Improve signature verification safeguards #8959

Gargron · 2018-10-11T22:09:17Z

Enforce a 12 hours time window on signed requests to prevent replayability of captured requests. Low importance, since HTTPS normally prevents MITM attacks that would allow capturing requests.
Ensure that the list of signed headers in the signature header is downcased. A differently-cased list could allow the sender to side-step the special-case verification of the Digest header. Low importance, since HTTPS normally prevents MITM attacks that would allow tampering with the request.

The HTTP Signatures draft does not mandate the “headers” field to be downcased, but mandates the header field names to be downcased in the signed string, which means that prior to this patch, Mastodon could fail to process signatures from some compliant clients. It also means that it would not actually check the Digest of non-compliant clients that wouldn't use a lowercased Digest field name. Thankfully, I don't know of any such client.

This reverts commit a00ce8c.

By checking the Date header, we can prevent replaying old vulnerable signatures. The focus is to prevent replaying old vulnerable requests from software that has been fixed in the meantime, so a somewhat long window should be fine and accounts for timezone misconfiguration.

Fixes possible HTML injection

Slightly improve performance by reducing class allocations from repeated Formatter#encode calls

* Downcase signed_headers string before building the signed string The HTTP Signatures draft does not mandate the “headers” field to be downcased, but mandates the header field names to be downcased in the signed string, which means that prior to this patch, Mastodon could fail to process signatures from some compliant clients. It also means that it would not actually check the Digest of non-compliant clients that wouldn't use a lowercased Digest field name. Thankfully, I don't know of any such client. * Revert "Remove dead code (#8919)" This reverts commit a00ce8c. * Restore time window checking, change it to 12 hours By checking the Date header, we can prevent replaying old vulnerable signatures. The focus is to prevent replaying old vulnerable requests from software that has been fixed in the meantime, so a somewhat long window should be fine and accounts for timezone misconfiguration. * Escape users' URLs when formatting them Fixes possible HTML injection * Escape all string interpolations in Formatter class Slightly improve performance by reducing class allocations from repeated Formatter#encode calls * Fix code style issues

* Downcase signed_headers string before building the signed string The HTTP Signatures draft does not mandate the “headers” field to be downcased, but mandates the header field names to be downcased in the signed string, which means that prior to this patch, Mastodon could fail to process signatures from some compliant clients. It also means that it would not actually check the Digest of non-compliant clients that wouldn't use a lowercased Digest field name. Thankfully, I don't know of any such client. * Revert "Remove dead code (mastodon#8919)" This reverts commit a00ce8c. * Restore time window checking, change it to 12 hours By checking the Date header, we can prevent replaying old vulnerable signatures. The focus is to prevent replaying old vulnerable requests from software that has been fixed in the meantime, so a somewhat long window should be fine and accounts for timezone misconfiguration. * Escape users' URLs when formatting them Fixes possible HTML injection * Escape all string interpolations in Formatter class Slightly improve performance by reducing class allocations from repeated Formatter#encode calls * Fix code style issues

Improve signature verification safeguards (mastodon#8959)

* Downcase signed_headers string before building the signed string The HTTP Signatures draft does not mandate the “headers” field to be downcased, but mandates the header field names to be downcased in the signed string, which means that prior to this patch, Mastodon could fail to process signatures from some compliant clients. It also means that it would not actually check the Digest of non-compliant clients that wouldn't use a lowercased Digest field name. Thankfully, I don't know of any such client. * Revert "Remove dead code (mastodon#8919)" This reverts commit a00ce8c. * Restore time window checking, change it to 12 hours By checking the Date header, we can prevent replaying old vulnerable signatures. The focus is to prevent replaying old vulnerable requests from software that has been fixed in the meantime, so a somewhat long window should be fine and accounts for timezone misconfiguration. * Escape users' URLs when formatting them Fixes possible HTML injection * Escape all string interpolations in Formatter class Slightly improve performance by reducing class allocations from repeated Formatter#encode calls * Fix code style issues

Improve signature verification safeguards (mastodon#8959)

* Downcase signed_headers string before building the signed string The HTTP Signatures draft does not mandate the “headers” field to be downcased, but mandates the header field names to be downcased in the signed string, which means that prior to this patch, Mastodon could fail to process signatures from some compliant clients. It also means that it would not actually check the Digest of non-compliant clients that wouldn't use a lowercased Digest field name. Thankfully, I don't know of any such client. * Revert "Remove dead code (mastodon#8919)" This reverts commit a00ce8c. * Restore time window checking, change it to 12 hours By checking the Date header, we can prevent replaying old vulnerable signatures. The focus is to prevent replaying old vulnerable requests from software that has been fixed in the meantime, so a somewhat long window should be fine and accounts for timezone misconfiguration. * Escape users' URLs when formatting them Fixes possible HTML injection * Escape all string interpolations in Formatter class Slightly improve performance by reducing class allocations from repeated Formatter#encode calls * Fix code style issues

hellekin · 2018-10-16T17:44:20Z

spec/controllers/concerns/signature_verification_spec.rb

@@ -73,6 +73,30 @@ def alternative_success
      end
    end

+    context 'with request older than a day' do


#matches_time_window? uses 12.hours.ago, spec mentions "older than a day", and the spec itself sets the header to 2.days.ago.

This reverts commit 1787704.

ClearlyClaire and others added 5 commits October 11, 2018 23:25

Revert "Remove dead code (#8919)"

9a117ab

This reverts commit a00ce8c.

Escape users' URLs when formatting them

1a3b154

Fixes possible HTML injection

Escape all string interpolations in Formatter class

4179e01

Slightly improve performance by reducing class allocations from repeated Formatter#encode calls

Gargron added the security Security issues and fixes, vulnerabilities label Oct 11, 2018

Fix code style issues

baf6e8e

Gargron merged commit 21ad21c into master Oct 11, 2018

Gargron deleted the fix-security-improvements branch October 11, 2018 22:15

abcang added a commit to pixiv/mastodon that referenced this pull request Oct 12, 2018

Merge pull request mastodon#863 from pixiv/cherry_pick_2_5_1

98393dc

Improve signature verification safeguards (mastodon#8959)

abcang added a commit to pixiv/mastodon that referenced this pull request Oct 12, 2018

Merge pull request mastodon#1221 from pixiv/cherry_pick_2_5_1

228f63f

Improve signature verification safeguards (mastodon#8959)

hellekin reviewed Oct 16, 2018

View reviewed changes

lindwurm added a commit to akane-blue/mastodon that referenced this pull request Nov 1, 2018

Revert "Improve signature verification safeguards (mastodon#8959)"

fccd3b1

This reverts commit 1787704.

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Improve signature verification safeguards #8959

Improve signature verification safeguards #8959

Gargron commented Oct 11, 2018

hellekin Oct 16, 2018

Improve signature verification safeguards #8959

Improve signature verification safeguards #8959

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Gargron commented Oct 11, 2018

hellekin Oct 16, 2018

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