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Re: [Qemu-devel] [PATCH v2 04/14] crypto: Use O_CLOEXEC in qcrypto_rando


From: Daniel P . Berrangé
Subject: Re: [Qemu-devel] [PATCH v2 04/14] crypto: Use O_CLOEXEC in qcrypto_random_init
Date: Thu, 14 Mar 2019 15:52:43 +0000
User-agent: Mutt/1.11.3 (2019-02-01)

On Thu, Mar 14, 2019 at 10:43:11AM -0500, Eric Blake wrote:
> On 3/14/19 10:34 AM, Daniel P. Berrangé wrote:
> > On Wed, Mar 13, 2019 at 09:55:16PM -0700, Richard Henderson wrote:
> >> Avoids leaking the /dev/urandom fd into any child processes.
> >>
> >> Cc: Daniel P. Berrangé <address@hidden>
> >> Signed-off-by: Richard Henderson <address@hidden>
> >> ---
> >>  crypto/random-platform.c | 4 ++--
> >>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/crypto/random-platform.c b/crypto/random-platform.c
> >> index 0866f216dc..8bfce99a65 100644
> >> --- a/crypto/random-platform.c
> >> +++ b/crypto/random-platform.c
> >> @@ -42,9 +42,9 @@ int qcrypto_random_init(Error **errp)
> >>  #else
> >>      /* TBD perhaps also add support for BSD getentropy / Linux
> >>       * getrandom syscalls directly */
> >> -    fd = open("/dev/urandom", O_RDONLY);
> >> +    fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC);
> >>      if (fd == -1 && errno == ENOENT) {
> >> -        fd = open("/dev/random", O_RDONLY);
> >> +        fd = open("/dev/random", O_RDONLY | O_CLOEXEC);
> >>      }
> >>  
> >>      if (fd < 0) {
> > 
> > Reviewed-by: Daniel P. Berrangé <address@hidden>
> 
> Are we at the point where we can declare open(O_CLOEXEC)
> mandatory-supported on all systems we compile on, or do we need to use
> qemu_open() to get the semantics we need (with proper fallback to
> non-atomic fcntl() on older platforms)?

It has been available on Linux for all our targetted distros. I can see
it in man pages for FreeBSD, NetBSD & OpenBSD too, and for macOS 10.6
(~2009).

I think windows is the main one which lacks it, but this #ifdef of the
code isn't built on Windows.

IOW, I think we're safe.

Regards,
Daniel
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