]> Cypherpunks repositories - gostls13.git/commitdiff
crypto/x509: support PSS signatures.
authorAdam Langley <agl@golang.org>
Tue, 5 Jul 2016 20:50:18 +0000 (13:50 -0700)
committerAdam Langley <agl@golang.org>
Thu, 18 Aug 2016 00:40:17 +0000 (00:40 +0000)
Although the term “RSA” is almost synonymous with PKCS#1 v1.5, that
standard is quite flawed, cryptographically speaking. Bellare and
Rogaway fixed PKCS#1 v1.5 with OAEP (for encryption) and PSS (for
signatures) but they only see a fraction of the use of v1.5.

This change adds support for creating and verifying X.509 certificates
that use PSS signatures. Sadly, every possible dimension of flexibility
seems to have been reflected in the integration of X.509 and PSS
resulting in a huge amount of excess complexity. This change only
supports one “sane” configuration for each of SHA-{256, 384, 512}.
Hopefully this is sufficient because it saves a lot of complexity in the
code.

Although X.509 certificates with PSS signatures are rare, I'm inclined
to look favourably on them because they are sufficiently superior.

Fixes #15958.

Change-Id: I7282e0b68ad0177209f8b2add473b94aa5224c07
Reviewed-on: https://go-review.googlesource.com/24743
Run-TryBot: Adam Langley <agl@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/crypto/x509/x509.go
src/crypto/x509/x509_test.go

index 7b61f5a88c2d82f39a19d3e64edc2fb1202cabb4..1ecb0e26cdbcb37cc10c32ee82cf76075ec2ea31 100644 (file)
@@ -178,21 +178,36 @@ const (
        ECDSAWithSHA256
        ECDSAWithSHA384
        ECDSAWithSHA512
+       SHA256WithRSAPSS
+       SHA384WithRSAPSS
+       SHA512WithRSAPSS
 )
 
+func (algo SignatureAlgorithm) isRSAPSS() bool {
+       switch algo {
+       case SHA256WithRSAPSS, SHA384WithRSAPSS, SHA512WithRSAPSS:
+               return true
+       default:
+               return false
+       }
+}
+
 var algoName = [...]string{
-       MD2WithRSA:      "MD2-RSA",
-       MD5WithRSA:      "MD5-RSA",
-       SHA1WithRSA:     "SHA1-RSA",
-       SHA256WithRSA:   "SHA256-RSA",
-       SHA384WithRSA:   "SHA384-RSA",
-       SHA512WithRSA:   "SHA512-RSA",
-       DSAWithSHA1:     "DSA-SHA1",
-       DSAWithSHA256:   "DSA-SHA256",
-       ECDSAWithSHA1:   "ECDSA-SHA1",
-       ECDSAWithSHA256: "ECDSA-SHA256",
-       ECDSAWithSHA384: "ECDSA-SHA384",
-       ECDSAWithSHA512: "ECDSA-SHA512",
+       MD2WithRSA:       "MD2-RSA",
+       MD5WithRSA:       "MD5-RSA",
+       SHA1WithRSA:      "SHA1-RSA",
+       SHA256WithRSA:    "SHA256-RSA",
+       SHA384WithRSA:    "SHA384-RSA",
+       SHA512WithRSA:    "SHA512-RSA",
+       SHA256WithRSAPSS: "SHA256-RSAPSS",
+       SHA384WithRSAPSS: "SHA384-RSAPSS",
+       SHA512WithRSAPSS: "SHA512-RSAPSS",
+       DSAWithSHA1:      "DSA-SHA1",
+       DSAWithSHA256:    "DSA-SHA256",
+       ECDSAWithSHA1:    "ECDSA-SHA1",
+       ECDSAWithSHA256:  "ECDSA-SHA256",
+       ECDSAWithSHA384:  "ECDSA-SHA384",
+       ECDSAWithSHA512:  "ECDSA-SHA512",
 }
 
 func (algo SignatureAlgorithm) String() string {
@@ -268,12 +283,19 @@ var (
        oidSignatureSHA256WithRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 11}
        oidSignatureSHA384WithRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 12}
        oidSignatureSHA512WithRSA   = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 13}
+       oidSignatureRSAPSS          = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 10}
        oidSignatureDSAWithSHA1     = asn1.ObjectIdentifier{1, 2, 840, 10040, 4, 3}
        oidSignatureDSAWithSHA256   = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 3, 2}
        oidSignatureECDSAWithSHA1   = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 1}
        oidSignatureECDSAWithSHA256 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 2}
        oidSignatureECDSAWithSHA384 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 3}
        oidSignatureECDSAWithSHA512 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 4}
+
+       oidSHA256 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 1}
+       oidSHA384 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 2}
+       oidSHA512 = asn1.ObjectIdentifier{2, 16, 840, 1, 101, 3, 4, 2, 3}
+
+       oidMGF1 = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 8}
 )
 
 var signatureAlgorithmDetails = []struct {
@@ -288,6 +310,9 @@ var signatureAlgorithmDetails = []struct {
        {SHA256WithRSA, oidSignatureSHA256WithRSA, RSA, crypto.SHA256},
        {SHA384WithRSA, oidSignatureSHA384WithRSA, RSA, crypto.SHA384},
        {SHA512WithRSA, oidSignatureSHA512WithRSA, RSA, crypto.SHA512},
+       {SHA256WithRSAPSS, oidSignatureRSAPSS, RSA, crypto.SHA256},
+       {SHA384WithRSAPSS, oidSignatureRSAPSS, RSA, crypto.SHA384},
+       {SHA512WithRSAPSS, oidSignatureRSAPSS, RSA, crypto.SHA512},
        {DSAWithSHA1, oidSignatureDSAWithSHA1, DSA, crypto.SHA1},
        {DSAWithSHA256, oidSignatureDSAWithSHA256, DSA, crypto.SHA256},
        {ECDSAWithSHA1, oidSignatureECDSAWithSHA1, ECDSA, crypto.SHA1},
@@ -296,12 +321,115 @@ var signatureAlgorithmDetails = []struct {
        {ECDSAWithSHA512, oidSignatureECDSAWithSHA512, ECDSA, crypto.SHA512},
 }
 
-func getSignatureAlgorithmFromOID(oid asn1.ObjectIdentifier) SignatureAlgorithm {
-       for _, details := range signatureAlgorithmDetails {
-               if oid.Equal(details.oid) {
-                       return details.algo
+// pssParameters reflects the parameters in an AlgorithmIdentifier that
+// specifies RSA PSS. See https://tools.ietf.org/html/rfc3447#appendix-A.2.3
+type pssParameters struct {
+       // The following three fields are not marked as
+       // optional because the default values specify SHA-1,
+       // which is no longer suitable for use in signatures.
+       Hash         pkix.AlgorithmIdentifier `asn1:"explicit,tag:0"`
+       MGF          pkix.AlgorithmIdentifier `asn1:"explicit,tag:1"`
+       SaltLength   int                      `asn1:"explicit,tag:2"`
+       TrailerField int                      `asn1:"optional,explicit,tag:3,default:1"`
+}
+
+// rsaPSSParameters returns an asn1.RawValue suitable for use as the Parameters
+// in an AlgorithmIdentifier that specifies RSA PSS.
+func rsaPSSParameters(hashFunc crypto.Hash) asn1.RawValue {
+       var hashOID asn1.ObjectIdentifier
+
+       switch hashFunc {
+       case crypto.SHA256:
+               hashOID = oidSHA256
+       case crypto.SHA384:
+               hashOID = oidSHA384
+       case crypto.SHA512:
+               hashOID = oidSHA512
+       }
+
+       params := pssParameters{
+               Hash: pkix.AlgorithmIdentifier{
+                       Algorithm: hashOID,
+                       Parameters: asn1.RawValue{
+                               Tag: 5, /* ASN.1 NULL */
+                       },
+               },
+               MGF: pkix.AlgorithmIdentifier{
+                       Algorithm: oidMGF1,
+               },
+               SaltLength:   hashFunc.Size(),
+               TrailerField: 1,
+       }
+
+       mgf1Params := pkix.AlgorithmIdentifier{
+               Algorithm: hashOID,
+               Parameters: asn1.RawValue{
+                       Tag: 5, /* ASN.1 NULL */
+               },
+       }
+
+       var err error
+       params.MGF.Parameters.FullBytes, err = asn1.Marshal(mgf1Params)
+       if err != nil {
+               panic(err)
+       }
+
+       serialized, err := asn1.Marshal(params)
+       if err != nil {
+               panic(err)
+       }
+
+       return asn1.RawValue{FullBytes: serialized}
+}
+
+func getSignatureAlgorithmFromAI(ai pkix.AlgorithmIdentifier) SignatureAlgorithm {
+       if !ai.Algorithm.Equal(oidSignatureRSAPSS) {
+               for _, details := range signatureAlgorithmDetails {
+                       if ai.Algorithm.Equal(details.oid) {
+                               return details.algo
+                       }
                }
+               return UnknownSignatureAlgorithm
+       }
+
+       // RSA PSS is special because it encodes important parameters
+       // in the Parameters.
+
+       var params pssParameters
+       if _, err := asn1.Unmarshal(ai.Parameters.FullBytes, &params); err != nil {
+               return UnknownSignatureAlgorithm
+       }
+
+       var mgf1HashFunc pkix.AlgorithmIdentifier
+       if _, err := asn1.Unmarshal(params.MGF.Parameters.FullBytes, &mgf1HashFunc); err != nil {
+               return UnknownSignatureAlgorithm
+       }
+
+       // PSS is greatly overburdened with options. This code forces
+       // them into three buckets by requiring that the MGF1 hash
+       // function always match the message hash function (as
+       // recommended in
+       // https://tools.ietf.org/html/rfc3447#section-8.1), that the
+       // salt length matches the hash length, and that the trailer
+       // field has the default value.
+       asn1NULL := []byte{0x05, 0x00}
+       if !bytes.Equal(params.Hash.Parameters.FullBytes, asn1NULL) ||
+               !params.MGF.Algorithm.Equal(oidMGF1) ||
+               !mgf1HashFunc.Algorithm.Equal(params.Hash.Algorithm) ||
+               !bytes.Equal(mgf1HashFunc.Parameters.FullBytes, asn1NULL) ||
+               params.TrailerField != 1 {
+               return UnknownSignatureAlgorithm
        }
+
+       switch {
+       case params.Hash.Algorithm.Equal(oidSHA256) && params.SaltLength == 32:
+               return SHA256WithRSAPSS
+       case params.Hash.Algorithm.Equal(oidSHA384) && params.SaltLength == 48:
+               return SHA384WithRSAPSS
+       case params.Hash.Algorithm.Equal(oidSHA512) && params.SaltLength == 64:
+               return SHA512WithRSAPSS
+       }
+
        return UnknownSignatureAlgorithm
 }
 
@@ -680,11 +808,11 @@ func checkSignature(algo SignatureAlgorithm, signed, signature []byte, publicKey
        switch algo {
        case SHA1WithRSA, DSAWithSHA1, ECDSAWithSHA1:
                hashType = crypto.SHA1
-       case SHA256WithRSA, DSAWithSHA256, ECDSAWithSHA256:
+       case SHA256WithRSA, SHA256WithRSAPSS, DSAWithSHA256, ECDSAWithSHA256:
                hashType = crypto.SHA256
-       case SHA384WithRSA, ECDSAWithSHA384:
+       case SHA384WithRSA, SHA384WithRSAPSS, ECDSAWithSHA384:
                hashType = crypto.SHA384
-       case SHA512WithRSA, ECDSAWithSHA512:
+       case SHA512WithRSA, SHA512WithRSAPSS, ECDSAWithSHA512:
                hashType = crypto.SHA512
        case MD2WithRSA, MD5WithRSA:
                return InsecureAlgorithmError(algo)
@@ -702,7 +830,11 @@ func checkSignature(algo SignatureAlgorithm, signed, signature []byte, publicKey
 
        switch pub := publicKey.(type) {
        case *rsa.PublicKey:
-               return rsa.VerifyPKCS1v15(pub, hashType, digest, signature)
+               if algo.isRSAPSS() {
+                       return rsa.VerifyPSS(pub, hashType, digest, signature, &rsa.PSSOptions{SaltLength: rsa.PSSSaltLengthEqualsHash})
+               } else {
+                       return rsa.VerifyPKCS1v15(pub, hashType, digest, signature)
+               }
        case *dsa.PublicKey:
                dsaSig := new(dsaSignature)
                if rest, err := asn1.Unmarshal(signature, dsaSig); err != nil {
@@ -737,7 +869,7 @@ func checkSignature(algo SignatureAlgorithm, signed, signature []byte, publicKey
 
 // CheckCRLSignature checks that the signature in crl is from c.
 func (c *Certificate) CheckCRLSignature(crl *pkix.CertificateList) error {
-       algo := getSignatureAlgorithmFromOID(crl.SignatureAlgorithm.Algorithm)
+       algo := getSignatureAlgorithmFromAI(crl.SignatureAlgorithm)
        return c.CheckSignature(algo, crl.TBSCertList.Raw, crl.SignatureValue.RightAlign())
 }
 
@@ -945,7 +1077,7 @@ func parseCertificate(in *certificate) (*Certificate, error) {
 
        out.Signature = in.SignatureValue.RightAlign()
        out.SignatureAlgorithm =
-               getSignatureAlgorithmFromOID(in.TBSCertificate.SignatureAlgorithm.Algorithm)
+               getSignatureAlgorithmFromAI(in.TBSCertificate.SignatureAlgorithm)
 
        out.PublicKeyAlgorithm =
                getPublicKeyAlgorithmFromOID(in.TBSCertificate.PublicKey.Algorithm.Algorithm)
@@ -1553,6 +1685,9 @@ func signingParamsForPublicKey(pub interface{}, requestedSigAlgo SignatureAlgori
                                err = errors.New("x509: cannot sign with hash function requested")
                                return
                        }
+                       if requestedSigAlgo.isRSAPSS() {
+                               sigAlgo.Parameters = rsaPSSParameters(hashFunc)
+                       }
                        found = true
                        break
                }
@@ -1641,8 +1776,17 @@ func CreateCertificate(rand io.Reader, template, parent *Certificate, pub, priv
        h.Write(tbsCertContents)
        digest := h.Sum(nil)
 
+       var signerOpts crypto.SignerOpts
+       signerOpts = hashFunc
+       if template.SignatureAlgorithm != 0 && template.SignatureAlgorithm.isRSAPSS() {
+               signerOpts = &rsa.PSSOptions{
+                       SaltLength: rsa.PSSSaltLengthEqualsHash,
+                       Hash:       hashFunc,
+               }
+       }
+
        var signature []byte
-       signature, err = key.Sign(rand, digest, hashFunc)
+       signature, err = key.Sign(rand, digest, signerOpts)
        if err != nil {
                return
        }
@@ -2047,7 +2191,7 @@ func parseCertificateRequest(in *certificateRequest) (*CertificateRequest, error
                RawSubject:               in.TBSCSR.Subject.FullBytes,
 
                Signature:          in.SignatureValue.RightAlign(),
-               SignatureAlgorithm: getSignatureAlgorithmFromOID(in.SignatureAlgorithm.Algorithm),
+               SignatureAlgorithm: getSignatureAlgorithmFromAI(in.SignatureAlgorithm),
 
                PublicKeyAlgorithm: getPublicKeyAlgorithmFromOID(in.TBSCSR.PublicKey.Algorithm.Algorithm),
 
index 87cd694b82ea43e539c88aaa9a6483f19bffa979..e7858295ab15d0788c2bc254e41bf80859855fba 100644 (file)
@@ -86,14 +86,21 @@ FF53oIpvxe/SCOymfWq/LW849Ytv3Xwod0+wzAP8STXG4HSELS4UedPYeHJJJYcZ
 -----END PUBLIC KEY-----
 `
 
-var pemPrivateKey = `-----BEGIN RSA PRIVATE KEY-----
-MIIBOgIBAAJBALKZD0nEffqM1ACuak0bijtqE2QrI/KLADv7l3kK3ppMyCuLKoF0
-fd7Ai2KW5ToIwzFofvJcS/STa6HA5gQenRUCAwEAAQJBAIq9amn00aS0h/CrjXqu
-/ThglAXJmZhOMPVn4eiu7/ROixi9sex436MaVeMqSNf7Ex9a8fRNfWss7Sqd9eWu
-RTUCIQDasvGASLqmjeffBNLTXV2A5g4t+kLVCpsEIZAycV5GswIhANEPLmax0ME/
-EO+ZJ79TJKN5yiGBRsv5yvx5UiHxajEXAiAhAol5N4EUyq6I9w1rYdhPMGpLfk7A
-IU2snfRJ6Nq2CQIgFrPsWRCkV+gOYcajD17rEqmuLrdIRexpg8N1DOSXoJ8CIGlS
-tAboUGBxTDq3ZroNism3DaMIbKPyYrAqhKov1h5V
+var pemPrivateKey = `
+-----BEGIN RSA PRIVATE KEY-----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 -----END RSA PRIVATE KEY-----
 `
 
@@ -128,13 +135,13 @@ func bigFromHexString(s string) *big.Int {
 
 var rsaPrivateKey = &rsa.PrivateKey{
        PublicKey: rsa.PublicKey{
-               N: bigFromString("9353930466774385905609975137998169297361893554149986716853295022578535724979677252958524466350471210367835187480748268864277464700638583474144061408845077"),
+               N: bigFromString("124737666279038955318614287965056875799409043964547386061640914307192830334599556034328900586693254156136128122194531292927142396093148164407300419162827624945636708870992355233833321488652786796134504707628792159725681555822420087112284637501705261187690946267527866880072856272532711620639179596808018872997"),
                E: 65537,
        },
-       D: bigFromString("7266398431328116344057699379749222532279343923819063639497049039389899328538543087657733766554155839834519529439851673014800261285757759040931985506583861"),
+       D: bigFromString("69322600686866301945688231018559005300304807960033948687567105312977055197015197977971637657636780793670599180105424702854759606794705928621125408040473426339714144598640466128488132656829419518221592374964225347786430566310906679585739468938549035854760501049443920822523780156843263434219450229353270690889"),
        Primes: []*big.Int{
-               bigFromString("98920366548084643601728869055592650835572950932266967461790948584315647051443"),
-               bigFromString("94560208308847015747498523884063394671606671904944666360068158221458669711639"),
+               bigFromString("11405025354575369741595561190164746858706645478381139288033759331174478411254205003127028642766986913445391069745480057674348716675323735886284176682955723"),
+               bigFromString("10937079261204603443118731009201819560867324167189758120988909645641782263430128449826989846631183550578761324239709121189827307416350485191350050332642639"),
        },
 }
 
@@ -341,6 +348,9 @@ func TestCreateSelfSignedCertificate(t *testing.T) {
                {"RSA/ECDSA", &testPrivateKey.PublicKey, ecdsaPriv, false, ECDSAWithSHA384},
                {"ECDSA/RSA", &ecdsaPriv.PublicKey, testPrivateKey, false, SHA256WithRSA},
                {"ECDSA/ECDSA", &ecdsaPriv.PublicKey, ecdsaPriv, true, ECDSAWithSHA1},
+               {"RSAPSS/RSAPSS", &testPrivateKey.PublicKey, testPrivateKey, true, SHA256WithRSAPSS},
+               {"ECDSA/RSAPSS", &ecdsaPriv.PublicKey, testPrivateKey, false, SHA256WithRSAPSS},
+               {"RSAPSS/ECDSA", &testPrivateKey.PublicKey, ecdsaPriv, false, ECDSAWithSHA384},
        }
 
        testExtKeyUsage := []ExtKeyUsage{ExtKeyUsageClientAuth, ExtKeyUsageServerAuth}
@@ -762,6 +772,58 @@ func TestVerifyCertificateWithDSASignature(t *testing.T) {
        }
 }
 
+var rsaPSSSelfSignedPEM = `-----BEGIN CERTIFICATE-----
+MIIGHjCCA9KgAwIBAgIBdjBBBgkqhkiG9w0BAQowNKAPMA0GCWCGSAFlAwQCAQUA
+oRwwGgYJKoZIhvcNAQEIMA0GCWCGSAFlAwQCAQUAogMCASAwbjELMAkGA1UEBhMC
+SlAxHDAaBgNVBAoME0phcGFuZXNlIEdvdmVybm1lbnQxKDAmBgNVBAsMH1RoZSBN
+aW5pc3RyeSBvZiBGb3JlaWduIEFmZmFpcnMxFzAVBgNVBAMMDmUtcGFzc3BvcnRD
+U0NBMB4XDTEzMDUxNDA1MDczMFoXDTI5MDUxNDA1MDczMFowbjELMAkGA1UEBhMC
+SlAxHDAaBgNVBAoME0phcGFuZXNlIEdvdmVybm1lbnQxKDAmBgNVBAsMH1RoZSBN
+aW5pc3RyeSBvZiBGb3JlaWduIEFmZmFpcnMxFzAVBgNVBAMMDmUtcGFzc3BvcnRD
+U0NBMIICIjANBgkqhkiG9w0BAQEFAAOCAg8AMIICCgKCAgEAx/E3WRVxcCDXhoST
+8nVSLjW6hwM4Ni99AegWzcGtfGFo0zjFA1Cl5URqxauvYu3gQgQHBGA1CovWeGrl
+yVSRzOL1imcYsSgLOcnhVYB3Xcrof4ebv9+W+TwNdc9YzAwcj8rNd5nP6PKXIQ+W
+PCkEOXdyb80YEnxuT+NPjkVfFSPBS7QYZpvT2fwy4fZ0eh48253+7VleSmTO0mqj
+7TlzaG56q150SLZbhpOd8jD8bM/wACnLCPR88wj4hCcDLEwoLyY85HJCTIQQMnoT
+UpqyzEeupPREIm6yi4d8C9YqIWFn2YTnRcWcmMaJLzq+kYwKoudfnoC6RW2vzZXn
+defQs68IZuK+uALu9G3JWGPgu0CQGj0JNDT8zkiDV++4eNrZczWKjr1YnAL+VbLK
+bApwL2u19l2WDpfUklimhWfraqHNIUKU6CjZOG31RzXcplIj0mtqs0E1r7r357Es
+yFoB28iNo4cz1lCulh0E4WJzWzLZcT4ZspHHRCFyvYnXoibXEV1nULq8ByKKG0FS
+7nn4SseoV+8PvjHLPhmHGMvi4mxkbcXdV3wthHT1/HXdqY84A4xHWt1+sB/TpTek
+tDhFlEfcUygvTu58UtOnysomOVVeERmi7WSujfzKsGJAJYeetiA5R+zX7BxeyFVE
+qW0zh1Tkwh0S8LRe5diJh4+6FG0CAwEAAaNfMF0wHQYDVR0OBBYEFD+oahaikBTV
+Urk81Uz7kRS2sx0aMA4GA1UdDwEB/wQEAwIBBjAYBgNVHSAEETAPMA0GCyqDCIaP
+fgYFAQEBMBIGA1UdEwEB/wQIMAYBAf8CAQAwQQYJKoZIhvcNAQEKMDSgDzANBglg
+hkgBZQMEAgEFAKEcMBoGCSqGSIb3DQEBCDANBglghkgBZQMEAgEFAKIDAgEgA4IC
+AQAaxWBQn5CZuNBfyzL57mn31ukHUFd61OMROSX3PT7oCv1Dy+C2AdRlxOcbN3/n
+li0yfXUUqiY3COlLAHKRlkr97mLtxEFoJ0R8nVN2IQdChNQM/XSCzSGyY8NVa1OR
+TTpEWLnexJ9kvIdbFXwUqdTnAkOI0m7Rg8j+E+lRRHg1xDAA1qKttrtUj3HRQWf3
+kNTu628SiMvap6aIdncburaK56MP7gkR1Wr/ichOfjIA3Jgw2PapI31i0GqeMd66
+U1+lC9FeyMAJpuSVp/SoiYzYo+79SFcVoM2yw3yAnIKg7q9GLYYqzncdykT6C06c
+15gWFI6igmReAsD9ITSvYh0jLrLHfEYcPTOD3ZXJ4EwwHtWSoO3gq1EAtOYKu/Lv
+C8zfBsZcFdsHvsSiYeBU8Oioe42mguky3Ax9O7D805Ek6R68ra07MW/G4YxvV7IN
+2BfSaYy8MX9IG0ZMIOcoc0FeF5xkFmJ7kdrlTaJzC0IE9PNxNaH5QnOAFB8vxHcO
+FioUxb6UKdHcPLR1VZtAdTdTMjSJxUqD/35Cdfqs7oDJXz8f6TXO2Tdy6G++YUs9
+qsGZWxzFvvkXUkQSl0dQQ5jO/FtUJcAVXVVp20LxPemfatAHpW31WdJYeWSQWky2
++f9b5TXKXVyjlUL7uHxowWrT2AtTchDH22wTEtqLEF9Z3Q==
+-----END CERTIFICATE-----`
+
+func TestRSAPSSSelfSigned(t *testing.T) {
+       der, _ := pem.Decode([]byte(rsaPSSSelfSignedPEM))
+       if der == nil {
+               t.Fatal("Failed to find PEM block")
+       }
+
+       cert, err := ParseCertificate(der.Bytes)
+       if err != nil {
+               t.Fatal(err)
+       }
+
+       if err = cert.CheckSignatureFrom(cert); err != nil {
+               t.Fatal(err)
+       }
+}
+
 const pemCertificate = `-----BEGIN CERTIFICATE-----
 MIIDATCCAemgAwIBAgIRAKQkkrFx1T/dgB/Go/xBM5swDQYJKoZIhvcNAQELBQAw
 EjEQMA4GA1UEChMHQWNtZSBDbzAeFw0xNjA4MTcyMDM2MDdaFw0xNzA4MTcyMDM2