Add IAM protection to Lambda function URLs

Requires a tool to v4-sign the request to AWS for testing.

Test can be run locally against a deployed function with:
```sh
aws-vault exec identity -- URL=$FUNCTION_URL make test-api
```

#minor

.github/workflows/env-test.yml

@@ -0,0 +1,49 @@
+name: "[Job] Test environment"
+
+on:
+  workflow_call:
+    inputs:
+      create_url:
+        description: "URL of the create endpoint"
+        required: true
+        type: string
+    secrets:
+      aws_access_key_id:
+        description: 'AWS Access Key ID'
+        required: true
+      aws_secret_access_key:
+        description: 'AWS Secret Access Key'
+        required: true
+
+defaults:
+  run:
+    shell: bash
+
+permissions:
+  id-token: write
+  contents: write
+  security-events: write
+  pull-requests: read
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    name: Test
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: "0"
+      - uses: unfor19/install-aws-cli-action@v1
+      - name: Configure AWS Credentials
+        uses: aws-actions/configure-aws-credentials@v4
+        with:
+          aws-access-key-id: ${{ secrets.AWS_ACCESS_KEY_ID }}
+          aws-secret-access-key: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
+          aws-region: eu-west-1
+          role-to-assume: arn:aws:iam::311462405659:role/lpa-store-ci
+          role-duration-seconds: 3600
+          role-session-name: GitHubActions
+      - name: POST to server
+        env:
+          URL: ${{ inputs.create_url }}
+        run: make test-api

.github/workflows/workflow-pr.yml

@@ -86,12 +86,9 @@ jobs:
   test-pr-env:
     name: Test PR Environment
     needs: [deploy-pr-env]
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v4
-        with:
-          fetch-depth: "0"
-      - name: POST to server
-        env:
-          URL: ${{ needs.deploy-pr-env.outputs.create_url }}
-        run: make test-api
+    uses: ./.github/workflows/env-test.yml
+    with:
+      create_url: ${{ needs.deploy-pr-env.outputs.create_url }}
+    secrets:
+      aws_access_key_id: ${{ secrets.AWS_ACCESS_KEY_ID }}
+      aws_secret_access_key: ${{ secrets.AWS_SECRET_ACCESS_KEY }}

.gitignore

@@ -14,6 +14,8 @@ secrets.auto.tfvars
 .env
 venv/
 env/
+# built items
+signer/test-api
 # structurizr
 .structurizr
 docs/architecture/dsl/**/workspace.json

Makefile

@@ -14,7 +14,9 @@ down:
 
 test-api: URL ?= http://localhost:9000/create
 test-api:
-	curl $(URL) -XPOST -H 'Content-type: application/json' -d '{"uid":"M-AL9A-7EY3-075D","version":"1"}' -q
+	go build -o ./signer/test-api ./signer && \
+	chmod +x ./signer/test-api && \
+	./signer/test-api POST $(URL) '{"uid":"M-AL9A-7EY3-075D","version":"1"}'
 
 create-tables:
 	docker compose run --rm aws dynamodb describe-table --table-name deeds || \

docker-compose.yml

@@ -16,6 +16,7 @@ services:
       AWS_DYNAMODB_ENDPOINT: http://ddb:8000
       AWS_ACCESS_KEY_ID: X
       AWS_SECRET_ACCESS_KEY: X
+      DDB_TABLE_NAME_DEEDS: deeds
     volumes:
       - "./lambda/.aws-lambda-rie:/aws-lambda"
     entrypoint: /aws-lambda/aws-lambda-rie /var/task/main

go.work

@@ -4,4 +4,5 @@ use (
 	./lambda/create
 	./lambda/shared
 	./mock-apigw
+	./signer
 )

signer/go.mod

@@ -0,0 +1,7 @@
+module github.com/ministryofjustice/opg-data-lpa-deed/signer
+
+go 1.20
+
+require github.com/aws/aws-sdk-go v1.45.24
+
+require github.com/jmespath/go-jmespath v0.4.0 // indirect

signer/go.sum

@@ -0,0 +1,42 @@
+github.com/aws/aws-sdk-go v1.45.24 h1:TZx/CizkmCQn8Rtsb11iLYutEQVGK5PK9wAhwouELBo=
+github.com/aws/aws-sdk-go v1.45.24/go.mod h1:aVsgQcEevwlmQ7qHE9I3h+dtQgpqhFB+i8Phjh7fkwI=
+github.com/davecgh/go-spew v1.1.0 h1:ZDRjVQ15GmhC3fiQ8ni8+OwkZQO4DARzQgrnXU1Liz8=
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/jmespath/go-jmespath v0.4.0 h1:BEgLn5cpjn8UN1mAw4NjwDrS35OdebyEtFe+9YPoQUg=
+github.com/jmespath/go-jmespath v0.4.0/go.mod h1:T8mJZnbsbmF+m6zOOFylbeCJqk5+pHWvzYPziyZiYoo=
+github.com/jmespath/go-jmespath/internal/testify v1.5.1 h1:shLQSRRSCCPj3f2gpwzGwWFoC7ycTf1rcQZHOlsJ6N8=
+github.com/jmespath/go-jmespath/internal/testify v1.5.1/go.mod h1:L3OGu8Wl2/fWfCI6z80xFu9LTZmf1ZRjMHUOPmWr69U=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
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+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/yuin/goldmark v1.4.13/go.mod h1:6yULJ656Px+3vBD8DxQVa3kxgyrAnzto9xy5taEt/CY=
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+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
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signer/main.go

@@ -0,0 +1,49 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"log"
+	"net/http"
+	"os"
+	"strings"
+	"time"
+
+	v4 "github.com/aws/aws-sdk-go/aws/signer/v4"
+	"github.com/aws/aws-sdk-go/awstesting/unit"
+)
+
+func main() {
+	creds := unit.Session.Config.Credentials
+	signer := v4.NewSigner(creds)
+
+	method := os.Args[1]
+	host := os.Args[2]
+	body := strings.NewReader(os.Args[3])
+
+	req, err := http.NewRequest(method, host, body)
+	if err != nil {
+		panic(err)
+	}
+
+	req.Header.Add("Content-type", "application/json")
+
+	signer.Sign(req, body, "lambda", "eu-west-1", time.Now())
+
+	log.Print(req.Header.Get("Authorization"))
+
+	client := http.Client{}
+	resp, err := client.Do(req)
+	if err != nil {
+		panic(err)
+	}
+
+	if resp.StatusCode >= 400 {
+		log.Printf("Response code %d", resp.StatusCode)
+		buf := new(strings.Builder)
+		_, _ = io.Copy(buf, resp.Body)
+		log.Printf(">%s<", buf.String())
+
+		panic(fmt.Sprintf("invalid status code %d", resp.StatusCode))
+	}
+}

terraform/modules/lambda/iam.tf

@@ -53,3 +53,10 @@ resource "aws_lambda_permission" "allow_lambda_execution_operator" {
   function_name = aws_lambda_function.main.function_name
   principal     = "arn:aws:iam::${data.aws_caller_identity.current.account_id}:role/operator"
 }
+
+resource "aws_lambda_permission" "allow_lambda_url_execution_operator" {
+  statement_id  = "AllowExecutionOperatorUrl"
+  action        = "lambda:InvokeFunctionUrl"
+  function_name = aws_lambda_function.main.function_name
+  principal     = "arn:aws:iam::${data.aws_caller_identity.current.account_id}:role/operator"
+}

terraform/modules/lambda/main.tf

@@ -25,5 +25,5 @@ resource "aws_lambda_function" "main" {
 
 resource "aws_lambda_function_url" "main" {
   function_name      = aws_lambda_function.main.function_name
-  authorization_type = "NONE"
+  authorization_type = "AWS_IAM"
 }