security: pass --end-of-options to git diff in DiffBinary#141
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A base or head revision that begins with a dash was passed positionally to "git diff --full-index --binary", so git could interpret it as a command-line option. A revision such as "--output=/path" made git write the diff to an arbitrary path, an attacker-controlled file write when the revision came from a user-supplied branch name.
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DiffBinarypasses thebaseandheadrevisions positionally togit diff --full-index --binary. When a revision begins with a dash, git can interpret it as a command-line option instead of a revision. A value such as--output=/pathmakes git write the diff to an arbitrary path, which is an attacker-controlled file write when the revision originates from a user-supplied branch name.This inserts
--end-of-optionsbefore the positional revisions so such a value is always treated as a revision, which then fails to resolve rather than changing the command's behavior.I verified against git 2.50 that
git diff --full-index --binaryaccepts--end-of-options(unlikegit reset, see #134) and that the marker turns the injection into a fatal "must come before non-option arguments" error with no file written. Added a regression test.Relates to gogs/gogs security advisory GHSA-2grc-qr7q-6m36.