ci: stop interpolating the dispatch tag into the release script

The compute step spliced ${{ github.event.inputs.tag }} straight into the
run: body, so a dispatch tag containing shell metacharacters was parsed as
script - arbitrary code in a job holding a contents:write token. Pass the
input through the environment instead (INPUT_TAG), the same shape
docker-release.yml already uses, so the value reaches bash as data.

Second vector: the old format check compared the sed output against the input
to decide validity, and sed anchors ^...$ per line. A tag carrying a newline
passed the check on its first line and the remaining lines flowed into
$GITHUB_ENV, setting arbitrary variables (PATH, LD_PRELOAD, ...) for every
later step. Replace it with a bash =~ whitelist anchored to the whole string,
which rejects any multi-line value up front.

Verified: a legal RELEASE.* tag is accepted and yields the right PKG_VERSION;
a `"; touch ...; #` injection and a newline-carrying PATH/LD_PRELOAD payload
are both rejected; an empty input falls back to the git ref name.

Co-authored-by: Claude <noreply@anthropic.com>

.github/workflows/release.yml

@@ -38,15 +38,24 @@ jobs:
           fi
 
       - name: Compute release variables
+        env:
+          # Passed through the environment, never interpolated into the script
+          # body: a dispatch input reaches bash as data, so it cannot inject
+          # commands the way a `${{ ... }}` splice into the source would.
+          INPUT_TAG: ${{ github.event.inputs.tag }}
         run: |
           set -euo pipefail
-          TAG="${{ github.event.inputs.tag || github.ref_name }}"
+          TAG="${INPUT_TAG:-${GITHUB_REF_NAME}}"
-          VERSION_HYPHEN="${TAG#RELEASE.}"
+          # Whitelist the exact tag shape before the value is used anywhere. bash
-          PKG_VERSION="$(echo "${VERSION_HYPHEN}" | sed -E 's/^([0-9]{4})-([0-9]{2})-([0-9]{2})T([0-9]{2})-([0-9]{2})-([0-9]{2})Z$/\1\2\3\4\5\6.0.0/')"
+          # =~ anchors ^...$ to the whole string (not per line, as sed would), so
-          if [ "${PKG_VERSION}" = "${VERSION_HYPHEN}" ]; then
+          # a tag carrying a newline cannot pass and then smuggle extra lines into
-            echo "Invalid release tag format: ${TAG}"
+          # $GITHUB_ENV below.
+          if [[ ! "${TAG}" =~ ^RELEASE\.[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}-[0-9]{2}-[0-9]{2}Z$ ]]; then
+            echo "Invalid release tag format: ${TAG}" >&2
             exit 1
           fi
+          VERSION_HYPHEN="${TAG#RELEASE.}"
+          PKG_VERSION="$(echo "${VERSION_HYPHEN}" | sed -E 's/^([0-9]{4})-([0-9]{2})-([0-9]{2})T([0-9]{2})-([0-9]{2})-([0-9]{2})Z$/\1\2\3\4\5\6.0.0/')"
           VERSION_COLON="$(echo "${VERSION_HYPHEN}" | sed -E 's/T([0-9]{2})-([0-9]{2})-([0-9]{2})Z$/T\1:\2:\3Z/')"
           LDFLAGS="$(MINIO_RELEASE=RELEASE go run buildscripts/gen-ldflags.go "${VERSION_COLON}")"