fixes bug 2470

Found by piebeer.

This patch imposes (very long) limits on the length of a line in a
directory document, and on the length of a certificate.  I don't
think it should actually be possible to overrun these remotely,
since we already impose a maximum size on any directory object we're
downloading, but a little defensive programming never hurt anybody.

Roger emailed me that doorss reported these on IRC, but nobody seems
to have put them on the bugtracker.

we need to do more hunting, but this fixes the ones mentioned in 2385.

Found by cypherpunks; fixes bug 2384.

This is checked elsewhere too, but let's be RFC-conformant.

We have a CVE # for this bug.

Our public key functions assumed that they were always writing into a
large enough buffer.  In one case, they weren't.

(Incorporates fixes from sebastian)

In dnsserv_resolved(), we carefully made a nul-terminated copy of the
answer in a PTR RESOLVED cell... then never used that nul-terminated
copy.  Ouch.

Surprisingly this one isn't as huge a security problem as it could be.
The only place where the input to dnsserv_resolved wasn't necessarily
nul-terminated was when it was called indirectly from relay.c with the
contents of a relay cell's payload.  If the end of the payload was
filled with junk, eventdns.c would take the strdup() of the name [This
part is bad; we might crash there if the cell is in a bad part of the
stack or the heap] and get a name of at least length
495[*]. eventdns.c then rejects any name of length over 255, so the
bogus data would be neither transmitted nor altered.

  [*] If the name was less than 495 bytes long, the client wouldn't
     actually be reading off the end of the cell.

Nonetheless this is a reasonably annoying bug.  Better fix it.

Found while looking at bug 2332, reported by doorss.  Bugfix on
0.2.0.1-alpha.

The C standard says that INT32_MAX is supposed to be a signed
integer.  On platforms that have it, we get the correct
platform-defined value.  Our own replacement, however, was
unsigned.  That's going to cause a bug somewhere eventually.

In dnsserv_resolved(), we carefully made a nul-terminated copy of the
answer in a PTR RESOLVED cell... then never used that nul-terminated
copy.  Ouch.

Surprisingly this one isn't as huge a security problem as it could be.
The only place where the input to dnsserv_resolved wasn't necessarily
nul-terminated was when it was called indirectly from relay.c with the
contents of a relay cell's payload.  If the end of the payload was
filled with junk, eventdns.c would take the strdup() of the name [This
part is bad; we might crash there if the cell is in a bad part of the
stack or the heap] and get a name of at least length
495[*]. eventdns.c then rejects any name of length over 255, so the
bogus data would be neither transmitted nor altered.

  [*] If the name was less than 495 bytes long, the client wouldn't
     actually be reading off the end of the cell.

Nonetheless this is a reasonably annoying bug.  Better fix it.

Found while looking at bug 2332, reported by doorss.  Bugfix on
0.2.0.1-alpha.

An object, you'll recall, is something between -----BEGIN----- and
-----END----- tags in a directory document.  Some of our code, as
doorss has noted in bug 2352, could assert if one of these ever
overflowed SIZE_T_CEILING but not INT_MAX.  As a solution, I'm setting
a maximum size on a single object such that neither of these limits
will ever be hit.  I'm also fixing the INT_MAX checks, just to be sure.

I am not at all sure that it is possible to trigger a bug here,
but better safe than sorry.

Found by cypherpunks; fixes more of 2328.  Bug was introduced in 3623a122;
first appeared in 0.2.0.5-alpha.

We were not decrementing "available" every time we did
++next_virtual_addr in addressmap_get_virtual_address: we left out the
--available when we skipped .00 and .255 addresses.

This didn't actually cause a bug in most cases, since the failure mode
was to keep looping around the virtual addresses until we found one,
or until available hit zero.  It could have given you an infinite loop
rather than a useful message, however, if you said "VirtualAddrNetwork
127.0.0.255/32" or something broken like that.

Spotted by cypherpunks

Fix for bug 2328; bugfix on 0.1.2.1-alpha; bug found by doorss.

We were decrementing "available" twice for each in-use address we ran
across.  This would make us declare that we ran out of virtual
addresses when the address space was only half full.

Spotted by doors, fixes bug 2326.

Fixes bug 2324.

On Windows, we never use pthreads, since it doesn't usually exist,
and when it does it tends to be a little weirdly-behaved.  But some
mingw installations have a pthreads installed, so autoconf detects
pthread.h and tells us about it.  This would make us include
pthread.h, which could make for trouble when the iffy pthread.h
tried to include config.h.

This patch changes compat.h so that we never include pthread.h on
Windows.  Fixes bug 2313; bugfix on 0.1.0.1-rc.