#0  krb5_k_verify_checksum (context=0x27e00, key=0x275b8, usage=17, 
    data=0xffbff220, cksum=0xffbff210, valid=0xffbff1fc)
    at ../../../../src/lib/crypto/krb/cksumtypes.h:134
#1  0xff25ca68 in krb5_c_verify_checksum (context=0x27e00, keyblock=0x275b8, 
    usage=17, data=0xffbff220, cksum=0xffbff210, valid=0xffbff1fc)
    at ../../../../src/lib/crypto/krb/verify_checksum.c:87
#2  0xff2d8b58 in k5_pac_verify_server_checksum (context=0x27e00, pac=0x23f98, 
    server=0xffbff450) at ../../../../src/lib/krb5/krb/pac.c:608
#3  0xff2d8cc8 in krb5_pac_verify (context=0x27e00, pac=0x23f98, 
    authtime=1277912392, principal=0x27658, server=0xffbff450, privsvr=0x0)
    at ../../../../src/lib/krb5/krb/pac.c:684
#4  0xff2d9714 in mspac_verify (kcontext=0x27e00, context=0x28a38, 
    plugin_context=0x0, request_context=0x29080, auth_context=0xffbff650, 
    key=0xffbff450, req=0x258) at ../../../../src/lib/krb5/krb/pac.c:1088
#5  0xff2c47e0 in krb5int_authdata_verify (kcontext=0x27e00, context=0x28a38, 
    usage=15, auth_context=0xffbff650, key=0xffbff450, ap_req=0x26d58)
    at ../../../../src/lib/krb5/krb/authdata.c:672
a

where:

(gdb) p *ktp
$37 = {etype = 18, name = 0xff265440 <error reading variable>, aliases = {
    0xff265458 <error reading variable>, 0x0}, 
  out_string = 0xff265468 <error reading variable>, enc = 0xff276128, 
  hash = 0xff276030, prf_length = 16, 
  crypto_length = 0xff24465c <krb5int_aes_crypto_length>, 
  encrypt = 0xff2446dc <krb5int_dk_encrypt>, 
  decrypt = 0xff2449f4 <krb5int_dk_decrypt>, 
  str2key = 0xff245348 <krb5int_aes_string_to_key>, 
  prf = 0xff24715c <krb5int_dk_prf>, required_ctype = 16, flags = 0}

(gdb) p *ctp
$39 = {ctype = -138, name = 0xff265088 <error reading variable>, aliases = {
    0xff265098 <error reading variable>, 0xff2650a8 <error reading variable>}, 
  out_string = 0xff2650c0 <error reading variable>, enc = 0xff2760d8, 
  hash = 0xff27601c, checksum = 0xff246d80 <krb5int_hmacmd5_checksum>, 
  verify = 0, compute_size = 16, output_size = 16, flags = 0}