/
main.go
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/
main.go
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// Copyright 2020 Fugue, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package main
import (
"context"
"errors"
"fmt"
"os"
"strings"
"github.com/aws/aws-lambda-go/events"
"github.com/aws/aws-lambda-go/lambda"
"github.com/aws/aws-sdk-go/aws"
"github.com/aws/aws-sdk-go/aws/session"
"github.com/aws/aws-sdk-go/service/dynamodb"
"github.com/aws/aws-sdk-go/service/dynamodb/dynamodbattribute"
"github.com/aws/aws-sdk-go/service/dynamodb/dynamodbiface"
"github.com/sirupsen/logrus"
)
var logger *logrus.Logger
func init() {
logger = logrus.New()
logger.SetFormatter(&logrus.JSONFormatter{})
}
type token struct {
Name string
Email string
}
type authHandler struct {
ddb dynamodbiface.DynamoDBAPI
table string
}
func (h *authHandler) HandleRequest(ctx context.Context, request events.APIGatewayCustomAuthorizerRequest) (events.APIGatewayCustomAuthorizerResponse, error) {
// Extract token from "Bearer <token>" string
tokenSlice := strings.Split(request.AuthorizationToken, " ")
var bearerToken string
if len(tokenSlice) > 1 {
bearerToken = tokenSlice[len(tokenSlice)-1]
}
// Lookup token in DynamoDB to see if it exists
token, err := h.getToken(ctx, bearerToken)
if err != nil {
// Not found or any other error: unauthorized!
logger.WithError(err).Info("Unauthorized")
return events.APIGatewayCustomAuthorizerResponse{}, errors.New("Unauthorized")
}
logger.WithFields(logrus.Fields{
"name": token.Name,
"email": token.Email,
}).Info("OK")
// Return policy that authorizes the request
return generatePolicy(token.Name, "Allow", request.MethodArn), nil
}
func (h *authHandler) getToken(ctx context.Context, id string) (*token, error) {
result, err := h.ddb.GetItem(&dynamodb.GetItemInput{
TableName: aws.String(h.table),
Key: map[string]*dynamodb.AttributeValue{
"Token": {S: aws.String(id)},
},
})
if err != nil {
return nil, err
}
if result.Item == nil {
return nil, fmt.Errorf("Not found: %s", id)
}
var t token
if err := dynamodbattribute.UnmarshalMap(result.Item, &t); err != nil {
return nil, err
}
return &t, nil
}
func generatePolicy(principalID, effect, resource string) events.APIGatewayCustomAuthorizerResponse {
authResponse := events.APIGatewayCustomAuthorizerResponse{PrincipalID: principalID}
if effect != "" && resource != "" {
authResponse.PolicyDocument = events.APIGatewayCustomAuthorizerPolicy{
Version: "2012-10-17",
Statement: []events.IAMPolicyStatement{
{
Action: []string{"execute-api:Invoke"},
Effect: effect,
Resource: []string{"*"},
},
},
}
}
return authResponse
}
func main() {
logger.Info("coldstart")
sess := session.Must(session.NewSession())
svc := dynamodb.New(sess)
tableName := os.Getenv("TABLE")
if tableName == "" {
logger.Fatal("TABLE is not set")
}
handler := &authHandler{
ddb: svc,
table: tableName,
}
lambda.Start(handler.HandleRequest)
}