feat: M4a host key 校验（TOFU pin，关闭 MITM 敞口）

- TXCore/SSH: SSHWire(string/mpint 编码)、ECDSAConv(DER→SSH 签名/P256 blob)、 HostKey(opensshFingerprint/evaluate/HostTriple/KnownHostsStore)，+10 单测（含真实指纹向量、高位 DER） - TXTransport: SSHConfig.hostKeyVerifier 闭包 + SSHError.hostKeyMismatch； SSHSession 握手后 libssh2_session_hostkey 取 blob 交 verifier，拒绝则断开抛错 - app: 文件后端 KnownHostsStore（未签名 app 无 keychain 权限 SecItem -34018，host key 是公钥非机密，沙盒文件对 TOFU 足够）+ TOFU verifier + firstUse 横幅 + mismatch alert(信任/取消) - 验证(192.168.9.199)：首次信任 pin+接受连上；假 pin→不符→断开+告警，本次指纹与 ssh-keygen 逐字符一致 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
2026-07-24 18:06:39 +08:00
parent 7abe61a71f
commit 1a257fae7f
9 changed files with 321 additions and 5 deletions
--- a/packages/TXCore/Tests/TXCoreTests/SSHWireTests.swift
+++ b/packages/TXCore/Tests/TXCoreTests/SSHWireTests.swift
@@ -0,0 +1,60 @@
+import XCTest
+@testable import TXCore
+
+final class SSHWireTests: XCTestCase {
+    func testStringEncoding() {
+        XCTAssertEqual(SSHWire.string([0xAA, 0xBB]), [0, 0, 0, 2, 0xAA, 0xBB])
+        XCTAssertEqual(SSHWire.string(""), [0, 0, 0, 0])
+        XCTAssertEqual(SSHWire.string("nistp256"), [0, 0, 0, 8] + Array("nistp256".utf8))
+    }
+
+    func testMpint() {
+        // 普通正数（高位为 0）：原样。
+        XCTAssertEqual(SSHWire.mpint([0x01, 0x02]), [0, 0, 0, 2, 0x01, 0x02])
+        // 高位为 1：前补 0x00（否则被当负数）。
+        XCTAssertEqual(SSHWire.mpint([0xFF]), [0, 0, 0, 2, 0x00, 0xFF])
+        // 前导零去除。
+        XCTAssertEqual(SSHWire.mpint([0x00, 0x00, 0x05]), [0, 0, 0, 1, 0x05])
+        // 值为 0 → 空串。
+        XCTAssertEqual(SSHWire.mpint([0x00, 0x00]), [0, 0, 0, 0])
+    }
+
+    func testDerToSSHSignatureHighBit() {
+        // 构造 DER SEQUENCE{ INTEGER r(高位1，含前导00), INTEGER s(高位0) }。
+        let r = [UInt8(0x00), 0xFF] + [UInt8](repeating: 0x11, count: 31)   // 33B DER 内容
+        let s = [UInt8(0x01)] + [UInt8](repeating: 0x22, count: 31)         // 32B DER 内容
+        var der: [UInt8] = [0x30, UInt8(2 + r.count + 2 + s.count)]
+        der += [0x02, UInt8(r.count)] + r
+        der += [0x02, UInt8(s.count)] + s
+
+        let sig = ECDSAConv.derToSSHSignature(der)
+        XCTAssertNotNil(sig)
+        // 应等于独立计算的 mpint(r)+mpint(s)。
+        let expected = SSHWire.mpint(r) + SSHWire.mpint(s)
+        XCTAssertEqual(sig, expected)
+        // r 高位为 1 → mpint 33 字节，长度前缀 0x21。
+        XCTAssertEqual(Array(sig!.prefix(4)), [0, 0, 0, 0x21])
+    }
+
+    func testP256Blob() {
+        let q = [UInt8(0x04)] + [UInt8](repeating: 0xAB, count: 64)   // X9.63 65B
+        let blob = ECDSAConv.p256PublicKeyBlob(x963: q)
+        // 开头必须是 string("ecdsa-sha2-nistp256")。
+        XCTAssertEqual(Array(blob.prefix(4)), [0, 0, 0, 0x13])
+        XCTAssertEqual(Array(blob[4 ..< 4 + 19]), Array("ecdsa-sha2-nistp256".utf8))
+    }
+
+    /// 真实向量：192.168.9.199 的 ecdsa host key，指纹须与 `ssh-keygen -lf` 一致。
+    func testOpenSSHFingerprintRealVector() {
+        let b64 = "AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBCkvFPRkGE8RGQ+scBa3JZMWnZnGUn7BWfsz8rfEtKjIojjqxxJLdZvQE9rUlaNNUFi8eGb9lfr5rO4yFS0dnsU="
+        let blob = Data(base64Encoded: b64)!
+        XCTAssertEqual(HostKey.opensshFingerprint(blob), "SHA256:dcpjdomtDzOZJuv/NHr1vYtm0mP5EbsEML0kClhgqxg")
+    }
+
+    func testEvaluate() {
+        let a = Data([1, 2, 3]); let b = Data([1, 2, 3]); let c = Data([9])
+        XCTAssertEqual(HostKey.evaluate(stored: nil, presented: a), .firstUse)
+        XCTAssertEqual(HostKey.evaluate(stored: b, presented: a), .trusted)
+        XCTAssertEqual(HostKey.evaluate(stored: c, presented: a), .mismatch(stored: c))
+    }
+}