LDAP/SSPI mutual authentication problem RRS feed

  • Question

  • Hi everyone!

    I would like to ask you a question about implementing mutual authentication with Kerberos, using SSPI and LDAP API.

    Here is the algorithm I am using: 

    // client side
    AcquireCredentialsHandle(NULL, "Kerberos", SECPKG_CRED_BOTH, NULL, &secIdent, NULL, NULL, &kClientCredential, &kClientTimeOut); 
    // AcquireCredentialsHandle returns SEC_E_OK
    // begin validation
    int iCliStatus = InitializeSecurityContext(&kClientCredential, isContextNull(kClientContext) ? NULL : &kClientContext, 
                                 pacTargetName, ulClientFlags, 0, SECURITY_NATIVE_DREP, pkServerToken, 
                                 0, &kClientContext, &kClientToken, &ulContextAttr, NULL);
    // InitializeSecurityContext returns SEC_I_CONTINUE_NEEDED
    // server side
    // ldap_init returns ok
    ldap_set_option(ld, LDAP_OPT_SIGN, LDAP_OPT_OFF);
    ldap_set_option(ld, LDAP_OPT_ENCRYPT, LDAP_OPT_OFF);
    unsigned long ulVersion = LDAP_VERSION3;
    ldap_set_option(ld, LDAP_OPT_VERSION, &ulVersion);
    // ldap_connect returns LDAP_SUCCESS
    // build the credentials based on what InitializeSecurityContext returned
    BERVAL creds;
    creds.bv_len = kClientToken.pBuffers[0].cbBuffer;
    creds.bv_val = reinterpret_cast<char*>(kClientToken.pBuffers[0].pvBuffer);
    BERVAL* pServerCreds = NULL;
    int iError = ldap_sasl_bind_s(ld, "", "GSSAPI", &creds, NULL, NULL, &pServerCreds);
    // ldap_sasl_bind_s returns LDAP_SUCCESS
    unsigned long ulError = 0;
    ldap_get_option(ld, LDAP_OPT_ERROR_NUMBER, &ulError);
    // ulError is equal to LDAP_SASL_BIND_IN_PROGRESS

    And here is the problem: both LDAP error codes are ok, but pServerCreds points to an empty BERVAL structure (not NULL, but bv_len equals to 0), and it should contain the server credential I have to pass to the next InitializeSecurityContext call. If I use that data to build the SecBufferDesc structure for the following call, it returns SEC_E_INVALID_TOKEN.

    Is ldap_sasl_bind_s supposed to return an empty BERVAL or am I doing something wrong?

    I have tested the authentication using full SSPI calls (AcceptSecurityContext for the server) and it works just as expected. The problem is that I need the server to be cross-platform, so I cannot use SSPI.

    Thanks for taking the time to answer!

    Juan Manuel Alvarez
    • Moved by Yi Feng Li Thursday, January 27, 2011 7:03 AM Authentication issue (From:Visual C++ General)
    Wednesday, January 26, 2011 4:07 AM

All replies

  • Hi Juan,

    I'm moving this thread to Security for Applications in Microsoft Windows Forum for better support.

    Thank you for your understanding.

    Yi Feng Li

    Yi Feng Li [MSFT]
    MSDN Community Support | Feedback to us
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    Please remember to mark the replies as answers if they help and unmark them if they provide no help.

    Thursday, January 27, 2011 7:02 AM
  • I found the problem. According to this thread (https://groups.google.com/group/microsoft.public.active.directory.interfaces/browse_thread/thread/9c13fe85e520f0b4/820a136e032946e9?pli=1) there is a bug with ldap_sasl_bind_s returning empty server credentials in Windows XP. I have tested my application under Windows 2008 Server and the credentials are properly returned. Thanks! Juan M.
    Juan Manuel Alvarez
    Monday, January 31, 2011 1:35 PM