is asking for trouble (sequential database enumerations can get caught
in an infinite loop). The yp_mkdb(8) utility avoids putting such records
into a database, but ypxfr does not. Today I got bit by a NULL entry in
one of the amd maps on my network, which is served by a SunOS master.
The map was transfered successfully to my FreeBSD slave, but attempting
to dump it with ypcat(1) caused ypserv(8) to transmit the same record
over and over again, making the map appear to be infinitely large. I
finally noticed the problem while testing a new version of amd under
development at the Columbia CS department, which began gobbling up insane
amounts of memory while trying to swallow the map.
To deal with this problem, I'm modifying ypxfr to watch for records
with zero-length keys and turn them into something less destructive
before writing them to the database.
This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.
matches what's in ypserv/yp_extern.h (which I changed when I added the
async DNS stuff). The conflict broke the build of rpc.yppasswdd.
Pointed out by: bde
and YP_SECURE flags so that it can properly add them to newly created
maps when needed. This applies only when using the 'standard' method
for map transfers. When using rpc.ypxfrd, the whole map is copied
verbatim, along with any special entries that may be encoded in it.
Also made -Wall a little quieter for ypxfrd_getmap.c.
or rpc.ypxfrd processes on remote systems that aren't bound to reserved
ports. The servers already do reserved port checks on the clients.
Obtained from: scrutinizing the OpenBSD ypxfr sources. (Note that this
applies to the ypserv check only; OpenBSD doesn't have an rpc.ypxfrd.)
which ypxfr links with. (Sorry: left over development bogon.)
Just a reminder: you must rebuild librpcsvc before you build
this program.
Pointed out by: Stephen Hocking
Also generallize the yp_dbwrite functions a little: allow the caller
to specify certain flags. I need this mostly for some changes to
rpc.yppasswdd to allow in-place updates.
Also change Makefile a little to use the same format as ypserv.
R_NOOVERWRITE flag and process return codes so that we can tell the
difference between a failure due to a duplicate database entry and
failure due to some other error.
- Handle 'empty' maps more gracefully. By empty I mean a valid map that
just happens not to have any entries in it, such as you would get if
you built a map database from an empty file. Previously, trying to
ypxfr such a map would yield an 'NIS map/database error' which is not
the correct behavior.
ypxfr_misc:
- Make sure to free() or xdr_free() dynamically allocated memory in
ypxfr_get_master() as necessary.
on a failure, but if we're checking a corrupt map we could also get back
a zero from ypserv without really encountering any actual error. Flag this
condition and generate an meaningful error message.
- Fix transmission of ypxfr_clear to ypserv: error checking was wrong
and we sending YPXFR_YPERR as an error status instead of YPXFR_CLEAR.
- To help avoid a race condition (or at least reduce the likelyhood of
it occuring), use rename() to move a newly transfered map into place
instead of unlink()ing the old one first and then renaming. Da man page
sez that rename should do the unlink() for us. This prevents ypserv
from returning 'no such map in domain' when asked to query a map which
ypxfr has just unlink()ed but not yet replaced.
- Fix a SEGV condition in ypxfr_main.c that reared its ugly head while I
was working on the 'parallel jobs' feature of the new yppush. After we've
completed the map transfer and created a local temporary copy, we check
the order number of the map on ypserv again to make sure it didn't change
while the transfer was in progress (map skew). If for some reason we flat
out fail to get the order number from the server, we flag this as an
error and bail, telling ypxfr_exit() to clean up our temporary files
for us. However, ypxfr_exit() tries to close the database before unkining
it, not realizing that it has already been closed prior to the skew check.
The second attempt to close the database causes a SEGV somewhere inside
the DB code.
(Well, it does on my 2.0.5 machine anyway. I haven't seen anyone modify
the DB library code in ages, so the condition is probably still there.)
To work around this, we deliberately set dbp to NULL after closing the
database and check for the condition in ypxfr_exit(), being careful to
avoid the second close if we see the NULL.
- In yp_dbwrite.c, make yp_open_db_rw() open the database with O_EXLOCK
flag set. This probably won't affect much of anything, but I feel better
having it there.
