Configuring django-csp

Content-Security-Policy is a complicated header. There are many values you may need to tweak here.

It’s worth reading the latest CSP spec and making sure you understand it before configuring django-csp.

Note

Many settings require a tuple or list. You may get very strange policies and even errors when mistakenly configuring them as a string.

Migrating from django-csp <= 3.8

Version 4.0 of django-csp introduces a new configuration format that breaks compatibility with previous versions. If you are migrating from django-csp 3.8 or lower, you will need to update your settings to the new format. See the migration guide for more information.

Configuration

All configuration of django-csp is done in your Django settings file with the CONTENT_SECURITY_POLICY setting or the CONTENT_SECURITY_POLICY_REPORT_ONLY setting. Each of these settings expects a dictionary representing a policy.

The CONTENT_SECURITY_POLICY setting is your enforceable policy.

The CONTENT_SECURITY_POLICY_REPORT_ONLY setting is your report-only policy. This policy is used to test the policy without breaking the site. It is useful when setting this policy to be slightly more strict than the default policy to see what would be blocked if the policy was enforced.

The following is an example of a policy configuration with a default policy and a report-only policy. The default policy is considered a “relaxed” policy that allows for the most flexibility while still providing a good level of security. The report-only policy is considered a step towards a more slightly strict policy and is used to test the policy without breaking the site.

from csp.constants import NONE, SELF

CONTENT_SECURITY_POLICY = {
    "EXCLUDE_URL_PREFIXES": ["/excluded-path/"],
    "DIRECTIVES": {
        "default-src": [SELF, "cdn.example.net"],
        "frame-ancestors": [SELF],
        "form-action": [SELF],
        "report-uri": "/csp-report/",
    },
}

CONTENT_SECURITY_POLICY_REPORT_ONLY = {
    "EXCLUDE_URL_PREFIXES": ["/excluded-path/"],
    "DIRECTIVES": {
        "default-src": [NONE],
        "connect-src": [SELF],
        "img-src": [SELF],
        "form-action": [SELF],
        "frame-ancestors": [SELF],
        "script-src": [SELF],
        "style-src": [SELF],
        "upgrade-insecure-requests": True,
        "report-uri": "/csp-report/",
    },
}

Note

In the above example, the constant NONE is converted to the CSP keyword "'none'" and is distinct from Python’s None value. The CSP keyword 'none' is a special value that signifies that you do not want any sources for this directive. The None value is a Python keyword that represents the absence of a value and when used as the value of a directive, it will remove the directive from the policy.

This is useful when using the @csp_replace decorator to effectively clear a directive from the base configuration as defined in the settings. For example, if the Django settings the frame-ancestors directive is set to a list of sources and you want to remove the frame-ancestors directive from the policy for this view:

from csp.decorators import csp_replace


@csp_replace({"frame-ancestors": None})
def my_view(request): ...

Policy Settings

At the top level of the policy dictionary, these are the keys that can be used to configure the policy.

EXCLUDE_URL_PREFIXES

A tuple of URL prefixes. URLs beginning with any of these will not get the CSP headers. ()

Warning

Excluding any path on your site will eliminate the benefits of CSP everywhere on your site. The typical browser security model for JavaScript considers all paths alike. A Cross-Site Scripting flaw on, e.g., excluded-page/ can therefore be leveraged to access everything on the same origin.

REPORT_PERCENTAGE

Percentage of requests that should see the report-uri directive. Use this to throttle the number of CSP violation reports made to your report-uri. A float between 0.0 and 100.0 (0.0 = no reports at all, 100.0 = always report). Ignored if report-uri isn’t set.

DIRECTIVES

A dictionary of policy directives. Each key in the dictionary is a directive and the value is a list of sources for that directive. The following is a list of all the directives that can be configured.

Note

The CSP keyword values of 'self', 'unsafe-inline', 'strict-dynamic', etc. must be quoted! e.g.: "default-src": ["'self'"]. Without quotes they will not work as intended.

New in version 4.0 are CSP keyword constants. Use these to minimize quoting mistakes and typos.

The following CSP keywords are available:

NONE = "'none'"

REPORT_SAMPLE = "'report-sample'"

SELF = "'self'"

STRICT_DYNAMIC = "'strict-dynamic'"

UNSAFE_ALLOW_REDIRECTS = "'unsafe-allow-redirects'"

UNSAFE_EVAL = "'unsafe-eval'"

UNSAFE_HASHES = "'unsafe-hashes'"

UNSAFE_INLINE = "'unsafe-inline'"

WASM_UNSAFE_EVAL = "'wasm-unsafe-eval'"

Example usage:

from csp.constants import SELF, STRICT_DYNAMIC

CONTENT_SECURITY_POLICY = {
    "DIRECTIVES": {
        "default-src": [SELF, "cdn.example.net"],
        "script-src": [SELF, STRICT_DYNAMIC],
        "style-src": [SELF],
    }
}

Note

Deprecated features of CSP in general have been moved to the bottom of this list.

Warning

The 'unsafe-inline' and 'unsafe-eval' sources are considered harmful and should be avoided. They are included here for completeness, but should not be used in production.

default-src

Set the default-src directive. A tuple or list of values, e.g.: ("'self'", 'cdn.example.net'). [“‘self’”]

script-src

Set the script-src directive. A tuple or list. None

script-src-attr

Set the script-src-attr directive. A tuple or list. None

script-src-elem

Set the script-src-elem directive. A tuple or list. None

img-src

Set the img-src directive. A tuple or list. None

object-src

Set the object-src directive. A tuple or list. None

media-src

Set the media-src directive. A tuple or list. None

frame-src

Set the frame-src directive. A tuple or list. None

font-src

Set the font-src directive. A tuple or list. None

connect-src

Set the connect-src directive. A tuple or list. None

style-src

Set the style-src directive. A tuple or list. None

style-src-attr

Set the style-src-attr directive. A tuple or list. None

style-src-elem

Set the style-src-elem directive. A tuple or list. None

base-uri

Set the base-uri directive. A tuple or list. None

Note: This doesn’t use default-src as a fall-back.

child-src

Set the child-src directive. A tuple or list. None

frame-ancestors

Set the frame-ancestors directive. A tuple or list. None

Note: This doesn’t use default-src as a fall-back.

navigate-to

Set the navigate-to directive. A tuple or list. None

Note: This doesn’t use default-src as a fall-back.

form-action

Set the FORM_ACTION directive. A tuple or list. None

Note: This doesn’t use default-src as a fall-back.

sandbox

Set the sandbox directive. A tuple or list. None

Note: This doesn’t use default-src as a fall-back.

report-uri

Set the report-uri directive. A tuple or list of URIs. Each URI can be a full or relative URI. None

Note: This doesn’t use default-src as a fall-back.

report-to

Set the report-to directive. A string describing a reporting group. None

See Section 1.2: https://w3c.github.io/reporting/#group

Also see this MDN note on report-uri and report-to.

manifest-src

Set the manifest-src directive. A tuple or list. None

worker-src

Set the worker-src directive. A tuple or list. None

require-sri-for

Set the require-sri-for directive. A tuple or list. None

Valid values: a list containing 'script', 'style', or both.

Spec: require-sri-for-known-tokens

upgrade-insecure-requests

Include upgrade-insecure-requests directive. A boolean. False

Spec: upgrade-insecure-requests

require-trusted-types-for

Include require-trusted-types-for directive. A tuple or list. None

Valid values: ["'script'"]

trusted-types

Include trusted-types directive. A tuple or list. None

Valid values: a list of allowed policy names that may include default and/or 'allow-duplicates'

Deprecated CSP settings

The following DIRECTIVES settings are still configurable, but are considered deprecated in terms of the latest implementation of the relevant spec.

block-all-mixed-content

Include block-all-mixed-content directive. A boolean. False

Related note on MDN.

Spec: block-all-mixed-content

plugin-types

Set the plugin-types directive. A tuple or list. None

Note: This doesn’t use default-src as a fall-back.

Related note on MDN.

prefetch-src

Set the prefetch-src directive. A tuple or list. None

Related note on MDN.

Changing the Policy

The policy can be changed on a per-view (or even per-request) basis. See the decorator documentation for more details.