diff options
Diffstat (limited to 'src/DotNetOpenAuth.OpenId/OpenId/Provider/PrivatePersonalIdentifierProviderBase.cs')
| -rw-r--r-- | src/DotNetOpenAuth.OpenId/OpenId/Provider/PrivatePersonalIdentifierProviderBase.cs | 224 |
1 files changed, 224 insertions, 0 deletions
diff --git a/src/DotNetOpenAuth.OpenId/OpenId/Provider/PrivatePersonalIdentifierProviderBase.cs b/src/DotNetOpenAuth.OpenId/OpenId/Provider/PrivatePersonalIdentifierProviderBase.cs new file mode 100644 index 0000000..46e172c --- /dev/null +++ b/src/DotNetOpenAuth.OpenId/OpenId/Provider/PrivatePersonalIdentifierProviderBase.cs @@ -0,0 +1,224 @@ +//----------------------------------------------------------------------- +// <copyright file="PrivatePersonalIdentifierProviderBase.cs" company="Andrew Arnott"> +// Copyright (c) Andrew Arnott. All rights reserved. +// </copyright> +//----------------------------------------------------------------------- + +namespace DotNetOpenAuth.OpenId.Provider { + using System; + using System.Collections.Generic; + using System.Diagnostics.CodeAnalysis; + using System.Diagnostics.Contracts; + using System.Globalization; + using System.Linq; + using System.Security.Cryptography; + using System.Text; + using DotNetOpenAuth.Messaging; + + /// <summary> + /// Provides standard PPID Identifiers to users to protect their identity from individual relying parties + /// and from colluding groups of relying parties. + /// </summary> + public abstract class PrivatePersonalIdentifierProviderBase : IDirectedIdentityIdentifierProvider { + /// <summary> + /// The type of hash function to use for the <see cref="Hasher"/> property. + /// </summary> + private const string HashAlgorithmName = "SHA256"; + + /// <summary> + /// The length of the salt to generate for first time PPID-users. + /// </summary> + private int newSaltLength = 20; + + /// <summary> + /// Initializes a new instance of the <see cref="PrivatePersonalIdentifierProviderBase"/> class. + /// </summary> + /// <param name="baseIdentifier">The base URI on which to append the anonymous part.</param> + protected PrivatePersonalIdentifierProviderBase(Uri baseIdentifier) { + Contract.Requires<ArgumentNullException>(baseIdentifier != null); + + this.Hasher = HashAlgorithm.Create(HashAlgorithmName); + this.Encoder = Encoding.UTF8; + this.BaseIdentifier = baseIdentifier; + this.PairwiseUnique = AudienceScope.Realm; + } + + /// <summary> + /// A granularity description for who wide of an audience sees the same generated PPID. + /// </summary> + [SuppressMessage("Microsoft.Design", "CA1034:NestedTypesShouldNotBeVisible", Justification = "Breaking change")] + public enum AudienceScope { + /// <summary> + /// A unique Identifier is generated for every realm. This is the highest security setting. + /// </summary> + Realm, + + /// <summary> + /// Only the host name in the realm is used in calculating the PPID, + /// allowing for some level of sharing of the PPID Identifiers between RPs + /// that are able to share the same realm host value. + /// </summary> + RealmHost, + + /// <summary> + /// Although the user's Identifier is still opaque to the RP so they cannot determine + /// who the user is at the OP, the same Identifier is used at all RPs so collusion + /// between the RPs is possible. + /// </summary> + Global, + } + + /// <summary> + /// Gets the base URI on which to append the anonymous part. + /// </summary> + public Uri BaseIdentifier { get; private set; } + + /// <summary> + /// Gets or sets a value indicating whether each Realm will get its own private identifier + /// for the authenticating uesr. + /// </summary> + /// <value>The default value is <see cref="AudienceScope.Realm"/>.</value> + [SuppressMessage("Microsoft.Naming", "CA1704:IdentifiersShouldBeSpelledCorrectly", MessageId = "Pairwise", Justification = "Meaningful word")] + public AudienceScope PairwiseUnique { get; set; } + + /// <summary> + /// Gets the hash function to use to perform the one-way transform of a personal identifier + /// to an "anonymous" looking one. + /// </summary> + protected HashAlgorithm Hasher { get; private set; } + + /// <summary> + /// Gets the encoder to use for transforming the personal identifier into bytes for hashing. + /// </summary> + protected Encoding Encoder { get; private set; } + + /// <summary> + /// Gets or sets the new length of the salt. + /// </summary> + /// <value>The new length of the salt.</value> + protected int NewSaltLength { + get { + return this.newSaltLength; + } + + set { + Contract.Requires<ArgumentOutOfRangeException>(value > 0); + this.newSaltLength = value; + } + } + + #region IDirectedIdentityIdentifierProvider Members + + /// <summary> + /// Gets the Identifier to use for the Claimed Identifier and Local Identifier of + /// an outgoing positive assertion. + /// </summary> + /// <param name="localIdentifier">The OP local identifier for the authenticating user.</param> + /// <param name="relyingPartyRealm">The realm of the relying party receiving the assertion.</param> + /// <returns> + /// A valid, discoverable OpenID Identifier that should be used as the value for the + /// openid.claimed_id and openid.local_id parameters. Must not be null. + /// </returns> + public Uri GetIdentifier(Identifier localIdentifier, Realm relyingPartyRealm) { + byte[] salt = this.GetHashSaltForLocalIdentifier(localIdentifier); + string valueToHash = localIdentifier + "#"; + switch (this.PairwiseUnique) { + case AudienceScope.Realm: + valueToHash += relyingPartyRealm; + break; + case AudienceScope.RealmHost: + valueToHash += relyingPartyRealm.Host; + break; + case AudienceScope.Global: + break; + default: + throw new InvalidOperationException( + string.Format( + CultureInfo.CurrentCulture, + OpenIdStrings.UnexpectedEnumPropertyValue, + "PairwiseUnique", + this.PairwiseUnique)); + } + + byte[] valueAsBytes = this.Encoder.GetBytes(valueToHash); + byte[] bytesToHash = new byte[valueAsBytes.Length + salt.Length]; + valueAsBytes.CopyTo(bytesToHash, 0); + salt.CopyTo(bytesToHash, valueAsBytes.Length); + byte[] hash = this.Hasher.ComputeHash(bytesToHash); + string base64Hash = Convert.ToBase64String(hash); + Uri anonymousIdentifier = this.AppendIdentifiers(base64Hash); + return anonymousIdentifier; + } + + /// <summary> + /// Determines whether a given identifier is the primary (non-PPID) local identifier for some user. + /// </summary> + /// <param name="identifier">The identifier in question.</param> + /// <returns> + /// <c>true</c> if the given identifier is the valid, unique identifier for some uesr (and NOT a PPID); otherwise, <c>false</c>. + /// </returns> + public virtual bool IsUserLocalIdentifier(Identifier identifier) + { + return !identifier.ToString().StartsWith(this.BaseIdentifier.AbsoluteUri, StringComparison.Ordinal); + } + + #endregion + + /// <summary> + /// Creates a new salt to assign to a user. + /// </summary> + /// <returns>A non-null buffer of length <see cref="NewSaltLength"/> filled with a random salt.</returns> + protected virtual byte[] CreateSalt() { + // We COULD use a crypto random function, but for a salt it seems overkill. + return MessagingUtilities.GetNonCryptoRandomData(this.NewSaltLength); + } + + /// <summary> + /// Creates a new PPID Identifier by appending a pseudonymous identifier suffix to + /// the <see cref="BaseIdentifier"/>. + /// </summary> + /// <param name="uriHash">The unique part of the Identifier to append to the common first part.</param> + /// <returns>The full PPID Identifier.</returns> + [SuppressMessage("Microsoft.Usage", "CA2234:PassSystemUriObjectsInsteadOfStrings", Justification = "NOT equivalent overload. The recommended one breaks on relative URIs.")] + protected virtual Uri AppendIdentifiers(string uriHash) { + Contract.Requires<ArgumentException>(!String.IsNullOrEmpty(uriHash)); + + if (string.IsNullOrEmpty(this.BaseIdentifier.Query)) { + // The uriHash will appear on the path itself. + string pathEncoded = Uri.EscapeUriString(uriHash.Replace('/', '_')); + return new Uri(this.BaseIdentifier, pathEncoded); + } else { + // The uriHash will appear on the query string. + string dataEncoded = Uri.EscapeDataString(uriHash); + return new Uri(this.BaseIdentifier + dataEncoded); + } + } + + /// <summary> + /// Gets the salt to use for generating an anonymous identifier for a given OP local identifier. + /// </summary> + /// <param name="localIdentifier">The OP local identifier.</param> + /// <returns>The salt to use in the hash.</returns> + /// <remarks> + /// It is important that this method always return the same value for a given + /// <paramref name="localIdentifier"/>. + /// New salts can be generated for local identifiers without previously assigned salt + /// values by calling <see cref="CreateSalt"/> or by a custom method. + /// </remarks> + protected abstract byte[] GetHashSaltForLocalIdentifier(Identifier localIdentifier); + +#if CONTRACTS_FULL + /// <summary> + /// Verifies conditions that should be true for any valid state of this object. + /// </summary> + [SuppressMessage("Microsoft.Performance", "CA1811:AvoidUncalledPrivateCode", Justification = "Called by code contracts.")] + [ContractInvariantMethod] + private void ObjectInvariant() { + Contract.Invariant(this.Hasher != null); + Contract.Invariant(this.Encoder != null); + Contract.Invariant(this.BaseIdentifier != null); + Contract.Invariant(this.NewSaltLength > 0); + } +#endif + } +} |