Remote GPG key info #2401
Remote GPG key info #2401
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Currently the verifier only imports all the GPG keys when verifying data, but it would also be useful for inspecting the trusted keys.
In order to use the GPG verifier, it needs to be seeded with GPG keys after instantation. Currently this is only used for verifying data, but it will also be used for getting a list of trusted GPG keys in a subsequent commit.
Currently the verifier decides whether to include the global keyrings based on whether the specified remote has its own keyring or not. Allow callers to exclude the global keyrings even when that's not the case. This will be used in a subsequent commit in order to get the GPG keys only associated with a remote.
This function enumerates the trusted GPG keys for a remote and returns an array of `GVariant`s describing them. This is useful to see which keys are collected by ostree for a particular remote. The same information can be gathered with `gpg`. However, since ostree allows multiple keyring locations, that's only really useful if you have knowledge of how ostree collects GPG keyrings. The format of the variants is documented in `OSTREE_GPG_KEY_GVARIANT_FORMAT`. This format is primarily a copy of selected fields within `gpgme_key_t` and its subtypes. The fields are placed within vardicts rather than using a more efficient tuple of concrete types. This will allow flexibility if more components of `gpgme_key_t` are desired in the future.
This provides a wrapper for the `ostree_repo_remote_get_gpg_keys` function to show the GPG keys associated with a remote. This is particularly useful for validating that GPG key updates have been applied. Tests are added, which checks the `ostree_repo_remote_get_gpg_keys` API by extension.
This will be used to implement the PGP Web Key Directory (WKD) URL generation. This is a slightly cleaned up implementation[1] taken from the zbase32 author's original implementation[2]. It provides a single zbase32_encode API to convert a set of bytes to the zbase32 encoding. I believe this should be acceptable for inclusion in ostree. The license in the source files is BSD style while the original repo LICENSE file claims the Creative Commons CC0 1.0 Universal license, which is public domain. 1. https://github.com/dbnicholson/libbase32/tree/for-ostree 2. https://github.com/zooko/libbase32
Calculate the advanced and direct update URLs for the key discovery portion[1] of the OpenPGP Web Key Directory specification, and include the URLs in the key listing in ostree_repo_remote_get_gpg_keys(). These URLs can be used to locate updated GPG keys for the remote. 1. https://datatracker.ietf.org/doc/html/draft-koch-openpgp-webkey-service#section-3.1
If the key UID contains a valid email address, include the GPG WKD update URLs in GVariant returned by ostree_repo_remote_get_gpg_keys().
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| return TRUE; | ||
| #else /* OSTREE_DISABLE_GPGME */ | ||
| return glnx_throw (error, "GPG feature is disabled in a build time"); |
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Right. I'm pretty sure I copied this from another optional GPG feature, but there's no reason to copy the slightly wrong grammar.
| * - key: `fingerprint`, value: `s`, key fingerprint hexadecimal string | ||
| * - key: `created`, value: `x`, key creation timestamp (seconds since | ||
| * the Unix epoch in UTC, big-endian) | ||
| * - key: `expires`, value: `x`, key expiration timestamp (seconds since |
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It sounds like this is really a mx perhaps?
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Possibly. This is copying the gpgme approach where 0 is no expiration (as noted a little later in the comment). I could special case 0 to allow for a mx. According to the OpenPGP RFC either missing or 0 are interpreted as not expiring. I think treating 0 as never expires is a little simpler and consistent with gpgme.
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| char * | ||
| zbase32_encode(const unsigned char *data, size_t length) |
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It looks like the existing code has a lot of possible integer overflows, though we are only ever using it with length == 20.
Do you think it would be reasonable to make this generic encoder static/private and only expose a small wrapper which enforces the expected input array size?
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Yeah, that makes sense. I think you could also add an assert that length is less than SIZE_MAX / 8. I don't see how the rest of the code could overflow that condition.
| @@ -65,6 +65,9 @@ Boston, MA 02111-1307, USA. | |||
| <cmdsynopsis> | |||
| <command>ostree remote gpg-import</command> <arg choice="opt" rep="repeat">OPTIONS</arg> <arg choice="req">NAME</arg> <arg choice="opt" rep="repeat">KEY-ID</arg> | |||
| </cmdsynopsis> | |||
| <cmdsynopsis> | |||
| <command>ostree remote list-gpg-keys</command> <arg choice="req">NAME</arg> | |||
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To align with the command above, gpg-list-keys or gpg-list maybe?
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Good catch. I like gpg-list-keys.
| if (tmp_dir != NULL) { | ||
| ot_gpgme_kill_agent (tmp_dir); | ||
| (void) glnx_shutil_rm_rf_at (AT_FDCWD, tmp_dir, NULL, NULL); |
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We can probably make these autocleanups too in the future.
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I think so. The gpgme code could use some sprucing up.
| { | ||
| g_auto(GVariantDict) subkey_dict = OT_VARIANT_BUILDER_INITIALIZER; | ||
| g_variant_dict_init (&subkey_dict, NULL); | ||
| g_variant_dict_insert_value (&subkey_dict, "fingerprint", |
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I'd love to figure out a good way to have reliable documentation for these keys. It's a downside of the gvariant approach.
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Agreed. You can do decently in the FORMAT documentation, but it could definitely be better.
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I could also just turn this into a few boxed structs if that would be better. I actually really prefer working with actual data structures rather than variants, but I chose a variant to allow more flexibility for future changes.
For the prep do you mean everything before |
Are you planning a release? Most of the outstanding stuff is pretty minimal, but @lucab's suggestion of |
This is split out from #2260. It adds an API,
ostree_repo_remote_get_gpg_keys, and CLI (remote list-gpg-keys) for getting information about GPG keys associated with a remote (or the global keys when no remote is specified).That's useful on its own, but the latter part of the PR adds an implementation to generate OpenPGP Web Key Directory URLs so that you can get a well defined place to download an updated key. In #2260 I was trying to go further and have ostree API to go fetch those and import them, but I think with the appropriate information available it would be easy to write a tool that does the fetching and importing itself. That part isn't strictly necessary for anything, but I found it convenient to have the implementation here so it could be usable by any OSTree consumer that relies on GPG verification.
There are a couple parts that I'm not really sure about. First, the key listing is basically a GVariant version of gpgme_key_t and friends. I'd kinda prefer to work with a real data structure, but I was unsure about committing to a type there.
Second, Web Key Directory (WKD) URLs use an obscure base32 encoding referred to as zbase32 that's supposed to be more usable for humans. I find the use dubious as what it's encoding is a SHA1 checksum, so the encoding is always 32 characters and I know I could never handle that in my head. Anyways, that's what's in the spec and I copied in the author's reference C implementation. If that's troublesome, I could also code up a naive implementation. It's just base32 with an alternate alphabet and this isn't in any fast path.