Add new document signature app

apps/document_signatures/models.py

@@ -0,0 +1,58 @@
+from django.db import models
+from django.utils.translation import ugettext_lazy as _
+
+from documents.models import DocumentVersion, get_filename_from_uuid
+from documents.conf.settings import STORAGE_BACKEND
+
+
+class DocumentVersionSignature(models.Model):
+    '''
+    Model that describes a document version signature properties
+    '''
+    document_version = models.ForeignKey(DocumentVersion, verbose_name=_(u'document version'), editable=False)
+    signature_state = models.CharField(blank=True, null=True, max_length=16, verbose_name=_(u'signature state'), editable=False)
+    signature_file = models.FileField(blank=True, null=True, upload_to=get_filename_from_uuid, storage=STORAGE_BACKEND(), verbose_name=_(u'signature file'), editable=False)
+        
+    def update_signed_state(self, save=True):
+        if self.exists():
+            try:
+                self.signature_state = gpg.verify_file(self.open()).status
+                # TODO: give use choice for auto public key fetch?
+                # OR maybe new config option
+            except GPGVerificationError:
+                self.signature_state = None
+           
+            if save:
+                self.save()
+
+    def add_detached_signature(self, detached_signature):
+        if not self.signature_state:
+            self.signature_file = detached_signature
+            self.save()
+        else:
+            raise Exception('document already has an embedded signature')
+    
+    def has_detached_signature(self):
+        if self.signature_file:
+            return self.signature_file.storage.exists(self.signature_file.path)
+        else:
+            return False
+    
+    def detached_signature(self):
+        return self.signature_file.storage.open(self.signature_file.path)
+        
+    def verify_signature(self):
+        try:
+            if self.has_detached_signature():
+                logger.debug('has detached signature')
+                signature = gpg.verify_w_retry(self.open(), self.detached_signature())
+            else:
+                signature = gpg.verify_w_retry(self.open(raw=True))
+        except GPGVerificationError:
+            signature = None
+            
+        return signature
+        
+    class Meta:
+        verbose_name = _(u'document version signature')
+        verbose_name_plural = _(u'document version signatures')