public override ReadOnlyMemory <byte> ExecuteCore(PreAuthenticationContext context)
{
// Now that we know who is requesting the ticket we can issue the ticket
//
// 3. Find the requested service principal
// 4. Determine if the requested service principal is in another realm and if so refer them
// 5. Evaluate whether the client identity should get a ticket to the service
// 6. Evaluate whether it should do U2U and if so extract that key instead
// 7. Generate a service ticket for the calling client to the service
// 8. return to client
var tgsReq = (KrbTgsReq)context.Message;
if (context.ServicePrincipal == null)
{
// we can't find what they're asking for, but maybe it's in a realm we can transit?
context.ServicePrincipal = ProposeTransitedRealm(tgsReq, context);
}
if (context.ServicePrincipal == null)
{
// we have no idea what service they're asking for and
// there isn't a realm we can refer them to that can issue a ticket
return(GenerateError(
KerberosErrorCode.KDC_ERR_S_PRINCIPAL_UNKNOWN,
"",
RealmService.Name,
tgsReq.Body.SName.FullyQualifiedName
));
}
// renewal is an odd case here because the SName will be krbtgt
// does this need to be validated more than the Decrypt call?
EvaluateSecurityPolicy(context.Principal, context.ServicePrincipal);
KerberosKey serviceKey;
if (tgsReq.Body.KdcOptions.HasFlag(KdcOptions.EncTktInSkey))
{
serviceKey = GetUserToUserTicketKey(tgsReq.Body.AdditionalTickets, context);
}
else
{
serviceKey = context.ServicePrincipal.RetrieveLongTermCredential();
}
var now = RealmService.Now();
TicketFlags flags = 0;
if (tgsReq.Body.KdcOptions.HasFlag(KdcOptions.Forwardable))
{
flags |= TicketFlags.Forwardable;
}
if (context.Ticket.Flags.HasFlag(TicketFlags.PreAuthenticated))
{
flags |= TicketFlags.PreAuthenticated;
}
var includePac = DetectPacRequirement(tgsReq);
if (includePac == null)
{
includePac = context.Ticket?.AuthorizationData?.Any(a => a.Type == AuthorizationDataType.AdIfRelevant) ?? false;
}
var tgsRep = KrbKdcRep.GenerateServiceTicket <KrbTgsRep>(
new ServiceTicketRequest
{
KdcAuthorizationKey = context.EvidenceTicketKey,
Principal = context.Principal,
EncryptedPartKey = context.EncryptedPartKey,
ServicePrincipal = context.ServicePrincipal,
ServicePrincipalKey = serviceKey,
RealmName = RealmService.Name,
Addresses = tgsReq.Body.Addresses,
RenewTill = context.Ticket.RenewTill,
StartTime = now - RealmService.Settings.MaximumSkew,
EndTime = now + RealmService.Settings.SessionLifetime,
Flags = flags,
Now = now,
Nonce = tgsReq.Body.Nonce,
IncludePac = includePac ?? false
}
);
return(tgsRep.EncodeApplication());
}
public override async Task <ReadOnlyMemory <byte> > ExecuteCore(IKerberosMessage message, PreAuthenticationContext context)
{
// the logic for a TGS-REQ is relatively simple in the primary case where you have a TGT and want
// to get a ticket to another service. It gets a bit more complicated when you need to do something
// like a U2U exchange, renew, or get a referral to another realm. Realm referral isn't supported yet.
// 1. Get the ApReq (TGT) from the PA-Data of the request
// 2. Decrypt the TGT and extract the client calling identity
// 3. Find the requested service principal
// 4. Evaluate whether the client identity should get a ticket to the service
// 5. Evaluate whether it should do U2U and if so extract that key instead
// 6. Generate a service ticket for the calling client to the service
// 7. return to client
var tgsReq = (KrbTgsReq)message;
logger.LogInformation("TGS-REQ incoming. SPN = {SPN}", tgsReq.Body.SName.FullyQualifiedName);
var krbtgtIdentity = await RealmService.Principals.RetrieveKrbtgt();
var krbtgtKey = await krbtgtIdentity.RetrieveLongTermCredential();
var servicePrincipal = await RealmService.Principals.Find(tgsReq.Body.SName.FullyQualifiedName);
// renewal is an odd case here because the SName will be krbtgt
// does this need to be validated more than the Decrypt call?
await EvaluateSecurityPolicy(context.Principal, servicePrincipal);
KerberosKey serviceKey;
if (tgsReq.Body.KdcOptions.HasFlag(KdcOptions.EncTktInSkey))
{
serviceKey = GetUserToUserTicketKey(tgsReq.Body.AdditionalTickets, krbtgtKey);
}
else
{
serviceKey = await servicePrincipal.RetrieveLongTermCredential();
}
var now = RealmService.Now();
TicketFlags flags = 0;
if (tgsReq.Body.KdcOptions.HasFlag(KdcOptions.Forwardable))
{
flags |= TicketFlags.Forwardable;
}
if (context.Ticket.Flags.HasFlag(TicketFlags.PreAuthenticated))
{
flags |= TicketFlags.PreAuthenticated;
}
var tgsRep = await KrbKdcRep.GenerateServiceTicket <KrbTgsRep>(
new ServiceTicketRequest
{
Principal = context.Principal,
EncryptedPartKey = context.EncryptedPartKey,
ServicePrincipal = servicePrincipal,
ServicePrincipalKey = serviceKey,
RealmName = RealmService.Name,
Addresses = tgsReq.Body.Addresses,
RenewTill = context.Ticket.RenewTill,
StartTime = now - RealmService.Settings.MaximumSkew,
EndTime = now + RealmService.Settings.SessionLifetime,
Flags = flags,
Now = now,
Nonce = tgsReq.Body.Nonce,
IncludePac = context.Ticket.AuthorizationData.Any(a => a.Type == AuthorizationDataType.AdIfRelevant)
}
);
return(tgsRep.EncodeApplication());
}
public override ReadOnlyMemory <byte> ExecuteCore(PreAuthenticationContext context)
{
// Now that we know who is requesting the ticket we can issue the ticket
//
// 3. Find the requested service principal
// 4. Determine if the requested service principal is in another realm and if so refer them
// 5. Evaluate whether the client identity should get a ticket to the service
// 6. Evaluate whether it should do U2U and if so extract that key instead
// 7. Generate a service ticket for the calling client to the service
// 8. return to client
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
var tgsReq = (KrbTgsReq)context.Message;
if (context.ServicePrincipal == null)
{
// we can't find what they're asking for, but maybe it's in a realm we can transit?
context.ServicePrincipal = this.ProposeTransitedRealm(tgsReq, context);
}
if (context.ServicePrincipal == null)
{
// we have no idea what service they're asking for and
// there isn't a realm we can refer them to that can issue a ticket
return(GenerateError(
KerberosErrorCode.KDC_ERR_S_PRINCIPAL_UNKNOWN,
string.Empty,
tgsReq.Body.Realm,
tgsReq.Body.SName.FullyQualifiedName
));
}
// renewal is an odd case here because the SName will be krbtgt
// does this need to be validated more than the Decrypt call?
this.EvaluateSecurityPolicy(context.Principal, context.ServicePrincipal);
KerberosKey serviceKey;
if (tgsReq.Body.KdcOptions.HasFlag(KdcOptions.EncTktInSkey))
{
serviceKey = GetUserToUserTicketKey(tgsReq.Body.AdditionalTickets, context);
}
else
{
serviceKey = context.ServicePrincipal.RetrieveLongTermCredential();
}
var now = this.RealmService.Now();
TicketFlags flags = 0;
if (tgsReq.Body.KdcOptions.HasFlag(KdcOptions.Forwardable))
{
flags |= TicketFlags.Forwardable;
}
if (context.Ticket.Flags.HasFlag(TicketFlags.PreAuthenticated))
{
flags |= TicketFlags.PreAuthenticated;
}
if (context.IncludePac == null)
{
context.IncludePac = DetectPacRequirement(tgsReq);
if (context.IncludePac == null)
{
context.IncludePac = context.Ticket?.AuthorizationData?.Any(a => a.Type == AuthorizationDataType.AdIfRelevant) ?? false;
}
}
var rst = new ServiceTicketRequest
{
KdcAuthorizationKey = context.EvidenceTicketKey,
Principal = context.Principal,
EncryptedPartKey = context.EncryptedPartKey,
EncryptedPartEType = context.EncryptedPartEType,
ServicePrincipal = context.ServicePrincipal,
ServicePrincipalKey = serviceKey,
RealmName = tgsReq.Body.Realm,
Addresses = tgsReq.Body.Addresses,
RenewTill = context.Ticket.RenewTill,
StartTime = tgsReq.Body.From ?? DateTimeOffset.MinValue,
EndTime = tgsReq.Body.Till,
MaximumTicketLifetime = this.RealmService.Settings.SessionLifetime,
Flags = flags,
Now = now,
Nonce = tgsReq.Body.Nonce,
IncludePac = context.IncludePac ?? false,
PreferredClientEType = GetPreferredEType(
tgsReq.Body.EType,
this.RealmService.Configuration.Defaults.PermittedEncryptionTypes,
this.RealmService.Configuration.Defaults.AllowWeakCrypto
),
Compatibility = this.RealmService.Settings.Compatibility,
};
if (tgsReq.Body.KdcOptions.HasFlag(KdcOptions.Canonicalize))
{
rst.SamAccountName = context.GetState <TgsState>(PaDataType.PA_TGS_REQ).DecryptedApReq.Ticket.CName.FullyQualifiedName;
}
// this is set here instead of in GenerateServiceTicket because GST is used by unit tests to
// generate tickets with weird lifetimes for scenario testing and we don't want to break that
rst.ClampLifetime();
var tgsRep = KrbKdcRep.GenerateServiceTicket <KrbTgsRep>(rst);
return(tgsRep.EncodeApplication());
}
