From f7452e837974dd39bf7452a8ee059ec7738f18ef Mon Sep 17 00:00:00 2001
From: Javier Ramos <javier.ramos@booking.com>
Date: Fri, 15 Mar 2019 09:18:33 +0100
Subject: [PATCH] Parse DNSNames from CSR into Lemur Certificate

---
 lemur/certificates/schemas.py |  6 +++++
 lemur/certificates/utils.py   | 42 +++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+)
 create mode 100644 lemur/certificates/utils.py

diff --git a/lemur/certificates/schemas.py b/lemur/certificates/schemas.py
index d20fd5a7..e9b61539 100644
--- a/lemur/certificates/schemas.py
+++ b/lemur/certificates/schemas.py
@@ -10,6 +10,7 @@ from marshmallow import fields, validate, validates_schema, post_load, pre_load
 from marshmallow.exceptions import ValidationError
 
 from lemur.authorities.schemas import AuthorityNestedOutputSchema
+from lemur.certificates import utils as cert_utils
 from lemur.common import missing, utils, validators
 from lemur.common.fields import ArrowDateTime, Hex
 from lemur.common.schema import LemurInputSchema, LemurOutputSchema
@@ -107,6 +108,11 @@ class CertificateInputSchema(CertificateCreationSchema):
     def load_data(self, data):
         if data.get('replacements'):
             data['replaces'] = data['replacements']  # TODO remove when field is deprecated
+        if data['csr']:
+            dns_names = cert_utils.get_dns_names_from_csr(data['csr'])
+            if not data['extensions']['subAltNames']['names']:
+                data['extensions']['subAltNames']['names'] = []
+            data['extensions']['subAltNames']['names'] += dns_names
         return missing.convert_validity_years(data)
 
 
diff --git a/lemur/certificates/utils.py b/lemur/certificates/utils.py
new file mode 100644
index 00000000..933fe45e
--- /dev/null
+++ b/lemur/certificates/utils.py
@@ -0,0 +1,42 @@
+"""
+Utils to parse certificate data.
+
+.. module: lemur.certificates.hooks
+    :platform: Unix
+    :copyright: (c) 2019 by Javier Ramos, see AUTHORS for more
+    :license: Apache, see LICENSE for more details.
+
+.. moduleauthor:: Javier Ramos <javier.ramos@booking.com>
+"""
+
+from cryptography import x509
+from cryptography.hazmat.backends import default_backend
+from marshmallow.exceptions import ValidationError
+
+
+def get_dns_names_from_csr(data):
+    """
+    Fetches DNSNames from CSR.
+    Potentially extendable to any kind of SubjectAlternativeName
+    :param data: PEM-encoded string with CSR
+    :return:
+    """
+    dns_names = []
+    try:
+        request = x509.load_pem_x509_csr(data.encode('utf-8'), default_backend())
+    except Exception:
+        raise ValidationError('CSR presented is not valid.')
+
+    try:
+        alt_names = request.extensions.get_extension_for_class(x509.SubjectAlternativeName)
+
+        for name in alt_names.value.get_values_for_type(x509.DNSName):
+            dns_name = {
+                'nameType': 'DNSName',
+                'value': name
+            }
+            dns_names.append(dns_name)
+    except x509.ExtensionNotFound:
+        pass
+
+    return dns_names