/// <summary>
/// Queries a the upstream DNS server(s) for specified records.
/// </summary>
/// <typeparam name="T"> Type of records, that should be returned </typeparam>
/// <param name="name"> Domain, that should be queried </param>
/// <param name="recordType"> Type the should be queried </param>
/// <param name="recordClass"> Class the should be queried </param>
/// <returns> A list of matching <see cref="DnsRecordBase">records</see> </returns>
public List <T> Resolve <T>(DomainName name, RecordType recordType = RecordType.A, RecordClass recordClass = RecordClass.INet)
where T : DnsRecordBase
{
if (name == null)
{
throw new ArgumentNullException(nameof(name), "Name must be provided");
}
List <T> records;
if (_cache.TryGetRecords(name, recordType, recordClass, out records))
{
return(records);
}
DnsMessage msg = _dnsClient.Resolve(name, recordType, recordClass);
if ((msg == null) || ((msg.ReturnCode != ReturnCode.NoError) && (msg.ReturnCode != ReturnCode.NxDomain)))
{
throw new Exception("DNS request failed");
}
CNameRecord cName = msg.AnswerRecords.Where(x => (x.RecordType == RecordType.CName) && (x.RecordClass == recordClass) && x.Name.Equals(name)).OfType <CNameRecord>().FirstOrDefault();
if (cName != null)
{
records = msg.AnswerRecords.Where(x => x.Name.Equals(cName.CanonicalName)).OfType <T>().ToList();
if (records.Count > 0)
{
_cache.Add(name, recordType, recordClass, records, DnsSecValidationResult.Indeterminate, records.Min(x => x.TimeToLive));
return(records);
}
records = Resolve <T>(cName.CanonicalName, recordType, recordClass);
if (records.Count > 0)
{
_cache.Add(name, recordType, recordClass, records, DnsSecValidationResult.Indeterminate, records.Min(x => x.TimeToLive));
}
return(records);
}
records = msg.AnswerRecords.Where(x => x.Name.Equals(name)).OfType <T>().ToList();
if (records.Count > 0)
{
_cache.Add(name, recordType, recordClass, records, DnsSecValidationResult.Indeterminate, records.Min(x => x.TimeToLive));
}
return(records);
}
private async Task <List <T> > ResolveAsyncInternal <T>(DomainName name, RecordType recordType, RecordClass recordClass, State state, CancellationToken token)
where T : DnsRecordBase
{
List <T> cachedResults;
if (_cache.TryGetRecords(name, recordType, recordClass, out cachedResults))
{
return(cachedResults);
}
List <CNameRecord> cachedCNames;
if (_cache.TryGetRecords(name, RecordType.CName, recordClass, out cachedCNames))
{
return(await ResolveAsyncInternal <T>(cachedCNames.First().CanonicalName, recordType, recordClass, state, token));
}
DnsMessage msg = await ResolveMessageAsync(name, recordType, recordClass, state, token);
// check for cname
List <DnsRecordBase> cNameRecords = msg.AnswerRecords.Where(x => (x.RecordType == RecordType.CName) && (x.RecordClass == recordClass) && x.Name.Equals(name)).ToList();
if (cNameRecords.Count > 0)
{
_cache.Add(name, RecordType.CName, recordClass, cNameRecords, DnsSecValidationResult.Indeterminate, cNameRecords.Min(x => x.TimeToLive));
DomainName canonicalName = ((CNameRecord)cNameRecords.First()).CanonicalName;
List <DnsRecordBase> matchingAdditionalRecords = msg.AnswerRecords.Where(x => (x.RecordType == recordType) && (x.RecordClass == recordClass) && x.Name.Equals(canonicalName)).ToList();
if (matchingAdditionalRecords.Count > 0)
{
_cache.Add(canonicalName, recordType, recordClass, matchingAdditionalRecords, DnsSecValidationResult.Indeterminate, matchingAdditionalRecords.Min(x => x.TimeToLive));
return(matchingAdditionalRecords.OfType <T>().ToList());
}
return(await ResolveAsyncInternal <T>(canonicalName, recordType, recordClass, state, token));
}
// check for "normal" answer
List <DnsRecordBase> answerRecords = msg.AnswerRecords.Where(x => (x.RecordType == recordType) && (x.RecordClass == recordClass) && x.Name.Equals(name)).ToList();
if (answerRecords.Count > 0)
{
_cache.Add(name, recordType, recordClass, answerRecords, DnsSecValidationResult.Indeterminate, answerRecords.Min(x => x.TimeToLive));
return(answerRecords.OfType <T>().ToList());
}
// check for negative answer
SoaRecord soaRecord = msg.AuthorityRecords
.Where(x =>
(x.RecordType == RecordType.Soa) &&
(name.Equals(x.Name) || name.IsSubDomainOf(x.Name)))
.OfType <SoaRecord>()
.FirstOrDefault();
if (soaRecord != null)
{
_cache.Add(name, recordType, recordClass, new List <DnsRecordBase>(), DnsSecValidationResult.Indeterminate, soaRecord.NegativeCachingTTL);
return(new List <T>());
}
// authoritive response does not contain answer
throw new Exception("Could not resolve " + name);
}
private async Task <DnsSecResult <T> > ResolveAsyncInternal <T>(DomainName name, RecordType recordType, RecordClass recordClass, State state, CancellationToken token)
where T : DnsRecordBase
{
DnsCacheRecordList <T> cachedResults;
if (_cache.TryGetRecords(name, recordType, recordClass, out cachedResults))
{
return(new DnsSecResult <T>(cachedResults, cachedResults.ValidationResult));
}
DnsCacheRecordList <CNameRecord> cachedCNames;
if (_cache.TryGetRecords(name, RecordType.CName, recordClass, out cachedCNames))
{
var cNameResult = await ResolveAsyncInternal <T>(cachedCNames.First().CanonicalName, recordType, recordClass, state, token);
return(new DnsSecResult <T>(cNameResult.Records, cachedCNames.ValidationResult == cNameResult.ValidationResult ? cachedCNames.ValidationResult : DnsSecValidationResult.Unsigned));
}
DnsMessage msg = await ResolveMessageAsync(name, recordType, recordClass, state, token);
// check for cname
List <DnsRecordBase> cNameRecords = msg.AnswerRecords.Where(x => (x.RecordType == RecordType.CName) && (x.RecordClass == recordClass) && x.Name.Equals(name)).ToList();
if (cNameRecords.Count > 0)
{
DnsSecValidationResult cNameValidationResult = await _validator.ValidateAsync(name, RecordType.CName, recordClass, msg, cNameRecords, state, token);
if ((cNameValidationResult == DnsSecValidationResult.Bogus) || (cNameValidationResult == DnsSecValidationResult.Indeterminate))
{
throw new DnsSecValidationException("CNAME record could not be validated");
}
_cache.Add(name, RecordType.CName, recordClass, cNameRecords, cNameValidationResult, cNameRecords.Min(x => x.TimeToLive));
DomainName canonicalName = ((CNameRecord)cNameRecords.First()).CanonicalName;
List <DnsRecordBase> matchingAdditionalRecords = msg.AnswerRecords.Where(x => (x.RecordType == recordType) && (x.RecordClass == recordClass) && x.Name.Equals(canonicalName)).ToList();
if (matchingAdditionalRecords.Count > 0)
{
DnsSecValidationResult matchingValidationResult = await _validator.ValidateAsync(canonicalName, recordType, recordClass, msg, matchingAdditionalRecords, state, token);
if ((matchingValidationResult == DnsSecValidationResult.Bogus) || (matchingValidationResult == DnsSecValidationResult.Indeterminate))
{
throw new DnsSecValidationException("CNAME matching records could not be validated");
}
DnsSecValidationResult validationResult = cNameValidationResult == matchingValidationResult ? cNameValidationResult : DnsSecValidationResult.Unsigned;
_cache.Add(canonicalName, recordType, recordClass, matchingAdditionalRecords, validationResult, matchingAdditionalRecords.Min(x => x.TimeToLive));
return(new DnsSecResult <T>(matchingAdditionalRecords.OfType <T>().ToList(), validationResult));
}
var cNameResults = await ResolveAsyncInternal <T>(canonicalName, recordType, recordClass, state, token);
return(new DnsSecResult <T>(cNameResults.Records, cNameValidationResult == cNameResults.ValidationResult ? cNameValidationResult : DnsSecValidationResult.Unsigned));
}
// check for "normal" answer
List <DnsRecordBase> answerRecords = msg.AnswerRecords.Where(x => (x.RecordType == recordType) && (x.RecordClass == recordClass) && x.Name.Equals(name)).ToList();
if (answerRecords.Count > 0)
{
DnsSecValidationResult validationResult = await _validator.ValidateAsync(name, recordType, recordClass, msg, answerRecords, state, token);
if ((validationResult == DnsSecValidationResult.Bogus) || (validationResult == DnsSecValidationResult.Indeterminate))
{
throw new DnsSecValidationException("Response records could not be validated");
}
_cache.Add(name, recordType, recordClass, answerRecords, validationResult, answerRecords.Min(x => x.TimeToLive));
return(new DnsSecResult <T>(answerRecords.OfType <T>().ToList(), validationResult));
}
// check for negative answer
SoaRecord soaRecord = msg.AuthorityRecords
.Where(x =>
(x.RecordType == RecordType.Soa) &&
(name.Equals(x.Name) || name.IsSubDomainOf(x.Name)))
.OfType <SoaRecord>()
.FirstOrDefault();
if (soaRecord != null)
{
DnsSecValidationResult validationResult = await _validator.ValidateAsync(name, recordType, recordClass, msg, answerRecords, state, token);
if ((validationResult == DnsSecValidationResult.Bogus) || (validationResult == DnsSecValidationResult.Indeterminate))
{
throw new DnsSecValidationException("Negative answer could not be validated");
}
_cache.Add(name, recordType, recordClass, new List <DnsRecordBase>(), validationResult, soaRecord.NegativeCachingTTL);
return(new DnsSecResult <T>(new List <T>(), validationResult));
}
// authoritive response does not contain answer
throw new Exception("Could not resolve " + name);
}
/// <summary>
/// Resolves specified records as an asynchronous operation.
/// </summary>
/// <typeparam name="T"> Type of records, that should be returned </typeparam>
/// <param name="name"> Domain, that should be queried </param>
/// <param name="recordType"> Type the should be queried </param>
/// <param name="recordClass"> Class the should be queried </param>
/// <param name="token"> The token to monitor cancellation requests </param>
/// <returns> A list of matching <see cref="DnsRecordBase">records</see> </returns>
public async Task <DnsSecResult <T> > ResolveSecureAsync <T>(DomainName name, RecordType recordType = RecordType.A, RecordClass recordClass = RecordClass.INet, CancellationToken token = default(CancellationToken))
where T : DnsRecordBase
{
if (name == null)
{
throw new ArgumentNullException(nameof(name), "Name must be provided");
}
DnsCacheRecordList <T> cacheResult;
if (_cache.TryGetRecords(name, recordType, recordClass, out cacheResult))
{
return(new DnsSecResult <T>(cacheResult, cacheResult.ValidationResult));
}
DnsMessage msg = await _dnsClient.ResolveAsync(name, recordType, recordClass, new DnsQueryOptions()
{
IsEDnsEnabled = true,
IsDnsSecOk = true,
IsCheckingDisabled = true,
IsRecursionDesired = true
}, token).ConfigureAwait(false);
if ((msg == null) || ((msg.ReturnCode != ReturnCode.NoError) && (msg.ReturnCode != ReturnCode.NxDomain)))
{
throw new Exception("DNS request failed");
}
DnsSecValidationResult validationResult;
CNameRecord cName = msg.AnswerRecords.Where(x => (x.RecordType == RecordType.CName) && (x.RecordClass == recordClass) && x.Name.Equals(name)).OfType <CNameRecord>().FirstOrDefault();
if (cName != null)
{
DnsSecValidationResult cNameValidationResult = await _validator.ValidateAsync(name, RecordType.CName, recordClass, msg, new List <CNameRecord>() { cName }, null, token).ConfigureAwait(false);
if ((cNameValidationResult == DnsSecValidationResult.Bogus) || (cNameValidationResult == DnsSecValidationResult.Indeterminate))
{
throw new DnsSecValidationException("CNAME record could not be validated");
}
var records = msg.AnswerRecords.Where(x => (x.RecordType == recordType) && (x.RecordClass == recordClass) && x.Name.Equals(cName.CanonicalName)).OfType <T>().ToList();
if (records.Count > 0)
{
DnsSecValidationResult recordsValidationResult = await _validator.ValidateAsync(cName.CanonicalName, recordType, recordClass, msg, records, null, token).ConfigureAwait(false);
if ((recordsValidationResult == DnsSecValidationResult.Bogus) || (recordsValidationResult == DnsSecValidationResult.Indeterminate))
{
throw new DnsSecValidationException("CNAME matching records could not be validated");
}
validationResult = cNameValidationResult == recordsValidationResult ? cNameValidationResult : DnsSecValidationResult.Unsigned;
_cache.Add(name, recordType, recordClass, records, validationResult, Math.Min(cName.TimeToLive, records.Min(x => x.TimeToLive)));
return(new DnsSecResult <T>(records, validationResult));
}
var cNameResults = await ResolveSecureAsync <T>(cName.CanonicalName, recordType, recordClass, token).ConfigureAwait(false);
validationResult = cNameValidationResult == cNameResults.ValidationResult ? cNameValidationResult : DnsSecValidationResult.Unsigned;
if (cNameResults.Records.Count > 0)
{
_cache.Add(name, recordType, recordClass, cNameResults.Records, validationResult, Math.Min(cName.TimeToLive, cNameResults.Records.Min(x => x.TimeToLive)));
}
return(new DnsSecResult <T>(cNameResults.Records, validationResult));
}
List <T> res = msg.AnswerRecords.Where(x => (x.RecordType == recordType) && (x.RecordClass == recordClass) && x.Name.Equals(name)).OfType <T>().ToList();
validationResult = await _validator.ValidateAsync(name, recordType, recordClass, msg, res, null, token).ConfigureAwait(false);
if ((validationResult == DnsSecValidationResult.Bogus) || (validationResult == DnsSecValidationResult.Indeterminate))
{
throw new DnsSecValidationException("Response records could not be validated");
}
if (res.Count > 0)
{
_cache.Add(name, recordType, recordClass, res, validationResult, res.Min(x => x.TimeToLive));
}
return(new DnsSecResult <T>(res, validationResult));
}