Validating ssh public keys using sshpubkeys

hosting/forms.py

@@ -6,6 +6,8 @@ import struct
 from django import forms
 from django.contrib.auth import authenticate
 from django.utils.translation import ugettext_lazy as _
+from sshpubkeys import SSHKey
+from sshpubkeys.exceptions import InvalidKeyException
 
 from membership.models import CustomUser
 from .models import UserHostingKey
@@ -89,28 +91,25 @@ class UserHostingKeyForm(forms.ModelForm):
 
     def clean_public_key(self):
         """
-        A simple validation of ssh public key
-        See https://www.ietf.org/rfc/rfc4716.txt
+        A function that validates a public ssh key using sshpubkeys module
         :return:
         """
         if 'generate' in self.request.POST:
             return self.data.get('public_key')
         KEY_ERROR_MESSAGE = _("Please input a proper SSH key")
-        openssh_pubkey = self.data.get('public_key')
-        data = None
+        openssh_pubkey_str = self.data.get('public_key')
+        ssh_key = SSHKey(openssh_pubkey_str)
         try:
-            key_type, key_string, comment = openssh_pubkey.split()
-            data = base64.decodebytes(key_string.encode('utf-8'))
-        except Exception as e:
-            logger.error("Exception while decoding ssh key {}".format(e))
+            ssh_key.parse()
+        except InvalidKeyException as err:
+            logger.error(
+                "InvalidKeyException while parsing ssh key {0}".format(err))
             raise forms.ValidationError(KEY_ERROR_MESSAGE)
-        int_len = 4
-        str_len = struct.unpack('>I', data[:int_len])[0]
-        if str_len != 7:
+        except NotImplementedError as err:
+            logger.error(
+                "NotImplementedError while parsing ssh key {0}".format(err))
             raise forms.ValidationError(KEY_ERROR_MESSAGE)
-        if data[int_len:int_len + str_len] != key_type.encode('utf-8'):
-            raise forms.ValidationError(KEY_ERROR_MESSAGE)
-        return openssh_pubkey
+        return openssh_pubkey_str
 
     def clean_name(self):
         return self.data.get('name')

hosting/locale/de/LC_MESSAGES/django.po

@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PACKAGE VERSION\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2017-09-02 03:08+0530\n"
+"POT-Creation-Date: 2017-09-06 22:27+0000\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
@@ -24,6 +24,9 @@ msgstr "Dein Benutzername und/oder Dein Passwort ist falsch."
 msgid "Your account is not activated yet."
 msgstr "Dein Account wurde noch nicht aktiviert."
 
+msgid "User does not exist"
+msgstr ""
+
 msgid "Paste here your public key"
 msgstr "Füge deinen Public Key ein"
 
@@ -33,6 +36,9 @@ msgstr "Gebe deinem SSH-Key einen Name"
 msgid "Key name"
 msgstr "Key-Name"
 
+msgid "Please input a proper SSH key"
+msgstr ""
+
 msgid "My Virtual Machines"
 msgstr "Meine virtuellen Maschinen"
 

requirements.txt

@@ -97,3 +97,4 @@ billiard==3.5.0.3
 amqp==2.2.1
 vine==1.1.4
 git+https://github.com/ungleich/cdist.git#egg=cdist
+sshpubkeys