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Use CSP header to treat served files as belonging to a separate origin #3341

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Mar 9, 2018
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Use CSP header to treat served files as belonging to a separate origin #3341

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Use CSP header to treat served files as belonging to a separate origin
takluyver Feb 15, 2018
694ed72
Use content_security_policy property to add restriction when serving …
takluyver Mar 8, 2018
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4 changes: 4 additions & 0 deletions notebook/base/handlers.py
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Original file line number Diff line number Diff line change
Expand Up @@ -629,6 +629,10 @@ def set_headers(self):
# disable browser caching, rely on 304 replies for savings
if "v" not in self.request.arguments:
self.add_header("Cache-Control", "no-cache")

# In case we're serving HTML/SVG, confine any Javascript to a unique
# origin so it can't interact with the notebook server.
self.set_header('Content-Security-Policy', 'sandbox allow-scripts')
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This also overrides any currently set Content-Security-Policy -- should we merge with the operator's settings?

Note: I refer to operator to mean whoever administers this deployment, whether a local server user or a jupyterhub administrator.

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Yes, good point. Do you think it's sufficient to use add_header() to do this, or should we get into checking any existing Content-Security-Policy headers?

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Can multiple CSP headers be set and do what we want? If not, we might want to override the inherited content_security_policy property instead.

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From MDN:

You can use the Content-Security-Policy header more than once... Adding additional policies can only further restrict the capabilities of the protected resource

I think that means this should work, but maybe the c_s_p property is a neater way to achieve the same thing?

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@rgbkrk rgbkrk Feb 15, 2018 •
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Interesting, I didn't realize we could add multiple headers with the same key. How does set_header work when there are multiple headers with the same key from add_header?

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I think set_header blows away anything that was set before.

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My question comes down to "what's the set of headers after running the following"

self.add_header("X", "y")
self.add_header("X", "z")
self.set_header("X", "x")

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AIUI, only X: x would remain.

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I'm thinking using only one header is good. For now I think the value you've set here is a very sane default and further enhancements on merging content security policies can be separate work.


def compute_etag(self):
return None
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4 changes: 4 additions & 0 deletions notebook/files/handlers.py
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Expand Up @@ -64,6 +64,10 @@ def get(self, path, include_body=True):
else:
self.set_header('Content-Type', 'text/plain; charset=UTF-8')

# In case we're serving HTML/SVG, confine any Javascript to a unique
# origin so it can't interact with the notebook server.
self.set_header('Content-Security-Policy', 'sandbox allow-scripts')

if include_body:
if model['format'] == 'base64':
b64_bytes = model['content'].encode('ascii')
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