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2020-01-15gpg-interface: add minTrustLevel as a configuration optionLibravatar Hans Jerry Illikainen1-0/+22
Previously, signature verification for merge and pull operations checked if the key had a trust-level of either TRUST_NEVER or TRUST_UNDEFINED in verify_merge_signature(). If that was the case, the process die()d. The other code paths that did signature verification relied entirely on the return code from check_commit_signature(). And signatures made with a good key, irregardless of its trust level, was considered valid by check_commit_signature(). This difference in behavior might induce users to erroneously assume that the trust level of a key in their keyring is always considered by Git, even for operations where it is not (e.g. during a verify-commit or verify-tag). The way it worked was by gpg-interface.c storing the result from the key/signature status *and* the lowest-two trust levels in the `result` member of the signature_check structure (the last of these status lines that were encountered got written to `result`). These are documented in GPG under the subsection `General status codes` and `Key related`, respectively [1]. The GPG documentation says the following on the TRUST_ status codes [1]: """ These are several similar status codes: - TRUST_UNDEFINED <error_token> - TRUST_NEVER <error_token> - TRUST_MARGINAL [0 [<validation_model>]] - TRUST_FULLY [0 [<validation_model>]] - TRUST_ULTIMATE [0 [<validation_model>]] For good signatures one of these status lines are emitted to indicate the validity of the key used to create the signature. The error token values are currently only emitted by gpgsm. """ My interpretation is that the trust level is conceptionally different from the validity of the key and/or signature. That seems to also have been the assumption of the old code in check_signature() where a result of 'G' (as in GOODSIG) and 'U' (as in TRUST_NEVER or TRUST_UNDEFINED) were both considered a success. The two cases where a result of 'U' had special meaning were in verify_merge_signature() (where this caused git to die()) and in format_commit_one() (where it affected the output of the %G? format specifier). I think it makes sense to refactor the processing of TRUST_ status lines such that users can configure a minimum trust level that is enforced globally, rather than have individual parts of git (e.g. merge) do it themselves (except for a grace period with backward compatibility). I also think it makes sense to not store the trust level in the same struct member as the key/signature status. While the presence of a TRUST_ status code does imply that the signature is good (see the first paragraph in the included snippet above), as far as I can tell, the order of the status lines from GPG isn't well-defined; thus it would seem plausible that the trust level could be overwritten with the key/signature status if they were stored in the same member of the signature_check structure. This patch introduces a new configuration option: gpg.minTrustLevel. It consolidates trust-level verification to gpg-interface.c and adds a new `trust_level` member to the signature_check structure. Backward-compatibility is maintained by introducing a special case in verify_merge_signature() such that if no user-configurable gpg.minTrustLevel is set, then the old behavior of rejecting TRUST_UNDEFINED and TRUST_NEVER is enforced. If, on the other hand, gpg.minTrustLevel is set, then that value overrides the old behavior. Similarly, the %G? format specifier will continue show 'U' for signatures made with a key that has a trust level of TRUST_UNDEFINED or TRUST_NEVER, even though the 'U' character no longer exist in the `result` member of the signature_check structure. A new format specifier, %GT, is also introduced for users that want to show all possible trust levels for a signature. Another approach would have been to simply drop the trust-level requirement in verify_merge_signature(). This would also have made the behavior consistent with other parts of git that perform signature verification. However, requiring a minimum trust level for signing keys does seem to have a real-world use-case. For example, the build system used by the Qubes OS project currently parses the raw output from verify-tag in order to assert a minimum trust level for keys used to sign git tags [2]. [1] https://git.gnupg.org/cgi-bin/gitweb.cgi?p=gnupg.git;a=blob;f=doc/doc/DETAILS;h=bd00006e933ac56719b1edd2478ecd79273eae72;hb=refs/heads/master [2] https://github.com/QubesOS/qubes-builder/blob/9674c1991deef45b1a1b1c71fddfab14ba50dccf/scripts/verify-git-tag#L43 Signed-off-by: Hans Jerry Illikainen <hji@dyntopia.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-11-07merge: handle --verify-signatures for unborn branchLibravatar Jeff King1-0/+7
When git-merge sees that we are on an unborn branch (i.e., there is no HEAD), it follows a totally separate code path than the usual merge logic. This code path does not know about verify_signatures, and so we fail to notice bad or missing signatures. This has been broken since --verify-signatures was added in efed002249 (merge/pull: verify GPG signatures of commits being merged, 2013-03-31). In an ideal world, we'd unify the flow for this case with the regular merge logic, which would fix this bug and avoid introducing similar ones. But because the unborn case is so different, it would be a burden on the rest of the function to continually handle the missing HEAD. So let's just port the verification check to this special case. Reported-by: Felix Eckhofer <felix@eckhofer.com> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2018-06-11tests: make forging GPG signed commits and tags more robustLibravatar SZEDER Gábor1-1/+1
A couple of test scripts create forged GPG signed commits or tags to check that such forgery can't fool various git commands' signature verification. All but one of those test scripts are prone to occasional failures because the forgery creates a bogus GPG signature, and git commands error out with an unexpected error message, e.g. "Commit deadbeef does not have a GPG signature" instead of "... has a bad GPG signature". 't5573-pull-verify-signatures.sh', 't7510-signed-commit.sh' and 't7612-merge-verify-signatures.sh' create forged signed commits like this: git commit -S -m "bad on side" && git cat-file commit side-bad >raw && sed -e "s/bad/forged bad/" raw >forged && git hash-object -w -t commit forged >forged.commit On rare occasions the given pattern occurs not only in the commit message but in the GPG signature as well, and after it's replaced in the signature the resulting signature becomes invalid, GPG will report CRC error and that it couldn't find any signature, which will then ultimately cause the test failure. Since in all three cases the pattern to be replaced during the forgery is the first word of the commit message's subject line, and since the GPG signature in the commit object is indented by a space, let's just anchor those patterns to the beginning of the line to prevent this issue. The test script 't7030-verify-tag.sh' creates a forged signed tag object in a similar way by replacing the pattern "seventh", but the GPG signature in tag objects is not indented by a space, so the above solution is not applicable in this case. However, in the tag object in question the pattern "seventh" occurs not only in the tag message but in the 'tag' header as well. To create a forged tag object it's sufficient to replace only one of the two occurences, so modify the sed script to limit the pattern to the 'tag' header (i.e. a line beginning with "tag ", which, because of the space character, can never occur in the base64-encoded GPG signature). Note that the forgery in 't7004-tag.sh' is not affected by this issue: while 't7004' does create a forged signed tag kind of the same way, it replaces "signed-tag" in the tag object, which, because of the '-' character, can never occur in the base64-encoded GPG signarute. Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-12-19t5573, t7612: clean up after unexpected success of 'pull' and 'merge'Libravatar Junio C Hamano1-5/+11
The previous steps added test_when_finished to tests that run 'git pull' or 'git merge' with expectation of success, so that the test after them can start from a known state even when their 'git pull' invocation unexpectedly fails. However, tests that run 'git pull' or 'git merge' expecting it not to succeed forgot to protect later tests the same way---if they unexpectedly succeed, the test after them would start from an unexpected state. Reset and checkout the initial commit after all these tests, whether they expect their invocations to succeed or fail. Signed-off-by: Junio C Hamano <gitster@pobox.com>
2017-12-12merge: add config option for verifySignaturesLibravatar Hans Jerry Illikainen1-0/+39
git merge --verify-signatures can be used to verify that the tip commit of the branch being merged in is properly signed, but it's cumbersome to have to specify that every time. Add a configuration option that enables this behaviour by default, which can be overridden by --no-verify-signatures. Signed-off-by: Hans Jerry Illikainen <hji@dyntopia.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-03-20t: fix trivial &&-chain breakageLibravatar Jeff King1-1/+1
These are tests which are missing a link in their &&-chain, but during a setup phase. We may fail to notice failure in commands that build the test environment, but these are typically not expected to fail at all (but it's still good to double-check that our test environment is what we expect). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-03-31merge/pull Check for untrusted good GPG signaturesLibravatar Sebastian Götte1-0/+9
When --verify-signatures is specified, abort the merge in case a good GPG signature from an untrusted key is encountered. Signed-off-by: Sebastian Götte <jaseg@physik-pool.tu-berlin.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>
2013-03-31merge/pull: verify GPG signatures of commits being mergedLibravatar Sebastian Götte1-0/+52
When --verify-signatures is specified on the command-line of git-merge or git-pull, check whether the commits being merged have good gpg signatures and abort the merge in case they do not. This allows e.g. auto-deployment from untrusted repo hosts. Signed-off-by: Sebastian Götte <jaseg@physik-pool.tu-berlin.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>