#!/usr/bin/env bash
# Vector 28: OAuth Takeover — Detects OAuth misconfigurations
# Desc: Tests OAuth flows for redirect_uri, state, and CSRF issues
# Severity: CRITICAL
# Proof: Account takeover proof via open redirect / token theft

vector_oauth_takeover() {
  local target="$1"
  local report="$2"
  local domain=$(get_domain "$target")
  local findings=0

  print_info "Hunting OAuth Misconfiguration..."

  local base=$(get_base "$target")
  local urls=$(get_discovered_urls "$domain" 2>/dev/null)
  local oauth_urls=$(echo "$urls" | grep -iE 'oauth|auth|login|signin|sso|callback|redirect|connect|authorize|token' | head -20)

  [ -z "$oauth_urls" ] && oauth_urls="$target"

  # OAuth redirect_uri tests
  local redirect_uris=(
    "https://evil.com"
    "https://${domain}.evil.com"
    "https://evil${domain}"
    "https://${domain}.attacker.com"
    "https://attacker.com/redirect?to=${domain}"
    "https://evil.com/?domain=${domain}"
    "https://${domain}.evil.com%2Fcallback"
    "https://evil.com%2F%40${domain}"
    "data:text/html,<script>alert(1)</script>"
    "javascript:alert(document.cookie)"
  )

  # OAuth state parameter tests
  local state_tests=(
    "state=test123"
    "state="
    "state=missing"
    ""  # missing state
  )

  # OpenID Connect discovery
  local oidc_paths=(
    "/.well-known/openid-configuration"
    "/.well-known/oauth-authorization-server"
    "/oauth2/.well-known/openid-configuration"
    "/api/.well-known/openid-configuration"
  )

  for oauth_url in $oauth_urls; do
    # Test for missing state parameter (CSRF on OAuth)
    if echo "$oauth_url" | grep -qi 'state='; then
      # Check if removing state still works
      local no_state_url=$(echo "$oauth_url" | sed 's/&state=[^&]*//;s/state=[^&]*&//')
      if [ "$no_state_url" != "$oauth_url" ]; then
        local resp_no_state=$(curl -s -o /dev/null -w "%{http_code}" --connect-timeout 5 --max-time 8 "$no_state_url" 2>/dev/null)
        local resp_state=$(curl -s -o /dev/null -w "%{http_code}" --connect-timeout 5 --max-time 8 "$oauth_url" 2>/dev/null)
        
        if [ "$resp_no_state" != "400" ] && [ "$resp_no_state" != "403" ]; then
          print_find "OAuth CSRF — Missing State!" "State parameter removal doesn't break flow"
          echo "SEVERITY: CRITICAL
VECTOR: OAuth CSRF (Missing State)
DETAIL: OAuth flow works without state parameter
URL: $oauth_url
EXPLOIT: CSRF attack to link attacker's account to victim" > "$REPORTS_DIR/.finding_oauth_csrf_$(date +%s).txt"
          findings=$((findings + 1))
        fi
      fi
    fi

    # Test redirect_uri open redirect
    for redirect in "${redirect_uris[@]}"; do
      local encoded_redirect=$(printf '%s' "$redirect" | jq -sRr @uri 2>/dev/null || echo "$redirect")
      
      for redirect_param in "redirect_uri" "redirect" "callback" "return_url" "return_to" "next" "goto"; do
        local test_url=$(echo "$oauth_url" | sed "s|redirect_uri=[^&]*|${redirect_param}=${encoded_redirect}|" 2>/dev/null)
        
        if [ "$test_url" != "$oauth_url" ] || [[ "$oauth_url" == *"$redirect_param"* ]]; then
          local final_url=$(curl -s -o /dev/null -w "%{redirect_url}" --connect-timeout 5 --max-time 8 "$test_url" 2>/dev/null)
          
          if echo "$final_url" | grep -qi 'evil.com\|attacker.com'; then
            print_find "OAuth Open Redirect!" "redirect_uri accepts external domains"
            echo "SEVERITY: HIGH
VECTOR: OAuth Redirect URI Bypass
DETAIL: OAuth allows external redirect_uri
URL: $test_url
REDIRECTS_TO: $final_url
EXPLOIT: Steal auth codes via open redirect" > "$REPORTS_DIR/.finding_oauth_redirect_$(date +%s).txt"
            findings=$((findings + 1))
            break 3
          fi
        fi
      done
    done

    # Check for token leakage in referer
    if echo "$oauth_url" | grep -qi 'access_token\|id_token\|token='; then
      print_find "OAuth Token in URL!" "Token exposed in URL (referer leakage risk)"
      echo "SEVERITY: HIGH
VECTOR: OAuth Token Leakage
DETAIL: Token transmitted in URL query string
EVIDENCE: Token present in OAuth redirect URL
EXPLOIT: Referer header leaks token to third-party resources" > "$REPORTS_DIR/.finding_oauth_token_$(date +%s).txt"
      findings=$((findings + 1))
    fi
  done

  # Test OIDC discovery endpoints
  for path in "${oidc_paths[@]}"; do
    local oidc_data=$(curl -s --connect-timeout 5 --max-time 8 "${base}${path}" 2>/dev/null)
    if echo "$oidc_data" | grep -qi '"issuer"\|"authorization_endpoint"\|"jwks_uri"'; then
      print_find "OIDC Discovery Exposed!" "OpenID Connect metadata at ${path}"
      echo "SEVERITY: MEDIUM
VECTOR: OIDC Discovery Exposed
DETAIL: OpenID Connect configuration publicly accessible
URL: ${base}${path}
ISSUER: $(echo "$oidc_data" | grep -o '"issuer":"[^"]*"' | cut -d'"' -f4)" > "$REPORTS_DIR/.finding_oidc_$(date +%s).txt"
      findings=$((findings + 1))
    fi
  done

  if [ "$findings" -eq 0 ]; then
    print_info "No OAuth misconfigurations found"
  fi

  return $findings
}