How to validate domain credentials

Question

I want to validate a set of credentials against the domain controller  e g    Username  STACKOVERFLOW joel Password  splotchy   Method 1  Query Active Directory with Impersonation  A lot of people suggest querying the Active Directory for something  If an exception is thrown  then you know the credentials are not valid - as is suggested in this stackoverflow question   There are some serious drawbacks to this approach however    You are not only authenticating a domain account  but you are also doing an implicit authorization check  That is  you are reading properties from the AD using an impersonation token  What if the otherwise valid account has no rights to read from the AD  By default all users have read access  but domain policies can be set to disable access permissions for restricted accounts  and or groups   Binding against the AD has a serious overhead  the AD schema cache has to be loaded at the client  ADSI cache in the ADSI provider used by DirectoryServices   This is both network  and AD server  resource consuming - and is too expensive for a simple operation like authenticating a user account  You re relying on an exception failure for a non-exceptional case  and assuming that means invalid username and password  Other problems  e g  network failure  AD connectivity failure  memory allocation error  etc  are then mis-intrepreted as authentication failure    Method 2  LogonUser Win32 API  Others have suggested using the LogonUser   API function  This sounds nice  but unfortunately the calling user sometimes needs a permission usually only given to the operating system itself      The process calling LogonUser requires   the SE TCB NAME privilege  If the   calling process does not have this   privilege  LogonUser fails and   GetLastError returns   ERROR PRIVILEGE NOT HELD        In some   cases  the process that calls   LogonUser must also have the   SE CHANGE NOTIFY NAME privilege   enabled  otherwise  LogonUser fails   and GetLastError returns   ERROR ACCESS DENIED  This privilege is   not required for the local system   account or accounts that are members   of the administrators group  By   default  SE CHANGE NOTIFY NAME is   enabled for all users  but some   administrators may disable it for   everyone    Handing out the  Act as a part of the operating system  privilege is not something you want to do willy-nilly - as Microsoft points out in a knowledge base article         the process that is calling   LogonUser must have the SE TCB NAME   privilege  in User Manager  this is   the  Act as part of the Operating   System  right   The SE TCB NAME   privilege is very powerful and   should not be granted to any arbitrary user just so that they can   run an application that needs to   validate credentials    Additionally  a call to LogonUser   will fail if a blank password is specified     What is the proper way to authenticate a set of domain credentials     I happen to be calling from managed code  but this is a a general Windows question  It can be assumed that the customers have the  NET Framework 2 0 installed

User · Answer

using System  using System Collections Generic  using System Text  using System DirectoryServices AccountManagement   class WindowsCred       private const string SPLIT 1              public static bool ValidateW string UserName  string Password                bool valid   false          string Domain                if  UserName IndexOf          -1                        string   arrT   UserName Split SPLIT 1 0                Domain   arrT 0               UserName   arrT 1                      if  Domain Length    0                        Domain   System Environment MachineName                     using  PrincipalContext context   new PrincipalContext ContextType Domain  Domain                          valid   context ValidateCredentials UserName  Password                      return valid            Kashif Mushtaq Ottawa  Canada

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C  in  NET 3 5 using System DirectoryServices AccountManagement    bool valid   false   using  PrincipalContext context   new PrincipalContext ContextType Domain           valid   context ValidateCredentials  username  password         This will validate against the current domain   Check out the parameterized PrincipalContext constructor for other options

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using System  using System Collections Generic  using System Linq  using System Text  using System Security  using System DirectoryServices AccountManagement   public struct Credentials       public string Username      public string Password     public class Domain Authentication       public Credentials Credentials      public string Domain       public Domain Authentication string Username  string Password  string SDomain                Credentials Username   Username          Credentials Password   Password          Domain   SDomain             public bool IsValid                 using  PrincipalContext pc   new PrincipalContext ContextType Domain  Domain                            validate the credentials             return pc ValidateCredentials Credentials Username  Credentials Password

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using System  using System Collections Generic  using System Text  using System DirectoryServices AccountManagement   class WindowsCred       private const string SPLIT 1              public static bool ValidateW string UserName  string Password                bool valid   false          string Domain                if  UserName IndexOf          -1                        string   arrT   UserName Split SPLIT 1 0                Domain   arrT 0               UserName   arrT 1                      if  Domain Length    0                        Domain   System Environment MachineName                     using  PrincipalContext context   new PrincipalContext ContextType Domain  Domain                          valid   context ValidateCredentials UserName  Password                      return valid            Kashif Mushtaq Ottawa  Canada

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Here s how to determine a local user       public bool IsLocalUser                 return windowsIdentity AuthenticationType     NTLM             Edit by Ian Boyd  You should not use NTLM anymore at all  It is so old  and so bad  that Microsoft s Application Verifier  which is used to catch common programming mistakes  will throw a warning if it detects you using NTLM   Here s a chapter from the Application Verifier documentation about why they have a test if someone is mistakenly using NTLM      Why the NTLM Plug-in is Needed      NTLM is an outdated authentication protocol with flaws that   potentially compromise the security of applications and the operating   system  The most important shortcoming is the lack of server   authentication  which could allow an attacker to trick users into   connecting to a spoofed server  As a corollary of missing server   authentication  applications using NTLM can also be vulnerable to a   type of attack known as a    reflection    attack  This latter allows an   attacker to hijack a user   s authentication conversation to a   legitimate server and use it to authenticate the attacker to the   user   s computer  NTLM   s vulnerabilities and ways of exploiting them   are the target of increasing research activity in the security   community       Although Kerberos has been available for many years many applications   are still written to use NTLM only  This needlessly reduces the   security of applications  Kerberos cannot however replace NTLM in all   scenarios     principally those where a client needs to authenticate to   systems that are not joined to a domain  a home network perhaps being   the most common of these   The Negotiate security package allows a   backwards-compatible compromise that uses Kerberos whenever possible   and only reverts to NTLM when there is no other option  Switching code   to use Negotiate instead of NTLM will significantly increase the   security for our customers while introducing few or no application   compatibilities  Negotiate by itself is not a silver bullet     there   are cases where an attacker can force downgrade to NTLM but these are   significantly more difficult to exploit  However  one immediate   improvement is that applications written to use Negotiate correctly   are automatically immune to NTLM reflection attacks       By way of a final word of caution against use of NTLM  in future   versions of Windows it will be possible to disable the use of NTLM at   the operating system  If applications have a hard dependency on NTLM   they will simply fail to authenticate when NTLM is disabled       How the Plug-in Works      The Verifier plug detects the following errors          The NTLM package is directly specified in the call to AcquireCredentialsHandle  or higher level wrapper API     The target name in the call to InitializeSecurityContext is NULL    The target name in the call to InitializeSecurityContext is not a properly-formed SPN  UPN or NetBIOS-style domain name          The latter two cases will force Negotiate to fall back to NTLM either directly  the first case  or indirectly  the domain controller will return a    principal not found    error in the second case causing Negotiate to fall back        The plug-in also logs warnings when it detects downgrades to NTLM  for example  when an SPN is not found by the Domain Controller  These are only logged as warnings since they are often legitimate cases     for example  when authenticating to a system that is not domain-joined       NTLM Stops      5000     Application Has Explicitly Selected NTLM Package      Severity     Error      The application or subsystem explicitly selects NTLM instead of Negotiate in the call to AcquireCredentialsHandle  Even though it may be possible for the client and server to authenticate using Kerberos this is prevented by the explicit selection of NTLM       How to Fix this Error      The fix for this error is to select the Negotiate package in place of NTLM  How this is done will depend on the particular Network subsystem being used by the client or server  Some examples are given below  You should consult the documentation on the particular library or API set that you are using   APIs parameter  Used by Application    Incorrect Value  Correct Value                                                                                    AcquireCredentialsHandle  pszPackage      NTLM              NEGOSSP NAME    Negotiate

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Here s how to determine a local user       public bool IsLocalUser                 return windowsIdentity AuthenticationType     NTLM             Edit by Ian Boyd  You should not use NTLM anymore at all  It is so old  and so bad  that Microsoft s Application Verifier  which is used to catch common programming mistakes  will throw a warning if it detects you using NTLM   Here s a chapter from the Application Verifier documentation about why they have a test if someone is mistakenly using NTLM      Why the NTLM Plug-in is Needed      NTLM is an outdated authentication protocol with flaws that   potentially compromise the security of applications and the operating   system  The most important shortcoming is the lack of server   authentication  which could allow an attacker to trick users into   connecting to a spoofed server  As a corollary of missing server   authentication  applications using NTLM can also be vulnerable to a   type of attack known as a    reflection    attack  This latter allows an   attacker to hijack a user   s authentication conversation to a   legitimate server and use it to authenticate the attacker to the   user   s computer  NTLM   s vulnerabilities and ways of exploiting them   are the target of increasing research activity in the security   community       Although Kerberos has been available for many years many applications   are still written to use NTLM only  This needlessly reduces the   security of applications  Kerberos cannot however replace NTLM in all   scenarios     principally those where a client needs to authenticate to   systems that are not joined to a domain  a home network perhaps being   the most common of these   The Negotiate security package allows a   backwards-compatible compromise that uses Kerberos whenever possible   and only reverts to NTLM when there is no other option  Switching code   to use Negotiate instead of NTLM will significantly increase the   security for our customers while introducing few or no application   compatibilities  Negotiate by itself is not a silver bullet     there   are cases where an attacker can force downgrade to NTLM but these are   significantly more difficult to exploit  However  one immediate   improvement is that applications written to use Negotiate correctly   are automatically immune to NTLM reflection attacks       By way of a final word of caution against use of NTLM  in future   versions of Windows it will be possible to disable the use of NTLM at   the operating system  If applications have a hard dependency on NTLM   they will simply fail to authenticate when NTLM is disabled       How the Plug-in Works      The Verifier plug detects the following errors          The NTLM package is directly specified in the call to AcquireCredentialsHandle  or higher level wrapper API     The target name in the call to InitializeSecurityContext is NULL    The target name in the call to InitializeSecurityContext is not a properly-formed SPN  UPN or NetBIOS-style domain name          The latter two cases will force Negotiate to fall back to NTLM either directly  the first case  or indirectly  the domain controller will return a    principal not found    error in the second case causing Negotiate to fall back        The plug-in also logs warnings when it detects downgrades to NTLM  for example  when an SPN is not found by the Domain Controller  These are only logged as warnings since they are often legitimate cases     for example  when authenticating to a system that is not domain-joined       NTLM Stops      5000     Application Has Explicitly Selected NTLM Package      Severity     Error      The application or subsystem explicitly selects NTLM instead of Negotiate in the call to AcquireCredentialsHandle  Even though it may be possible for the client and server to authenticate using Kerberos this is prevented by the explicit selection of NTLM       How to Fix this Error      The fix for this error is to select the Negotiate package in place of NTLM  How this is done will depend on the particular Network subsystem being used by the client or server  Some examples are given below  You should consult the documentation on the particular library or API set that you are using   APIs parameter  Used by Application    Incorrect Value  Correct Value                                                                                    AcquireCredentialsHandle  pszPackage      NTLM              NEGOSSP NAME    Negotiate

User · Answer

using System  using System Collections Generic  using System Linq  using System Text  using System Security  using System DirectoryServices AccountManagement   public struct Credentials       public string Username      public string Password     public class Domain Authentication       public Credentials Credentials      public string Domain       public Domain Authentication string Username  string Password  string SDomain                Credentials Username   Username          Credentials Password   Password          Domain   SDomain             public bool IsValid                 using  PrincipalContext pc   new PrincipalContext ContextType Domain  Domain                            validate the credentials             return pc ValidateCredentials Credentials Username  Credentials Password

User · Answer

C  in  NET 3 5 using System DirectoryServices AccountManagement    bool valid   false   using  PrincipalContext context   new PrincipalContext ContextType Domain           valid   context ValidateCredentials  username  password         This will validate against the current domain   Check out the parameterized PrincipalContext constructor for other options

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I m using the following code to validate credentials  The method shown below will confirm if the credentials are correct and if not wether the password is expired or needs change   I ve been looking for something like this for ages    So i hope this helps someone     using System  using System DirectoryServices  using System DirectoryServices AccountManagement  using System Runtime InteropServices   namespace User       public static class UserValidation                DllImport  advapi32 dll   SetLastError   true           static extern bool LogonUser string principal  string authority  string password  LogonTypes logonType  LogonProviders logonProvider  out IntPtr token            DllImport  kernel32 dll   SetLastError   true           static extern bool CloseHandle IntPtr handle           enum LogonProviders   uint                       Default   0     default for platform  use this               WinNT35         sends smoke signals to authority             WinNT40         uses NTLM             WinNT50         negotiates Kerb or NTLM                   enum LogonTypes   uint                       Interactive   2              Network   3              Batch   4              Service   5              Unlock   7              NetworkCleartext   8              NewCredentials   9                   public  const int ERROR PASSWORD MUST CHANGE   1907          public  const int ERROR LOGON FAILURE   1326          public  const int ERROR ACCOUNT RESTRICTION   1327          public  const int ERROR ACCOUNT DISABLED   1331          public  const int ERROR INVALID LOGON HOURS   1328          public  const int ERROR NO LOGON SERVERS   1311          public  const int ERROR INVALID WORKSTATION   1329          public  const int ERROR ACCOUNT LOCKED OUT   1909         It gives this error if the account is locked  REGARDLESS OF WHETHER VALID CREDENTIALS WERE PROVIDED            public  const int ERROR ACCOUNT EXPIRED   1793          public  const int ERROR PASSWORD EXPIRED   1330           public static int CheckUserLogon string username  string password  string domain fqdn                        int errorCode   0              using  PrincipalContext pc   new PrincipalContext ContextType Domain  domain fqdn   ADMIN USER    PASSWORD                                  if   pc ValidateCredentials username  password                                         IntPtr token   new IntPtr                        try                                               if   LogonUser username  domain fqdn  password  LogonTypes Network  LogonProviders Default  out token                                                         errorCode   Marshal GetLastWin32Error                                                                        catch  Exception                                                throw                                            finally                                               CloseHandle token                                                                     return errorCode

User · Answer

C  in  NET 3 5 using System DirectoryServices AccountManagement    bool valid   false   using  PrincipalContext context   new PrincipalContext ContextType Domain           valid   context ValidateCredentials  username  password         This will validate against the current domain   Check out the parameterized PrincipalContext constructor for other options

User · Answer

I m using the following code to validate credentials  The method shown below will confirm if the credentials are correct and if not wether the password is expired or needs change   I ve been looking for something like this for ages    So i hope this helps someone     using System  using System DirectoryServices  using System DirectoryServices AccountManagement  using System Runtime InteropServices   namespace User       public static class UserValidation                DllImport  advapi32 dll   SetLastError   true           static extern bool LogonUser string principal  string authority  string password  LogonTypes logonType  LogonProviders logonProvider  out IntPtr token            DllImport  kernel32 dll   SetLastError   true           static extern bool CloseHandle IntPtr handle           enum LogonProviders   uint                       Default   0     default for platform  use this               WinNT35         sends smoke signals to authority             WinNT40         uses NTLM             WinNT50         negotiates Kerb or NTLM                   enum LogonTypes   uint                       Interactive   2              Network   3              Batch   4              Service   5              Unlock   7              NetworkCleartext   8              NewCredentials   9                   public  const int ERROR PASSWORD MUST CHANGE   1907          public  const int ERROR LOGON FAILURE   1326          public  const int ERROR ACCOUNT RESTRICTION   1327          public  const int ERROR ACCOUNT DISABLED   1331          public  const int ERROR INVALID LOGON HOURS   1328          public  const int ERROR NO LOGON SERVERS   1311          public  const int ERROR INVALID WORKSTATION   1329          public  const int ERROR ACCOUNT LOCKED OUT   1909         It gives this error if the account is locked  REGARDLESS OF WHETHER VALID CREDENTIALS WERE PROVIDED            public  const int ERROR ACCOUNT EXPIRED   1793          public  const int ERROR PASSWORD EXPIRED   1330           public static int CheckUserLogon string username  string password  string domain fqdn                        int errorCode   0              using  PrincipalContext pc   new PrincipalContext ContextType Domain  domain fqdn   ADMIN USER    PASSWORD                                  if   pc ValidateCredentials username  password                                         IntPtr token   new IntPtr                        try                                               if   LogonUser username  domain fqdn  password  LogonTypes Network  LogonProviders Default  out token                                                         errorCode   Marshal GetLastWin32Error                                                                        catch  Exception                                                throw                                            finally                                               CloseHandle token                                                                     return errorCode

User · Answer

C  in  NET 3 5 using System DirectoryServices AccountManagement    bool valid   false   using  PrincipalContext context   new PrincipalContext ContextType Domain           valid   context ValidateCredentials  username  password         This will validate against the current domain   Check out the parameterized PrincipalContext constructor for other options

[c#] How to validate domain credentials?

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