/// <summary>
/// Tries to parse the textual representation of a SPF string
/// </summary>
/// <param name="s"> Textual representation to check </param>
/// <param name="value"> Parsed spf record in case of successful parsing </param>
/// <returns> true in case of successful parsing </returns>
public static bool TryParse(string s, out SpfRecord value)
{
if (!IsSpfRecord(s))
{
value = null;
return false;
}
string[] terms = s.Split(new[] { ' ' }, StringSplitOptions.RemoveEmptyEntries);
List<SpfTerm> parsedTerms;
if (TryParseTerms(terms, out parsedTerms))
{
value = new SpfRecord { Terms = parsedTerms };
return true;
}
else
{
value = null;
return false;
}
}
internal SpfQualifier CheckHost(SpfCheckHostParameter parameters)
{
DnsMessage dnsMessage;
SpfMechanism spfMechanism = this as SpfMechanism;
if (spfMechanism != null)
{
switch (spfMechanism.Type)
{
case SpfMechanismType.All:
return(spfMechanism.Qualifier);
case SpfMechanismType.A:
bool?isAMatch = IsIpMatch(String.IsNullOrEmpty(spfMechanism.Domain) ? parameters.CurrentDomain : spfMechanism.Domain, parameters.ClientAddress, spfMechanism.Prefix, spfMechanism.Prefix6);
if (!isAMatch.HasValue)
{
return(SpfQualifier.TempError);
}
if (isAMatch.Value)
{
return(spfMechanism.Qualifier);
}
break;
case SpfMechanismType.Mx:
dnsMessage = DnsClient.Default.Resolve(ExpandDomain(String.IsNullOrEmpty(spfMechanism.Domain) ? parameters.CurrentDomain : spfMechanism.Domain, parameters), RecordType.Mx);
if ((dnsMessage == null) || ((dnsMessage.ReturnCode != ReturnCode.NoError) && (dnsMessage.ReturnCode != ReturnCode.NxDomain)))
{
return(SpfQualifier.TempError);
}
int mxCheckedCount = 0;
foreach (DnsRecordBase dnsRecord in dnsMessage.AnswerRecords)
{
MxRecord mxRecord = dnsRecord as MxRecord;
if (mxRecord != null)
{
if (++mxCheckedCount == 10)
{
break;
}
bool?isMxMatch = IsIpMatch(mxRecord.ExchangeDomainName, parameters.ClientAddress, spfMechanism.Prefix, spfMechanism.Prefix6);
if (!isMxMatch.HasValue)
{
return(SpfQualifier.TempError);
}
if (isMxMatch.Value)
{
return(spfMechanism.Qualifier);
}
}
}
break;
case SpfMechanismType.Ip4:
case SpfMechanismType.Ip6:
IPAddress compareAddress;
if (IPAddress.TryParse(spfMechanism.Domain, out compareAddress))
{
if (spfMechanism.Prefix.HasValue)
{
if (parameters.ClientAddress.GetNetworkAddress(spfMechanism.Prefix.Value).Equals(compareAddress.GetNetworkAddress(spfMechanism.Prefix.Value)))
{
return(spfMechanism.Qualifier);
}
}
else if (parameters.ClientAddress.Equals(compareAddress))
{
return(spfMechanism.Qualifier);
}
}
else
{
return(SpfQualifier.PermError);
}
break;
case SpfMechanismType.Ptr:
dnsMessage = DnsClient.Default.Resolve(parameters.ClientAddress.GetReverseLookupAddress(), RecordType.Ptr);
if ((dnsMessage == null) || ((dnsMessage.ReturnCode != ReturnCode.NoError) && (dnsMessage.ReturnCode != ReturnCode.NxDomain)))
{
return(SpfQualifier.TempError);
}
string ptrCompareName = String.IsNullOrEmpty(spfMechanism.Domain) ? parameters.CurrentDomain : spfMechanism.Domain;
int ptrCheckedCount = 0;
if ((from ptrRecord in dnsMessage.AnswerRecords.OfType <PtrRecord>().TakeWhile(ptrRecord => ++ ptrCheckedCount != 10)
let isPtrMatch = IsIpMatch(ptrRecord.PointerDomainName, parameters.ClientAddress, 0, 0)
where isPtrMatch.HasValue && isPtrMatch.Value
select ptrRecord).Any(ptrRecord => ptrRecord.PointerDomainName.Equals(ptrCompareName, StringComparison.InvariantCultureIgnoreCase) || (ptrRecord.PointerDomainName.EndsWith("." + ptrCompareName, StringComparison.InvariantCultureIgnoreCase))))
{
return(spfMechanism.Qualifier);
}
break;
case SpfMechanismType.Exist:
if (String.IsNullOrEmpty(spfMechanism.Domain))
{
return(SpfQualifier.PermError);
}
dnsMessage = DnsClient.Default.Resolve(ExpandDomain(spfMechanism.Domain, parameters), RecordType.A);
if ((dnsMessage == null) || ((dnsMessage.ReturnCode != ReturnCode.NoError) && (dnsMessage.ReturnCode != ReturnCode.NxDomain)))
{
return(SpfQualifier.TempError);
}
if (dnsMessage.AnswerRecords.Count(record => (record.RecordType == RecordType.A)) > 0)
{
return(spfMechanism.Qualifier);
}
break;
case SpfMechanismType.Include:
if (String.IsNullOrEmpty(spfMechanism.Domain))
{
return(SpfQualifier.PermError);
}
string includeDomain = ExpandDomain(spfMechanism.Domain, parameters);
switch (SpfRecord.CheckHost(includeDomain, new SpfCheckHostParameter(includeDomain, parameters)))
{
case SpfQualifier.Pass:
return(spfMechanism.Qualifier);
case SpfQualifier.Fail:
case SpfQualifier.SoftFail:
case SpfQualifier.Neutral:
return(SpfQualifier.None);
case SpfQualifier.TempError:
return(SpfQualifier.TempError);
case SpfQualifier.PermError:
case SpfQualifier.None:
return(SpfQualifier.PermError);
}
break;
default:
return(SpfQualifier.PermError);
}
}
SpfModifier spfModifier = this as SpfModifier;
if (spfModifier != null)
{
switch (spfModifier.Type)
{
case SpfModifierType.Redirect:
if (String.IsNullOrEmpty(spfModifier.Domain))
{
return(SpfQualifier.PermError);
}
string redirectDomain = ExpandDomain(spfModifier.Domain, parameters);
return(SpfRecord.CheckHost(redirectDomain, new SpfCheckHostParameter(redirectDomain, parameters)));
case SpfModifierType.Exp:
break;
default:
return(SpfQualifier.PermError);
}
}
return(SpfQualifier.None);
}