diff --git a/ber.go b/ber.go
index bf3e804..1a0d8c0 100644
--- a/ber.go
+++ b/ber.go
@@ -240,7 +240,7 @@ func readObject(ber []byte, offset int) (asn1Object, int, error) {
 }
 
 func isIndefiniteTermination(ber []byte, offset int) (bool, error) {
-	if len(ber) - offset < 2 {
+	if len(ber)-offset < 2 {
 		return false, errors.New("ber2der: Invalid BER format")
 	}
 
diff --git a/internal/x509util/x509util.go b/internal/x509util/x509util.go
index 5eca640..f4f4f11 100644
--- a/internal/x509util/x509util.go
+++ b/internal/x509util/x509util.go
@@ -55,6 +55,30 @@ func SignatureAlgorithmDetailsForOid(oid asn1.ObjectIdentifier) (x509.SignatureA
 		fmt.Errorf("could not find SignatureAlgorithm details for oid: %s", oid)
 }
 
+// SignatureAlgorithmDetailsForOid returns a matching SignatureAlgorithm and
+// crypto.Hash function from a provided oid.
+func SignatureAlgorithmDetailsForOidPair(oidSig, oidEnc asn1.ObjectIdentifier) (x509.SignatureAlgorithm, crypto.Hash, error) {
+	algo, hash, err := SignatureAlgorithmDetailsForOid(oidSig)
+	if err == nil {
+		return algo, hash, err
+	}
+
+	switch {
+	case oidEnc.Equal(oidRSA):
+		switch {
+		case oidSig.Equal(oidSHA256):
+			return x509.SHA256WithRSA, crypto.SHA256, nil
+		case oidSig.Equal(oidSHA384):
+			return x509.SHA384WithRSA, crypto.SHA384, nil
+		case oidSig.Equal(oidSHA512):
+			return x509.SHA512WithRSA, crypto.SHA512, nil
+		}
+	}
+
+	return x509.UnknownSignatureAlgorithm, crypto.Hash(0),
+		fmt.Errorf("could not find SignatureAlgorithm details for oids: %s, %s", oidSig, oidEnc)
+}
+
 // SigningParamsForPublicKey returns the parameters to use for signing.
 // If requestedSigAlgo is not zero then it overrides the default
 // signature algorithm.
@@ -139,6 +163,8 @@ var (
 	oidSignatureECDSAWithSHA384 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 3}
 	oidSignatureECDSAWithSHA512 = asn1.ObjectIdentifier{1, 2, 840, 10045, 4, 3, 4}
 
+	oidRSA = asn1.ObjectIdentifier{1, 2, 840, 113549, 1, 1, 1}
+
 	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}
diff --git a/pkcs7.go b/pkcs7.go
index 8a96146..197a19c 100644
--- a/pkcs7.go
+++ b/pkcs7.go
@@ -121,6 +121,10 @@ type signerInfo struct {
 	UnauthenticatedAttributes []attribute `asn1:"optional,tag:1"`
 }
 
+func (si *signerInfo) SignatureAlgorithmDetails() (x509.SignatureAlgorithm, crypto.Hash, error) {
+	return x509util.SignatureAlgorithmDetailsForOidPair(si.DigestAlgorithm.Algorithm, si.DigestEncryptionAlgorithm.Algorithm)
+}
+
 // Parse decodes a DER encoded PKCS7 package
 func Parse(data []byte) (p7 *PKCS7, err error) {
 	if len(data) == 0 {
@@ -225,6 +229,22 @@ func (p7 *PKCS7) Verify() (err error) {
 
 func verifySignature(p7 *PKCS7, signer signerInfo) error {
 	signedData := p7.Content
+
+	var algo x509.SignatureAlgorithm
+	var hash crypto.Hash
+	var err error
+
+	oid := signer.DigestAlgorithm.Algorithm
+	if oid.Equal(oidDigestAlgorithmSHA1) || oid.Equal(oidISOSignatureSHA1WithRSA) {
+		algo = x509.SHA1WithRSA
+		hash = crypto.SHA1
+	} else {
+		algo, hash, err = signer.SignatureAlgorithmDetails()
+		if err != nil {
+			return err
+		}
+	}
+
 	if len(signer.AuthenticatedAttributes) > 0 {
 		// TODO(fullsailor): First check the content type match
 		var digest []byte
@@ -232,10 +252,6 @@ func verifySignature(p7 *PKCS7, signer signerInfo) error {
 		if err != nil {
 			return err
 		}
-		hash, err := getHashForOID(signer.DigestAlgorithm.Algorithm)
-		if err != nil {
-			return err
-		}
 		h := hash.New()
 		if _, err := h.Write(p7.Content); err != nil {
 			return err
@@ -254,23 +270,12 @@ func verifySignature(p7 *PKCS7, signer signerInfo) error {
 			return err
 		}
 	}
+
 	cert := getCertFromCertsByIssuerAndSerial(p7.Certificates, signer.IssuerAndSerialNumber)
 	if cert == nil {
 		return errors.New("pkcs7: No certificate for signer")
 	}
 
-	oid := signer.DigestAlgorithm.Algorithm
-	var algo x509.SignatureAlgorithm
-	switch {
-	case oid.Equal(oidDigestAlgorithmSHA1):
-		algo = x509.SHA1WithRSA
-	default:
-		var err error
-		algo, _, err = x509util.SignatureAlgorithmDetailsForOid(oid)
-		if err != nil {
-			return err
-		}
-	}
 	return cert.CheckSignature(algo, signedData, signer.EncryptedDigest)
 }