httpserver: Improve MITM tests for Chrome on iOS, BlueCoat connections

caddyhttp/httpserver/mitm.go

@@ -58,6 +58,11 @@ func (h *tlsHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	} else if strings.Contains(ua, "Chrome") {
 		checked = true
 		mitm = !info.looksLikeChrome()
+	} else if strings.Contains(ua, "CriOS") {
+		// Chrome on iOS sometimes uses iOS-provided TLS stack (which looks exactly like Safari)
+		// but for connections that don't render a web page (favicon, etc.) it uses its own...
+		checked = true
+		mitm = !info.looksLikeChrome() && !info.looksLikeSafari()
 	} else if strings.Contains(ua, "Firefox") {
 		checked = true
 		mitm = !info.looksLikeFirefox()
@@ -338,6 +343,10 @@ func (info rawHelloInfo) looksLikeFirefox() bool {
 		}
 	}
 
+	if hasGreaseCiphers(info.cipherSuites) {
+		return false
+	}
+
 	// We check for order of cipher suites but not presence, since
 	// according to the paper, cipher suites may be not be added
 	// or reordered by the user, but they may be disabled.
@@ -412,6 +421,10 @@ func (info rawHelloInfo) looksLikeChrome() bool {
 		}
 	}
 
+	if !hasGreaseCiphers(info.cipherSuites) {
+		return false
+	}
+
 	return true
 }
 
@@ -449,6 +462,10 @@ func (info rawHelloInfo) looksLikeEdge() bool {
 		}
 	}
 
+	if hasGreaseCiphers(info.cipherSuites) {
+		return false
+	}
+
 	return true
 }
 
@@ -483,6 +500,10 @@ func (info rawHelloInfo) looksLikeSafari() bool {
 		return false
 	}
 
+	if hasGreaseCiphers(info.cipherSuites) {
+		return false
+	}
+
 	// We check for order and presence of cipher suites
 	expectedCipherSuiteOrder := []uint16{
 		tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, // 0xc02c
@@ -540,6 +561,34 @@ func assertPresenceAndOrdering(requiredItems, candidateList []uint16, requiredIs
 	return true
 }
 
+func hasGreaseCiphers(cipherSuites []uint16) bool {
+	for _, cipher := range cipherSuites {
+		if _, ok := greaseCiphers[cipher]; ok {
+			return true
+		}
+	}
+	return false
+}
+
+var greaseCiphers = map[uint16]struct{}{
+	0x0A0A: {},
+	0x1A1A: {},
+	0x2A2A: {},
+	0x3A3A: {},
+	0x4A4A: {},
+	0x5A5A: {},
+	0x6A6A: {},
+	0x7A7A: {},
+	0x8A8A: {},
+	0x9A9A: {},
+	0xAAAA: {},
+	0xBABA: {},
+	0xCACA: {},
+	0xDADA: {},
+	0xEAEA: {},
+	0xFAFA: {},
+}
+
 const (
 	extensionOCSPStatusRequest = 5
 	extensionSupportedCurves   = 10 // also called "SupportedGroups"

caddyhttp/httpserver/mitm_test.go

@@ -3,6 +3,8 @@ package httpserver
 import (
 	"crypto/tls"
 	"encoding/hex"
+	"net/http"
+	"net/http/httptest"
 	"reflect"
 	"testing"
 )
@@ -68,11 +70,12 @@ func TestParseClientHello(t *testing.T) {
 	}
 }
 
-func TestHeuristicFunctions(t *testing.T) {
+func TestHeuristicFunctionsAndHandler(t *testing.T) {
 	// To test the heuristics, we assemble a collection of real
-	// ClientHello messages from various TLS clients. Please be
-	// sure to hex-encode them and document the User-Agent
-	// associated with the connection.
+	// ClientHello messages from various TLS clients, both genuine
+	// and intercepted. Please be sure to hex-encode them and
+	// document the User-Agent associated with the connection
+	// as well as any intercepting proxy as thoroughly as possible.
 	//
 	// If the TLS client used is not an HTTP client (e.g. s_client),
 	// you can leave the userAgent blank, but please use a comment
@@ -85,6 +88,8 @@ func TestHeuristicFunctions(t *testing.T) {
 	type clientHello struct {
 		userAgent    string
 		helloHex     string      // do NOT include the header, just the ClientHello message
+		interception bool        // if test case shows an interception, set to true
+		reqHeaders   http.Header // if the request should set any headers to imitate a browser or proxy
 	}
 
 	// clientHellos groups samples of true (real) ClientHellos by the
@@ -101,89 +106,137 @@ func TestHeuristicFunctions(t *testing.T) {
 			{
 				userAgent:    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36",
 				helloHex:     `010000c003031dae75222dae1433a5a283ddcde8ddabaefbf16d84f250eee6fdff48cdfff8a00000201a1ac02bc02fc02cc030cca9cca8cc14cc13c013c014009c009d002f0035000a010000777a7a0000ff010001000000000e000c0000096c6f63616c686f73740017000000230000000d00140012040308040401050308050501080606010201000500050100000000001200000010000e000c02683208687474702f312e3175500000000b00020100000a000a0008aaaa001d001700182a2a000100`,
+				interception: false,
+			},
+			// TODO: Chrome on iOS will use iOS' TLS stack for requests that load
+			// the web page (apparently required by the dev ToS) but will use its
+			// own TLS stack for everything else, it seems. Figure out a decent way
+			// to test this with a nice, unified corpus that allows for this variance.
+			// {
+			// 	// Chrome on iOS
+			// 	userAgent: "Mozilla/5.0 (iPhone; CPU iPhone OS 10_0_2 like Mac OS X) AppleWebKit/602.1.50 (KHTML, like Gecko) CriOS/56.0.2924.79 Mobile/14A456 Safari/602.1",
+			// 	helloHex:  `010000de030358b062c509b21410a6496b5a82bfec74436cdecebe8ea1da29799939bbd3c17200002c00ffc02cc02bc024c023c00ac009c008c030c02fc028c027c014c013c012009d009c003d003c0035002f000a0100008900000014001200000f66696e6572706978656c732e636f6d000a00080006001700180019000b00020100000d00120010040102010501060104030203050306033374000000100030002e0268320568322d31360568322d31350568322d313408737064792f332e3106737064792f3308687474702f312e310005000501000000000012000000170000`,
+			// },
+			// {
+			// 	// Chrome on iOS (requesting favicon)
+			// 	userAgent: "Mozilla/5.0 (iPhone; CPU iPhone OS 10_0_2 like Mac OS X) AppleWebKit/602.1.50 (KHTML, like Gecko) CriOS/56.0.2924.79 Mobile/14A456 Safari/602.1",
+			// 	helloHex:  `010000c20303863eb64788e3b9638c261300318411cbdd8f09576d58eec1e744b6ce944f574f0000208a8acca9cca8cc14cc13c02bc02fc02cc030c013c014009c009d002f0035000a01000079baba0000ff0100010000000014001200000f66696e6572706978656c732e636f6d0017000000230000000d00140012040308040401050308050501080606010201000500050100000000001200000010000e000c02683208687474702f312e31000b00020100000a000a00083a3a001d001700184a4a000100`,
+			// },
+			{
+				userAgent:    "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36",
+				helloHex:     `010000c603036f717a88212c3e9e41940f82c42acb3473e0e4a64e8f52d9af33d34e972e08a30000206a6ac02bc02fc02cc030cca9cca8cc14cc13c013c014009c009d002f0035000a0100007d7a7a0000ff0100010000000014001200000f66696e6572706978656c732e636f6d0017000000230000000d00140012040308040401050308050501080606010201000500050100000000001200000010000e000c02683208687474702f312e3175500000000b00020100000a000a00087a7a001d001700188a8a000100`,
+				interception: false,
+			},
+			{
+				userAgent:    "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36",
+				helloHex:     `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`,
+				interception: false,
 			},
 		},
 		"Firefox": {
 			{
 				userAgent:    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:51.0) Gecko/20100101 Firefox/51.0",
 				helloHex:     `010000bd030375f9022fc3a6562467f3540d68013b2d0b961979de6129e944efe0b35531323500001ec02bc02fcca9cca8c02cc030c00ac009c013c01400330039002f0035000a010000760000000e000c0000096c6f63616c686f737400170000ff01000100000a000a0008001d001700180019000b00020100002300000010000e000c02683208687474702f312e31000500050100000000ff030000000d0020001e040305030603020308040805080604010501060102010402050206020202`,
+				interception: false,
 			},
 		},
 		"Edge": {
 			{
 				userAgent:    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.79 Safari/537.36 Edge/14.14393",
 				helloHex:     `010000bd030358a3c9bf05f734842e189fb6ce653b67b846e990bc1fc5fb8c397874d06020f1000038c02cc02bc030c02f009f009ec024c023c028c027c00ac009c014c01300390033009d009c003d003c0035002f000a006a00400038003200130100005c000500050100000000000a00080006001d00170018000b00020100000d00140012040105010201040305030203020206010603002300000010000e000c02683208687474702f312e310017000055000006000100020002ff01000100`,
+				interception: false,
 			},
 		},
 		"Safari": {
 			{
 				userAgent:    "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_3) AppleWebKit/602.4.8 (KHTML, like Gecko) Version/10.0.3 Safari/602.4.8",
 				helloHex:     `010000d2030358a295b513c8140c6ff880f4a8a73cc830ed2dab2c4f2068eb365228d828732e00002600ffc02cc02bc024c023c00ac009c030c02fc028c027c014c013009d009c003d003c0035002f010000830000000e000c0000096c6f63616c686f7374000a00080006001700180019000b00020100000d00120010040102010501060104030203050306033374000000100030002e0268320568322d31360568322d31350568322d313408737064792f332e3106737064792f3308687474702f312e310005000501000000000012000000170000`,
+				interception: false,
 			},
 		},
 		"Other": { // these are either non-browser clients or intercepted client hellos
 			{
-				// openssl s_client (OpenSSL 0.9.8zh 14 Jan 2016)
+				// openssl s_client (OpenSSL 0.9.8zh 14 Jan 2016) - NOT an interception, but not a browser either
 				helloHex: `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`,
+				// NOTE: This test case is not actually an interception, but s_client is not a browser
+				// or any client we support MITM checking for, either. Since it advertises heartbeat,
+				// our heuristics still flag it as a MITM.
+				interception: true,
 			},
 			{
 				// curl 7.51.0 (x86_64-apple-darwin16.0) libcurl/7.51.0 SecureTransport zlib/1.2.8
 				userAgent:    "curl/7.51.0",
 				helloHex:     `010000a6030358a28c73a71bdfc1f09dee13fecdc58805dcce42ac44254df548f14645f7dc2c00004400ffc02cc02bc024c023c00ac009c008c030c02fc028c027c014c013c012009f009e006b0067003900330016009d009c003d003c0035002f000a00af00ae008d008c008b01000039000a00080006001700180019000b00020100000d00120010040102010501060104030203050306030005000501000000000012000000170000`,
+				interception: false,
 			},
 			{
 				// Avast 17.1.2286 (Feb. 2017) on Windows 10 x64 build 14393, intercepting Edge
 				userAgent:    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.79 Safari/537.36 Edge/14.14393",
 				helloHex:     `010000ce0303b418fdc4b6cf6436a5e2bfb06b96ed5faa7285c20c7b49341a78be962a9dc40000003ac02cc02bc030c02f009f009ec024c023c028c027c00ac009c014c01300390033009d009c003d003c0035002f000a006a004000380032001300ff0100006b00000014001200000f66696e6572706978656c732e636f6d000b000403000102000a00080006001d0017001800230000000d001400120401050102010403050302030202060106030005000501000000000010000e000c02683208687474702f312e310016000000170000`,
+				interception: true,
 			},
 			{
 				// Kaspersky Internet Security 17.0.0.611 on Windows 10 x64 build 14393, intercepting Edge
 				userAgent:    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.79 Safari/537.36 Edge/14.14393",
 				helloHex:     `010000eb030361ce302bf4b0d5adf1ff30b2cf433c4a4b68f33e07b2651695e7ae6ec3cf126400003ac02cc02bc030c02f009f009ec024c023c028c027c00ac009c014c01300390033009d009c003d003c0035002f000a006a004000380032001300ff0100008800000014001200000f66696e6572706978656c732e636f6d000b000403000102000a001c001a00170019001c001b0018001a0016000e000d000b000c0009000a00230000000d0020001e060106020603050105020503040104020403030103020303020102020203000500050100000000000f0001010010000e000c02683208687474702f312e31`,
+				interception: true,
 			},
 			{
 				// Kaspersky Internet Security 17.0.0.611 on Windows 10 x64 build 14393, intercepting Firefox 51
 				userAgent:    "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:51.0) Gecko/20100101 Firefox/51.0",
 				helloHex:     `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`,
+				interception: true,
 			},
 			{
 				// Kaspersky Internet Security 17.0.0.611 on Windows 10 x64 build 14393, intercepting Chrome 56
 				userAgent:    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36",
 				helloHex:     `010000c903033481e7af24e647ba5a79ec97e9264c1a1f990cf842f50effe22be52130d5af82000018c02bc02fc02cc030c013c014009c009d002f0035000a00ff0100008800000014001200000f66696e6572706978656c732e636f6d000b000403000102000a001c001a00170019001c001b0018001a0016000e000d000b000c0009000a00230000000d0020001e060106020603050105020503040104020403030103020303020102020203000500050100000000000f0001010010000e000c02683208687474702f312e31`,
+				interception: true,
 			},
 			{
 				// AVG 17.1.3006 (build 17.1.3354.20) on Windows 10 x64 build 14393, intercepting Edge
 				userAgent:    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.79 Safari/537.36 Edge/14.14393",
 				helloHex:     `010000ca0303fd83091207161eca6b4887db50587109c50e463beb190362736b1fcf9e05f807000036c02cc02bc030c02f009f009ec024c023c028c027c00ac009c014c01300390033009d009c003d003c0035002f006a00400038003200ff0100006b00000014001200000f66696e6572706978656c732e636f6d000b000403000102000a00080006001d0017001800230000000d001400120401050102010403050302030202060106030005000501000000000010000e000c02683208687474702f312e310016000000170000`,
+				interception: true,
 			},
 			{
 				// IE 11 on Windows 7, this connection was intercepted by Blue Coat
+				// no sensible User-Agent value, since Blue Coat changes it to something super generic
+				// By the way, here's another reason we hate Blue Coat: they break TLS 1.3:
+				// https://twitter.com/FiloSottile/status/835269932929667072
 				helloHex:     `010000b1030358a3f3bae627f464da8cb35976b88e9119640032d41e62a107d608ed8d3e62b9000034c028c027c014c013009f009e009d009cc02cc02bc024c023c00ac009003d003c0035002f006a004000380032000a0013000500040100005400000014001200000f66696e6572706978656c732e636f6d000500050100000000000a00080006001700180019000b00020100000d0014001206010603040105010201040305030203020200170000ff01000100`,
+				interception: true,
+				reqHeaders:   http.Header{"X-Bluecoat-Via": {"66808702E9A2CF4"}}, // actual field name would be "X-BlueCoat-Via" but Go canonicalizes field names
 			},
 			{
 				// Firefox 51.0.1 being intercepted by burp 1.7.17
 				userAgent:    "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:51.0) Gecko/20100101 Firefox/51.0",
 				helloHex:     `010000d8030358a92f4daca95acc2f6a10a9c50d736135eae39406d3090238464540d482677600003ac023c027003cc025c02900670040c009c013002fc004c00e00330032c02bc02f009cc02dc031009e00a2c008c012000ac003c00d0016001300ff01000075000a0034003200170001000300130015000600070009000a0018000b000c0019000d000e000f001000110002001200040005001400080016000b00020100000d00180016060306010503050104030401040202030201020201010000001700150000126a61677561722e6b796877616e612e6f7267`,
+				interception: true,
 			},
 			{
 				// Chrome 56 on Windows 10 being intercepted by Fortigate (on some public school network); note: I had to enable TLS 1.0 for this test (proxy was issuing a SHA-1 cert to client)
 				userAgent:    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36",
 				helloHex:     `010000e5030158ac612125c83bae95282113b2a4c572cf613c160d234350fb6d0ddce879ffec000064003300320039003800160013c013c009c014c00ac012c008002f0035000a00150012003d003c00670040006b006ac011c0070096009a009900410084004500440088008700ba00be00bd00c000c400c3c03cc044c042c03dc045c04300090005000400ff01000058000a003600340000000100020003000400050006000700080009000a000b000c000d000e000f0010001100120013001400150016001700180019000b0002010000000014001200000f66696e6572706978656c732e636f6d`,
+				interception: true,
 			},
 			{
-				// IE 11 on Windows 10, intercepted by Fortigate (same as above)
+				// IE 11 on Windows 10, intercepted by Fortigate (same firewallas above)
 				userAgent:    "Mozilla/5.0 (Windows NT 10.0; WOW64; Trident/7.0; rv:11.0) like Gecko",
 				helloHex:     `010000e5030158ac634c5278d7b17421f23a64cc91d68c470c6b247322fe867ba035b373d05c000064003300320039003800160013c013c009c014c00ac012c008002f0035000a00150012003d003c00670040006b006ac011c0070096009a009900410084004500440088008700ba00be00bd00c000c400c3c03cc044c042c03dc045c04300090005000400ff01000058000a003600340000000100020003000400050006000700080009000a000b000c000d000e000f0010001100120013001400150016001700180019000b0002010000000014001200000f66696e6572706978656c732e636f6d`,
+				interception: true,
 			},
 			{
 				// Edge 38.14393.0.0 on Windows 10, intercepted by Fortigate (same as above)
 				userAgent:    "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.79 Safari/537.36 Edge/14.14393",
 				helloHex:     `010000e5030158ac6421a45794b8ade6a0ac6c910cde0f99c49bb1ba737b88638ec8dcf0d077000064003300320039003800160013c013c009c014c00ac012c008002f0035000a00150012003d003c00670040006b006ac011c0070096009a009900410084004500440088008700ba00be00bd00c000c400c3c03cc044c042c03dc045c04300090005000400ff01000058000a003600340000000100020003000400050006000700080009000a000b000c000d000e000f0010001100120013001400150016001700180019000b0002010000000014001200000f66696e6572706978656c732e636f6d`,
+				interception: true,
 			},
 			{
 				// Firefox 50.0.1 on Windows 10, intercepted by Fortigate (same as above)
 				userAgent:    "Mozilla/5.0 (Windows NT 10.0; WOW64; rv:50.0) Gecko/20100101 Firefox/50.0",
 				helloHex:     `010000e5030158ac64e40495e77b7baf2031281451620bfe354b0c37521ebc0a40f5dc0c0cb6000064003300320039003800160013c013c009c014c00ac012c008002f0035000a00150012003d003c00670040006b006ac011c0070096009a009900410084004500440088008700ba00be00bd00c000c400c3c03cc044c042c03dc045c04300090005000400ff01000058000a003600340000000100020003000400050006000700080009000a000b000c000d000e000f0010001100120013001400150016001700180019000b0002010000000014001200000f66696e6572706978656c732e636f6d`,
+				interception: true,
 			},
 		},
 	}
@@ -226,6 +279,33 @@ func TestHeuristicFunctions(t *testing.T) {
 				t.Errorf("[%s] Test %d: Chrome=%v, Firefox=%v, Safari=%v, Edge=%v; parsed hello: %+v",
 					client, i, isChrome, isFirefox, isSafari, isEdge, parsed)
 			}
+
+			// test the handler too
+			var got, checked bool
+			want := ch.interception
+			handler := &tlsHandler{
+				next: http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+					got, checked = r.Context().Value(CtxKey("mitm")).(bool)
+				}),
+				listener: newTLSListener(nil, nil),
+			}
+			handler.listener.helloInfos[""] = parsed
+			w := httptest.NewRecorder()
+			r, err := http.NewRequest("GET", "/", nil)
+			if err != nil {
+				t.Fatal(err)
+			}
+			r.Header.Set("User-Agent", ch.userAgent)
+			if ch.reqHeaders != nil {
+				for field, values := range ch.reqHeaders {
+					r.Header[field] = values // NOTE: field names not standardized when setting directly like this!
+				}
+			}
+			handler.ServeHTTP(w, r)
+			if got != want {
+				t.Errorf("[%s] Test %d: Expected MITM=%v but got %v (type assertion OK (checked)=%v)",
+					client, i, want, got, checked)
+			}
 		}
 	}
 }