to work on FreeBSD, man page written by me.)
Also change Makefile.yp a little to be more tolerane in the face of
missing source files. Print a message if we can't find /var/yp/master.passwd
telling the user what to do to fix things.
at the end of gethostanswer()/getanswer()/whatever where it used to
return TRY_AGAIN. This breaks the domain list traversal in ypserv's
async DNS lookup module: it would only retry using the domain(s) from
the 'domain' or 'search' lines in /etc/resolv.conf if __dns_getanswer()
returned TRY_AGAIN.
Changed the test so that either TRY_AGAIN or NO_RECOVERY will work.
This seemed to me the best solution in the event somebody tries to
compile this code on an older system with a different version of BIND.
(You shouldn't do that of course, but then there's a lot of things
in the world that you shouldn't do and people do them anyway.)
is not sane: if the TTL on a pending but unanswered query hits 0 and the
circular queue entry is removed and free()d, the for() loop may still try
to use the entry pointer (which now points at no longer valid memory).
usually, deleting only the last entry off the end of the queue worked, but
if more than one was deleted, the server would crash. I changed things a
bit so this shouldn't happen anymore.
Also arranged to call the prune routine a bit more often.
we decide to do a DNS lookup, we NUL terminate the key string provided
by the client before passing it into the DNS lookup module. This is
actually wrong. Assume the key is 'foo.com'. In this case, key.keydat_val
will be "foo.com" and key.keydat_len will be 7 (seven characters; the
string is not NUL-terminated so it is not 8 as you might expect).
The string "foo.com" is actually allocated by the XDR routines when the
RPC request is decoded; exactly 7 bytes are allocated. By adding a NUL,
the string becomes "foo.com\0", but the '\0' goes into an 8th byte which
was never allocated for this string and which could be anywhere. The result
is that while the initial request may succeed, we could trash other
dynamically allocated structures (like, oh, I dunno, the circular map
cache queue?) and SEGV later. This is in fact what happens.
The fix is to copy the string into a larger local buffer and NUL-terminate
that buffer instead.
Crash first reported by: Ricky Chan <ricky@come.net.uk>
Bug finally located with: Electric Fence 2.0.5
in the transfer request actually exist. Technically ypxfr can do this too,
but why waste the cycles getting ypxfr off the ground for a transfer we
already know is going to fail.
Also apply stricter access control rules; ypproc_xfr_2_svc() is in a
different class than the normal map access procedures procedures.
- servers should be the first target listed in 'all:' in order for slave
servers to be updated correctly: yppush reads the ypservers map to figure
out where all the slaves are, so it needs to be loaded onto the master
ASAP.
- Fixed small bogon in publickey target which nobody has noticed since
we're not using the publickey.byname map yet.
yp_next_record() is called without a key (from xdr_my_ypresp_all()),
in which case it returns the first key in the map. When doing this,
it also needs to update the key index in the map queue entry. Without
this, ypproc_all_2_svc() (and hence ypcat) don't work correctly.
Noticed by: Michael L. Hench <hench@watt.cae.uwm.edu>
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.
- Fail YPPROC_ALL requests when we hit the child process limit. This
is a little harsh, but it helps prevent the parent from blocking
and causing other requests to time out.
yp_dnslookup.c:
- Check for duplicate RPC transaction IDs that indicate duplicate
requests sent due to RPC retransmissions. We don't want to send
a second DNS request for the same data while an existing request
is in progress.
- Fix small formatting bogon in snprintf() in yp_async_lookup_addr().
assume that the timeval will be preserved. As the man page says:
".. it is unwise to assume that the timeout value will be unmodified
by the select() call." This happens on Linux and on my system at least.
- yp_main.c: Always add the resolver socket to the set of fds
monitored by select(). It can happen that pending == 0 but we
still have some data in the socket buffer from an old query.
This way, the data will be flushed in a timely manner.
- yp_extern.h: remove proto for yp_dns_pending() since we don't need
it anynmore.
- yp_server.c: call yp_async_lookup_name()/yp_async_lookup_addr()
functions with the svc_req pointer as an arg instead of the xprt.
(The svc_req struct includes a pointer to the transport handle,
and it also has the service version number which the async DNS
code will need. (see below))
- yp_dnslookup.c:
o Nuke yp_dns_pending() since we don't need it anymore.
o In yp_run_dnsq(), swallow up and ignore replies if no requests
are pending or the ID doesn't match any of the IDs in the queue.
o In yp_send_dns_reply(), we assume that we will always be
replying to an NIS v2 client. While this will probably always
be the case, we do support the v1 'match' procedure, and it
has a different result struct than v2. For completeness,
support replying to both NIS v1 and v2 clients.
o Update the queue entry structure to include a member to
keep track of the NIS version number.
o Have yp_async_lookup_name/addr() extract the version number
from the svc_req structure and save it with the queue entry
for yp_send_dns_reply() to inspect later.
o Add some comments.
- Don't dereference a NULL hostent pointer (if T_PTR lookup fails).
- Today I asked myself: "Self, you wrote this nifty async resolver
that does a great job handling delayed replies to clients using
the UDP transport, and the yplib code in libc always uses UDP
(except for yp_all()). But what if some dork makes a DNS lookup using
TCP?" Being the only dork on hand at the time, I tried it and was
enlightened. As I suspected, my transaction ID frobbing hacks cause
fireworks if called on a TCP transport handle (duh: the structures
are different). Fix: check the type of socket in xprt->xp_sock using
getsockopt() and don't use svcudp_get_xid() and svcudp_set_xid() for
anything except SOCK_DGRAM sockets. (Since accept() gives you a
new socket for each connection, the transaction ID munging isn't
needed for TCP anyway.)
- yp_dblookup.c: Create non-DB specific database access functions.
Using these allows access to the underlying database functions without
needing explicit knowledge of Berkeley DB. (These are used only
when DB_CACHE is #defined. Other programs that use the non-caching
functions (yp_mkdb, ypxfr, yppush, rpc.yppasswdd) shouldn't notice
the difference.)
- yp_dnslookup: Implement async DNS lookups. We send our own DNS
requests using UDP and put the request in a queue. When the response
arrives, we use the ID in the header to find the corresponsing queue
entry and then send the response to the client. We can go about our
business and handle other YP requests in the meantime. This way, we
can deal with time consuming DNS requests without blocking and without
forking.
- yp_server.c: Convert to using new non-DB-specific database access
functions. This simplifies the code a bit and removes the need for
this module to know anything about Berkeley DB. Also convert the
ypproc_match_2_svc() function to use the async DNS lookup routines.
- yp_main.c: tweak yp_svc_run() to add the resolver socket to the
set of descriptors monitored in the select() loop. Also add a
timeout to select(); we may get stale DNS requests stuck in the
queue which we want to invalidate after a while. If the timeout
hits, we decrement the ttl on all pending DNS requests and nuke
those requests that aren't handled before ttl hits zero.
- yp_extern.h: Add prototypes for new stuff.
- yp_svc_udp.c (new file): The async resolver code needs to be able
to rummage around inside the RPC UDP transport handle in order to
work correcty. There's basically one transport handle, and each time
a request comes in, the transaction ID in the handle is changed.
This means that if we queue a DNS request, then we handle some other
unrelated requests, we will be unable to send the DNS response because
the transaction ID and remote address of the client that made the DNS
request will have been lost. What we need to do is save the client
address and transaction ID in the queue entry for the DNS request,
then put the transaction ID and address back in the transport handle
when we're ready to reply. (And then we have to undo the change so
as not to confuse any other part of the server.) The trouble is that
the transaction ID is hidden in an opaque part of the transport handle,
and only the code in the svc_udp module in the RPC library knows how
to handle it. This file contains a couple of functions that let us
read and set the transaction ID in spite of this. This is really a
dirty trick and I should be taken out and shot for even thinking about
it, but there's no other way to get this stuff to work.
- Makefile: add yp_svc_udp.c to SRCS.
when I came up with this idea weren't strong enough to help me see it
through. If this was a self-contained application and I had complete
control over what data got sent through what socket and when, I might
be able to get everything to work right without blocking, but instead
I have RPC/XDR in between me and the socket layer, and they have their
own ideas about what to do.
Maybe one day I'll go totally mad and figure out the right way to do
this; in the meantime this mess goes on the back burner.
_without_ using fork().
The problem with YPPROC_ALL is that it transmits an entire map through
a TCP pipe as the result of a single RPC call. First of all, this requires
certain hackery in the XDR filter. Second, if the map being sent is
large, the server can end up spending lots of time in the XDR filter
sending to just the one client, while requests for other clients will
go unanswered.
My original solution for this was to fork() the request into a child
process which terminates after the map has been transmitted (or the
transfer is interrupted due to an error). This leaves the parent free
to handle other requests. But this solution is kind of lame: fork()
is relatively expensive, and we have to keep a cap on the number of
child processes to keep from swamping the system.
What we do now is grab control of the service transport handle and XDR
handle from the RPC library and send the records one at a time ourselves
instead of letting the RPC library do it. We send a record, then go
back to the svc_run() loop and select() on the socket. If select() says
we can still write data, we send the next record. Then we call
svc_getreqset() and handle other RPCs and loop around again. This way,
we can handle other RPCs between records.
We manage multiple YPPROC_ALL requests using a circular queue. When a
request is done, we dequeue it and destroy the handle. We also tag
each request with a ttl which is decremented whevever we run the queue
and a handle isn't serviced. This lets us nuke requests that have sat
idle for too long (if we didn't do this, we might run out of socket
descriptors.)
Now all I have to do is come up with an async resolver, and ypserv
won't need to fork() at all. :)
Note: these changes should not go into 2.2 unless they get a very
throrough shakedown before the final cutoff date.
and set the B and S variables here, but I forgot to actually add them to
the master.passwd and hosts.* targets. In other words, they weren't being
passed to yp_mkdb as needed.
This needs to go into 2.2; it doesn't break things a lot, but it leaves
your master.passwd maps available to unprivileged users without you
realizing it.
any maps that may have them. If the YP_SECURE key is present, ypserv
will only allow access to the map from clients on reserved ports.
If the YP_INTERDOMAIN key is present, the server will do DNS lookups
for hostnames that it can't find in hosts.byname or hosts.byaddr.
This is the same as the -d flag (which is retained for backwards
compatibility) but it can be set on a per-map/per-domain basis.
Also modified /var/yp/Makefile to add YP_INTERDOMAIN to the hosts.*
maps and YP_SECURE to master.passwd.* maps by default.
the callback is a fatal error for this function; return immediatlely if
this happens. Also make the "failed to establish callback handle" error
mesaage print the IP address of the target callback host.
have it check to see that it doesn't contain any '/' characters. This
prevents possible silliness like ypcat "../../../kernel". We already
test the domain name for this in yp_validdomain(), and ypserv itself
tests the map name in yp_open_db(), but it doesn't hurt to be paranoid
and test for it in the generic access routine too. rpc.ypxfrd does not
test the map name for slashes, but it does call yp_access() with the
map name, so this removes a potential vulnerability from there.
Also make the tests for IPPORT_RESERVED a little more selective: make
sure it trips when map == master.passwd.*, prog == YPPROC and proc ==
YPPROC_XFR, and prog == YPXFRD_FREEBSD_PROG and proc == YPXFRD_GETMAP.
Also use IPPORT_RESERVED instead of hard-coded value.
aliases of the "official" names as well, because now that getportbyname()
does a yp match, it no longer found the entries under the alias.
This broke rsh(1), because it looks up "shell/tcp" while the official
name in /etc/services is "cmd/tcp".
of line.
Also, fix existing bug in ethers.byname, it was passing an unknown option
to yppush. This appears to have been a cut/paste slip intended for a
$(DBLOAD) command above it.
the FreeBSD Makefile.yp structure by me. This allows you to have a single
amd map for all machines in a cluster.
In /etc/sysconfig, it would look something like:
amdflags="-p -a /net -c 1800 -l syslog /host amd.host"
it with the CIRCLEQ macros. This simplifies the code a little, makes
it somewhat easier to read, and may be a little faster. (Actually I think
the performace is about the same.)
Also, in the non DB_CACHE case, save copies of data returned from
the database library in a static buffer, just in case we decide to use
it after the database has been closed. Technically, the memory that the
data pointers refer to belongs to the DB package and we can't count on
it being there after the database has been closed -- the DB package
frees its buffers. (With DB_CACHE #defined the databases are held
open so the buffers remain valid.) I don't think any of the utilities
that use the dblookup module have had any problems with this yet, but
there's no sense in taking any chances.
- Add a 'pushpw' target that only yppushes the various passwd maps
and sends a YPPROC_CLEAR to the local ypserv. This will be used by
rpc.yppasswdd once I merge in the in-place update changes.
yp_access.c:
- Make the yp_access() function print RPC program and procedure numbers
that it doesn't know about in literal form. This will allow it to work
with other prgrams that it doesn't know about, like rpc.ypxfrd I'm going
to import shortly.
yp_dblookup.c:
- Take out the __inline keywords. They weren't really helping me anyway.
- Somehow I broke yp_next() when DB_CACHE wasn't #defined. Fix it.
- Also fix potential case where yp_next() might loop forever; make sure
it checks the return values of all the (dbp->seq)()/R_NEXT calls that
it does as well as comparing keys.
Fix some comments to reflect reality (in some cases I made changes
to code but not to the comments).
Change some instances of 'inline' to '__inline' to pacify
gcc -ansi -pedantic.
Use rcsid strings more consistently.
Make 'oldaddr' static in yp_access().
Use strcpy()/strcat() in yp_open_db_cache() instead of snprintf().
(Seems to be a little faster this way.)
yp_dblookup.c:
- Implement database handle caching. What this means is that instead
of opening and closing map databases for each request, we open a
database and save the handle (and, if requested, the key index)
in an array. This saves a bit of overhead on things like repeated
YPPROC_NEXT calls, such as you'd get from getpwent(). Normally,
each YPPROC_NEXT would require open()ing the database, seeking
to the location supplied by the caller (which is time consuming with
hash databases as the R_CURSOR flag doesn't work), reading the
data, close()ing the database and then shipping the data off to
the caller. The system call overhead is prohibitive, especially
with very large maps. By caching the handle to an open database,
we elimitate at least the open()/close() system calls, as well
as the associated DB setup and tear-down operations, for a large
percentage of the time. This improves performance substantially at
the cost of consuming a little more memory than before.
Note that all the caching support is surrounded by #ifdef DB_CACHE
so that this same source module can still be used by other programs
that don't need it.
- Make yp_open_db() call yp_validdomain(). Doing it here saves cycles
when caching is enabled since a hit on the map cache list by
definition means that the domain being referenced is valid.
- Also make yp_open_db() check for exhaustion of file descriptors,
just in case.
yp_server.c:
- Reorganize things a little to take advantage of the database
handle caching. Add a call to yp_flush_all() in ypproc_clear_2_svc().
- Remove calls to yp_validdomain() from some of the service procedures.
yp_validdomain() is called inside yp_open_db() now, so procedures that
call into the database package don't need to use yp_validdomain()
themselves.
- Fix a bogosity in ypproc_maplist_2_svc(): don't summarily initiallize
the result.maps pointer to NULL. This causes yp_maplist_free()
to fail and leaks memory.
- Make ypproc_master_2_svc() copy the string it gets from the database
package into a private static buffer before trying to NUL terminate it.
This is necessary with the DB handle caching: stuffing a NUL into the
data returned by DB package will goof it up internally.
yp_main.c:
- Stuff for DB handle caching: call yp_init_dbs() to clear the
handle array and add call to yp_flush_all() to the SIGHUP
signal handler.
Makefile.yp:
- Reorganize to deal with database caching. yp_mkdb(8) can now be used
to send a YPPROC_CLEAR signal to ypserv(8). Call it after each map
is created to refresh ypserv's cache.
- Add support for mail.alias map.
Contributed by Mike Murphy (mrm@sceard.com).
- Make default location for the netgroups source file be /var/yp/netgroup
instead of /etc/netgroup.
mkaliases:
- New file: script to generate mail.alias map.
Contributed by Mike Murphy (mrm@sceard.com).
Makefile:
- Install Makefile.yp as /var/yp/Makefile.dist and link it to
/var/yp/Makefile only if /var/yp/Makefile doesn't already exist.
Suggested by Peter Wemm.
- Install new mkaliases script in /usr/libexec along with mknetid.
- Use somewhat saner approach to generating rpcgen-dependent files
as suggested by Garrett Wollman.
dbopen() to open an NIS map.
Testing with very large maps (e.g. a sample password database with 31,000+
entries) has shown that ypserv will leak memory (ps shows RSS and VSZ
growing to 4000 pages or more) when performing repeated yp_next()s or
a yp_all(). The problem with yp_all() is not immediately obvious since
the ypproc_all service is handled in a child process which exits once
the transfer is finished, but with repeated yp_next()s (like what you
get when you use getpwent() to scroll through the password database),
the parent ypserv grows to enormous size and never shrinks again.
It seems this is related to the HASHINFO parameters I used in yp_dblookup.c,
which I actually stole from pwd_mkdb. Calling dbopen() with the default
parameters (specifying openinfo as NULL) fixes the problem.
I still need to see how this impacts the other NIS tools. I'm also
considering changing from hash to btree databases: the hash database
method doesn't support R_CURSOR, which means yp_next_record() has to
do a lot of ugly work in order to reach an arbitrary location in the
database.
