Merge branch 'feature/detached_signatures' into development

apps/django_gpg/__init__.py

@@ -16,6 +16,8 @@ PERMISSION_KEY_VIEW = {'namespace': 'django_gpg', 'name': 'key_view', 'label': _
 PERMISSION_KEY_DELETE = {'namespace': 'django_gpg', 'name': 'key_delete', 'label': _(u'Delete keys')}
 PERMISSION_KEYSERVER_QUERY = {'namespace': 'django_gpg', 'name': 'keyserver_query', 'label': _(u'Query keyservers')}
 PERMISSION_KEY_RECEIVE = {'namespace': 'django_gpg', 'name': 'key_receive', 'label': _(u'Import key from keyservers')}
+PERMISSION_SIGNATURE_UPLOAD = {'namespace': 'django_gpg', 'name': 'signature_upload', 'label': _(u'Upload detached signatures')}
+PERMISSION_SIGNATURE_DOWNLOAD = {'namespace': 'django_gpg', 'name': 'key_receive', 'label': _(u'Download detached signatures')}
 
 # Permission setup
 set_namespace_title('django_gpg', _(u'Signatures'))
@@ -24,6 +26,11 @@ register_permission(PERMISSION_KEY_VIEW)
 register_permission(PERMISSION_KEY_DELETE)
 register_permission(PERMISSION_KEYSERVER_QUERY)
 register_permission(PERMISSION_KEY_RECEIVE)
+register_permission(PERMISSION_SIGNATURE_UPLOAD)
+register_permission(PERMISSION_SIGNATURE_DOWNLOAD)
+
+def has_embedded_signature(context):
+    return context['object'].signature_state
 
 # Setup views
 private_keys = {'text': _(u'private keys'), 'view': 'key_private_list', 'args': 'object.pk', 'famfam': 'key', 'icon': 'key.png', 'permissions': [PERMISSION_KEY_VIEW]}
@@ -31,12 +38,16 @@ public_keys = {'text': _(u'public keys'), 'view': 'key_public_list', 'args': 'ob
 key_delete = {'text': _(u'delete'), 'view': 'key_delete', 'args': ['object.fingerprint', 'object.type'], 'famfam': 'key_delete', 'permissions': [PERMISSION_KEY_DELETE]}
 key_query = {'text': _(u'Query keyservers'), 'view': 'key_query', 'famfam': 'zoom', 'permissions': [PERMISSION_KEYSERVER_QUERY]}
 key_receive = {'text': _(u'Import'), 'view': 'key_receive', 'args': 'object.keyid', 'famfam': 'key_add', 'keep_query': True, 'permissions': [PERMISSION_KEY_RECEIVE]}
+document_signature_upload = {'text': _(u'Upload signature'), 'view': 'document_signature_upload', 'args': 'object.pk', 'famfam': 'pencil_add', 'permissions': [PERMISSION_SIGNATURE_UPLOAD], 'conditional_disable': has_embedded_signature}
+document_signature_download = {'text': _(u'Download signature'), 'view': 'document_signature_download', 'args': 'object.pk', 'famfam': 'disk', 'permissions': [PERMISSION_SIGNATURE_DOWNLOAD], 'conditional_disable': has_embedded_signature}
 
 # Document views
 document_verify = {'text': _(u'signatures'), 'view': 'document_verify', 'args': 'object.pk', 'famfam': 'text_signature', 'permissions': [PERMISSION_DOCUMENT_VERIFY]}
 
 register_links(Document, [document_verify], menu_name='form_header')
 
+register_links(['document_verify', 'document_signature_upload', 'document_signature_download'], [document_signature_upload, document_signature_download], menu_name='sidebar')
+
 register_links(['key_delete', 'key_private_list', 'key_public_list', 'key_query'], [private_keys, public_keys, key_query], menu_name='sidebar')
 
 register_links(Key, [key_delete])
@@ -44,3 +55,6 @@ register_links(KeyServerKey, [key_receive])
 
 register_setup(private_keys)
 register_setup(public_keys)
+
+
+

apps/django_gpg/api.py

@@ -2,6 +2,8 @@ import types
 from StringIO import StringIO
 from pickle import dumps
 import logging
+import tempfile
+import os
 
 from django.core.files.base import File
 from django.utils.translation import ugettext_lazy as _
@@ -164,7 +166,7 @@ class GPG(object):
 
         self.gpg = gnupg.GPG(**kwargs)
 
-    def verify_w_retry(self, file_input):
+    def verify_w_retry(self, file_input, detached_signature=None):
         if isinstance(file_input, types.StringTypes):
             input_descriptor = open(file_input, 'rb')
         elif isinstance(file_input, types.FileType) or isinstance(file_input, File):
@@ -175,12 +177,12 @@ class GPG(object):
             raise ValueError('Invalid file_input argument type')        
 
         try:
-            verify = self.verify_file(input_descriptor)
+            verify = self.verify_file(input_descriptor, detached_signature)
             if verify.status == 'no public key':
                 # Try to fetch the public key from the keyservers
                 try:
                     self.receive_key(verify.key_id)
-                    return self.verify_w_retry(file_input)
+                    return self.verify_w_retry(file_input, detached_signature)
                 except KeyFetchingError:
                     return verify
             else:
@@ -188,7 +190,7 @@ class GPG(object):
         except IOError:
             return False
 
-    def verify_file(self, file_input):
+    def verify_file(self, file_input, detached_signature=None):
         """
         Verify the signature of a file.
         """
@@ -199,7 +201,17 @@ class GPG(object):
         else:
             raise ValueError('Invalid file_input argument type')
         
-        verify = self.gpg.verify_file(descriptor)
+        if detached_signature:
+            # Save the original data and invert the argument order
+            # Signature first, file second
+            file_descriptor, filename = tempfile.mkstemp(prefix='django_gpg')
+            file_data = file_input.read()
+            file_input.close()
+            os.write(file_descriptor, file_data)
+            os.close(file_descriptor)
+            verify = self.gpg.verify_file(detached_signature, data_filename=filename)
+        else:
+            verify = self.gpg.verify_file(descriptor)
         descriptor.close()
         
         if verify:

apps/django_gpg/forms.py

@@ -11,3 +11,9 @@ class KeySearchForm(forms.Form):
         label=_(u'Term'),
         help_text=_(u'Name, e-mail, key ID or key fingerprint to look for.')
     )
+
+
+class DetachedSignatureForm(forms.Form):
+    file = forms.FileField(
+        label=_(u'Signature file'),
+    )

apps/django_gpg/urls.py

@@ -5,7 +5,8 @@ urlpatterns = patterns('django_gpg.views',
     url(r'^list/private/$', 'key_list', {'secret': True}, 'key_private_list'),
     url(r'^list/public/$', 'key_list', {'secret': False}, 'key_public_list'),
     url(r'^verify/(?P<document_pk>\d+)/$', 'document_verify', (), 'document_verify'),
+    url(r'^upload/signature/(?P<document_pk>\d+)/$', 'document_signature_upload', (), 'document_signature_upload'),
+    url(r'^download/signature/(?P<document_pk>\d+)/$', 'document_signature_download', (), 'document_signature_download'),
     url(r'^query/$', 'key_query', (), 'key_query'),
     url(r'^receive/(?P<key_id>.+)/$', 'key_receive', (), 'key_receive'),
-    
 )

apps/django_gpg/views.py

@@ -15,14 +15,16 @@ from documents.models import Document, RecentDocument
 from permissions.api import check_permissions
 from common.utils import pretty_size, parse_range, urlquote, \
     return_diff, encapsulate
-    
+from filetransfers.api import serve_file
+   
 from django_gpg.api import Key, SIGNATURE_STATES
 from django_gpg.runtime import gpg
 from django_gpg.exceptions import GPGVerificationError, KeyFetchingError
 from django_gpg import (PERMISSION_DOCUMENT_VERIFY, PERMISSION_KEY_VIEW,
     PERMISSION_KEY_DELETE, PERMISSION_KEYSERVER_QUERY, 
-    PERMISSION_KEY_RECEIVE)
-from django_gpg.forms import KeySearchForm
+    PERMISSION_KEY_RECEIVE, PERMISSION_SIGNATURE_UPLOAD,
+    PERMISSION_SIGNATURE_DOWNLOAD)
+from django_gpg.forms import KeySearchForm, DetachedSignatureForm
 
 logger = logging.getLogger(__name__)
 
@@ -193,10 +195,8 @@ def document_verify(request, document_pk):
     document = get_object_or_404(Document, pk=document_pk)
 
     RecentDocument.objects.add_document_for_user(request.user, document)
-    try:
-        signature = gpg.verify_w_retry(document.open(raw=True))
-    except GPGVerificationError:
-        signature = None
+   
+    signature = document.verify_signature()
     
     signature_state = SIGNATURE_STATES.get(getattr(signature, 'status', None))
     
@@ -230,3 +230,56 @@ def document_verify(request, document_pk):
         'document': document,
         'paragraphs': paragraphs,
     }, context_instance=RequestContext(request))
+    
+    
+def document_signature_upload(request, document_pk):
+    check_permissions(request.user, [PERMISSION_SIGNATURE_UPLOAD])
+    document = get_object_or_404(Document, pk=document_pk)
+
+    RecentDocument.objects.add_document_for_user(request.user, document)
+        
+    post_action_redirect = None
+    previous = request.POST.get('previous', request.GET.get('previous', request.META.get('HTTP_REFERER', '/')))
+    next = request.POST.get('next', request.GET.get('next', post_action_redirect if post_action_redirect else request.META.get('HTTP_REFERER', '/')))
+
+    if request.method == 'POST':
+        form = DetachedSignatureForm(request.POST, request.FILES)
+        if form.is_valid():
+            try:
+                document.add_detached_signature(request.FILES['file'])
+                messages.success(request, _(u'Detached signature uploaded successfully.'))
+                return HttpResponseRedirect(next)
+            except Exception, msg:
+                messages.error(request, msg)
+                return HttpResponseRedirect(previous)
+    else:
+        form = DetachedSignatureForm()
+
+    return render_to_response('generic_form.html', {
+        'title': _(u'Upload detached signature for: %s') % document,
+        'form_icon': 'key_delete.png',
+        'next': next,
+        'form': form,
+        'previous': previous,
+        'object': document,
+    }, context_instance=RequestContext(request))
+    
+    
+def document_signature_download(request, document_pk):
+    check_permissions(request.user, [PERMISSION_SIGNATURE_DOWNLOAD])
+    document = get_object_or_404(Document, pk=document_pk)
+        
+    try:
+        if document.has_detached_signature():
+            signature = document.detached_signature()
+            return serve_file(
+                request,
+                signature,
+                save_as=u'"%s.sig"' % document.filename,
+                content_type=u'application/octet-stream'
+            )
+    except Exception, e:
+        messages.error(request, e)
+        return HttpResponseRedirect(request.META['HTTP_REFERER'])
+
+    return HttpResponseRedirect(request.META['HTTP_REFERER'])

apps/documents/migrations/0012_auto__add_field_documentversion_signature_file.py

@@ -0,0 +1,157 @@
+# encoding: utf-8
+import datetime
+from south.db import db
+from south.v2 import SchemaMigration
+from django.db import models
+
+class Migration(SchemaMigration):
+
+    def forwards(self, orm):
+        
+        # Adding field 'DocumentVersion.signature_file'
+        db.add_column('documents_documentversion', 'signature_file', self.gf('django.db.models.fields.files.FileField')(max_length=100, null=True, blank=True), keep_default=False)
+
+
+    def backwards(self, orm):
+        
+        # Deleting field 'DocumentVersion.signature_file'
+        db.delete_column('documents_documentversion', 'signature_file')
+
+
+    models = {
+        'auth.group': {
+            'Meta': {'object_name': 'Group'},
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'unique': 'True', 'max_length': '80'}),
+            'permissions': ('django.db.models.fields.related.ManyToManyField', [], {'to': "orm['auth.Permission']", 'symmetrical': 'False', 'blank': 'True'})
+        },
+        'auth.permission': {
+            'Meta': {'ordering': "('content_type__app_label', 'content_type__model', 'codename')", 'unique_together': "(('content_type', 'codename'),)", 'object_name': 'Permission'},
+            'codename': ('django.db.models.fields.CharField', [], {'max_length': '100'}),
+            'content_type': ('django.db.models.fields.related.ForeignKey', [], {'to': "orm['contenttypes.ContentType']"}),
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '50'})
+        },
+        'auth.user': {
+            'Meta': {'object_name': 'User'},
+            'date_joined': ('django.db.models.fields.DateTimeField', [], {'default': 'datetime.datetime.now'}),
+            'email': ('django.db.models.fields.EmailField', [], {'max_length': '75', 'blank': 'True'}),
+            'first_name': ('django.db.models.fields.CharField', [], {'max_length': '30', 'blank': 'True'}),
+            'groups': ('django.db.models.fields.related.ManyToManyField', [], {'to': "orm['auth.Group']", 'symmetrical': 'False', 'blank': 'True'}),
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'is_active': ('django.db.models.fields.BooleanField', [], {'default': 'True'}),
+            'is_staff': ('django.db.models.fields.BooleanField', [], {'default': 'False'}),
+            'is_superuser': ('django.db.models.fields.BooleanField', [], {'default': 'False'}),
+            'last_login': ('django.db.models.fields.DateTimeField', [], {'default': 'datetime.datetime.now'}),
+            'last_name': ('django.db.models.fields.CharField', [], {'max_length': '30', 'blank': 'True'}),
+            'password': ('django.db.models.fields.CharField', [], {'max_length': '128'}),
+            'user_permissions': ('django.db.models.fields.related.ManyToManyField', [], {'to': "orm['auth.Permission']", 'symmetrical': 'False', 'blank': 'True'}),
+            'username': ('django.db.models.fields.CharField', [], {'unique': 'True', 'max_length': '30'})
+        },
+        'comments.comment': {
+            'Meta': {'ordering': "('submit_date',)", 'object_name': 'Comment', 'db_table': "'django_comments'"},
+            'comment': ('django.db.models.fields.TextField', [], {'max_length': '3000'}),
+            'content_type': ('django.db.models.fields.related.ForeignKey', [], {'related_name': "'content_type_set_for_comment'", 'to': "orm['contenttypes.ContentType']"}),
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'ip_address': ('django.db.models.fields.IPAddressField', [], {'max_length': '15', 'null': 'True', 'blank': 'True'}),
+            'is_public': ('django.db.models.fields.BooleanField', [], {'default': 'True'}),
+            'is_removed': ('django.db.models.fields.BooleanField', [], {'default': 'False'}),
+            'object_pk': ('django.db.models.fields.TextField', [], {}),
+            'site': ('django.db.models.fields.related.ForeignKey', [], {'to': "orm['sites.Site']"}),
+            'submit_date': ('django.db.models.fields.DateTimeField', [], {'default': 'None'}),
+            'user': ('django.db.models.fields.related.ForeignKey', [], {'blank': 'True', 'related_name': "'comment_comments'", 'null': 'True', 'to': "orm['auth.User']"}),
+            'user_email': ('django.db.models.fields.EmailField', [], {'max_length': '75', 'blank': 'True'}),
+            'user_name': ('django.db.models.fields.CharField', [], {'max_length': '50', 'blank': 'True'}),
+            'user_url': ('django.db.models.fields.URLField', [], {'max_length': '200', 'blank': 'True'})
+        },
+        'contenttypes.contenttype': {
+            'Meta': {'ordering': "('name',)", 'unique_together': "(('app_label', 'model'),)", 'object_name': 'ContentType', 'db_table': "'django_content_type'"},
+            'app_label': ('django.db.models.fields.CharField', [], {'max_length': '100'}),
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'model': ('django.db.models.fields.CharField', [], {'max_length': '100'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '100'})
+        },
+        'documents.document': {
+            'Meta': {'ordering': "['-date_added']", 'object_name': 'Document'},
+            'date_added': ('django.db.models.fields.DateTimeField', [], {'db_index': 'True'}),
+            'description': ('django.db.models.fields.TextField', [], {'db_index': 'True', 'null': 'True', 'blank': 'True'}),
+            'document_type': ('django.db.models.fields.related.ForeignKey', [], {'to': "orm['documents.DocumentType']", 'null': 'True', 'blank': 'True'}),
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'uuid': ('django.db.models.fields.CharField', [], {'max_length': '48', 'blank': 'True'})
+        },
+        'documents.documentpage': {
+            'Meta': {'ordering': "['page_number']", 'object_name': 'DocumentPage'},
+            'content': ('django.db.models.fields.TextField', [], {'db_index': 'True', 'null': 'True', 'blank': 'True'}),
+            'document_version': ('django.db.models.fields.related.ForeignKey', [], {'to': "orm['documents.DocumentVersion']"}),
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'page_label': ('django.db.models.fields.CharField', [], {'max_length': '32', 'null': 'True', 'blank': 'True'}),
+            'page_number': ('django.db.models.fields.PositiveIntegerField', [], {'default': '1', 'db_index': 'True'})
+        },
+        'documents.documentpagetransformation': {
+            'Meta': {'ordering': "('order',)", 'object_name': 'DocumentPageTransformation'},
+            'arguments': ('django.db.models.fields.TextField', [], {'null': 'True', 'blank': 'True'}),
+            'document_page': ('django.db.models.fields.related.ForeignKey', [], {'to': "orm['documents.DocumentPage']"}),
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'order': ('django.db.models.fields.PositiveIntegerField', [], {'default': '0', 'null': 'True', 'db_index': 'True', 'blank': 'True'}),
+            'transformation': ('django.db.models.fields.CharField', [], {'max_length': '128'})
+        },
+        'documents.documenttype': {
+            'Meta': {'ordering': "['name']", 'object_name': 'DocumentType'},
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '32'})
+        },
+        'documents.documenttypefilename': {
+            'Meta': {'ordering': "['filename']", 'object_name': 'DocumentTypeFilename'},
+            'document_type': ('django.db.models.fields.related.ForeignKey', [], {'to': "orm['documents.DocumentType']"}),
+            'enabled': ('django.db.models.fields.BooleanField', [], {'default': 'True'}),
+            'filename': ('django.db.models.fields.CharField', [], {'max_length': '128', 'db_index': 'True'}),
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'})
+        },
+        'documents.documentversion': {
+            'Meta': {'unique_together': "(('document', 'major', 'minor', 'micro', 'release_level', 'serial'),)", 'object_name': 'DocumentVersion'},
+            'checksum': ('django.db.models.fields.TextField', [], {'null': 'True', 'blank': 'True'}),
+            'comment': ('django.db.models.fields.TextField', [], {'blank': 'True'}),
+            'document': ('django.db.models.fields.related.ForeignKey', [], {'to': "orm['documents.Document']"}),
+            'encoding': ('django.db.models.fields.CharField', [], {'default': "''", 'max_length': '64'}),
+            'file': ('django.db.models.fields.files.FileField', [], {'max_length': '100'}),
+            'filename': ('django.db.models.fields.CharField', [], {'default': "u''", 'max_length': '255', 'db_index': 'True'}),
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'major': ('django.db.models.fields.PositiveIntegerField', [], {'default': '1'}),
+            'micro': ('django.db.models.fields.PositiveIntegerField', [], {'default': '0'}),
+            'mimetype': ('django.db.models.fields.CharField', [], {'default': "''", 'max_length': '64'}),
+            'minor': ('django.db.models.fields.PositiveIntegerField', [], {'default': '0'}),
+            'release_level': ('django.db.models.fields.PositiveIntegerField', [], {'default': '1'}),
+            'serial': ('django.db.models.fields.PositiveIntegerField', [], {'default': '0'}),
+            'signature_file': ('django.db.models.fields.files.FileField', [], {'max_length': '100', 'null': 'True', 'blank': 'True'}),
+            'signature_state': ('django.db.models.fields.CharField', [], {'max_length': '16', 'null': 'True', 'blank': 'True'}),
+            'timestamp': ('django.db.models.fields.DateTimeField', [], {})
+        },
+        'documents.recentdocument': {
+            'Meta': {'ordering': "('-datetime_accessed',)", 'object_name': 'RecentDocument'},
+            'datetime_accessed': ('django.db.models.fields.DateTimeField', [], {'db_index': 'True'}),
+            'document': ('django.db.models.fields.related.ForeignKey', [], {'to': "orm['documents.Document']"}),
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'user': ('django.db.models.fields.related.ForeignKey', [], {'to': "orm['auth.User']"})
+        },
+        'sites.site': {
+            'Meta': {'ordering': "('domain',)", 'object_name': 'Site', 'db_table': "'django_site'"},
+            'domain': ('django.db.models.fields.CharField', [], {'max_length': '100'}),
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '50'})
+        },
+        'taggit.tag': {
+            'Meta': {'object_name': 'Tag'},
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'name': ('django.db.models.fields.CharField', [], {'max_length': '100'}),
+            'slug': ('django.db.models.fields.SlugField', [], {'unique': 'True', 'max_length': '100', 'db_index': 'True'})
+        },
+        'taggit.taggeditem': {
+            'Meta': {'object_name': 'TaggedItem'},
+            'content_type': ('django.db.models.fields.related.ForeignKey', [], {'related_name': "'taggit_taggeditem_tagged_items'", 'to': "orm['contenttypes.ContentType']"}),
+            'id': ('django.db.models.fields.AutoField', [], {'primary_key': 'True'}),
+            'object_id': ('django.db.models.fields.IntegerField', [], {'db_index': 'True'}),
+            'tag': ('django.db.models.fields.related.ForeignKey', [], {'related_name': "'taggit_taggeditem_items'", 'to': "orm['taggit.Tag']"})
+        }
+    }
+
+    complete_apps = ['documents']

apps/documents/models.py

@@ -290,8 +290,20 @@ class Document(models.Model):
         return version.save()
 
     filename = property(_get_filename, _set_filename)
-            
+        
+    def add_detached_signature(self, *args, **kwargs):
+        return self.latest_version.add_detached_signature(*args, **kwargs)
 
+    def has_detached_signature(self):
+        return self.latest_version.has_detached_signature()
+    
+    def detached_signature(self):
+        return self.latest_version.detached_signature()
+
+    def verify_signature(self):
+        return self.latest_version.verify_signature()
+        
+        
 class DocumentVersion(models.Model):
     '''
     Model that describes a document version and its properties
@@ -320,6 +332,7 @@ class DocumentVersion(models.Model):
     filename = models.CharField(max_length=255, default=u'', editable=False, db_index=True)
     checksum = models.TextField(blank=True, null=True, verbose_name=_(u'checksum'), 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)
     
     class Meta:
         unique_together = ('document', 'major', 'minor', 'micro', 'release_level', 'serial')
@@ -534,7 +547,35 @@ class DocumentVersion(models.Model):
             return self.file.storage.size(self.file.path)
         else:
             return None
+   
+    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 DocumentTypeFilename(models.Model):
     '''