https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=267944
Bug ID: 267944
Summary: free() of uninitialized pointer from
kadmind_dispatch() and ret_principal_ent()
Product: Base System
Version: CURRENT
Hardware: Any
OS: Any
Status: New
Severity: Affects Only Me
Priority: ---
Component: bin
Assignee: [email protected]
Reporter: [email protected]
Attachment #238276 text/plain
mime type:
Created attachment 238276
--> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=238276&action=edit
provoke a free() of an uninitialized pointer in kadmin
kadmind_dispatch() says:
kadm5_principal_ent_rec ent;
...;
case kadm_create:{
ret = kadm5_ret_principal_ent(sp, &ent);
...;
ret = krb5_ret_int32(sp, &mask);
if(ret){
kadm5_free_principal_ent(contextp->context, &ent);
kadm5_free_pincipal_ent(hand, princ) frees ent.mod_name (and in
particular ent->mod_name->name.name_string.val):
if(princ->mod_name)
krb5_free_principal(context->context, princ->mod_name);
However, certain client messages can cause princ->mod_name to be
uninitialized (and contain a non-NULL garbage value).
kadmind_dispatch() doesn't zero out ent. ret_principal_ent() in
lib/kadm5/marshall.c is in charge of setting all fields from values
sent by the client. For mod_name:
if (mask & KADM5_MOD_NAME) {
krb5_ret_int32(sp, &tmp);
if(tmp)
krb5_ret_principal(sp, &princ->mod_name);
else
princ->mod_name = NULL;
}
In this situation the mask bit is always set. krb5_ret_principal() can
return an error for some client inputs -- but ret_principal_ent()
ignores the error, and on such a code path mode_name is never set, and
continues to hold the uninitialized value. One way this can happen is
if the client message is too short, so that krb5_ret_principal() hits
the end before it has read everything it needs.
I've attached a demo; kdc and kadmind should be running, and the user
must have kerberos tickets.
# cc kadmind14a.c -lkrb5
# ./a.out
A backtrace from kadmind. valgrind also sees the bad free().
#0 der_free_general_string (str=0x11ad9e1000000000)
at /usr/rtm/symbsd/src/crypto/heimdal/lib/asn1/der_free.c:43
#1 0x000000070731254c in free_PrincipalName (data=0x67fafadac <recenti>)
at asn1_krb5_asn1.c:961
#2 0x00000007073129ae in free_Principal (data=0x67fafadac <recenti>)
at asn1_krb5_asn1.c:1122
#3 0x0000000704e6919c in krb5_free_principal (context=<optimized out>,
p=0x67fafadac <recenti>)
at /usr/rtm/symbsd/src/crypto/heimdal/lib/krb5/principal.c:84
#4 0x0000000701eaff68 in kadm5_free_principal_ent (server_handle=0x711ad9e10,
princ=0x7009e6390)
at /usr/rtm/symbsd/src/crypto/heimdal/lib/kadm5/free.c:66
#5 0x000000067faf6146 in kadmind_dispatch (kadm_handlep=0x711b1f4c0,
initial=0, in=<optimized out>, out=0x7009e6568)
at /usr/rtm/symbsd/src/crypto/heimdal/kadmin/server.c:122
#6 0x000000067faf5f16 in v5_loop (contextp=<optimized out>,
ac=<optimized out>, initial=<optimized out>, kadm_handlep=<optimized out>,
fd=<optimized out>)
at /usr/rtm/symbsd/src/crypto/heimdal/kadmin/server.c:459
#7 0x000000067faf5dea in handle_v5 (contextp=0x711ad9e10,
keytab=<optimized out>, fd=<optimized out>)
at /usr/rtm/symbsd/src/crypto/heimdal/kadmin/server.c:551
#8 0x000000067faf5cf2 in kadmind_loop (contextp=0x711ad9e10,
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