acme/autocert: add support for RFC 3492 to Manager.GetCertificate

Author: aofei

Diff for: acme/autocert/autocert.go

@@ -32,6 +32,7 @@ import (
 	"time"
 
 	"golang.org/x/crypto/acme"
+	"golang.org/x/net/idna"
 )
 
 // createCertRetryAfter is how much time to wait before removing a failed state
@@ -63,12 +64,15 @@ type HostPolicy func(ctx context.Context, host string) error
 // Only exact matches are currently supported. Subdomains, regexp or wildcard
 // will not match.
 //
-// Note that all hosts will be converted to lowercase via strings.ToLower so that
-// Manager.GetCertificate can handle mixedcase hosts correctly.
+// Note that all hosts will be converted to Punycode via idna.Lookup.ToASCII so that
+// Manager.GetCertificate can handle the Unicode IDN and mixedcase hosts correctly.
+// Invlaid hosts will be silently ignored.
 func HostWhitelist(hosts ...string) HostPolicy {
 	whitelist := make(map[string]bool, len(hosts))
 	for _, h := range hosts {
-		whitelist[strings.ToLower(h)] = true
+		if h, err := idna.Lookup.ToASCII(h); err == nil {
+			whitelist[h] = true
+		}
 	}
 	return func(_ context.Context, host string) error {
 		if !whitelist[host] {
@@ -239,14 +243,25 @@ func (m *Manager) GetCertificate(hello *tls.ClientHelloInfo) (*tls.Certificate,
 		return nil, errors.New("acme/autocert: Manager.Prompt not set")
 	}
 
-	name := strings.ToLower(hello.ServerName)
+	name := hello.ServerName
 	if name == "" {
 		return nil, errors.New("acme/autocert: missing server name")
 	}
 	if !strings.Contains(strings.Trim(name, "."), ".") {
 		return nil, errors.New("acme/autocert: server name component count invalid")
 	}
-	if strings.ContainsAny(name, `+/\`) {
+
+	// Note that this conversion is necessary because some server names in the handshakes
+	// made by some clients (like cURL) is not implicitly converted to Punycode, which will
+	// cause the certificate to fail to be obtained. In addition, we should also treat
+	// example.com and EXAMPLE.COM as equivalent and must return the same certificate for
+	// them. Fortunately, this conversion also helped us deal with this kind of mixedcase
+	// problems.
+	//
+	// Due to the "σςΣ" problem (see https://unicode.org/faq/idn.html#22), we can't use
+	// idna.Punycode.ToASCII (or just idna.ToASCII) here.
+	name, err := idna.Lookup.ToASCII(hello.ServerName)
+	if err != nil {
 		return nil, errors.New("acme/autocert: server name contains invalid character")
 	}
 

Diff for: acme/autocert/autocert_test.go

@@ -209,15 +209,26 @@ func TestGetCertificate_trailingDot(t *testing.T) {
 	testGetCertificate(t, man, "example.org", hello)
 }
 
+func TestGetCertificate_unicodeIDN(t *testing.T) {
+	man := &Manager{Prompt: AcceptTOS}
+	defer man.stopRenew()
+
+	hello := clientHelloInfo("σσσ.com", true)
+	testGetCertificate(t, man, "xn--4xaaa.com", hello)
+
+	hello = clientHelloInfo("σςΣ.com", true)
+	testGetCertificate(t, man, "xn--4xaaa.com", hello)
+}
+
 func TestGetCertificate_mixedcase(t *testing.T) {
 	man := &Manager{Prompt: AcceptTOS}
 	defer man.stopRenew()
 
-	lowercaseHello := clientHelloInfo("example.org", true)
-	testGetCertificate(t, man, "example.org", lowercaseHello)
+	hello := clientHelloInfo("example.org", true)
+	testGetCertificate(t, man, "example.org", hello)
 
-	uppercaseHello := clientHelloInfo("EXAMPLE.ORG", true)
-	testGetCertificate(t, man, "example.org", uppercaseHello)
+	hello = clientHelloInfo("EXAMPLE.ORG", true)
+	testGetCertificate(t, man, "example.org", hello)
 }
 
 func TestGetCertificate_ForceRSA(t *testing.T) {
@@ -917,13 +928,14 @@ func TestCache(t *testing.T) {
 }
 
 func TestHostWhitelist(t *testing.T) {
-	policy := HostWhitelist("example.com", "EXAMPLE.ORG", "*.example.net")
+	policy := HostWhitelist("example.com", "EXAMPLE.ORG", "*.example.net", "σςΣ.com")
 	tt := []struct {
 		host  string
 		allow bool
 	}{
 		{"example.com", true},
 		{"example.org", true},
+		{"xn--4xaaa.com", true},
 		{"one.example.com", false},
 		{"two.example.org", false},
 		{"three.example.net", false},

Diff for: go.mod

@@ -1,3 +1,6 @@
 module golang.org/x/crypto
 
-require golang.org/x/sys v0.0.0-20190403152447-81d4e9dc473e
+require (
+	golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3
+	golang.org/x/sys v0.0.0-20190412213103-97732733099d
+)

Diff for: go.sum

@@ -1,2 +1,8 @@
-golang.org/x/sys v0.0.0-20190403152447-81d4e9dc473e h1:nFYrTHrdrAOpShe27kaFHjsqYSEQ0KWqdWLu3xuZJts=
-golang.org/x/sys v0.0.0-20190403152447-81d4e9dc473e/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3 h1:0GoQqolDA55aaLxZyTzK/Y2ePZzZTUrRacwib7cNsYQ=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d h1:+R4KGOnez64A81RvjARKc4UT5/tI9ujCIVX+P5KiHuI=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/text v0.3.0 h1:g61tztE5qeGQ89tm6NTjjM9VPIm088od1l6aSorWRWg=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=