gochat/backend/internal/middleware/platform_app_auth.go

package middleware

// Reference: Chatwoot PlatformController — AccessToken authentication
// Chatwoot authenticates Platform API requests via the api_access_token header,
// which maps to a PlatformApp owner. This middleware replicates that pattern:
//
//   1. Read api_access_token from request headers
//   2. Look up the AccessToken record (token is SHA-256 hashed in DB)
//   3. Verify the owner is a PlatformApp (not a User personal token)
//   4. Set platform_app in Gin context for downstream handlers
//
// Permissible validation is handled per-resource in each handler,
// matching Chatwoot's validate_platform_app_permissible callback.

import (
	"crypto/sha256"
	"encoding/hex"
	"net/http"

	"github.com/gin-gonic/gin"

	"github.com/gochat/gochat/internal/model"
	"github.com/gochat/gochat/pkg/response"
	"gorm.io/gorm"
)

// PlatformAppAuth creates a middleware that authenticates Platform API requests
// via the api_access_token header (Chatwoot-compatible).
//
// The middleware:
//   - Extracts api_access_token from request headers
//   - Hashes the token (SHA-256) and queries the access_tokens table
//   - Verifies the token owner is a PlatformApp
//   - Loads the PlatformApp with its Permissibles for downstream checks
//   - Sets platform_app_id and platform_app in Gin context
//
// If no token is provided, or the token is invalid, or the owner is not
// a PlatformApp, the request is rejected with 401 Unauthorized.
func PlatformAppAuth(db *gorm.DB) gin.HandlerFunc {
	return func(c *gin.Context) {
		// Step 1: Extract api_access_token from headers
		// Chatwoot reads both :api_access_token and :HTTP_API_ACCESS_TOKEN
		token := c.GetHeader("api_access_token")
		if token == "" {
			token = c.GetHeader("HTTP_API_ACCESS_TOKEN")
		}
		if token == "" {
			response.AbortWithStatusError(c, http.StatusUnauthorized, response.ErrUnauthorized,
				"api_access_token header required")
			return
		}

		// Step 2: Hash the token (SHA-256) to match stored hash
		hash := sha256.Sum256([]byte(token))
		tokenHash := hex.EncodeToString(hash[:])

		// Step 3: Query AccessToken by hashed token
		var accessToken model.AccessToken
		if err := db.Where("token = ? AND owner_type = ?", tokenHash, model.AccessTokenOwnerTypePlatformApp).
			First(&accessToken).Error; err != nil {
			if err == gorm.ErrRecordNotFound {
				response.AbortWithStatusError(c, http.StatusUnauthorized, response.ErrUnauthorized,
					"Invalid access_token")
				return
			}
			response.AbortWithStatusError(c, http.StatusInternalServerError, response.ErrInternal,
				"Failed to verify access token")
			return
		}

		// Step 4: Load the PlatformApp with its Permissibles
		var platformApp model.PlatformApp
		if err := db.Preload("Permissibles").First(&platformApp, accessToken.OwnerID).Error; err != nil {
			response.AbortWithStatusError(c, http.StatusUnauthorized, response.ErrUnauthorized,
				"Invalid access_token")
			return
		}

		// Step 5: Set platform_app in Gin context for downstream handlers
		c.Set("platform_app", platformApp)
		c.Set("platform_app_id", platformApp.ID)
		c.Set("access_token_id", accessToken.ID)

		c.Next()
	}
}