Accept request header should either be missing, contain */*, or specify b2 as one of the accepted versions.

• Check in a self-signed cert/key pair and toml
• Update CONTRIBUTING.md with instructions on running a dev server, lint/tests, dep ensure, etc.
• Presubmit hook would be nice.

Currently only tested indirectly in packager_test.go. This function should be tested directly, with a variety of urlSets and fetch/sign URLs, to cover all the combinations.

We need to decide how AMP packages should be discovered on the web. Options include <link rel=amppackage>, request headers, and sitemap.xml (or some combination).

If the packager happens to proxy invalid AMP, and an attacker captures such an SXG and serves it somewhere that doesn't valid, the page would have its charset misinterpreted.

Packager currently only provides a null validityUrl response for all signed exchanges. It would be nice to support validity updates, to save on network bandwidth when responding to intermediaries and to allow client-side reverification of signed exchanges as a downgrade mitigation.

Note that this will require a refetch of the document to get the message to sign, unless a cache is added. If a cache is added, it should obey the usual HTTP caching semantics re: freshness and validation.

Add X-Content-Type-Options: nosniff to the SXG outer response headers.

This is necessary for the same-origin policy imposed in https://crrev.com/c/1075833.

This is a sub-bug of #15.

Use correct rtv endpoint

Add an option to use a remote signing oracle to sign messages, rather than needing filesystem access to the key. The Go Keyless client library will probably be of use, here.

b2 format is still in development, and it seems plans are for WICG/webpackage to support b1/b2 as a flag (see WICG/webpackage#291, WICG/webpackage#292).

Related Chromium changes:

• Signed Exchange: Update to draft-thomson-http-mice-03 https://crrev.com/c/1180955
• SignedExchange: Switch to b2 format parser. https://crrev.com/c/1183053

1. Make the request format match whatever the standard style is (e.g. https://en.wikipedia.org/wiki/Common_Log_Format).
2. Log error messages to a different file (per https://httpd.apache.org/docs/1.3/logs.html).
3. Gate debug messages behind -development or maybe a new flag.

Follow the Standard Go Project Layout. That entails:

• moving the .go files from the root into internal/pkg/
• moving the fuzz tests into test/
• moving the example toml into configs/

and maybe some other stuff.

certcache.go should serve the cert-chain+cbor with a max-age corresponding to the OCSP midpoint.

This is a tracking bug to make sure the AMP packager serves valid signed exchanges per the evolving v=b1 spec. Support for v=b0 would need to co-exist for a few months.

Spec changes being drafted here: WICG/webpackage#232

At present, these Chromium changes seem relevant:

• restrict :url scheme to https https://crrev.com/c/1114407
• Apply scheme restriction to {cert,validity}-url https://crrev.com/c/1114403
• Require CanSignHttpExchangesDraft cert extension https://crrev.com/c/1111485 (modulo WICG/webpackage#238)
• Add CT verification for Signed Exchange https://crrev.com/c/1056776
• SignedExchange: Forbid RSA signatures https://crrev.com/c/1096578
• Signed exchange: Check content-type of certificate chain https://crrev.com/c/1082175
• Signed Exchange: Switch to b1 envelope format https://crrev.com/c/1081773
• Update Signed Exchange's Signature header format to b1 https://crrev.com/c/1077111
• Check the validity URL is same-origin with the request url https://crrev.com/c/1075833
• Signed exchange: Drop b0 support https://crrev.com/c/1074670
• Introduce SignedExchangePrologue, the prologue parser for the b1 format https://crrev.com/c/1075883
• Don't handle signed exchange transferred over plain HTTP https://crrev.com/c/1074915
• Add OCSP check for Signed Exchange https://crrev.com/c/1060933
• SignedExchangeVerifier: Support ecdsa_secp256r1_sha256 signature algorithm. https://crrev.com/c/979377

(I may eventually split out bugs for larger subprojects, like OCSP stapling.)

See also http://b/92515679.

Currently, the toml parser just silently ignores any fields that don't match the struct. This means that typos are hard to diagnose, and backwards-incompatible changes to the config will require special care to notify existing users.

If the fetch redirects to another URL, the packager will follow the redirect(s), but sign it with the original request URL. This has the following problems (at least):

• relative URLs included in the payload of the final response may be broken
• the final URL may not be one that's intended for a signed exchange (e.g. a login server on a different domain)

When the packager gets a 30x, it should simply respond with that instead of following it and signing the result.

When [URLSet.Fetch] is not configured, then fetch and sign are the same URL object, so the destructive modifications that fetchURL() does to the query end up affecting the signed URL, too.

It may be useful for a single packager instance to sign for multiple domains that are authenticated by different certs. (This should be an uncommon case, though, as it is very simple and possibly more secure to run different instances each with access to only one certificate.)

https://github.com/WICG/webpackage/pull/267/files added some instructions on submitting a cert to CT and getting an SCT in return, in cases where the CA has not already attached it. This would be nice for the packager to support automatically, though not strictly necessary. At the very least, the documentation should be updated to include a reference to this.

This should parse https://github.com/ampproject/amphtml/blob/master/spec/amp-cache-transform.md from the request and ensure target is any or google, and no params are specified.

This would integrate the transform library with no transformers (except maybe a transformed="..." attribute).

WICG/webpackage#121 will change the SXG signed message to include the OCSP response attached to the cert-chain+cbor. This means that:

1. Every ~3.5 days, the cert-url will change, to reflect the different OCSP response attached. (Or else old SXGs won't validate any more.)
2. When signing a document, the packager must request the freshest cert-url from the certcache.

Currently the default case is to respond 502.

Implement versioning according to the AMP-Cache-Transform spec.

At a minimum, it needs to specify:

• Content-Security-Policy
• Content-Type: text/html

At the very least, call https://golang.org/pkg/log/#New from main and pass to the handler constructors. This way we can make our tests less noisy.

Maybe upgrade to https://godoc.org/github.com/golang/glog or https://github.com/op/go-logging or https://github.com/juju/loggo or something, though https://dave.cheney.net/2015/11/05/lets-talk-about-logging argues against it.

Currently, amppkg only loads the cert file at startup. If it expires while the packager is running, the packager continues to sign with it and serve it. Instead, it should attempt to reload automatically starting a few days before expiry, and continuing at some regular interval until no longer imminently expiring. If the cert is expired, it should stop signing exchanges, and log a warning.

In addition, it should serve the cert-url with an http expiry no longer than the cert expiry (as a follow-up to #85).

Rewrite the documentation to be action-oriented -- e.g. start with running the packager, and then move backwards up the chain to adding a FE and all that.

Users of the packager may mistakenly transform and sign non-amp content. The AMP Cache will reject this, but for security we want some light protections against this content being usable. This issue tracks removing non-amp javascript from the document in a new transformer.

The steps we should take are:

For each <script> tag on the page, if any one of of the following is true:

• It has a src attribute whose value is not prefixed by https://cdn.ampproject.org/ (case-insensitive match).
• It has no src attribute and no type attribute (case-insensitive match).
• It has a type attribute whose value is neither application/json nor application/ld+json (case-insensitive match on both name and value).

Then, remove the <script> tag and all descendant nodes of <script> tag, including text / cdata nodes.

For example:

• <script async src="https://cdn.ampproject.org/v0.js"> should not be removed
• <script async custom-element='amp-analytics' src='https://cdn.ampproject.org/v0/amp-analytics-0.1.js'> should not be removed.
• <script src='http://example.com/example.js'> should be removed.
• <script>foo</script> should be removed
• <script type=application/javascript>foo</script> should be removed
• <script type=application/json>foo</script>should not be removed
• <script type=application/json src="https://cdn.ampproject.org/v0.js">

For every tag on the page, if the tag has an attribute with a case-insensitive prefix of on followed by another alphabetic character ([A-Za-z]), then remove that attribute. For example:

• on should not be removed.
• on-foo should not be removed
• onfoo should be removed

Currently each method call performs a copy of this, which is unnecessarily costly.

Periodically (hourly?) poll to get the latest rtv (and css url), store in memory.

Pass these values into the local transformer library for writing the correct rtv script and css.

Amend the README to advise that publishers only package AMP documents, and that they audit those documents for validity offline (e.g. at publication time, or a weekly cronjob that audits a random 1%).

This could be a collection of scripts, or packages of various formats (Docker, Flatpak, .deb, etc.). Broad coverage of most of the production environments probably necessitates multiple formats, though we should prefer a solution that covers as many as possible in as few variants as possible. This will reduce the cost of maintenance and the chance of error in one or more of them. Googlers, see go/amp-packager-deployment-requirements for more info.

At the very least, go over the code, figure out what tests need adding and file bugs for them.

HTTPError.LogAndRespond calls http.Error, which does not set Cache-Control: no-store. Update it to do so.

http://crrev.com/c/1060933 adds a requirement that certUrls be OCSP-stapled, as part of the new v=b1 spec. The packager should have a flag for outputting b1 format, and doing the necessary stapling things. A set of requirements to start with is https://gist.github.com/sleevi/5efe9ef98961ecfb4da8, and a good implementation to look at is mholt/caddy/caddytls.

Provide a config flag to allow non-transformed AMP to be served (i.e. not going through the AMP CDN). This is just for debugging.

Improve the error messages such that they are actionable by people who don't know code. Currently, they're pretty cryptic and mostly useful for devs.

This will also depend on a TBD versioning/update strategy.

The packager should handle conditional requests.

1. The fetch issued by fetchURL() in packager.go should pass along any of the conditional headers it received in ServeHTTP().

2. If the fetchResp is a 304 not modified, then ServeHTTP() should respond in kind, and not try to package up that 304 in an application/signed-exchange.

See also http://b/110430571.

Add support for /priv/doc/https://example.com/foo.html?query=param as an alternative to /priv/doc?sign=https%3a%2f%2fexample.com%2ffoo.html%3fquery%3dparam, as nginx doesn't support URL-encoding during rewriting [1].

[1] See https://stackoverflow.com/questions/31266629/nginx-encoding-normalizing-part-of-uri or https://forum.nginx.org/read.php?2,221867,221874 for instance. Possible with a custom build, though, using https://github.com/vozlt/nginx-module-url.

Add relevant preloads as determined based on the fetch response body. This is dependent on the implementation of the local transformer.

PR #34 addresses #19 but does not include a test.

Adding a test to packager_test.go will require changing the mock CDN that's set up in TestMain.

If -development is not true, then the packager should refuse to run or sign exchanges if given a non-SXG cert.

If the fetchResp is not valid for packaging (either via validateFetch or because of stateful headers), instead of returning an error code, the packager should simply proxy the content unsigned. This is a friendlier error response.

This would implement the changes in ampproject/amphtml#18334.

As an alternative to reading the .pem from the local filesystem, allow the use of Vault's Read Certificate call to retrieve the certificate PEM at packager startup.

Transforms may have unintended effects on invalid documents. There may be cases where the SXG is fetched and served by third parties without validation. Since full validation at serve time is too expensive, it should perform some light validation; at least to verify that the document intends to be AMP.

Copy ETag and Last-Modified from the fetchResp to the outer resp. This enables clients to transparently take advantage of #34 without having to understand the SXG format.