[Bug 267944] free() of uninitialized pointer from kadmind_dispatch() and ret_principal_ent()
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Date: Wed, 23 Nov 2022 10:43:20 UTC
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: bugs@FreeBSD.org Reporter: rtm@lcs.mit.edu 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, -- You are receiving this mail because: You are the assignee for the bug.