Poodle Attack in Gin with Dynamodb

The Poodle attack (Padding Oracle On Downgraded Legacy Encryption) targets systems that negotiate TLS 3.0 and rely on block ciphers in CBC mode without proper integrity protection. In a Gin-based Go service that interacts with DynamoDB, the vulnerability arises when TLS 3.0 is accidentally enabled or when session tokens / cookies are encrypted using CBC-mode ciphers without HMAC-then-Encrypt integrity checks. An attacker who can inject plaintext requests and observe error timing or behavior can recover sensitive data such as authentication tokens or API keys, even if the data is stored encrypted in DynamoDB.

With DynamoDB, a Gin service typically performs unauthenticated or weakly authenticated scans that expose endpoints used to retrieve or query items. If a token or session identifier is stored in a cookie or header and encrypted with a CBC cipher lacking integrity, the Poodle attack can decrypt it byte-by-byte by exploiting the padding oracle presented via error messages (e.g., BadPadding errors from decryption). DynamoDB itself does not introduce the weakness, but if the decrypted item contains sensitive credentials or keys used to access DynamoDB, the exposure has severe downstream impact.

During a black-box scan, middleBrick runs 12 security checks in parallel, including TLS configuration and authentication surface analysis. For a Gin endpoint backed by DynamoDB, the scan tests whether TLS 3.0 is negotiable and whether error responses reveal padding oracle behavior. The LLM/AI Security checks additionally verify whether system prompt leakage or prompt injection could coexist with weak session handling, which can compound data exposure risks. middleBrick reports findings aligned with OWASP API Top 10 and references CVEs such as CVE-2014-3566 that describe Poodle in TLS contexts, while noting that weak crypto usage in application code can create similar oracle conditions.

Remediation focuses on disabling TLS 3.0, enforcing strong cipher suites, and ensuring that any data encrypted before storage in DynamoDB uses authenticated encryption. For Gin services, this means configuring the underlying HTTP server with modern TLS settings and applying proper cryptographic practices for items stored in DynamoDB.

1. Disable TLS 3.0 and enforce strong ciphers in Gin

Ensure your Gin server does not advertise or accept TLS 3.0. Use tls.Config with modern min/max versions and restrict to strong cipher suites. This removes the padding oracle vector exploited by Poodle.

import (
	"crypto/tls"
	"github.com/gin-gonic/gin"
)

func NewSecureRouter() *gin.Engine {
	r := gin.Default()
	server := &http.Server{
		Addr: ":8443",
		TLSConfig: &tls.Config{
			MinVersion:               tls.VersionTLS12,
			PreferServerCipherSuites: true,
			CipherSuites: []uint16{
				tls.TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384,
				tls.TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384,
				tls.TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305,
				tls.TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305,
			},
		},
	}
	// configure routes as needed
	return r
}

2. Authenticated encryption for DynamoDB-stored secrets

When storing sensitive values in DynamoDB, use authenticated encryption (e.g., AES-GCM) rather than raw CBC. This ensures integrity and prevents padding oracle attacks on decrypted data. Use KMS for envelope encryption where applicable and avoid deterministic encryption for sensitive fields.

import (
	"context"
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/base64"
	"fmt"
	"io"

	"github.com/aws/aws-sdk-go-v2/service/dynamodb"
)

// encryptAESGCM encrypts plaintext using AES-GCM and returns base64 ciphertext + nonce.
func encryptAESGCM(plaintext, key []byte) (string, error) {
	block, err := aes.NewCipher(key)
	if err != nil {
		return "", err
	}
	nonce := make([]byte, 12)
	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
		return "", err
	}
	aesgcm, err := cipher.NewGCM(block)
	if err != nil {
		return "", err
	}
	ciphertext := aesgcm.Seal(nil, nonce, plaintext, nil)
	combined := append(nonce, ciphertext...)
	return base64.StdEncoding.EncodeToString(combined), nil
}

// storeItem stores an encrypted item in DynamoDB.
func storeItem(ctx context.Context, svc *dynamodb.Client, tableName string, id, sensitive string) error {
	key, err := encryptAESGCM([]byte(sensitive), []byte("32-byte-long-key-32-byte-long-key-1234"))
	if err != nil {
		return fmt.Errorf("encrypt failed: %w", err)
	}
	_, err = svc.PutItem(ctx, &dynamodb.PutItemInput{
		TableName: &tableName,
		Item: map[string]types.AttributeValue{
			"id": &types.AttributeValueMemberS{Value: id},
			"data": &types.AttributeValueMemberS{Value: key},
		},
	})
	return err
}

3. Validate and secure session handling

Avoid storing session material in cookies without integrity protection. Use signed, HttpOnly cookies with Secure and SameSite attributes. If you must store tokens retrieved from DynamoDB, prefer JWTs with strong signing and validate them on each request.