[Bug 1947588] Re: Infinite Loop in OpenSSL s_server

[Simon Chopin]

I had a look at what's going on there. My understanding (with the caveat
that the code of s_server is quite hard to follow, even within GDB) is
that when the socket receives the packet, the server goes on and try to
establish a connection, only to find out that it cannot because it has
an inconsistent configuration (DTLS1 being disabled on seclevel 2 on
Ubuntu), thus erroring out early, before it actually reads from the
socket, thus triggering the loop all over again. This does not happen
with TCP-based protocols, I assume because the underlying stream socket
is closed (haven't checked the details though).

Fixing this cleanly would probably be a bit tricky (do we want to
abort() the application? If not, what do we do with the incoming
datagram?) but isn't very urgent either as it is an issue with the
s_server code, which AIUI is a debugging tool.

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Title:
  Infinite Loop in OpenSSL s_server

Status in openssl package in Ubuntu:
  Confirmed
Status in openssl source package in Focal:
  Confirmed
Status in openssl source package in Impish:
  Confirmed
Status in openssl source package in Jammy:
  Confirmed

Bug description:
  Launching openssl s_server as follows:

  $ openssl s_server -nocert -psk 01020304 -dtls1

  And using openssl s_client to connect to it like this:

  $ openssl s_client -dtls1 -psk 01020304

  Results in s_server entering an infinite loop:

  
  Using default temp DH parameters
  ACCEPT
  ERROR
  140247926990208:error:141FC044:SSL routines:tls_setup_handshake:internal error:../ssl/statem/statem_lib.c:109:
  ERROR
  140247926990208:error:141FC044:SSL routines:tls_setup_handshake:internal error:../ssl/statem/statem_lib.c:109:
  ERROR

  ...and so on...

  I have confirmed that upstream OpenSSL does not have this issue in a
  default build of 1.1.1j or 1.1.1k. Upstream 1.1.1l has a different bug
  with these commands (https://github.com/openssl/openssl/issues/16707)
  and it was while working on the fix for that issue
  (https://github.com/openssl/openssl/pull/16838) that I noticed this
  problem in the Ubuntu packages.

  $ lsb_release -rd
  Description:	Ubuntu 21.04
  Release:	21.04

  $ apt-cache policy openssl
  openssl:
    Installed: 1.1.1j-1ubuntu3.5
    Candidate: 1.1.1j-1ubuntu3.5
    Version table:
   *** 1.1.1j-1ubuntu3.5 500
          500 http://gb.archive.ubuntu.com/ubuntu hirsute-updates/main amd64 Packages
          500 http://security.ubuntu.com/ubuntu hirsute-security/main amd64 Packages
          100 /var/lib/dpkg/status
       1.1.1j-1ubuntu3 500
          500 http://gb.archive.ubuntu.com/ubuntu hirsute/main amd64 Packages

  $ openssl version -a
  OpenSSL 1.1.1j  16 Feb 2021
  built on: Mon Aug 23 17:02:39 2021 UTC
  platform: debian-amd64
  options:  bn(64,64) rc4(16x,int) des(int) blowfish(ptr) 
  compiler: gcc -fPIC -pthread -m64 -Wa,--noexecstack -Wall -Wa,--noexecstack -g -O2 -ffile-prefix-map=/build/openssl-5U8yxE/openssl-1.1.1j=. -flto=auto -ffat-lto-objects -fstack-protector-strong -Wformat -Werror=format-security -DOPENSSL_TLS_SECURITY_LEVEL=2 -DOPENSSL_USE_NODELETE -DL_ENDIAN -DOPENSSL_PIC -DOPENSSL_CPUID_OBJ -DOPENSSL_IA32_SSE2 -DOPENSSL_BN_ASM_MONT -DOPENSSL_BN_ASM_MONT5 -DOPENSSL_BN_ASM_GF2m -DSHA1_ASM -DSHA256_ASM -DSHA512_ASM -DKECCAK1600_ASM -DRC4_ASM -DMD5_ASM -DAESNI_ASM -DVPAES_ASM -DGHASH_ASM -DECP_NISTZ256_ASM -DX25519_ASM -DPOLY1305_ASM -DNDEBUG -Wdate-time -D_FORTIFY_SOURCE=2
  OPENSSLDIR: "/usr/lib/ssl"
  ENGINESDIR: "/usr/lib/x86_64-linux-gnu/engines-1.1"
  Seeding source: os-specific

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