Added a dedicated revocation subpackage

The newly created dedicated revocation package is used to encode and
decode revocation information. Signing and verification can now use the
same structures.

While the InfoArchival stucsture can now be created this stucture is currenlty
not embedded into the document. Test cases for obtaining and embedding revocation
information into the InfoArchival struct are also availible.

verify/verify.go

@@ -11,26 +11,13 @@ import (
 	"time"
 
 	"bitbucket.org/digitorus/pdf"
+	"bitbucket.org/digitorus/pdfsign/revocation"
 	"github.com/digitorus/pkcs7"
 	"github.com/digitorus/timestamp"
-	"go/src/log"
+	"log"
 	"golang.org/x/crypto/ocsp"
 )
 
-type RevocationInfoArchival struct {
-	CRL          RevCRL       `asn1:"tag:0,optional,explicit"`
-	OCSP         RevOCSP      `asn1:"tag:1,optional,explicit"`
-	OtherRevInfo OtherRevInfo `asn1:"tag:2,optional,explicit"`
-}
-
-type RevCRL []asn1.RawValue
-type RevOCSP []asn1.RawValue
-
-type OtherRevInfo struct {
-	Type  asn1.ObjectIdentifier
-	Value []byte
-}
-
 type Response struct {
 	Error string
 
@@ -192,7 +179,7 @@ func Verify(file *os.File) (apiResp *Response, err error) {
 		}
 
 		// PDF signature certificate revocation information attribute (1.2.840.113583.1.1.8)
-		var revInfo RevocationInfoArchival
+		var revInfo revocation.InfoArchival
 		p7.UnmarshalSignedAttribute(asn1.ObjectIdentifier{1, 2, 840, 113583, 1, 1, 8}, &revInfo)
 
 		// Parse OCSP response