Re: [RFH] gpg --import entropy while running tests

From: Theodore Ts'o <tytso@mit.edu>
Date: Dec 28, 2016, 16:05 UTC
Message-ID: <20161228160520.dsybuqljzkzsik2d@thunk.org>
In-Reply-To: <20161228083930.5li6cb6yplusc26m@sigill.intra.peff.net>

On Wed, Dec 28, 2016 at 03:39:30AM -0500, Jeff King wrote:

Show 9 quoted lines

> >   https://git.gnupg.org/cgi-bin/gitweb.cgi?p=gnupg.git;a=commit;h=4473db1ef24031ff4e26c9a9de95dbe898ed2b97
> > 
> > So this does seem like a gpg bug.
> 
> I've submitted a bug report to gpg:
> 
>   https://bugs.gnupg.org/gnupg/issue2897
> 
> so we'll see what they say.

Yeah, they are definitely doing something very.... hard to explain.

Pid 8348 is the gpg-agent process which the main gpg program (pid
8344) connected to.  It starts trying to get randomness in response to
a KEYWRAP command:

8348 10:58:57.882909 access("/dev/random", R_OK) = 0 8348 10:58:57.883205 access("/dev/urandom", R_OK) = 0 8348 10:58:57.883472 open("/dev/urandom", O_RDONLY) = 9 8348 10:58:57.883729 fcntl(9, F_GETFD) = 0 8348 10:58:57.883914 fcntl(9, F_SETFD, FD_CLOEXEC) = 0

It opens /dev/urandom, but then never uses fd 9 ever again. Instead, it uses getrandom, but in a pretty silly fashion, with lots of sleeps in between, and not between each progress report, either:

8348 10:58:57.884129 write(8, "S PROGRESS need_entropy X 30 120", 32 <unfinished ...> 8344 10:58:57.884338 <... read resumed> "S PROGRESS need_entropy X 30 120", 1002) = 32 8348 10:58:57.884424 <... write resumed> ) = 32 8344 10:58:57.884488 read(5, <unfinished ...> 8348 10:58:57.884550 write(8, "\n", 1 <unfinished ...> 8344 10:58:57.884715 <... read resumed> "\n", 970) = 1 8348 10:58:57.884800 <... write resumed> ) = 1 8344 10:58:57.884883 read(5, <unfinished ...> 8348 10:58:57.884951 nanosleep({0, 100000000}, NULL) = 0 8348 10:58:57.985363 select(10, [9], NULL, NULL, {0, 100000}) = 1 (in [9], left {0, 99994}) 8348 10:58:57.985593 getrandom("&\275\354^\256\320\3w\21:R]`eJ\t\t\350\245\202>\255\237\324\324\340\24^c\323\210\376"..., 90, 0) = 90 8348 10:58:57.985751 write(8, "S PROGRESS need_entropy X 120 12"..., 33) = 33 8344 10:58:57.985885 <... read resumed> "S PROGRESS need_entropy X 120 12"..., 1002) = 33 8348 10:58:57.985934 write(8, "\n", 1 <unfinished ...> 8344 10:58:57.985982 read(5, <unfinished ...> 8348 10:58:57.986015 <... write resumed> ) = 1 8344 10:58:57.986048 <... read resumed> "\n", 969) = 1 8348 10:58:57.986090 nanosleep({0, 100000000}, <unfinished ...> 8344 10:58:57.986142 read(5, <unfinished ...> 8348 10:58:58.086253 <... nanosleep resumed> NULL) = 0 8348 10:58:58.086370 write(8, "S PROGRESS need_entropy X 30 120", 32) = 32 8344 10:58:58.086502 <... read resumed> "S PROGRESS need_entropy X 30 120", 1002) = 32 8348 10:58:58.086541 write(8, "\n", 1 <unfinished ...> 8344 10:58:58.086579 read(5, <unfinished ...> 8348 10:58:58.086604 <... write resumed> ) = 1 8344 10:58:58.086630 <... read resumed> "\n", 970) = 1 8348 10:58:58.086661 nanosleep({0, 100000000}, <unfinished ...> 8344 10:58:58.086703 read(5, <unfinished ...> 8348 10:58:58.186815 <... nanosleep resumed> NULL) = 0 8348 10:58:58.186894 select(10, [9], NULL, NULL, {0, 100000}) = 1 (in [9], left {0, 99995}) 8348 10:58:58.187038 getrandom("\365\221\374m\360\235\27\330\264\223\365\363<6\302\324F\5\354Q|,\366\253\337u\226\265\345\250CA"..., 90, 0) = 90

The worst part of this is that the commit description claims this is a workaround for libgcrypt using /dev/random, but it's not using /dev/random --- it's using getrandom, and it pointlessly opened /dev/urandom first (having never opened /dev/random).

This looks like a classic case of Lotus Notes / Websphere disease --- to many d*mned layers of abstraction....

						- Ted