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Thread: Segmentation fault on starting krb-kdc/krb5kdc, Kerberos set up with LDAP backend

  1. #1
    Join Date
    Jun 2012

    Exclamation Segmentation fault on starting krb-kdc/krb5kdc, Kerberos set up with LDAP backend

    Hello all.

    Not sure if this is the right place to post this question, since I'm new, therefore please move to the appropriate section.

    I installed Kerberos with LDAP backend, was working on the installation following a couple of guides, had populated the LDAP backend, had almost everything in place except the final testing. Prior to this, point, as far as I know, everythign was working fine, even starting the kadmin/kdc services. But now I'm getting a segfault on launching the service. Below, I've copied the error from my syslog -

    Jun 29 15:12:02 k1 kernel: [2971837.133606] krb5kdc[3369]: segfault at 4 ip 00007fba76e4b7ae sp 00007fff9a093f20 error 4 in[7fba76e43000+10000]
    I'm running Ubuntu 12.04 x64, all updates have been applied, etc., and so far the only other problem I have had was with using GNUTLS with LDAP (which was fixed by editing the config in LDAP). Google has been my friend thus far, but this time I have not had any luck on finding a fix. My krb5.conf file is also pretty standard, and I'm posting the config file as well as additional info in case someone is facing/has faced a similar issue.

    Thanks in advance.


    root@k1:# cat /etc/krb5.conf 
       default_realm = bitxtiger.NET
    bitxtiger.NET = {
       default_domain =
       kdc =
       admin_server =
       database_module = openldap_ldapconf
    [domain_realm] = bitxtiger.NET = bitxtiger.NET
       ldap_kerberos_container_dn = ou=krb5,dc=bitxtiger,dc=net
       openldap_ldapconf = {
          db_library = kldap
          ldap_kdc_dn = cn=kdcsvc,ou=krb5,dc=bitxtiger,dc=net
          ldap_kadmind_dn = cn=kadmin,ou=krb5,dc=bitxtiger,dc=net
          ldap_service_password_file = /etc/krb5kdc/service.keyfile
          ldap_servers = ldap://
          ldap_conns_per_server = 3
       default = FILE:/var/log/kerberos/klib.log
       kdc = FILE:/var/log/kerberos/kdc.log
       admin_server = FILE:/var/log/kerberos/kadmin.log
    root@k1:# ltrace /usr/sbin/krb5kdc
    __libc_start_main(0x405810, 1, 0x7fffeba9b438, 0x4183b0, 0x418440 <unfinished ...>
    setlocale(5, "")                                                     = "en_US.UTF-8"
    strrchr("/usr/sbin/krb5kdc", '/')                                    = "/krb5kdc"
    malloc(256)                                                          = 0x02121f20
    krb5int_init_context_kdc(0x7fffeba9b308, 131312, 0x2121f20, 0, 3)    = 0
    krb5_klog_init(0x2122120, 0x419e40, 0x7fffeba9b940, 1, 0x2122898)    = 0
    malloc(16)                                                           = 0x02122690
    krb5_aprof_init(0x419d55, 0x419d44, 0x7fffeba9b200, 0x7f76f2c56728, 0x21226f0) = 0
    krb5_aprof_get_string(0x2123e00, 0x7fffeba9b1c0, 1, 0x7fffeba9b1f0, 0x7f76f3763e28) = 0
    krb5_aprof_get_string(0x2123e00, 0x7fffeba9b1c0, 1, 0x7fffeba9b1f8, 0x2122898) = 0xffffffffaaca6003
    krb5_aprof_get_int32(0x2123e00, 0x7fffeba9b1c0, 1, 0x61e9a0, 0x2122898) = 0xaaca6003
    krb5_aprof_get_boolean(0x2123e00, 0x7fffeba9b1c0, 1, 0x7fffeba9b21c, 0x2122898) = 0xaaca6003
    krb5_aprof_get_string_all(0x2123e00, 0x7fffeba9b1c0, 0x7fffeba9b208, 0x7f76f2c56748, 0x2122898) = 0xaaca6003
    krb5_aprof_get_string_all(0x2123e00, 0x7fffeba9b1c0, 0x7fffeba9b210, 0x7f76f2c56748, 0x2122898) = 0xaaca6003
    krb5_aprof_finish(0x2123e00, 0xffffffff, 0, 0x7f76f2c56748, 0x2122898) = 0
    calloc(1, 1)                                                         = 0x02123e50
    getopt(1, 0x7fffeba9b438, "x:r:d:mM:k:R:e:P:p:s:nw:4:X3")            = -1
    krb5_get_default_realm(0x2122120, 0x7fffeba9b1e8, 0x7f76f2c56258, 0, 0) = 0
    malloc(144)                                                          = 0x02122c30
    __strdup(0x2122b00, 0x2122b00, 0, 0, 0x2122700)                      = 0x2122ae0
    krb5int_init_context_kdc(0x2122c38, 0x2122b0e, 0, 0x54454e2e524547, 0x2123e60) = 0
    krb5_read_realm_params(0x21249e0, 0x2122ae0, 0x7fffeba9b130, 75, 0x2122898) = 0
    malloc(4)                                                            = 0x02122b70
    __strdup(0x2123d40, 0x7f76f2c56720, 0x7f76f2c56720, 0x7f76f2c56728, 0x2123fc0) = 0x2123fd0
    __strdup(0x2123e50, 0x2123d47, 0, 0x38382c, 0x2123fa0)               = 0x2123fb0
    __strdup(0x2123db0, 0x2123e51, 0, 0, 0x2123fe0)                      = 0x2123ff0
    krb5_free_realm_params(0x21249e0, 0x2123ec0, 604800, 0x646b3562726b2f63, 0x68736174732f63) = 0
    krb5_set_default_realm(0x21249e0, 0x2122b00, 0, 0x7f76f2c56750, 0x68736174732f63) = 0
    krb5_db_open(0x21249e0, 0, 256, 0x54454e2e524547, 0x2123d30)         = 0
    krb5_db_setup_mkey_name(0x21249e0, 0x2122b70, 0x2122ae0, 0, 0x2122c70) = 0
    krb5_db_fetch_mkey(0x21249e0, 0x213ae40, 16, 0, 0)                   = 0
    krb5_db_fetch_mkey_list(0x21249e0, 0x213ae40, 0x2122c78, 1, 0x2122c90 <unfinished ...>
    --- SIGSEGV (Segmentation fault) ---
    +++ killed by SIGSEGV +++
    root@k1:# ldd /usr/sbin/krb5kdc
   =>  (0x00007fff6bfd7000)
   => /usr/lib/x86_64-linux-gnu/ (0x00007f11cada9000)
   => /usr/lib/x86_64-linux-gnu/ (0x00007f11cab98000)
   => /usr/lib/x86_64-linux-gnu/ (0x00007f11ca97b000)
   => /usr/lib/x86_64-linux-gnu/ (0x00007f11ca6ad000)
   => /usr/lib/x86_64-linux-gnu/ (0x00007f11ca485000)
   => /lib/x86_64-linux-gnu/ (0x00007f11ca280000)
   => /usr/lib/x86_64-linux-gnu/ (0x00007f11ca078000)
   => /usr/lib/x86_64-linux-gnu/ (0x00007f11c9e73000)
   => /lib/x86_64-linux-gnu/ (0x00007f11c9ab5000)
   => /usr/lib/x86_64-linux-gnu/ (0x00007f11c9877000)
   => /lib/x86_64-linux-gnu/ (0x00007f11c9673000)
   => /lib/x86_64-linux-gnu/ (0x00007f11c9456000)
   => /lib/x86_64-linux-gnu/ (0x00007f11c9239000)
            /lib64/ (0x00007f11cafd6000)
   => /lib/x86_64-linux-gnu/ (0x00007f11c9035000)

  2. #2
    Join Date
    Jun 2012

    Re: Segmentation fault on starting krb-kdc/krb5kdc, Kerberos set up with LDAP backend

    Still stuck. Anyone with any suggestions/input on this? Thanks.

  3. #3
    Join Date
    Jan 2013

    Re: Segmentation fault on starting krb-kdc/krb5kdc, Kerberos set up with LDAP backend

    Old thread, but I had this same trouble In fact, exactly the same.

    Turns out its related to a bug in libkbd5 when using LDAP as a back end, and the krbPrincipalKey is NULL, most likely.

    What I did the first time I encountered this issue was:

    - Followed the Ubuntu OpenLDAP guide and The Kerberos/LDAP guide carefully
    - Realized there was no guideline as to how to setup an LDAP Consumer for use by a secondary kdc, so put in the kerberos schema AND created the realm on the LDAP secondary before setting up the Consumer
    - followed by segfaults

    I wiped the secondary slapd using apt-get purge, rebuilt according to the guidelines, and did NOT create the realm but DID import the kerberos schema, and then configured the consumer

    Worked like a charm. Replication brought over all the kerberos attributes and I didn't need to create the realm on the LDAP consumer.

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