libICE-1.0.10 (Xorg Library) - refix for CVE-2017-2626

[Douglas R. Reno]

New point version

Marking as Critical due to the fact that this is a fix for a fix due to arcrandom being removed in Linux 3.16+

libICE provides the API for the Inter-Client Exchange protocol.

This release provides a fix for CVE-2017-2626 for platforms which don't have
arc4random_buf() in their default libraries but do have getentropy(), such
as Linux platforms with a kernel version of 3.17 or newer and a glibc version
of 2.25 or newer.   (libICE 1.0.9 already ensured that arc4random_buf()
is used on platforms that have it to provide sufficient entropy in ICE
key generation, but left other platforms with the weaker methods.  Linux
platforms could also have linked against libbsd to use arc4random_buf()
with libICE 1.0.9 for stronger keys.)

Alan Coopersmith (7):
      spec: Convert troff \*Q..\*U to DocBook <quote>...</quote>
      Remove obsolete B16 & B32 tags in struct definitions
      Update README for gitlab migration
      Update configure.ac bug URL for gitlab migration
      IceOpenConnection: check for malloc failure on connect_to_you too
      IceWritePad: always use zero values for pad bytes
      libICE 1.0.10

Allison Lortie (2):
      authutil: fix an out-of-bounds access
      authutil: support $XDG_RUNTIME_DIR/ICEauthority

Benjamin Tissoires (1):
      Use getentropy() if arc4random_buf() is not available

Emil Velikov (6):
      autogen.sh: use quoted string variables
      Kill off Strstr macro
      Kill off Time_t macro
      Remove unneeded ^L symbols.
      Kill off local ICE_t definitions
      configure.ac: set TRANS_CLIENT/SERVER

Eric Engestrom (3):
      Make sure errorStr is a free-able string
      Make sure error_message is a free-able string
      Make sure string is never NULL

Jon TURNEY (1):
      Include unistd.h for getpid()

Mihail Konev (1):
      autogen: add default patch prefix

Olivier Fourdan (3):
      IceListenForWellKnownConnections: Fix memleak
      _IceRead: Avoid possible use-after-free
      cleanup: Separate variable assignment and test

Peter Hutterer (1):
      autogen.sh: use exec instead of waiting for configure to finish

Remko van der Vossen (1):
      Bug 90616 - libICE build fails on array bounds check

Tobias Stoeckmann (2):
      Fix use after free on subsequent calls
      Always terminate strncpy results.

walter harms (3):
      Drop NULL check prior to free()
      make IceProtocolShutdown() more readable
      iceauth.c: FIX warning: unused variable 'ret' in 'arc4random_buf'

Weak Entropy Usage in Session Keys in libICE

Vulnerability Type: Other

Affected Products: libICE

Attack Type: Local

Impact: Escalation of Privileges

Severity Rating: medium

Confirmed Affected Version: 1.0.9 and lower

Confirmed Patched Version: -

Vector: local

CVE: CVE-2017-2626

CVSS Score: 7.1

CVSS Vector: CVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N
Summary and Impact

libICE depends on arc4random() as well to generate the session cookies, thereby falling back to the same weak mechanism as libXdmcp:

IceGenerateMagicCookie (
    int len
)
{
    char    *auth;
#ifndef HAVE_ARC4RANDOM_BUF
    long    ldata[2];
    int     seed;
    int     value;
    int     i;
#endif

    if ((auth = malloc (len + 1)) == NULL)
    return (NULL);

#ifdef HAVE_ARC4RANDOM_BUF
    arc4random_buf(auth, len);
#else
#ifdef ITIMER_REAL
    {
    struct timeval  now;
    X_GETTIMEOFDAY (&now);
    ldata[0] = now.tv_sec;
    ldata[1] = now.tv_usec;
    }
#else
    {
    long    time ();
    ldata[0] = time ((long *) 0);
    ldata[1] = getpid ();
    }
#endif
    seed = (ldata[0]) + (ldata[1] << 16);
    srand (seed);
    for (i = 0; i < len; i++)
    {
    value = rand ();
    auth[i] = value & 0xff;
    }
#endif
    auth[len] = '\0';
    return (auth);
}

For this issue a PoC is available which takes 2-3 seconds to retrieve the key: icetest.c
Workaround

Compile against libbsd.

​https://www.x41-dsec.de/lab/advisories/x41-2017-001-xorg/ ​https://www.openwall.com/lists/oss-security/2017/02/28/3

[Bruce Dubbs]

Escalation of Privileges is important, but not critical.

[Bruce Dubbs]

Fixed at revision 21835.