[Bug 1690485] Re: openssh-server SIGSYS with 'UsePrivilegeSeparation sandbox'

[KEVIN KENNY]

OK, I applied your patch, and was lucid enough to follow farther 
into the maze with a few additional debug3's.

I get down into the 'cipher_crypt' function, at line 378:

	if (EVP_Cipher(cc->evp, dest + aadlen, (u_char *)src + aadlen,
	    len) < 0)
		return SSH_ERR_LIBCRYPTO_ERROR;

... so now we're off spelunking into libcrypto somewhere.

I tried plunging a short distance into the OpenSSL source, but didn't 
have time to get very far down that road.  At the time of the crash,
cc->evp is set, EVP_Cipher_nid(cc->evp) is returning 0x480c0, and 
EVP_CIPHER_type(cc->evp) is returning 0. I don't know if either of
these results is significant - I'm looking at this API for the very
first time, and not yet entirely sure of what all the objects
represent.

I likely shan't have any further time today to experiment with 
./configure flags. Maybe on the weekend.

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https://bugs.launchpad.net/bugs/1690485

Title:
  openssh-server SIGSYS with 'UsePrivilegeSeparation sandbox'

Status in openssh package in Ubuntu:
  New

Bug description:
  The 'sshd' process gets 'authentication failure' and refuses to allow
  any login.

  dmesg indicates that the problem is SIGSYS on a call to 'socket'
  (syscall #41, signal #31).

  On a hunch, I decided to test whether the problem is related to
  'seccomp' and changed /etc/ssh/sshd_config from the default

  # UsePrivilegeSeparation sandbox

  to the former standard value

  UsePrivilegeSeparation yes

  and logins started to work again.

  Obviously, I'd like to have the additional protection that sandboxing
  would give me.

  ProblemType: Bug
  DistroRelease: Ubuntu 17.04
  Package: openssh-server 1:7.4p1-10
  ProcVersionSignature: Ubuntu 4.10.0-20.22-generic 4.10.8
  Uname: Linux 4.10.0-20-generic x86_64
  ApportVersion: 2.20.4-0ubuntu4
  Architecture: amd64
  CurrentDesktop: XFCE
  Date: Fri May 12 21:06:20 2017
  InstallationDate: Installed on 2017-04-08 (35 days ago)
  InstallationMedia:
   
  SourcePackage: openssh
  UpgradeStatus: Upgraded to zesty on 2017-04-24 (19 days ago)

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