feat: Implement remote signing for CAWG `X509CredentialHolder` by BadrTad · Pull Request #1865 · contentauth/c2pa-rs

BadrTad · 2026-02-18T09:14:26Z

Changes in this pull request

This PR implements CAWG remote signing (as requested in #1777 ) by introducing a new type raw_signer:: RemoteRawSigner

The feature could be tested by enabling the "remote_signing" feature during compilation. and remote signers created with this new method create_signer::from_remote_url

The remote_signing is supported only for openssl crypto provider.

The code snippet that converts X509 certificates from PEM to DER in raw_signature::openssl crate was also refactored as a macro under raw_signature::openssl::cert_chain::cert_chain_to_der!

The remote signer could be created by providing a setting configuration to Context struct or by instantiating X509CredentialHolder from a openssl::signers::remote_signer::RemoteRawSigner.

Tests use the httpmock crate to create mock servers that responds with valid signature using a (local) signer instantiated with create_signer::from_keys.

Checklist

This PR represents a single feature, fix, or change.
All applicable changes have been documented.
Any TO DO items (or similar) have been entered as GitHub issues and the link to that issue has been included in a comment.

# Conflicts: # Cargo.lock

scouten-adobe

I'm leaving on vacation shortly and won't have time to do a full review before I go. I've asked @gpeacock to review it hopefully next week.

… of impl functions with RawSigner trait definition

BadrTad · 2026-03-12T00:03:04Z

The remote_signing crate feature requires the openssl crypto provider and lacks support for rust_native crypto provider.
In this case the crypro providers are used mainly to verify and parse the certificate chain.
Issue #1926 documents the lack of support for the remote_signing feature with rust_native crypto provider.

scouten-adobe

Looks great. A few tweaks I'd like to see, but I'm eager to see this land.

scouten-adobe · 2026-03-12T18:55:57Z

        Ok(self.cert_chain.clone())
    }
+
+    fn reserve_size(&self) -> usize {


Would you mind putting this back where it was? I'd prefer to keep the diffs as minimal as possible. (Applies to other signer implementations also.)

BTW, please consider ticking the box that says "Allow maintainers to edit this PR." I'd have made this change already if that was enabled.

Unfortunately, the "Allow maintainers to edit this PR" is not supported for an organization repos type (see https://github.com/orgs/community/discussions/5634). Next time, I will make sure to make PRs from my personal repo.

As for the diffs, my intention was to make sure the implementing structs of a trait follow the same method definition order as that trait.

I understand that you want to keep the diffs minimal. I reverted these changes back.

scouten-adobe · 2026-03-12T19:01:12Z

    BoxedSigner, Error, Result, Signer, SigningAlg,
 };

+/// Enum representing the CAWG X.509 signing mode: local (with private key) or remote (via URL).


@gpeacock @ok-nick would one of you please review this part for settings API changes?

scouten-adobe · 2026-03-12T19:03:02Z

        self.0.reserve_size()
    }

-    async fn ocsp_val(&self) -> Option<Vec<u8>> {


Same comment as on the RawSigner implementations earlier: Please avoid adding refactoring diffs.

scouten-adobe · 2026-03-12T19:10:01Z

@BadrTad I see Clippy has some warnings. Please add the necessary #[allow(clippy:...)] declarations, assuming the unwrap and expect calls are in test code.

codspeed-hq · 2026-03-12T19:14:00Z

Merging this PR will improve performance by 10.24%

⚡ 1 improved benchmark
✅ 15 untouched benchmarks
⏩ 2 skipped benchmarks¹

Performance Changes

	Benchmark	`BASE`	`HEAD`	Efficiency
⚡	`sign 100kb jpeg`	5 ms	4.5 ms	+10.24%

_{Comparing Security4Media:feat/cawg-remote-signing (f298d15) with main (455683f)}

2 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

BadrTad · 2026-03-12T21:40:07Z

Thank you @scouten-adobe once again for your review. I have made the requested changes. And looking forward for @gpeacock and @ok-nick 's reviews.

scouten-adobe

Approved pending review from @gpeacock or @ok-nick and fixing the remaining Clippy warning and unit test failures.

fix unit tests fix clippy errors

BadrTad · 2026-03-13T14:52:16Z

Hi @scouten-adobe @gpeacock, to fix the tests I had to add a utility method to create context::Context directly from settings::Settings for the remote signing test cases. Combining compilation flags: test and feature=remote_signing in Context::default() cannot satisfy both settings::signer::test_make_cawg_c2pa_remote_signers test and builder::tests test cases.

Why not use `Context::new().with_settings(...)`?

Testing remote signers created from contexts requires SignerState::FromSettings as a state, this is not satisfied with Context::new().with_settings(...) which yields SignerState::Custom. Changing this behavior is not possible as other builder::tests cases requires it.

I will be curious to learn from you if we can do this in a better way.

scouten-adobe · 2026-03-13T17:49:39Z

@ok-nick is asking why this is specific to OpenSSL.

BadrTad · 2026-03-30T13:56:53Z

@scouten-adobe @gpeacock @ok-nick I am working on supporting rust native crypto provider and fix the failling tests

- use certificate parsing and validation according to crypto provider - updates unit tests - fix cfg for wasm unittests

BadrTad · 2026-03-30T22:01:25Z

@scouten-adobe @gpeacock @ok-nick , raw remote signer now supports both rust native crypto and openssl providers. As stated in #1995, we are missing tests for wasm build because httpmock is not supported yet for wasm.

# Conflicts: # sdk/src/settings/signer.rs

BadrTad and others added 6 commits February 17, 2026 21:26

Implement remote signing for cawg

6ef799c

Merge branch 'main' into feat/cawg-remote-signing

d29c87e

Bump httpmock to version 0.8.3

fb916c5

# Conflicts: # Cargo.lock

Add conditional compilation for feature and its tests

a74a6e6

add feature flag to makefile test command

928cc45

Fix clippy errors for cert_chain.rs tests

fa6bec5

BadrTad force-pushed the feat/cawg-remote-signing branch from 496acb6 to fa6bec5 Compare February 19, 2026 15:40

scouten-adobe reviewed Feb 19, 2026

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Comment thread sdk/src/crypto/raw_signature/openssl/cert_chain.rs Outdated

scouten-adobe reviewed Feb 19, 2026

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BadrTad and others added 2 commits February 20, 2026 16:33

Make cert_chain_to_der a function rather than a macro and align order…

763bf93

… of impl functions with RawSigner trait definition

Merge branch 'contentauth:main' into feat/cawg-remote-signing

a4432b6

BadrTad mentioned this pull request Mar 12, 2026

Support raw remote signing with rust_native crypto provider #1926

Open

BadrTad and others added 2 commits March 12, 2026 01:03

document remote signing functions

fd1da11

Merge branch 'contentauth:main' into feat/cawg-remote-signing

c4ace52

BadrTad marked this pull request as ready for review March 12, 2026 00:06

scouten-adobe changed the title ~~feat(cawg): Implement remote signing for X509CredentialHolder~~ feat: Implement remote signing for CAWG X509CredentialHolder Mar 12, 2026

scouten-adobe requested changes Mar 12, 2026

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scouten-adobe added the safe to test label Mar 12, 2026

BadrTad and others added 3 commits March 12, 2026 21:59

revert back function order

b1a585d

disable clippy warnings for expect and unwrap in tests

0ba2626

Merge branch 'contentauth:main' into feat/cawg-remote-signing

306cda6

scouten-adobe approved these changes Mar 12, 2026

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gpeacock approved these changes Mar 12, 2026

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Introduce test utility method to create context from settings

f298d15

fix unit tests fix clippy errors

scouten-adobe mentioned this pull request Mar 13, 2026

Remote signer certificate fails validation because it is never converted to DER #1903

Open

Refactor certificate parsing for openssl and rust_native_crypto

ec5de8a

BadrTad mentioned this pull request Mar 30, 2026

Use httpmock for WASM build of remote_signing feat #1995

Open

Refactor remote signing to its own crate and support rust_native_crypto

cde8ceb

- use certificate parsing and validation according to crypto provider - updates unit tests - fix cfg for wasm unittests

Merge branch 'main' into feat/cawg-remote-signing

9920a81

BadrTad requested review from gpeacock and scouten-adobe April 1, 2026 08:35

BadrTad and others added 2 commits April 29, 2026 14:26

Merge branch 'main' into feat/cawg-remote-signing

6e478ef

# Conflicts: # sdk/src/settings/signer.rs

Merge branch 'main' into feat/cawg-remote-signing

b840f8e

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BadrTad commented Feb 18, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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scouten-adobe commented Mar 12, 2026

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codspeed-hq Bot commented Mar 12, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Merging this PR will improve performance by 10.24%

Performance Changes

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BadrTad commented Mar 12, 2026

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BadrTad commented Mar 13, 2026

Why not use Context::new().with_settings(...)?

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BadrTad commented Feb 18, 2026 •

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codspeed-hq Bot commented Mar 12, 2026 •

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Why not use `Context::new().with_settings(...)`?