1 files changed, 40 insertions, 0 deletions
diff --git a/wqflask/utility/hmac.py b/wqflask/utility/hmac.py
new file mode 100644
index 00000000..b08be97e
--- /dev/null
+++ b/wqflask/utility/hmac.py
@@ -0,0 +1,40 @@
+from __future__ import print_function, division, absolute_import
+
+import hmac
+import hashlib
+
+from flask import url_for
+
+from wqflask import app
+
+def hmac_creation(stringy):
+    """Helper function to create the actual hmac"""
+
+    secret = app.config['SECRET_HMAC_CODE']
+
+    hmaced = hmac.new(secret, stringy, hashlib.sha1)
+    hm = hmaced.hexdigest()
+    # ZS: Leaving the below comment here to ask Pjotr about
+    # "Conventional wisdom is that you don't lose much in terms of security if you throw away up to half of the output."
+    # http://www.w3.org/QA/2009/07/hmac_truncation_in_xml_signatu.html
+    hm = hm[:20]
+    return hm
+
+def data_hmac(stringy):
+    """Takes arbitray data string and appends :hmac so we know data hasn't been tampered with"""
+    return stringy + ":" + hmac_creation(stringy)
+
+def url_for_hmac(endpoint, **values):
+    """Like url_for but adds an hmac at the end to insure the url hasn't been tampered with"""
+
+    url = url_for(endpoint, **values)
+
+    hm = hmac_creation(url)
+    if '?' in url:
+        combiner = "&"
+    else:
+        combiner = "?"
+    return url + combiner + "hm=" + hm
+
+app.jinja_env.globals.update(url_for_hmac=url_for_hmac,
+                             data_hmac=data_hmac)
+\ No newline at end of file