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| title | author | description | ms.author | ms.custom | ms.date | no-loc | uid | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Safe storage of app secrets in development in ASP.NET Core | rick-anderson | Learn how to store and retrieve sensitive information as app secrets during the development of an ASP.NET Core app. | scaddie | mvc | 4/20/2020 |
|
security/app-secrets |
Safe storage of app secrets in development in ASP.NET Core
::: moniker range=">= aspnetcore-3.0"
By Rick Anderson, Kirk Larkin, Daniel Roth, and Scott Addie
View or download sample code (how to download)
This document explains techniques for storing and retrieving sensitive data during development of an ASP.NET Core app on a development machine. Never store passwords or other sensitive data in source code. Production secrets shouldn't be used for development or test. Secrets shouldn't be deployed with the app. Instead, secrets should be made available in the production environment through a controlled means like environment variables, Azure Key Vault, etc. You can store and protect Azure test and production secrets with the Azure Key Vault configuration provider.
Environment variables
Environment variables are used to avoid storage of app secrets in code or in local configuration files. Environment variables override configuration values for all previously specified configuration sources.
Consider an ASP.NET Core web app in which Individual User Accounts security is enabled. A default database connection string is included in the project's appsettings.json file with the key DefaultConnection. The default connection string is for LocalDB, which runs in user mode and doesn't require a password. During app deployment, the DefaultConnection key value can be overridden with an environment variable's value. The environment variable may store the complete connection string with sensitive credentials.
[!WARNING] Environment variables are generally stored in plain, unencrypted text. If the machine or process is compromised, environment variables can be accessed by untrusted parties. Additional measures to prevent disclosure of user secrets may be required.
Secret Manager
The Secret Manager tool stores sensitive data during the development of an ASP.NET Core project. In this context, a piece of sensitive data is an app secret. App secrets are stored in a separate location from the project tree. The app secrets are associated with a specific project or shared across several projects. The app secrets aren't checked into source control.
[!WARNING] The Secret Manager tool doesn't encrypt the stored secrets and shouldn't be treated as a trusted store. It's for development purposes only. The keys and values are stored in a JSON configuration file in the user profile directory.
How the Secret Manager tool works
The Secret Manager tool abstracts away the implementation details, such as where and how the values are stored. You can use the tool without knowing these implementation details. The values are stored in a JSON configuration file in a system-protected user profile folder on the local machine:
Windows
File system path:
%APPDATA%\Microsoft\UserSecrets\<user_secrets_id>\secrets.json
Linux / macOS
File system path:
~/.microsoft/usersecrets/<user_secrets_id>/secrets.json
In the preceding file paths, replace <user_secrets_id> with the UserSecretsId value specified in the .csproj file.
Don't write code that depends on the location or format of data saved with the Secret Manager tool. These implementation details may change. For example, the secret values aren't encrypted, but could be in the future.
Enable secret storage
The Secret Manager tool operates on project-specific configuration settings stored in your user profile.
The Secret Manager tool includes an init command in .NET Core SDK 3.0.100 or later. To use user secrets, run the following command in the project directory:
dotnet user-secrets init
The preceding command adds a UserSecretsId element within a PropertyGroup of the .csproj file. By default, the inner text of UserSecretsId is a GUID. The inner text is arbitrary, but is unique to the project.
In Visual Studio, right-click the project in Solution Explorer, and select Manage User Secrets from the context menu. This gesture adds a UserSecretsId element, populated with a GUID, to the .csproj file.
Set a secret
Define an app secret consisting of a key and its value. The secret is associated with the project's UserSecretsId value. For example, run the following command from the directory in which the .csproj file exists:
dotnet user-secrets set "Movies:ServiceApiKey" "12345"
In the preceding example, the colon denotes that Movies is an object literal with a ServiceApiKey property.
The Secret Manager tool can be used from other directories too. Use the --project option to supply the file system path at which the .csproj file exists. For example:
dotnet user-secrets set "Movies:ServiceApiKey" "12345" --project "C:\apps\WebApp1\src\WebApp1"
JSON structure flattening in Visual Studio
Visual Studio's Manage User Secrets gesture opens a secrets.json file in the text editor. Replace the contents of secrets.json with the key-value pairs to be stored. For example:
{
"Movies": {
"ConnectionString": "Server=(localdb)\\mssqllocaldb;Database=Movie-1;Trusted_Connection=True;MultipleActiveResultSets=true",
"ServiceApiKey": "12345"
}
}
The JSON structure is flattened after modifications via dotnet user-secrets remove or dotnet user-secrets set. For example, running dotnet user-secrets remove "Movies:ConnectionString" collapses the Movies object literal. The modified file resembles the following:
{
"Movies:ServiceApiKey": "12345"
}
Set multiple secrets
A batch of secrets can be set by piping JSON to the set command. In the following example, the input.json file's contents are piped to the set command.
Windows
Open a command shell, and execute the following command:
type .\input.json | dotnet user-secrets set
Linux / macOS
Open a command shell, and execute the following command:
cat ./input.json | dotnet user-secrets set
Access a secret
The ASP.NET Core Configuration API provides access to Secret Manager secrets.
The user secrets configuration source is automatically added in development mode when the project calls xref:Microsoft.Extensions.Hosting.Host.CreateDefaultBuilder%2A to initialize a new instance of the host with preconfigured defaults. CreateDefaultBuilder calls xref:Microsoft.Extensions.Configuration.UserSecretsConfigurationExtensions.AddUserSecrets%2A when the xref:Microsoft.Extensions.Hosting.IHostEnvironment.EnvironmentName is xref:Microsoft.Extensions.Hosting.EnvironmentName.Development:
When CreateDefaultBuilder isn't called, add the user secrets configuration source explicitly by calling xref:Microsoft.Extensions.Configuration.UserSecretsConfigurationExtensions.AddUserSecrets%2A. Call AddUserSecrets only when the app runs in the Development environment, as shown in the following example:
User secrets can be retrieved via the Configuration API:
Map secrets to a POCO
Mapping an entire object literal to a POCO (a simple .NET class with properties) is useful for aggregating related properties.
[!INCLUDEsecrets.json file]
To map the preceding secrets to a POCO, use the Configuration API's object graph binding feature. The following code binds to a custom MovieSettings POCO and accesses the ServiceApiKey property value:
The Movies:ConnectionString and Movies:ServiceApiKey secrets are mapped to the respective properties in MovieSettings:
String replacement with secrets
Storing passwords in plain text is insecure. For example, a database connection string stored in appsettings.json may include a password for the specified user:
A more secure approach is to store the password as a secret. For example:
dotnet user-secrets set "DbPassword" "pass123"
Remove the Password key-value pair from the connection string in appsettings.json. For example:
The secret's value can be set on a xref:System.Data.SqlClient.SqlConnectionStringBuilder object's xref:System.Data.SqlClient.SqlConnectionStringBuilder.Password%2A property to complete the connection string:
List the secrets
[!INCLUDEsecrets.json file]
Run the following command from the directory in which the .csproj file exists:
dotnet user-secrets list
The following output appears:
Movies:ConnectionString = Server=(localdb)\mssqllocaldb;Database=Movie-1;Trusted_Connection=True;MultipleActiveResultSets=true
Movies:ServiceApiKey = 12345
In the preceding example, a colon in the key names denotes the object hierarchy within secrets.json.
Remove a single secret
[!INCLUDEsecrets.json file]
Run the following command from the directory in which the .csproj file exists:
dotnet user-secrets remove "Movies:ConnectionString"
The app's secrets.json file was modified to remove the key-value pair associated with the MoviesConnectionString key:
{
"Movies": {
"ServiceApiKey": "12345"
}
}
dotnet user-secrets list displays the following message:
Movies:ServiceApiKey = 12345
Remove all secrets
[!INCLUDEsecrets.json file]
Run the following command from the directory in which the .csproj file exists:
dotnet user-secrets clear
All user secrets for the app have been deleted from the secrets.json file:
{}
Running dotnet user-secrets list displays the following message:
No secrets configured for this application.
Additional resources
- See this issue for information on accessing Secret Manager from IIS.
- xref:fundamentals/configuration/index
- xref:security/key-vault-configuration
::: moniker-end
::: moniker range="< aspnetcore-3.0"
By Rick Anderson, Daniel Roth, and Scott Addie
View or download sample code (how to download)
This document explains techniques for storing and retrieving sensitive data during development of an ASP.NET Core app on a development machine. Never store passwords or other sensitive data in source code. Production secrets shouldn't be used for development or test. Secrets shouldn't be deployed with the app. Instead, secrets should be made available in the production environment through a controlled means like environment variables, Azure Key Vault, etc. You can store and protect Azure test and production secrets with the Azure Key Vault configuration provider.
Environment variables
Environment variables are used to avoid storage of app secrets in code or in local configuration files. Environment variables override configuration values for all previously specified configuration sources.
Consider an ASP.NET Core web app in which Individual User Accounts security is enabled. A default database connection string is included in the project's appsettings.json file with the key DefaultConnection. The default connection string is for LocalDB, which runs in user mode and doesn't require a password. During app deployment, the DefaultConnection key value can be overridden with an environment variable's value. The environment variable may store the complete connection string with sensitive credentials.
[!WARNING] Environment variables are generally stored in plain, unencrypted text. If the machine or process is compromised, environment variables can be accessed by untrusted parties. Additional measures to prevent disclosure of user secrets may be required.
Secret Manager
The Secret Manager tool stores sensitive data during the development of an ASP.NET Core project. In this context, a piece of sensitive data is an app secret. App secrets are stored in a separate location from the project tree. The app secrets are associated with a specific project or shared across several projects. The app secrets aren't checked into source control.
[!WARNING] The Secret Manager tool doesn't encrypt the stored secrets and shouldn't be treated as a trusted store. It's for development purposes only. The keys and values are stored in a JSON configuration file in the user profile directory.
How the Secret Manager tool works
The Secret Manager tool abstracts away the implementation details, such as where and how the values are stored. You can use the tool without knowing these implementation details. The values are stored in a JSON configuration file in a system-protected user profile folder on the local machine:
Windows
File system path:
%APPDATA%\Microsoft\UserSecrets\<user_secrets_id>\secrets.json
Linux / macOS
File system path:
~/.microsoft/usersecrets/<user_secrets_id>/secrets.json
In the preceding file paths, replace <user_secrets_id> with the UserSecretsId value specified in the .csproj file.
Don't write code that depends on the location or format of data saved with the Secret Manager tool. These implementation details may change. For example, the secret values aren't encrypted, but could be in the future.
Enable secret storage
The Secret Manager tool operates on project-specific configuration settings stored in your user profile.
To use user secrets, define a UserSecretsId element within a PropertyGroup of the .csproj file. The inner text of UserSecretsId is arbitrary, but is unique to the project. Developers typically generate a GUID for the UserSecretsId.
[!TIP] In Visual Studio, right-click the project in Solution Explorer, and select Manage User Secrets from the context menu. This gesture adds a
UserSecretsIdelement, populated with a GUID, to the .csproj file.
Set a secret
Define an app secret consisting of a key and its value. The secret is associated with the project's UserSecretsId value. For example, run the following command from the directory in which the .csproj file exists:
dotnet user-secrets set "Movies:ServiceApiKey" "12345"
In the preceding example, the colon denotes that Movies is an object literal with a ServiceApiKey property.
The Secret Manager tool can be used from other directories too. Use the --project option to supply the file system path at which the .csproj file exists. For example:
dotnet user-secrets set "Movies:ServiceApiKey" "12345" --project "C:\apps\WebApp1\src\WebApp1"
JSON structure flattening in Visual Studio
Visual Studio's Manage User Secrets gesture opens a secrets.json file in the text editor. Replace the contents of secrets.json with the key-value pairs to be stored. For example:
{
"Movies": {
"ConnectionString": "Server=(localdb)\\mssqllocaldb;Database=Movie-1;Trusted_Connection=True;MultipleActiveResultSets=true",
"ServiceApiKey": "12345"
}
}
The JSON structure is flattened after modifications via dotnet user-secrets remove or dotnet user-secrets set. For example, running dotnet user-secrets remove "Movies:ConnectionString" collapses the Movies object literal. The modified file resembles the following:
{
"Movies:ServiceApiKey": "12345"
}
Set multiple secrets
A batch of secrets can be set by piping JSON to the set command. In the following example, the input.json file's contents are piped to the set command.
Windows
Open a command shell, and execute the following command:
type .\input.json | dotnet user-secrets set
Linux / macOS
Open a command shell, and execute the following command:
cat ./input.json | dotnet user-secrets set
Access a secret
The ASP.NET Core Configuration API provides access to Secret Manager secrets.
If your project targets .NET Framework, install the Microsoft.Extensions.Configuration.UserSecrets NuGet package.
In ASP.NET Core 2.0 or later, the user secrets configuration source is automatically added in development mode when the project calls xref:Microsoft.AspNetCore.WebHost.CreateDefaultBuilder%2A to initialize a new instance of the host with preconfigured defaults. CreateDefaultBuilder calls xref:Microsoft.Extensions.Configuration.UserSecretsConfigurationExtensions.AddUserSecrets%2A when the xref:Microsoft.AspNetCore.Hosting.IHostingEnvironment.EnvironmentName is xref:Microsoft.AspNetCore.Hosting.EnvironmentName.Development:
When CreateDefaultBuilder isn't called, add the user secrets configuration source explicitly by calling xref:Microsoft.Extensions.Configuration.UserSecretsConfigurationExtensions.AddUserSecrets%2A in the Startup constructor. Call AddUserSecrets only when the app runs in the Development environment, as shown in the following example:
User secrets can be retrieved via the Configuration API:
Map secrets to a POCO
Mapping an entire object literal to a POCO (a simple .NET class with properties) is useful for aggregating related properties.
[!INCLUDEsecrets.json file]
To map the preceding secrets to a POCO, use the Configuration API's object graph binding feature. The following code binds to a custom MovieSettings POCO and accesses the ServiceApiKey property value:
The Movies:ConnectionString and Movies:ServiceApiKey secrets are mapped to the respective properties in MovieSettings:
String replacement with secrets
Storing passwords in plain text is insecure. For example, a database connection string stored in appsettings.json may include a password for the specified user:
A more secure approach is to store the password as a secret. For example:
dotnet user-secrets set "DbPassword" "pass123"
Remove the Password key-value pair from the connection string in appsettings.json. For example:
The secret's value can be set on a xref:System.Data.SqlClient.SqlConnectionStringBuilder object's xref:System.Data.SqlClient.SqlConnectionStringBuilder.Password%2A property to complete the connection string:
List the secrets
[!INCLUDEsecrets.json file]
Run the following command from the directory in which the .csproj file exists:
dotnet user-secrets list
The following output appears:
Movies:ConnectionString = Server=(localdb)\mssqllocaldb;Database=Movie-1;Trusted_Connection=True;MultipleActiveResultSets=true
Movies:ServiceApiKey = 12345
In the preceding example, a colon in the key names denotes the object hierarchy within secrets.json.
Remove a single secret
[!INCLUDEsecrets.json file]
Run the following command from the directory in which the .csproj file exists:
dotnet user-secrets remove "Movies:ConnectionString"
The app's secrets.json file was modified to remove the key-value pair associated with the MoviesConnectionString key:
{
"Movies": {
"ServiceApiKey": "12345"
}
}
Running dotnet user-secrets list displays the following message:
Movies:ServiceApiKey = 12345
Remove all secrets
[!INCLUDEsecrets.json file]
Run the following command from the directory in which the .csproj file exists:
dotnet user-secrets clear
All user secrets for the app have been deleted from the secrets.json file:
{}
Running dotnet user-secrets list displays the following message:
No secrets configured for this application.
Additional resources
- See this issue for information on accessing Secret Manager from IIS.
- xref:fundamentals/configuration/index
- xref:security/key-vault-configuration
::: moniker-end