Validate ssh keys as they are entered in the profile

In particular, reject ssh-dss keys here. They don't work anymore since
an upgrade, for security reasons, but there was not really a way for the
user to know why. With this they will at least know if when they try to
save or change the keys.

diff --git a/pgweb/core/models.py b/pgweb/core/models.py
index 20269bcb5e970eb45600a364d4596eb1eb0af6ef..8dfef50a1661eb03833ea743d9fd7e0251092795 100644 (file)
--- a/pgweb/core/models.py
+++ b/pgweb/core/models.py
@@ -1,7 +1,10 @@
 from django.db import models
+from django.core.validators import ValidationError
 from django.contrib.auth.models import User
 from pgweb.util.misc import varnish_purge
 
+import base64
+
 TESTING_CHOICES = (
        (0, 'Release'),
        (1, 'Release candidate'),
@@ -162,10 +165,30 @@ class ImportedRSSItem(models.Model):
                return self.posttime.strftime("%Y-%m-%d")
 
 
+# From man sshd, except for ssh-dss
+_valid_keytypes = ['ecdsa-sha2-nistp256', 'ecdsa-sha2-nistp384', 'ecdsa-sha2-nistp521', 'ssh-ed25519', 'ssh-rsa']
+# Options, keytype, key, comment. But we don't support options.
+def validate_sshkey(key):
+       lines = key.splitlines()
+       for k in lines:
+               pieces = k.split()
+               if len(pieces) == 0:
+                       raise ValidationError("Empty keys are not allowed")
+               if len(pieces) > 3:
+                       raise ValidationError('Paste each ssh key without options, e.g. "ssh-rsa AAAAbbbcc mykey@machine"')
+               if pieces[0] == 'ssh-dss':
+                       raise ValidationError("For security reasons, ssh-dss keys are not supported")
+               if pieces[0] not in _valid_keytypes:
+                       raise ValidationError("Only keys of types {0} are supported, not {1}.".format(", ".join(_valid_keytypes), pieces[0]))
+               try:
+                       base64.b64decode(pieces[1])
+               except:
+                       raise ValidationError("Incorrect base64 encoded key!")
+
 # Extra attributes for users (if they have them)
 class UserProfile(models.Model):
        user = models.OneToOneField(User, null=False, blank=False, primary_key=True)
-       sshkey = models.TextField(null=False, blank=True, verbose_name="SSH key", help_text= "Paste one or more public keys in OpenSSH format, one per line.")
+       sshkey = models.TextField(null=False, blank=True, verbose_name="SSH key", help_text= "Paste one or more public keys in OpenSSH format, one per line.", validators=[validate_sshkey, ])
        lastmodified = models.DateTimeField(null=False, blank=False, auto_now=True)
 
 # Notifications sent for any moderated content.