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rust: validate object map insert algorithms#2350

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wufengwind:object-map-insert-validation
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rust: validate object map insert algorithms#2350
wufengwind wants to merge 1 commit into
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wufengwind:object-map-insert-validation

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@wufengwind

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ObjectMap::insert() accepts a storage OID and a compatible OID in either
order, but it currently checks whether oid1 uses the compatible algorithm,
and if not, assumes oid2 is the compatible one without validating oid2.

That means inputs with two OIDs using the same hash algorithm, or an OID
using an unknown hash algorithm, are accepted and one of them is silently
treated as the storage OID. This breaks the object map invariant that each
entry must contain exactly one storage hash and one compatible hash.

Teach ObjectMap::insert() to decode and validate both OID algorithms before
inserting anything. The function now accepts only the two valid permutations:
(storage, compat) and (compat, storage). Unknown algorithms and mismatched
algorithm pairs are rejected via ObjectMapInsertError.

The tests cover successful insertion in either order, same-algorithm input,
and unknown-algorithm input.

Tested with:

  • cargo fmt --all -- --check
  • git diff --check
  • cargo test

The loose object map stores entries keyed by the repository's storage
hash and the compatible hash.  ObjectMap::insert() accepts its two object
IDs in either order, but it currently checks only whether oid1 uses the
compatible hash algorithm.  If it does not, oid2 is assumed to be the
compatible ID without validating oid2's algorithm.

That means callers can pass two IDs with the same algorithm, or an ID
using an unknown algorithm, and have one of them silently treated as the
storage ID.  This does not match the map invariant that each entry must
contain exactly one storage hash and one compatible hash.

Make the invariant explicit by decoding both object ID algorithms and
rejecting unknown or mismatched pairs before inserting anything.  Introduce
ObjectMapInsertError with InvalidHashAlgorithm and MismatchedAlgorithms
variants for clear error reporting.

Update the existing tests to unwrap successful insertions, and add tests
for same-algorithm and unknown-algorithm inputs.

Signed-off-by: Feng Wu <wufengwufengwufeng@gmail.com>
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@wufengwind

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This is my first contribution via GitGitGadget. Could someone please /allow me so that I can submit the patch to the mailing list? Thanks.

@dscho

dscho commented Jun 26, 2026

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/allow

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User wufengwind is now allowed to use GitGitGadget.

WARNING: wufengwind has no public email address set on GitHub; GitGitGadget needs an email address to Cc: you on your contribution, so that you receive any feedback on the Git mailing list. Go to https://github.com/settings/profile to make your preferred email public to let GitGitGadget know which email address to use.

@wufengwind

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/submit

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Error: Could not determine full name of wufengwind

@wufengwind

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/submit

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Submitted as pull.2350.git.git.1782489506255.gitgitgadget@gmail.com

To fetch this version into FETCH_HEAD:

git fetch https://github.com/gitgitgadget/git/ pr-git-2350/wufengwind/object-map-insert-validation-v1

To fetch this version to local tag pr-git-2350/wufengwind/object-map-insert-validation-v1:

git fetch --no-tags https://github.com/gitgitgadget/git/ tag pr-git-2350/wufengwind/object-map-insert-validation-v1

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