/// <summary>
/// Revokes an authorized key so it can no longer unlock the archive.
/// </summary>
/// <param name="authorizationId">The authorization ID of the key to revoke.</param>
/// <exception cref="InvalidOperationException">The specified authorization record was not found.</exception>
public void RevokeKey(Guid authorizationId)
{
var matchingAuthorizations = this.ArchiveMetadata.UserKeyAuthorizations
.Where(k => k.AuthorizationId == authorizationId)
.ToArray();
if (!matchingAuthorizations.Any())
{
throw new EntityNotFoundException(
$"Authorization with ID '{authorizationId}' was not found.");
}
if (matchingAuthorizations.Length > 1)
{
// There should never be two authorizations with the same ID.
// If this happens, fail closed to avoid any further archive corruption.
throw new ArchiveCorruptedException(
$"Found 2 key authorizations with ID '{authorizationId}'. Cancelling revocation operation.");
}
if (this.ArchiveMetadata.UserKeyAuthorizations.Count == 1)
{
throw new InvalidOperationException($"Can't revoke the last authorized key.");
}
// We'll track the item being removed. If saving the changes fails, we'll
// revert the removal to put the in-memory structure back into a consistent state.
UserKeyAuthorization removedAuthorization = null;
int removedIndex = -1;
for (int i = 0; i < this.ArchiveMetadata.UserKeyAuthorizations.Count; i++)
{
if (this.ArchiveMetadata.UserKeyAuthorizations[i].AuthorizationId == authorizationId)
{
removedAuthorization = this.ArchiveMetadata.UserKeyAuthorizations[i];
removedIndex = i;
this.ArchiveMetadata.UserKeyAuthorizations.RemoveAt(i);
break;
}
}
try
{
this.PersistMetadata();
}
catch
{
// Revert the change. Keep in-memory structure consistent.
this.ArchiveMetadata.UserKeyAuthorizations.Insert(
removedIndex,
removedAuthorization);
throw;
}
}
public static bool TryDecryptArchiveKey(
this UserKeyAuthorization authorization,
UserKey userKey,
SecuritySettings securitySettings,
out ArchiveKey archiveKey)
{
ArgCheck.NotNull(authorization, nameof(authorization));
ArgCheck.NotNull(userKey, nameof(userKey));
ArgCheck.IsValid(securitySettings, nameof(securitySettings));
archiveKey = null;
if (!CryptoHelpers.SecureEquals(userKey.KeyId, authorization.KeyId))
{
return(false);
}
try
{
// The SecureArchive file format requires that the friendly name and keyId be
// checked for tampering when using authenticated cyphers.
var additionalData = Encoding.UTF8.GetBytes(authorization.FriendlyName + authorization.KeyId);
var cryptoStrategy = CryptoHelpers.GetCryptoStrategy(securitySettings.EncryptionAlgo);
var decryptedArchiveKey = userKey.Decrypt(cryptoStrategy, authorization.EncryptedArchiveKey, additionalData);
if (!decryptedArchiveKey.IsEmpty)
{
archiveKey = new ArchiveKey(decryptedArchiveKey.ToArray());
}
}
catch
{
return(false);
}
return(archiveKey != null);
}
