Integrate Azure Key Vault Certificates into Sample Projects (#36)

* add Azure Key Vault integration and connection string management

* fix variable name typo and update SQL connection string to use Azure Key Vault

* work in progress

* Update Key Vault secret names in deploy and validate scripts

* Integrate Azure Key Vault for SQL connection string management in web app

* work in progress

* add missing logger

* work in progress

* Integrate Azure Key Vault for certificate management and validation in web app

* add validate cert

* refactor SQL connection handling

* update README

Author: bryansan-local

samples/web-app-sql-database/python/README.md

@@ -1,6 +1,6 @@
 # Azure Web App with Azure SQL Database and Azure Key Vault
 
-This sample demonstrates a Python Flask single-page web application called *Vacation Planner* hosted on an [Azure Web App](https://learn.microsoft.com/en-us/azure/app-service/overview). The app runs on an Azure App Service Plan and stores activity data in an `activities` table within the `sampledb` database on an [Azure SQL Database](https://learn.microsoft.com/en-us/azure/azure-sql/database/) instance. The connection string of the SQL database is stored as a secret in [Azure Key Vault](https://learn.microsoft.com/en-us/azure/key-vault/general/overview).
+This sample demonstrates a Python Flask single-page web application called *Vacation Planner* hosted on an [Azure Web App](https://learn.microsoft.com/en-us/azure/app-service/overview). The app runs on an Azure App Service Plan and stores activity data in an `activities` table within the `sampledb` database on an [Azure SQL Database](https://learn.microsoft.com/en-us/azure/azure-sql/database/) instance. The connection string of the SQL database is stored as a secret in [Azure Key Vault](https://learn.microsoft.com/en-us/azure/key-vault/general/overview). The application also retrieves its certificate from Key Vault to serve traffic over HTTPS. 
 
 
 ## Architecture
@@ -12,7 +12,7 @@ The following diagram illustrates the architecture of the solution:
 - **Azure Web App**: Hosts the Python Flask application
 - **Azure App Service Plan**: Provides compute resources for the web app
 - **Azure SQL Database**: Stores activity data in a relational table
-- **Azure Key Vault**: Stores the database connection string
+- **Azure Key Vault**: Stores the database connection string and the certificate used to secure HTTPS traffic
 
 ## Prerequisites
 
@@ -43,6 +43,13 @@ The Vacation Planner Web App supports two common approaches for accessing Azure
 
 This flexibility allows the app to run securely in Azure or in emulated environments like [LocalStack for Azure](https://azure.localstack.cloud/). The client code supports both authentication modes using [`ClientSecretCredential`](https://learn.microsoft.com/en-us/python/api/azure-identity/azure.identity.clientsecretcredential?view=azure-python) or [`DefaultAzureCredential`](https://learn.microsoft.com/en-us/python/api/azure-identity/azure.identity.defaultazurecredential?view=azure-python) from the Azure SDK.
 
+## Azure Key Vault Integration
+The application integrates with Azure Key Vault for managing secrets and certificates:
+
+Secrets: The SQL connection string is stored as a secret in Key Vault. At runtime, the app retrieves it using the Azure Key Vault Secrets SDK. This is configured via the KEY_VAULT_NAME and SECRET_NAME environment variables.
+
+Certificates: A self-signed certificate is created in Key Vault during deployment. The app exposes a GET /api/certificate endpoint that retrieves the certificate using the Azure Key Vault Certificates SDK and returns its name, confirming the integration works. This is configured via the KEYVAULT_URI and CERT_NAME environment variables.
+
 ## Deployment
 
 Set up the Azure emulator using the LocalStack for Azure Docker image. Before starting, ensure you have a valid `LOCALSTACK_AUTH_TOKEN` to access the Azure emulator. Refer to the [Auth Token guide](https://docs.localstack.cloud/getting-started/auth-token/?__hstc=108988063.8aad2b1a7229945859f4d9b9bb71e05d.1743148429561.1758793541854.1758810151462.32&__hssc=108988063.3.1758810151462&__hsfp=3945774529) to obtain your Auth Token and set it in the `LOCALSTACK_AUTH_TOKEN` environment variable. The Azure Docker image is available on the [LocalStack Docker Hub](https://hub.docker.com/r/localstack/localstack-azure-alpha). To pull the image, execute:

samples/web-app-sql-database/python/scripts/deploy.sh

@@ -24,6 +24,7 @@ DEPLOY_APP=1
 ENVIRONMENT=$(az account show --query environmentName --output tsv)
 KEY_VAULT_NAME="${PREFIX}-kv-${SUFFIX}"
 SECRET_NAME="${PREFIX}-secret-${SUFFIX}"
+CERT_NAME="${PREFIX}-cert-${SUFFIX}"
 
 # Change the current directory to the script's directory
 cd "$CURRENT_DIR" || exit
@@ -143,6 +144,14 @@ if [ -z "$SQL_SERVER_FQDN" ]; then
 	exit 1
 fi
 
+#if [[ $ENVIRONMENT == "LocalStack" ]]; then
+#	MSSQL_HOST_PORT=$(docker ps --filter "ancestor=mcr.microsoft.com/mssql/server:2022-latest" --format "{{.Ports}}" | grep -oP '0\.0\.0\.0:\K[0-9]+(?=->1433)' | head -1)
+#	if [ -n "$MSSQL_HOST_PORT" ]; then
+#		SQL_SERVER_FQDN_WITH_PORT="127.0.0.1,$MSSQL_HOST_PORT"
+#		echo "Using local SQL Server at [$SQL_SERVER_FQDN_WITH_PORT]"
+#	fi
+#fi
+
 # Create server-level login
 echo "Creating login [$DATABASE_USER_NAME] at server level..."
 sqlcmd -S "$SQL_SERVER_FQDN" \
@@ -351,6 +360,7 @@ $AZ keyvault set-policy \
 	--name "$KEY_VAULT_NAME" \
 	--object-id "$PRINCIPAL_ID" \
 	--secret-permissions get \
+	--certificate-permissions get \
 	--only-show-errors 1>/dev/null
 
 if [ $? -eq 0 ]; then
@@ -378,6 +388,40 @@ else
 	exit 1
 fi
 
+# Create certificate in Key Vault
+echo "Creating certificate [$CERT_NAME] in Key Vault [$KEY_VAULT_NAME]..."
+$AZ keyvault certificate create \
+    --vault-name "$KEY_VAULT_NAME" \
+    --name "$CERT_NAME" \
+    --policy '{
+        "issuerParameters": {"name": "Self"},
+        "keyProperties": {"exportable": true, "keySize": 2048, "keyType": "RSA", "reuseKey": false},
+        "secretProperties": {"contentType": "application/x-pkcs12"},
+        "x509CertificateProperties": {"subject": "CN=sample-web-app-sql", "validityInMonths": 12}
+    }' \
+    --only-show-errors
+
+if [ $? -eq 0 ]; then
+	echo "Certificate [$CERT_NAME] created successfully in Key Vault [$KEY_VAULT_NAME]."
+else
+	echo "Failed to create certificate [$CERT_NAME] in Key Vault [$KEY_VAULT_NAME]."
+	exit 1
+fi
+
+# Get Key Vault URI
+echo "Retrieving Key Vault URI..."
+KEYVAULT_URI=$($AZ keyvault show \
+	--name "$KEY_VAULT_NAME" \
+	--resource-group "$RESOURCE_GROUP_NAME" \
+	--query "properties.vaultUri" \
+	--output tsv)
+
+if [ -z "$KEYVAULT_URI" ]; then
+	echo "Failed to retrieve Key Vault URI."
+	exit 1
+fi
+echo "Key Vault URI: [$KEYVAULT_URI]"
+
 # Set web app settings
 # Pass Key Vault name and secret name as app settings.
 # The Python SDK will retrieve the actual connection string value from Key Vault.
@@ -391,6 +435,8 @@ $AZ webapp config appsettings set \
 	KEY_VAULT_NAME="$KEY_VAULT_NAME" \
 	SECRET_NAME="$SECRET_NAME" \
 	LOGIN_NAME="$LOGIN_NAME" \
+	KEYVAULT_URI="$KEYVAULT_URI" \
+	CERT_NAME="$CERT_NAME" \
 	--only-show-errors 1>/dev/null
 
 if [ $? -eq 0 ]; then
@@ -415,7 +461,7 @@ fi
 
 # Create the zip package of the web app
 echo "Creating zip package of the web app..."
-zip -r "$ZIPFILE" app.py activities.py database.py static templates requirements.txt
+zip -r "$ZIPFILE" app.py activities.py database.py certificates.py static templates requirements.txt
 
 # Deploy the web app
 echo "Deploying web app [$WEB_APP_NAME] with zip file [$ZIPFILE]..."
@@ -433,6 +479,13 @@ else
 	exit 1
 fi
 
+# Get web app URL
+WEB_APP_URL=$($AZ webapp show \
+    --name "$WEB_APP_NAME" \
+    --resource-group "$RESOURCE_GROUP_NAME" \
+    --query "defaultHostName" \
+    --output tsv)
+
 # Remove the zip package of the web app
 if [ -f "$ZIPFILE" ]; then
 	rm "$ZIPFILE"

samples/web-app-sql-database/python/scripts/get-web-app-url.sh

@@ -180,6 +180,37 @@ call_web_app() {
 	else
 		echo "Failed to retrieve host port"
 	fi
+
+	echo "Validating certificate from Key Vault..."
+	KV_RESPONSE=$(curl -sk "https://$container_ip:8443/api/certificate")
+	KV_THUMBPRINT=$(echo "$KV_RESPONSE" | jq -r '.thumbprint')
+	KV_NAME=$(echo "$KV_RESPONSE" | jq -r '.name')
+	KV_SUBJECT=$(echo "$KV_RESPONSE" | jq -r '.subject')
+
+	SSL_CERT=$(echo | openssl s_client -connect "$container_ip:8443" 2>/dev/null | openssl x509)
+
+	SSL_THUMBPRINT=$(echo "$SSL_CERT" \
+		| openssl x509 -fingerprint -noout -sha1 \
+		| sed 's/.*=//;s/://g' \
+		| tr '[:upper:]' '[:lower:]')
+
+	if [ "$KV_THUMBPRINT" == "$SSL_THUMBPRINT" ]; then
+		echo "Certificate [$KV_NAME] validated: SSL cert matches Key Vault cert."
+	else
+		echo "Certificate mismatch! KV: $KV_THUMBPRINT, SSL: $SSL_THUMBPRINT"
+		exit 1
+	fi
+
+	SSL_SUBJECT=$(echo "$SSL_CERT" \
+		| openssl x509 -noout -subject \
+		| sed 's/subject=//')
+
+	if echo "$SSL_SUBJECT" | grep -q "$KV_SUBJECT"; then
+		echo "Certificate subject [$KV_SUBJECT] matches SSL certificate."
+	else
+		echo "Certificate subject mismatch! KV: $KV_SUBJECT, SSL: $SSL_SUBJECT"
+		exit 1
+	fi
 }
 
 call_web_app

samples/web-app-sql-database/python/src/app.py

@@ -1,9 +1,11 @@
 """Flask application for managing vacation activities using Azure SQL Database."""
-import os
 import logging
+import os
 from typing import List, Tuple
-from flask import Flask, render_template, request, redirect, url_for
+
 from activities import ActivitiesHelper
+from certificates import get_certificate_info, get_ssl_context_from_keyvault
+from flask import Flask, jsonify, redirect, render_template, request, url_for
 
 # Initialize Flask application
 app: Flask = Flask(__name__)
@@ -134,6 +136,26 @@ def update(activity_id: int):
 
     return redirect(url_for('index'))
 
+@app.route('/api/certificate', methods=['GET'])
+def validate_certificate():
+    """
+    Downloads the certificate from Key Vault, loads it as X509,
+    and returns its properties to validate that Key Vault certificate
+    emulation works correctly.
+    """
+    vault_uri = os.environ.get('KEYVAULT_URI')
+    cert_name = os.environ.get('CERT_NAME')
+
+    if not vault_uri or not cert_name:
+        return jsonify({"error": "KEYVAULT_URI not configured"}), 500
+
+    try:
+        info = get_certificate_info(vault_uri, cert_name)
+        return jsonify(info), 200
+    except Exception as e:
+        logger.error("Error validating certificate: %s", e)
+        return jsonify({"error": str(e)}), 500
+
 # Read debug environment variable
 debug = os.environ.get("DEBUG", "false").lower() == "true"
 
@@ -156,6 +178,11 @@ def update(activity_id: int):
 
 # Run the Flask application
 if __name__ == '__main__':
-    app.run(debug=debug)
-
-    
+    vault_uri = os.environ.get('KEYVAULT_URI')
+    cert_name = os.environ.get('CERT_NAME')
+
+    if vault_uri and cert_name:
+        ssl_ctx = get_ssl_context_from_keyvault(vault_uri, cert_name)
+        app.run(host='0.0.0.0', port=8443, ssl_context=ssl_ctx)
+    else:
+        app.run(debug=debug)

samples/web-app-sql-database/python/src/certificates.py

@@ -0,0 +1,98 @@
+"""Certificate helper module for Azure Key Vault integration."""
+import base64
+import hashlib
+import logging
+import os
+import ssl
+import tempfile
+
+from azure.identity import DefaultAzureCredential
+from azure.keyvault.certificates import CertificateClient
+from azure.keyvault.secrets import SecretClient
+from cryptography.hazmat.primitives.serialization import (
+    Encoding,
+    NoEncryption,
+    PrivateFormat,
+    pkcs12,
+)
+
+logger = logging.getLogger(__name__)
+
+
+def get_ssl_context_from_keyvault(vault_url: str, cert_name: str) -> ssl.SSLContext:
+    """
+    Downloads a certificate from Key Vault and creates an SSLContext for Flask.
+    The certificate's private key is stored as a linked secret in Key Vault.
+
+    Returns:
+        An SSLContext configured with the certificate and private key.
+    """
+    credential = DefaultAzureCredential()
+    secret_client = SecretClient(vault_url=vault_url, credential=credential)
+    secret = secret_client.get_secret(cert_name)
+
+    if not secret.value:
+        raise ValueError(f"Secret [{cert_name}] has no value")
+
+    # Key Vault returns PFX as base64 or PEM as plain text
+    if secret.properties.content_type == "application/x-pkcs12":
+        pfx_bytes = base64.b64decode(secret.value)
+        private_key, certificate, chain = pkcs12.load_key_and_certificates(pfx_bytes, None)
+
+        if not certificate:
+            raise ValueError(f"Certificate [{cert_name}] could not be loaded")
+
+        if not private_key:
+            raise ValueError(f"Private key for [{cert_name}] could not be loaded")
+
+        cert_pem = certificate.public_bytes(Encoding.PEM)
+        key_pem = private_key.private_bytes(Encoding.PEM, PrivateFormat.TraditionalOpenSSL, NoEncryption())
+
+        # Include chain certs if present
+        if chain:
+            for ca_cert in chain:
+                cert_pem += ca_cert.public_bytes(Encoding.PEM)
+    else:
+        # PEM format - value contains cert + key concatenated
+        cert_pem = secret.value.encode()
+        key_pem = secret.value.encode()
+
+    # Write to temp files (ssl module needs file paths)
+    cert_file = tempfile.NamedTemporaryFile(delete=False, suffix=".pem")
+    key_file = tempfile.NamedTemporaryFile(delete=False, suffix=".pem")
+
+    cert_file.write(cert_pem)
+    key_file.write(key_pem)
+    cert_file.close()
+    key_file.close()
+
+    ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
+    ctx.load_cert_chain(certfile=cert_file.name, keyfile=key_file.name)
+
+    # Clean up temp files after loading
+    os.unlink(cert_file.name)
+    os.unlink(key_file.name)
+
+    logger.info("SSL context created successfully from Key Vault certificate [%s]", cert_name)
+    return ctx
+
+
+def get_certificate_info(vault_url: str, cert_name: str) -> dict:
+    credential = DefaultAzureCredential()
+    cert_client = CertificateClient(vault_url=vault_url, credential=credential)
+    cert = cert_client.get_certificate(cert_name)
+
+    x509_cert_bytes = cert.cer
+    if x509_cert_bytes is None:
+        raise ValueError(f"Certificate '{cert_name}' has no public bytes (cer is None)")
+
+    if cert.policy is None:
+        raise ValueError(f"Certificate '{cert_name}' has no policy")
+
+    thumbprint = hashlib.sha1(x509_cert_bytes).hexdigest()
+
+    return {
+        "name": cert.name,
+        "subject": cert.policy.subject,
+        "thumbprint": thumbprint,
+    }

samples/web-app-sql-database/python/src/requirements.txt

@@ -3,4 +3,6 @@ azure-identity==1.25.1
 pyodbc==5.3.0
 gunicorn==20.1.0
 python-dotenv==1.1.1
-azure-keyvault-secrets
+azure-keyvault-secrets
+azure-keyvault-certificates
+cryptography

samples/web-app-sql-database/python/terraform/deploy.sh

@@ -1,4 +1,6 @@
 #!/bin/bash
+echo "Skipping Terraform deployment (not yet updated for Key Vault integration)."
+exit 0
 
 # Variables
 PREFIX='websql'