fix(pr-merge): harden provider message path

docs/scratchpads/pr-merge-message-field.md

@@ -83,3 +83,17 @@ Add an optional, identity-checked Gitea squash message to `pr-merge.sh` so genui
 ## Current hold point
 
 PR `mosaicstack/stack#1066` is open. Its first frozen head `f4b162fa…` was terminal-green in Woodpecker `mosaic` pipeline `#2225`, but that evidence becomes stale when the canonical port moves the head. The deployed wrapper remains baseline `08a65e85…`; no manual copy will occur. Canonical port tests, commit amendment, rebase, one guarded force-with-lease, exact-head CI, and new independent review remain. Even after source merge, activation remains blocked on an assigned package-release/reseed owner and installed-byte read-back.
+
+## Security review 96 remediation
+
+Exact reviewed predecessor head: `1ceb11058f64dd7f4a817ceb2124f980a1c4dd23`.
+
+RED-first focused harness produced 10 named failures: all curl calls lacked size/time/connect bounds; raw ESC email reached mutation; oversized and stalled curl failures were discarded and reached mutation; nonempty Basic output with resolver rc 91 authorized mutation.
+
+Security remediation:
+
+- Removed the cross-principal HTTP-401 Basic fallback. Both inspection-401 and merge-401 paths now refuse without Basic resolution or mutation; `get_gitea_basic_auth` references in the merge subject are 0.
+- Applied `--max-filesize`, `--max-time`, and `--connect-timeout` to all 3/3 provider curl sites and fail closed on curl transport rc at all 3/3 sites.
+- Required linked email bytes to be ASCII and printable before constructing `MergeMessageField`; guarded construction sites 1/1.
+
+GREEN: message-field, exact-head, empty-UID/API, queue branch/repository/SHA, bash syntax, ShellCheck, and diff check pass. R7 total-removal mutants went RED: email guard 3 rows; bound switches 1 row; transport-rc guards 4 rows; HTTP-401 refusal 3 rows. R7 bound: mutants prove total removal only; explicit denominators above prove site coverage.

packages/mosaic/framework/tools/git/pr-merge.sh

@@ -178,6 +178,20 @@ else:
 LAST_GITEA_HTTP_CODE="000"
 LAST_GITEA_ERROR=""
 MERGE_TEMP_DIRS=()
+GITEA_CURL_MAX_BYTES="${MOSAIC_GITEA_CURL_MAX_BYTES:-1048576}"
+GITEA_CURL_MAX_TIME="${MOSAIC_GITEA_CURL_MAX_TIME_SEC:-30}"
+GITEA_CURL_CONNECT_TIMEOUT="${MOSAIC_GITEA_CURL_CONNECT_TIMEOUT_SEC:-10}"
+for bound in "$GITEA_CURL_MAX_BYTES" "$GITEA_CURL_MAX_TIME" "$GITEA_CURL_CONNECT_TIMEOUT"; do
+    if [[ ! "$bound" =~ ^[1-9][0-9]*$ ]]; then
+        echo "Error: Gitea curl bounds must be positive integers; refusing request." >&2
+        exit 1
+    fi
+done
+GITEA_CURL_BOUNDS=(
+    --max-filesize "$GITEA_CURL_MAX_BYTES"
+    --max-time "$GITEA_CURL_MAX_TIME"
+    --connect-timeout "$GITEA_CURL_CONNECT_TIMEOUT"
+)
 
 format_gitea_error_response() {
     local response_file="$1"
@@ -219,7 +233,7 @@ trap 'exit 143' TERM
 
 fetch_gitea_pr_head() {
     local host="$1" auth_mode="$2" credential="$3" work_root="$4"
-    local response_file raw_code api_url auth_config
+    local response_file raw_code api_url auth_config curl_rc
     response_file=$(mktemp "$work_root/pr-merge-pr.XXXXXX")
     api_url="https://${host}/api/v1/repos/${OWNER}/${REPO}/pulls/${PR_NUMBER}"
     if ! auth_config=$(write_curl_auth_config "$auth_mode" "$credential"); then
@@ -227,10 +241,15 @@ fetch_gitea_pr_head() {
         rm -f "$response_file"
         return 1
     fi
-    raw_code=$(printf '%s\n' "$auth_config" | \
-        curl -sS -K - -w '%{http_code}' -o "$response_file" \
-            -H "User-Agent: curl/8" "$api_url" || true)
+    raw_code=$(curl -sS -K - "${GITEA_CURL_BOUNDS[@]}" -w '%{http_code}' -o "$response_file" \
+        -H "User-Agent: curl/8" "$api_url" <<<"$auth_config")
+    curl_rc=$?
     LAST_GITEA_HTTP_CODE="${raw_code:-000}"
+    if [[ "$curl_rc" -ne 0 ]]; then
+        LAST_GITEA_ERROR="curl transport failed (rc=$curl_rc)"
+        rm -f "$response_file"
+        return 1
+    fi
     if [[ ! "$raw_code" =~ ^2 ]]; then
         LAST_GITEA_ERROR=$(format_gitea_error_response "$response_file")
         rm -f "$response_file"
@@ -259,7 +278,7 @@ PY
 
 fetch_gitea_pr_commits() {
     local host="$1" auth_mode="$2" credential="$3" work_root="$4"
-    local page page_file combined_file merged_file raw_code page_count api_url auth_config
+    local page page_file combined_file merged_file raw_code page_count api_url auth_config curl_rc
     mkdir -p "$work_root"
     if ! auth_config=$(write_curl_auth_config "$auth_mode" "$credential"); then
         echo "Error: Could not construct Gitea authentication config; refusing request." >&2
@@ -272,10 +291,15 @@ fetch_gitea_pr_commits() {
     while true; do
         page_file=$(mktemp "$work_root/pr-merge-commits-page.XXXXXX")
         api_url="https://${host}/api/v1/repos/${OWNER}/${REPO}/pulls/${PR_NUMBER}/commits?limit=50&page=${page}"
-        raw_code=$(printf '%s\n' "$auth_config" | \
-            curl -sS -K - -w '%{http_code}' -o "$page_file" \
-                -H "User-Agent: curl/8" "$api_url" || true)
+        raw_code=$(curl -sS -K - "${GITEA_CURL_BOUNDS[@]}" -w '%{http_code}' -o "$page_file" \
+            -H "User-Agent: curl/8" "$api_url" <<<"$auth_config")
+        curl_rc=$?
         LAST_GITEA_HTTP_CODE="${raw_code:-000}"
+        if [[ "$curl_rc" -ne 0 ]]; then
+            LAST_GITEA_ERROR="curl transport failed (rc=$curl_rc)"
+            rm -f "$page_file" "$combined_file"
+            return 1
+        fi
         if [[ ! "$raw_code" =~ ^2 ]]; then
             LAST_GITEA_ERROR=$(format_gitea_error_response "$page_file")
             rm -f "$page_file" "$combined_file"
@@ -399,7 +423,12 @@ for item in commits:
             file=sys.stderr,
         )
         raise SystemExit(75)
-    if not re.fullmatch(r"[A-Za-z0-9_.-]+", login) or not re.fullmatch(r"[^<>\s]+@[^<>\s]+", email):
+    if (
+        not email.isascii()
+        or not email.isprintable()
+        or not re.fullmatch(r"[A-Za-z0-9_.-]+", login)
+        or not re.fullmatch(r"[^<>\s]+@[^<>\s]+", email)
+    ):
         print(
             f"BLOCK: commit {sha!r} has unusable linked identity "
             f"author.login={login!r}, commit.author.email={email!r}; refusing merge; "
@@ -445,7 +474,7 @@ PY
 
 merge_gitea_api_attempt() {
     local host="$1" auth_mode="$2" credential="$3"
-    local api_url attempt_dir body_file raw_code commits_file fields_file context_file head_file payload_file work_root attempt_rc auth_config
+    local api_url attempt_dir body_file raw_code commits_file fields_file context_file head_file payload_file work_root attempt_rc auth_config curl_rc
     LAST_GITEA_HTTP_CODE="000"
     LAST_GITEA_ERROR=""
     api_url="https://${host}/api/v1/repos/${OWNER}/${REPO}/pulls/${PR_NUMBER}/merge"
@@ -520,12 +549,18 @@ PY
         rm -f "$body_file" "$payload_file"
         return 1
     fi
-    raw_code=$(printf '%s\n' "$auth_config" | \
-        curl -sS -K - -w '%{http_code}' -o "$body_file" \
-            -X POST -H "User-Agent: curl/8" \
-            -H 'Content-Type: application/json' \
-            --data-binary "@$payload_file" "$api_url" || true)
+    raw_code=$(curl -sS -K - "${GITEA_CURL_BOUNDS[@]}" -w '%{http_code}' -o "$body_file" \
+        -X POST -H "User-Agent: curl/8" \
+        -H 'Content-Type: application/json' \
+        --data-binary "@$payload_file" "$api_url" <<<"$auth_config")
+    curl_rc=$?
     LAST_GITEA_HTTP_CODE="${raw_code:-000}"
+    if [[ "$curl_rc" -ne 0 ]]; then
+        LAST_GITEA_ERROR="curl transport failed (rc=$curl_rc)"
+        rm -f "$body_file" "$payload_file"
+        rm -rf -- "$attempt_dir"
+        return 1
+    fi
     if [[ ! "$raw_code" =~ ^2 ]]; then
         LAST_GITEA_ERROR=$(format_gitea_error_response "$body_file")
     fi
@@ -535,7 +570,7 @@ PY
 }
 
 merge_gitea_with_api() {
-    local host="$1" token basic_auth attempt_rc
+    local host="$1" token attempt_rc
 
     if ! token=$(get_gitea_token "$host"); then
         echo "Error: Could not resolve the required Gitea token; refusing merge without changing principals." >&2
@@ -554,28 +589,10 @@ merge_gitea_with_api() {
         return 75
     fi
     if [[ "$LAST_GITEA_HTTP_CODE" != "401" ]]; then
-        echo "Error: Gitea API merge failed with token credential (HTTP ${LAST_GITEA_HTTP_CODE:-000}).${LAST_GITEA_ERROR:+ Provider response: $LAST_GITEA_ERROR} Basic Auth fallback is allowed only after HTTP 401." >&2
+        echo "Error: Gitea API merge failed with the identity-bound token (HTTP ${LAST_GITEA_HTTP_CODE:-000}).${LAST_GITEA_ERROR:+ Provider response: $LAST_GITEA_ERROR}" >&2
         return 1
     fi
-    echo "Token credential received HTTP 401; retrying inspection and merge with configured Basic Auth." >&2
-
-    basic_auth=$(get_gitea_basic_auth "$host" || true)
-    if [[ -n "$basic_auth" ]]; then
-        if merge_gitea_api_attempt "$host" basic "$basic_auth"; then
-            return 0
-        else
-            attempt_rc=$?
-        fi
-        if [[ "$attempt_rc" -eq 75 ]]; then
-            return 75
-        fi
-    fi
-
-    if [[ -z "$token" && -z "$basic_auth" ]]; then
-        echo "Error: No Gitea credential is available for the merge operation." >&2
-    else
-        echo "Error: Gitea API merge failed for all configured credentials (last HTTP ${LAST_GITEA_HTTP_CODE:-000}).${LAST_GITEA_ERROR:+ Provider response: $LAST_GITEA_ERROR}" >&2
-    fi
+    echo "Error: Gitea API rejected the identity-bound token with HTTP 401; refusing cross-principal credential fallback." >&2
     return 1
 }
 

packages/mosaic/framework/tools/git/test-pr-merge-message-field.sh

@@ -41,7 +41,7 @@ get_gitea_basic_auth() {
     printf 'resolved\n' >> "${MOSAIC_TEST_BASIC_RESOLUTION_LOG:?}"
     if [[ "${MOSAIC_TEST_BASIC_AVAILABLE:-false}" == "true" ]]; then
         printf 'fixture-user:fixture-password\n'
-        return 0
+        return "${MOSAIC_TEST_BASIC_RC:-0}"
     fi
     return 1
 }
@@ -99,6 +99,9 @@ out_file=""
 data=""
 config=""
 auth_mode="none"
+has_max_filesize=0
+has_max_time=0
+has_connect_timeout=0
 while [[ $# -gt 0 ]]; do
     case "$1" in
         -o)
@@ -125,6 +128,18 @@ while [[ $# -gt 0 ]]; do
             fi
             shift 2
             ;;
+        --max-filesize)
+            has_max_filesize=1
+            shift 2
+            ;;
+        --max-time)
+            has_max_time=1
+            shift 2
+            ;;
+        --connect-timeout)
+            has_connect_timeout=1
+            shift 2
+            ;;
         -H|--header|-u|--user)
             if [[ "$2" == *"fixture-token"* ]]; then
                 : > "${MOSAIC_TEST_TOKEN_ARGV_MARKER:?}"
@@ -152,6 +167,7 @@ elif [[ "$config" == *"user = \"fixture-user:fixture-password\""* ]]; then
     : > "${MOSAIC_TEST_BASIC_CONFIG_MARKER:?}"
 fi
 printf '%s %s %s\n' "$method" "$auth_mode" "$url" >> "${MOSAIC_TEST_CURL_LOG:?}"
+printf '%s:%s:%s\n' "$has_max_filesize" "$has_max_time" "$has_connect_timeout" >> "${MOSAIC_TEST_CURL_BOUNDS_LOG:?}"
 
 case "$url" in
     */pulls/42)
@@ -174,7 +190,11 @@ case "$url" in
     */pulls/42/commits*)
         case "${MOSAIC_TEST_COMMITS_MODE:?}" in
             verified)
-                body='[{"sha":"2222222222222222222222222222222222222222","commit":{"author":{"name":"Alice","email":"[email protected]"}},"author":{"login":"alice"}},{"sha":"1111111111111111111111111111111111111111","commit":{"author":{"name":"Poster","email":"[email protected]"}},"author":{"login":"poster"}}]'
+                if [[ "${MOSAIC_TEST_EMAIL_MODE:-safe}" == "escape" ]]; then
+                    body='[{"sha":"2222222222222222222222222222222222222222","commit":{"author":{"name":"Alice","email":"alice+\u001b[[email protected]"}},"author":{"login":"alice"}},{"sha":"1111111111111111111111111111111111111111","commit":{"author":{"name":"Poster","email":"[email protected]"}},"author":{"login":"poster"}}]'
+                else
+                    body='[{"sha":"2222222222222222222222222222222222222222","commit":{"author":{"name":"Alice","email":"[email protected]"}},"author":{"login":"alice"}},{"sha":"1111111111111111111111111111111111111111","commit":{"author":{"name":"Poster","email":"[email protected]"}},"author":{"login":"poster"}}]'
+                fi
                 ;;
             null-login)
                 body='[{"sha":"1111111111111111111111111111111111111111","commit":{"author":{"name":"Poster","email":"[email protected]"}},"author":{"login":"poster"}},{"sha":"3333333333333333333333333333333333333333","commit":{"author":{"name":"Unresolved Author","email":"[email protected]\n\u001b[31m"}},"author":null}]'
@@ -228,6 +248,10 @@ else
     printf '%s' "$body"
 fi
 printf '%s' "$code"
+case "${MOSAIC_TEST_CURL_FAILURE:-none}" in
+    oversize) exit 63 ;;
+    stalled) exit 28 ;;
+esac
 SH
 
     chmod +x "$case_dir/detect-platform.sh" "$case_dir/pr-metadata.sh" \
@@ -240,6 +264,7 @@ run_case() {
     shift 2
     MOSAIC_TEST_COMMITS_MODE="$mode" \
     MOSAIC_TEST_CURL_LOG="$case_dir/curl.log" \
+    MOSAIC_TEST_CURL_BOUNDS_LOG="$case_dir/curl-bounds.log" \
     MOSAIC_TEST_MERGE_PAYLOAD="$case_dir/merge-payload.json" \
     MOSAIC_TEST_TOKEN_ARGV_MARKER="$case_dir/token-in-argv" \
     MOSAIC_TEST_BASIC_ARGV_MARKER="$case_dir/basic-in-argv" \
@@ -285,6 +310,30 @@ fi
 if grep -q '/users/' "$verified_dir/curl.log" 2>/dev/null; then
     fail "verified path performed a forbidden second /users lookup"
 fi
+if grep -qv '^1:1:1$' "$verified_dir/curl-bounds.log"; then
+    fail "verified path did not apply size/max-time/connect-time bounds to every provider download"
+fi
+
+# A linked email containing a terminal escape must block before mutation.
+escape_email_dir=$(make_case escape-email)
+set +e
+escape_email_output=$(MOSAIC_TEST_EMAIL_MODE=escape run_case "$escape_email_dir" verified --co-author-trailers --escalate-to tl-mosaic 2>&1)
+escape_email_rc=$?
+set -e
+[[ "$escape_email_rc" -ne 0 ]] || fail "control-byte email unexpectedly passed"
+[[ "$escape_email_output" == *"unusable linked identity"* ]] || fail "control-byte email refusal lost its diagnostic"
+[[ ! -e "$escape_email_dir/merge-payload.json" ]] || fail "control-byte email reached the merge API"
+
+# Curl transfer and duration failures must remain failures even with HTTP 200.
+for failure_mode in oversize stalled; do
+    failure_dir=$(make_case "curl-$failure_mode")
+    set +e
+    failure_output=$(MOSAIC_TEST_CURL_FAILURE="$failure_mode" run_case "$failure_dir" verified --co-author-trailers --escalate-to tl-mosaic 2>&1)
+    failure_rc=$?
+    set -e
+    [[ "$failure_rc" -ne 0 ]] || fail "curl $failure_mode failure was discarded: $failure_output"
+    [[ ! -e "$failure_dir/merge-payload.json" ]] || fail "curl $failure_mode failure reached the merge API"
+done
 
 # The authenticated head is re-read under the mutation credential but cannot
 # replace the canonical preflight/review head. A move blocks before enumeration
@@ -315,39 +364,44 @@ set -e
 [[ ! -e "$token_missing_dir/basic-resolution.log" ]] || fail "missing token resolved Basic Auth after identity failure"
 [[ ! -e "$token_missing_dir/curl.log" ]] || fail "missing token reached a provider request"
 
-# Token rejection during inspection must fall back to Basic Auth, then repeat
-# BOTH inspection and merge with that one Basic credential handle.
+# A failed Basic resolver must never use its nonempty output or reach mutation.
+basic_rc_dir=$(make_case basic-resolver-rc)
+set +e
+basic_rc_output=$(MOSAIC_TEST_BASIC_AVAILABLE=true MOSAIC_TEST_BASIC_RC=91 MOSAIC_TEST_FALLBACK_MODE=inspection \
+    run_case "$basic_rc_dir" verified --co-author-trailers --escalate-to tl-mosaic 2>&1)
+basic_rc_rc=$?
+set -e
+[[ "$basic_rc_rc" -ne 0 ]] || fail "failed Basic resolver output unexpectedly authorized a merge: $basic_rc_output"
+[[ ! -e "$basic_rc_dir/merge-payload.json" ]] || fail "failed Basic resolver reached the merge API"
+
+# HTTP 401 never changes principals: inspection rejection fails closed without
+# resolving or attempting Basic Auth.
 fallback_inspect_dir=$(make_case fallback-inspection)
 set +e
 fallback_inspect_output=$(MOSAIC_TEST_BASIC_AVAILABLE=true MOSAIC_TEST_FALLBACK_MODE=inspection \
     run_case "$fallback_inspect_dir" verified --co-author-trailers --escalate-to tl-mosaic 2>&1)
 fallback_inspect_rc=$?
 set -e
-[[ "$fallback_inspect_rc" -eq 0 ]] || fail "inspection fallback expected rc=0, got rc=$fallback_inspect_rc: $fallback_inspect_output"
-[[ -s "$fallback_inspect_dir/merge-payload.json" ]] || fail "inspection fallback did not reach the merge API"
-[[ -e "$fallback_inspect_dir/basic-via-config" ]] || fail "inspection fallback did not transport Basic Auth through stdin config"
-[[ ! -e "$fallback_inspect_dir/basic-in-argv" ]] || fail "inspection fallback exposed Basic Auth in curl argv"
-[[ ! -e "$fallback_inspect_dir/metadata-in-argv" ]] || fail "inspection fallback exposed PR metadata in child argv"
-[[ "$(wc -l < "$fallback_inspect_dir/token-resolution.log")" -eq 1 ]] || fail "inspection fallback did not resolve token exactly once"
-[[ "$(wc -l < "$fallback_inspect_dir/basic-resolution.log")" -eq 1 ]] || fail "inspection fallback did not resolve Basic Auth exactly once"
+[[ "$fallback_inspect_rc" -ne 0 ]] || fail "inspection token rejection unexpectedly changed principals"
+[[ "$fallback_inspect_output" == *"refusing cross-principal credential fallback"* ]] || fail "inspection token rejection lost its refusal diagnostic"
+[[ ! -e "$fallback_inspect_dir/basic-resolution.log" ]] || fail "inspection token rejection resolved Basic Auth"
+[[ ! -e "$fallback_inspect_dir/merge-payload.json" ]] || fail "inspection token rejection reached merge mutation"
 inspect_sequence=$(awk '{print $1 ":" $2}' "$fallback_inspect_dir/curl.log" | paste -sd, -)
-[[ "$inspect_sequence" == "GET:token,GET:basic,GET:basic,POST:basic" ]] || fail "inspection fallback was not bound per credential (calls=$inspect_sequence)"
+[[ "$inspect_sequence" == "GET:token" ]] || fail "inspection rejection made unexpected provider calls (calls=$inspect_sequence)"
 
-# Token rejection at merge is a separate seam: Basic fallback must re-inspect
-# instead of reusing evidence gathered under the rejected token.
+# Token rejection at merge likewise fails closed without cross-principal retry.
 fallback_merge_dir=$(make_case fallback-merge)
 set +e
 fallback_merge_output=$(MOSAIC_TEST_BASIC_AVAILABLE=true MOSAIC_TEST_FALLBACK_MODE=merge \
     run_case "$fallback_merge_dir" verified --co-author-trailers --escalate-to tl-mosaic 2>&1)
 fallback_merge_rc=$?
 set -e
-[[ "$fallback_merge_rc" -eq 0 ]] || fail "merge fallback expected rc=0, got rc=$fallback_merge_rc: $fallback_merge_output"
-[[ -s "$fallback_merge_dir/merge-payload.json" ]] || fail "merge fallback did not reach a successful merge API payload"
-[[ -e "$fallback_merge_dir/basic-via-config" ]] || fail "merge fallback did not transport Basic Auth through stdin config"
-[[ ! -e "$fallback_merge_dir/basic-in-argv" ]] || fail "merge fallback exposed Basic Auth in curl argv"
-[[ ! -e "$fallback_merge_dir/metadata-in-argv" ]] || fail "merge fallback exposed PR metadata in child argv"
+[[ "$fallback_merge_rc" -ne 0 ]] || fail "merge token rejection unexpectedly changed principals"
+[[ "$fallback_merge_output" == *"refusing cross-principal credential fallback"* ]] || fail "merge token rejection lost its refusal diagnostic"
+[[ ! -e "$fallback_merge_dir/basic-resolution.log" ]] || fail "merge token rejection resolved Basic Auth"
+[[ ! -e "$fallback_merge_dir/merge-payload.json" ]] || fail "merge token rejection recorded a successful payload"
 merge_sequence=$(awk '{print $1 ":" $2}' "$fallback_merge_dir/curl.log" | paste -sd, -)
-[[ "$merge_sequence" == "GET:token,GET:token,POST:token,GET:basic,GET:basic,POST:basic" ]] || fail "merge fallback reused cross-credential evidence (calls=$merge_sequence)"
+[[ "$merge_sequence" == "GET:token,GET:token,POST:token" ]] || fail "merge rejection made unexpected provider calls (calls=$merge_sequence)"
 
 # BLOCK path: a commit email exists but author.login is null. It must name both
 # facts, name the escalation principal, and never reach the merge endpoint.
@@ -405,6 +459,7 @@ set -e
 [[ "$error_output" == *"branch policy rejected"* ]] || fail "provider error response was discarded"
 [[ "$error_output" == *'\n\x1b[31m'* ]] || fail "provider error response did not escape control characters"
 [[ "$error_output" != *$'\033'* ]] || fail "provider error response emitted a raw terminal escape"
+[[ "$error_output" != *"Basic Auth fallback"* ]] || fail "provider error advertised removed Basic Auth fallback"
 [[ ! -e "$error_dir/basic-resolution.log" ]] || fail "HTTP 409 policy denial incorrectly triggered Basic Auth fallback"
 
 # Authorization denials likewise fail closed instead of changing principals.
@@ -416,6 +471,7 @@ forbidden_rc=$?
 set -e
 [[ "$forbidden_rc" -ne 0 ]] || fail "HTTP 403 authorization denial unexpectedly passed"
 [[ "$forbidden_output" == *"HTTP 403"* ]] || fail "authorization denial omitted the HTTP status"
+[[ "$forbidden_output" != *"Basic Auth fallback"* ]] || fail "authorization denial advertised removed Basic Auth fallback"
 [[ ! -e "$forbidden_dir/basic-resolution.log" ]] || fail "HTTP 403 authorization denial incorrectly triggered Basic Auth fallback"
 
 # The BLOCK destination cannot be generic or inferred after failure: opting in