[API Proposal]: Customizable IConfigurationRoot.GetDebugView() for hiding the value

[oskrabanek]

Background and motivation

As the GetDebugView() method will display the whole configuration, we want to have it in logs for debug purposes. This brings a security risk as some secrets such as connection string, Identity credentials and others might be included in the configuration.

API Proposal

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Microsoft.Extensions.Configuration
{
    /// <summary>
    /// Extension methods for <see cref="IConfigurationRoot"/>.
    /// </summary>
    public static class ConfigurationRootExtensions
    {
        /// <summary>
        /// Generates a human-readable view of the configuration showing where each value came from.
        /// </summary>
        /// <returns> The debug view. </returns>
        public static string GetDebugView(this IConfigurationRoot root)
        {
            return GetDebugView(root, null);
        }

        /// <summary>
        /// Generates a human-readable view of the configuration showing where each value came from.
        /// </summary>
        /// <param name="root">Configuration root</param>
        /// <param name="processValue">
        /// Function for processing the value e.g. hiding secrets
        /// Parameters:
        ///   Key: Key of the current configuration section
        ///   Path: Full path to the configuration section
        ///   Value: Value of the configuration section
        ///   ConfigurationProvider: Provider of the value of the configuration section
        ///   returns: Value is used to assign as the Value of the configuration section
        /// </param>
        /// <returns> The debug view. </returns>
        public static string GetDebugView(this IConfigurationRoot root, Func<string, string, string, IConfigurationProvider, string> processValue)
        {
            void RecurseChildren(
                StringBuilder stringBuilder,
                IEnumerable<IConfigurationSection> children,
                string indent)
            {
                foreach (IConfigurationSection child in children)
                {
                    (string Value, IConfigurationProvider Provider) valueAndProvider = GetValueAndProvider(root, child.Path);

                    if (valueAndProvider.Provider != null)
                    {
                        var value = processValue != null
                            ? processValue(child.Key, child.Path, valueAndProvider.Value, valueAndProvider.Provider)
                            : valueAndProvider.Value;

                        stringBuilder
                            .Append(indent)
                            .Append(child.Key)
                            .Append('=')
                            .Append(value)
                            .Append(" (")
                            .Append(valueAndProvider.Provider)
                            .AppendLine(")");
                    }
                    else
                    {
                        stringBuilder
                            .Append(indent)
                            .Append(child.Key)
                            .AppendLine(":");
                    }

                    RecurseChildren(stringBuilder, child.GetChildren(), indent + "  ");
                }
            }

            var builder = new StringBuilder();

            RecurseChildren(builder, root.GetChildren(), "");

            return builder.ToString();
        }

        private static (string Value, IConfigurationProvider Provider) GetValueAndProvider(
            IConfigurationRoot root,
            string key)
        {
            foreach (IConfigurationProvider provider in root.Providers.Reverse())
            {
                if (provider.TryGet(key, out string value))
                {
                    return (value, provider);
                }
            }

            return (null, null);
        }
    }
}

API Usage

public Startup(IWebHostEnvironment env, IConfiguration configuration)
{
    ...
  
    if (configuration is IConfigurationRoot configurationRoot)
    {
        var startupLoggerFactory = StartupLoggerHelper.CreateStartupLoggerFactory(configuration, env);
        var startupLogger = startupLoggerFactory.CreateLogger<Startup>();
        startupLogger.LogDebug(configurationRoot.GetDebugView(HideSecrets));
    }
}

private string HideSecrets(string key, string path, string value, IConfigurationProvider provider)
{
    var providerName = provider.ToString();
    if (providerName.Contains("KeyVault"))
    {
        return "*** secret ***";
    }

    return value;
}

Risks

None as far as I know.

Tagging subscribers to this area: @maryamariyan, @safern
See info in area-owners.md if you want to be subscribed.

Issue Details

---

Background and motivation

As the GetDebugView() method will display the whole configuration, we want to have it in logs for debug purposes. This brings a security risk as some secrets such as connection string, Identity credentials and others might be included in the configuration.

API Proposal

// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Microsoft.Extensions.Configuration
{
    /// <summary>
    /// Extension methods for <see cref="IConfigurationRoot"/>.
    /// </summary>
    public static class ConfigurationRootExtensions
    {
        /// <summary>
        /// Generates a human-readable view of the configuration showing where each value came from.
        /// </summary>
        /// <returns> The debug view. </returns>
        public static string GetDebugView(this IConfigurationRoot root)
        {
            return GetDebugView(root, null);
        }

        /// <summary>
        /// Generates a human-readable view of the configuration showing where each value came from.
        /// </summary>
        /// <param name="root">Configuration root</param>
        /// <param name="processValue">
        /// Function for processing the value e.g. hiding secrets
        /// Parameters:
        ///   Key: Key of the current configuration section
        ///   Path: Full path to the configuration section
        ///   Value: Value of the configuration section
        ///   ConfigurationProvider: Provider of the value of the configuration section
        ///   returns: Value is used to assign as the Value of the configuration section
        /// </param>
        /// <returns> The debug view. </returns>
        public static string GetDebugView(this IConfigurationRoot root, Func<string, string, string, IConfigurationProvider, string> processValue)
        {
            void RecurseChildren(
                StringBuilder stringBuilder,
                IEnumerable<IConfigurationSection> children,
                string indent)
            {
                foreach (IConfigurationSection child in children)
                {
                    (string Value, IConfigurationProvider Provider) valueAndProvider = GetValueAndProvider(root, child.Path);

                    if (valueAndProvider.Provider != null)
                    {
                        var value = processValue != null
                            ? processValue(child.Key, child.Path, valueAndProvider.Value, valueAndProvider.Provider)
                            : valueAndProvider.Value;

                        stringBuilder
                            .Append(indent)
                            .Append(child.Key)
                            .Append('=')
                            .Append(value)
                            .Append(" (")
                            .Append(valueAndProvider.Provider)
                            .AppendLine(")");
                    }
                    else
                    {
                        stringBuilder
                            .Append(indent)
                            .Append(child.Key)
                            .AppendLine(":");
                    }

                    RecurseChildren(stringBuilder, child.GetChildren(), indent + "  ");
                }
            }

            var builder = new StringBuilder();

            RecurseChildren(builder, root.GetChildren(), "");

            return builder.ToString();
        }

        private static (string Value, IConfigurationProvider Provider) GetValueAndProvider(
            IConfigurationRoot root,
            string key)
        {
            foreach (IConfigurationProvider provider in root.Providers.Reverse())
            {
                if (provider.TryGet(key, out string value))
                {
                    return (value, provider);
                }
            }

            return (null, null);
        }
    }
}

API Usage

public Startup(IWebHostEnvironment env, IConfiguration configuration)
{
    ...
  
    if (configuration is IConfigurationRoot configurationRoot)
    {
        var startupLoggerFactory = StartupLoggerHelper.CreateStartupLoggerFactory(configuration, env);
        var startupLogger = startupLoggerFactory.CreateLogger<Startup>();
        startupLogger.LogDebug(configurationRoot.GetDebugView(HideSecrets));
    }
}

private string HideSecrets(string key, string path, string value, IConfigurationProvider provider)
{
    var providerName = provider.ToString();
    if (providerName.Contains("KeyVault"))
    {
        return "*** secret ***";
    }

    return value;
}

Risks

None as far as I know.

Author:	Andree643
Assignees:	-
Labels:	api-suggestion, untriaged, area-Extensions-Configuration
Milestone:	-

[safern]

@Andree643 seems reasonable to me. I do have a question, do you see a scenario where someone might care about the key and the path when processing the value, or is the Provider enough to know if it is a secret value or not?

[oskrabanek]

@Andree643 seems reasonable to me. I do have a question, do you see a scenario where someone might care about the key and the path when processing the value, or is the Provider enough to know if it is a secret value or not?

@safern I actually do. At least the path is really useful when you want to hide only a single specific value by exact path or to check the path for existence of some substring such as "ConnectionString". At least I assume it would be helpful to give the developers access to these properties since we have them and might be useful for them.

The key might not be needed as it's already as a suffix of the path, but it can be more efficient to check only the key when needed rather then parsing the path.

[safern]

Sounds good. I'll mark it as ready for review as it looks good as proposed, we can discuss if we want the key or not during the review of the API.

[terrajobst]

Video

• The scenario makes sense but we don't like the use of Func because it's not clear what the first three strings
• Should Value be nullable?

namespace Microsoft.Extensions.Configuration
{
    public readonly struct ConfigurationDebugViewContext
    {
        public ConfigurationDebugViewContext(string path, string key, string value, IConfigurationProvider configurationProvider);
        public string Path { get; }
        public string Key { get; }
        public string Value { get; }
        public IConfigurationProvider ConfigurationProvider { get; }
    }

    public static class ConfigurationRootExtensions
    {
        // Existing
        // public static string GetDebugView(this IConfigurationRoot root);
        public static string GetDebugView(this IConfigurationRoot root, Func<ConfigurationDebugViewContext, string> processValue);
    }
}