crypto/x509: Fix bug in UnknownAuthorityError.Error

Fix bug in UnknownAuthorityError.Error that would never allow Org
Name to be inserted into error message if the Common Name was empty.
Create tests for all three paths in UnknownAuthorityError.Error

Change-Id: Id8afc444e897ef549df682d93a8563fd9de22a2b
Reviewed-on: https://go-review.googlesource.com/27992
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/crypto/x509/verify.go

@@ -108,8 +108,9 @@ func (e UnknownAuthorityError) Error() string {
 		if len(certName) == 0 {
 			if len(e.hintCert.Subject.Organization) > 0 {
 				certName = e.hintCert.Subject.Organization[0]
+			} else {
+				certName = "serial:" + e.hintCert.SerialNumber.String()
 			}
-			certName = "serial:" + e.hintCert.SerialNumber.String()
 		}
 		s += fmt.Sprintf(" (possibly because of %q while trying to verify candidate authority certificate %q)", e.hintErr, certName)
 	}

src/crypto/x509/verify_test.go

@@ -8,6 +8,7 @@ import (
 	"crypto/x509/pkix"
 	"encoding/pem"
 	"errors"
+	"fmt"
 	"runtime"
 	"strings"
 	"testing"
@@ -1131,3 +1132,90 @@ pl01FCBGTcncVqr6RK1r4fTpeCCfRIERD+YRJz8TtPH6ydesfLL8jIV40H8NiDfG
 vRAvOtNiKtPzFeQVdbRPOskC4rcHyPeiDAMAMixeLi63+CFty4da3r5lRezeedCE
 cw3ESZzThBwWqvPOtJdpXdm+r57pDW8qD+/0lY8wfImMNkQAyCUCLg/1Lxt/hrBj
 -----END CERTIFICATE-----`
+
+var unknownAuthorityErrorTests = []struct {
+	cert     string
+	expected string
+}{
+	{selfSignedWithCommonName, "x509: certificate signed by unknown authority (possibly because of \"empty\" while trying to verify candidate authority certificate \"test\")"},
+	{selfSignedNoCommonNameWithOrgName, "x509: certificate signed by unknown authority (possibly because of \"empty\" while trying to verify candidate authority certificate \"ca\")"},
+	{selfSignedNoCommonNameNoOrgName, "x509: certificate signed by unknown authority (possibly because of \"empty\" while trying to verify candidate authority certificate \"serial:0\")"},
+}
+
+func TestUnknownAuthorityError(t *testing.T) {
+	for i, tt := range unknownAuthorityErrorTests {
+		der, _ := pem.Decode([]byte(tt.cert))
+		if der == nil {
+			t.Errorf("#%d: Unable to decode PEM block", i)
+		}
+		c, err := ParseCertificate(der.Bytes)
+		if err != nil {
+			t.Errorf("#%d: Unable to parse certificate -> %s", i, err)
+		}
+		uae := &UnknownAuthorityError{
+			cert:     c,
+			hintErr:  fmt.Errorf("empty"),
+			hintCert: c,
+		}
+		actual := uae.Error()
+		if strings.Compare(actual, tt.expected) != 0 {
+			t.Errorf("#%d: UnknownAuthorityError.Error() response invalid actual: %s expected: %s", i, actual, tt.expected)
+		}
+	}
+}
+
+const selfSignedWithCommonName = `-----BEGIN CERTIFICATE-----
+MIIDCjCCAfKgAwIBAgIBADANBgkqhkiG9w0BAQsFADAaMQswCQYDVQQKEwJjYTEL
+MAkGA1UEAxMCY2EwHhcNMTYwODI4MTcwOTE4WhcNMjEwODI3MTcwOTE4WjAcMQsw
+CQYDVQQKEwJjYTENMAsGA1UEAxMEdGVzdDCCASIwDQYJKoZIhvcNAQEBBQADggEP
+ADCCAQoCggEBAOH55PfRsbvmcabfLLko1w/yuapY/hk13Cgmc3WE/Z1ZStxGiVxY
+gQVH9n4W/TbUsrep/TmcC4MV7xEm5252ArcgaH6BeQ4QOTFj/6Jx0RT7U/ix+79x
+8RRysf7OlzNpGIctwZEM7i/G+0ZfqX9ULxL/EW9tppSxMX1jlXZQarnU7BERL5cH
++G2jcbU9H28FXYishqpVYE9L7xrXMm61BAwvGKB0jcVW6JdhoAOSfQbbgp7JjIlq
+czXqUsv1UdORO/horIoJptynTvuARjZzyWatya6as7wyOgEBllE6BjPK9zpn+lp3
+tQ8dwKVqm/qBPhIrVqYG/Ec7pIv8mJfYabMCAwEAAaNZMFcwDgYDVR0PAQH/BAQD
+AgOoMB0GA1UdJQQWMBQGCCsGAQUFBwMCBggrBgEFBQcDATAMBgNVHRMBAf8EAjAA
+MAoGA1UdDgQDBAEAMAwGA1UdIwQFMAOAAQAwDQYJKoZIhvcNAQELBQADggEBAAAM
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+v/NErK6SgWnkQiPJBZNX1Q9+aSbLT/sbaCTdbWqcGNRuLGJkmqfIyoxRt0Hhpqsx
+jP5cBaVl50t4qoCuVIE9cOucnxYXnI7X5HpXWvu8Pfxo4SwVjb1az8Fk5s8ZnxGe
+fPB6Q3L/pKBe0SEe5GywpwtokPLB3lAygcuHbxp/1FlQ1NQZqq+vgXRIla26bNJf
+IuYkJwt6w+LH/9HZgf8=
+-----END CERTIFICATE-----`
+const selfSignedNoCommonNameWithOrgName = `-----BEGIN CERTIFICATE-----
+MIIC+zCCAeOgAwIBAgIBADANBgkqhkiG9w0BAQsFADAaMQswCQYDVQQKEwJjYTEL
+MAkGA1UEAxMCY2EwHhcNMTYwODI4MTgxMzQ4WhcNMjEwODI3MTgxMzQ4WjANMQsw
+CQYDVQQKEwJjYTCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAL5EjrUa
+7EtOMxWiIgTzp2FlQvncPsG329O3l3uNGnbigb8TmNMw2M8UhoDjd84pnU5RAfqd
+8t5TJyw/ybnIKBN131Q2xX+gPQ0dFyMvcO+i1CUgCxmYZomKVA2MXO1RD1hLTYGS
+gOVjc3no3MBwd8uVQp0NStqJ1QvLtNG4Uy+B28qe+ZFGGbjGqx8/CU4A8Szlpf7/
+xAZR8w5qFUUlpA2LQYeHHJ5fQVXw7kyL1diNrKNi0G3qcY0IrBh++hT+hnEEXyXu
+g8a0Ux18hoE8D6rAr34rCZl6AWfqW5wjwm+N5Ns2ugr9U4N8uCKJYMPHb2CtdubU
+46IzVucpTfGLdaMCAwEAAaNZMFcwDgYDVR0PAQH/BAQDAgOoMB0GA1UdJQQWMBQG
+CCsGAQUFBwMCBggrBgEFBQcDATAMBgNVHRMBAf8EAjAAMAoGA1UdDgQDBAEAMAwG
+A1UdIwQFMAOAAQAwDQYJKoZIhvcNAQELBQADggEBAEn5SgVpJ3zjsdzPqK7Qd/sB
+bYd1qtPHlrszjhbHBg35C6mDgKhcv4o6N+fuC+FojZb8lIxWzJtvT9pQbfy/V6u3
+wOb816Hm71uiP89sioIOKCvSAstj/p9doKDOUaKOcZBTw0PS2m9eja8bnleZzBvK
+rD8cNkHf74v98KvBhcwBlDifVzmkWzMG6TL1EkRXUyLKiWgoTUFSkCDV927oXXMR
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+29ssJSqjUPyp58dlV6ZuynxPho1QVZUOQgnJToXIQ3/5vIvJRXy52GJCs4/Gh/w=
+-----END CERTIFICATE-----`
+const selfSignedNoCommonNameNoOrgName = `-----BEGIN CERTIFICATE-----
+MIIC7jCCAdagAwIBAgIBADANBgkqhkiG9w0BAQsFADAaMQswCQYDVQQKEwJjYTEL
+MAkGA1UEAxMCY2EwHhcNMTYwODI4MTgxOTQ1WhcNMjEwODI3MTgxOTQ1WjAAMIIB
+IjANBgkqhkiG9w0BAQEFAAOCAQ8AMIIBCgKCAQEAp3E+Jl6DpgzogHUW/i/AAcCM
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+2gETTT2tEpoF2S4soaYfm0DBeT8K0/rogAaf+oeUS6V+v3miRcAooJgpNJGu9kqm
+S0xKPn1RCFVjpiRd6YNS0xZirjYQIBMFBvoSoHjaOdgJptNRBprYPOxVJ/ItzGf0
+kPmzPFCx2tKfxV9HLYBPgxi+fP3IIx8aIYuJn8yReWtYEMYU11hDPeAFN5Gm+wID
+AQABo1kwVzAOBgNVHQ8BAf8EBAMCA6gwHQYDVR0lBBYwFAYIKwYBBQUHAwIGCCsG
+AQUFBwMBMAwGA1UdEwEB/wQCMAAwCgYDVR0OBAMEAQAwDAYDVR0jBAUwA4ABADAN
+BgkqhkiG9w0BAQsFAAOCAQEATZVOFeiCpPM5QysToLv+8k7Rjoqt6L5IxMUJGEpq
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+9z1NSe2aQKnyBb++DM3ZdikpHn/xEpGV19pYKFQVn35x3lpPh2XijqRDO/erKemb
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+4R+gnfLd37FWflMHwztFbVTuNtPOljCX0LN7KcuoXYlr05RhQrmoN7fQHsrZMNLs
+8FVjHdKKu+uPstwd04Uy4BR/H2y1yerN9j/L6ZkMl98iiA==
+-----END CERTIFICATE-----`