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Switch Content Security Policy from report-only to enforceable #498

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merged 1 commit into from Dec 17, 2017
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Switch Content Security Policy from report-only to enforceable #498

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10 changes: 5 additions & 5 deletions liberapay/security/__init__.py
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Expand Up @@ -30,17 +30,17 @@ def set_default_security_headers(website, response, request=None):
# https://scotthelme.co.uk/content-security-policy-an-introduction/
if b'content-security-policy' not in response.headers:
csp = (
b"default-src %(main_domain)s;"
b"script-src %(main_domain)s 'unsafe-inline';"
b"style-src %(main_domain)s 'unsafe-inline';"
b"default-src 'self' %(main_domain)s;"
b"script-src 'self' %(main_domain)s 'unsafe-inline';"
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The comment above this section of code suggests that we are using this CSP to prevent XSS, but by using 'unsafe-inline' you are doing precisely the opposite.

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Proof of concept: http://output.jsbin.com/segekehedo.

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We're not ready to drop 'unsafe-inline'. It's still better to have some protection than none at all.

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@Changaco, I agree, but is there a ticket addressing this concern somewhere?

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There is now: #879.

b"style-src 'self' %(main_domain)s 'unsafe-inline';"
b"connect-src *;" # for credit card data
b"img-src *;"
b"reflected-xss block;"
) % {b'main_domain': website.canonical_host.encode('ascii')}
csp += website.env.csp_extra.encode()
if website.canonical_scheme == 'https':
csp += b"upgrade-insecure-requests;block-all-mixed-content;"
response.headers[b'content-security-policy-report-only'] = csp
csp += b"upgrade-insecure-requests;"
response.headers[b'content-security-policy'] = csp

# https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-XSS-Protection
if b'X-XSS-Protection' not in response.headers:
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