missingKeys
}
let shared = try localEphemeral.sharedSecretFromKeyAgreement(with: remoteStatic)
symmetricState.mixKey(shared.withUnsafeBytes { Data($0) })
var sharedData = shared.withUnsafeBytes { Data($0) }
symmetricState.mixKey(sharedData)
// Clear sensitive shared secret
keychain.secureClear(&sharedData)
}
case .ss:
@@ -724,8 +736,11 @@ final class NoiseHandshakeState {
throw NoiseError.missingKeys
}
let shared = try localEphemeral.sharedSecretFromKeyAgreement(with: remoteEphemeral)
symmetricState.mixKey(shared.withUnsafeBytes { Data($0) })
var sharedData = shared.withUnsafeBytes { Data($0) }
symmetricState.mixKey(sharedData)
// Clear sensitive shared secret
keychain.secureClear(&sharedData)
case .es:
if role == .initiator {
guard let localEphemeral = localEphemeralPrivate,
@@ -778,8 +793,11 @@ final class NoiseHandshakeState {
throw NoiseError.missingKeys
}
let shared = try localStatic.sharedSecretFromKeyAgreement(with: remoteStatic)
symmetricState.mixKey(shared.withUnsafeBytes { Data($0) })
var sharedData = shared.withUnsafeBytes { Data($0) }
symmetricState.mixKey(sharedData)
// Clear sensitive shared secret
keychain.secureClear(&sharedData)
case .e, .s:
break
}