Add configuration for cookie 'SameSite' value.

[k-wall]

Expose the samesite cookie option for configuration.

Values of lax and strict can improve and mitigate some categories of cross-site traffic tampering.

As oauth-proxy is used to front other components, having this configuration option available makes a useful defence.

Based on Paul Groudas' paul@clubhouse.io work (https://github.com/oauth2-proxy/oauth2-proxy/commit/5d0827a)

[openshift-ci-robot]

Hi @k-wall. Thanks for your PR.

I'm waiting for a openshift member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

I understand the commands that are listed here.

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[k-wall]

I see the Travis build, which uses Go 1.12, failed like so:

./oauthproxy.go:873:10: undefined: http.SameSiteNoneMode
253FAIL github.com/openshift/oauth-proxy [build failed]

http.SameSiteNoneMode is a Go 1.13 symbol. I thought this was safe as the go.mod declares 1.13. Is the Travis config out of date, or should I avoid the 1.13 symbol? Please advise me, @stlaz or @sttts?

[sttts]

/assign @stlaz

[stlaz]

/ok-to-test /lgtm Using golang 1.13 should be fine, I'll try to see whether I can disable the Travis job here, it's quite obsolete anyway

[openshift-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: k-wall, stlaz

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/openshift/oauth-proxy/blob/master/OWNERS)~~ [stlaz] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[openshift-bot]

/retest

Please review the full test history for this PR and help us cut down flakes.

[openshift-bot]

/retest

Please review the full test history for this PR and help us cut down flakes.

[openshift-bot]

/retest

Please review the full test history for this PR and help us cut down flakes.