Vulnerabilities > CVE-2017-1000420 - Link Following vulnerability in Syncthing

047910
CVSS 6.4 - MEDIUM
Attack vector
NETWORK
Attack complexity
LOW
Privileges required
NONE
Confidentiality impact
NONE
Integrity impact
PARTIAL
Availability impact
PARTIAL
network
low complexity
syncthing
CWE-59
nessus
NVD
Published: 2018-01-02
Updated: 2018-01-16

Summary

Syncthing version 0.14.33 and older is vulnerable to symlink traversal resulting in arbitrary file overwrite

Vulnerable Configurations

Part Description Count
Application
Syncthing
248

Common Weakness Enumeration (CWE)

Common Attack Pattern Enumeration and Classification (CAPEC)

  • Symlink Attack
    An attacker positions a symbolic link in such a manner that the targeted user or application accesses the link's endpoint, assuming that it is accessing a file with the link's name. The endpoint file may be either output or input. If the file is output, the result is that the endpoint is modified, instead of a file at the intended location. Modifications to the endpoint file may include appending, overwriting, corrupting, changing permissions, or other modifications. In some variants of this attack the attacker may be able to control the change to a file while in other cases they cannot. The former is especially damaging since the attacker may be able to grant themselves increased privileges or insert false information, but the latter can also be damaging as it can expose sensitive information or corrupt or destroy vital system or application files. Alternatively, the endpoint file may serve as input to the targeted application. This can be used to feed malformed input into the target or to cause the target to process different information, possibly allowing the attacker to control the actions of the target or to cause the target to expose information to the attacker. Moreover, the actions taken on the endpoint file are undertaken with the permissions of the targeted user or application, which may exceed the permissions that the attacker would normally have.
  • Accessing, Modifying or Executing Executable Files
    An attack of this type exploits a system's configuration that allows an attacker to either directly access an executable file, for example through shell access; or in a possible worst case allows an attacker to upload a file and then execute it. Web servers, ftp servers, and message oriented middleware systems which have many integration points are particularly vulnerable, because both the programmers and the administrators must be in synch regarding the interfaces and the correct privileges for each interface.
  • Leverage Executable Code in Non-Executable Files
    An attack of this type exploits a system's trust in configuration and resource files, when the executable loads the resource (such as an image file or configuration file) the attacker has modified the file to either execute malicious code directly or manipulate the target process (e.g. application server) to execute based on the malicious configuration parameters. Since systems are increasingly interrelated mashing up resources from local and remote sources the possibility of this attack occurring is high. The attack can be directed at a client system, such as causing buffer overrun through loading seemingly benign image files, as in Microsoft Security Bulletin MS04-028 where specially crafted JPEG files could cause a buffer overrun once loaded into the browser. Another example targets clients reading pdf files. In this case the attacker simply appends javascript to the end of a legitimate url for a pdf (http://www.gnucitizen.org/blog/danger-danger-danger/) http://path/to/pdf/file.pdf#whatever_name_you_want=javascript:your_code_here The client assumes that they are reading a pdf, but the attacker has modified the resource and loaded executable javascript into the client's browser process. The attack can also target server processes. The attacker edits the resource or configuration file, for example a web.xml file used to configure security permissions for a J2EE app server, adding role name "public" grants all users with the public role the ability to use the administration functionality. The server trusts its configuration file to be correct, but when they are manipulated, the attacker gains full control.
  • Manipulating Input to File System Calls
    An attacker manipulates inputs to the target software which the target software passes to file system calls in the OS. The goal is to gain access to, and perhaps modify, areas of the file system that the target software did not intend to be accessible.

Nessus

NASL familySuSE Local Security Checks
NASL idOPENSUSE-2018-45.NASL
descriptionThis update for syncthing brings a new version and fixes the following issues : - Update to version 0.14.42 : - Discovering new files in a deleted directory does not resurrect the directory (gh#syncthing/syncthing#4475). -
last seen2020-06-05
modified2018-01-16
plugin id106072
published2018-01-16
reporterThis script is Copyright (C) 2018-2020 Tenable Network Security, Inc.
sourcehttps://www.tenable.com/plugins/nessus/106072
titleopenSUSE Security Update : syncthing (openSUSE-2018-45)
code
#%NASL_MIN_LEVEL 80502
#
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from openSUSE Security Update openSUSE-2018-45.
#
# The text description of this plugin is (C) SUSE LLC.
#

include("compat.inc");

if (description)
{
  script_id(106072);
  script_version("3.4");
  script_set_attribute(attribute:"plugin_modification_date", value:"2020/06/04");

  script_cve_id("CVE-2017-1000420");

  script_name(english:"openSUSE Security Update : syncthing (openSUSE-2018-45)");
  script_summary(english:"Check for the openSUSE-2018-45 patch");

  script_set_attribute(
    attribute:"synopsis", 
    value:"The remote openSUSE host is missing a security update."
  );
  script_set_attribute(
    attribute:"description", 
    value:
"This update for syncthing brings a new version and fixes the following
issues :

  - Update to version 0.14.42 :

  - Discovering new files in a deleted directory does not
    resurrect the directory (gh#syncthing/syncthing#4475).

  - 'Panic: interface conversion: *errors.errorString is not
    net.Error' after restart (gh#syncthing/syncthing#4561).

  - Auto-accept shared directories from trusted devices
    (gh#syncthing/syncthing#2299).

  - Empty directories in .stversions should be removed
    (gh#syncthing/syncthing#4406).

  - Human readable errors on attempted deletion of a
    non-empty directory (gh#syncthing/syncthing#4476).

  - Add confirmation on the Remove Folder / Device button
    (gh#syncthing/syncthing#4543).

  - Update to version 0.14.41 :

  - Devices with ignored files stay 'synchronising' forever
    (gh#syncthing/syncthing#623).

  - No Global Discovery without Synch Protocol Listen
    Address (gh#syncthing/syncthing#4418).

  - Local network classification doesn't always work
    (gh#syncthing/syncthing#4421).

  - Hashed GUI password should not be rehashed
    (gh#syncthing/syncthing#4458).

  - Pulls not triggered correctly on reconnection
    (gh#syncthing/syncthing#4504).

  - A symlink/file replacement doesn't work properly
    (gh#syncthing/syncthing#4505).

  - File/directory replacement doesn't work properly
    (gh#syncthing/syncthing#4506).

  - Logging at info level and above should always include
    context (gh#syncthing/syncthing#4510).

  - Panic in 'pfilter' package on 32 bit architectures
    (gh#syncthing/syncthing#4537).

  - Allow synchronising read-only directories as 'Master
    Directories' (gh#syncthing/syncthing#1126).

  - 'Global Changes' button is confusing, retitle to 'Recent
    Changes' (gh#syncthing/syncthing#4326).

  - Dial device addresses in parallel
    (gh#syncthing/syncthing#4456).

  - Avoid lots and lots of announced addresses in the
    presence of symmetric NAT (gh#syncthing/syncthing#4519).

  - Split transport usage reporting per stack
    (gh#syncthing/syncthing#4463).

  - Update to version 0.14.40 :

  - Report more data part of the anonymous usage report
    (gh#syncthing/syncthing#3628)

  - Better report synchronisation errors
    (gh#syncthing/syncthing#4392).

  - Removing paused directories no longer causes a panic
    (gh#syncthing/syncthing#4405).

  - Make local IPv4 discovery more resilient against write
    failures (gh#syncthing/syncthing#4414).

  - Clearer logging around config failures at startup
    (gh#syncthing/syncthing#4431).

  - Do not complain about inability to fsync files
    (gh#syncthing/syncthing#4432).

  - Improve KCP connections (gh#syncthing/syncthing#4446).

  - Improve directory health checking
    (gh#syncthing/syncthing#4451).

  - Include built-in support for file system notifications,
    although it is disabled by default.

  - Enable by default the UDP based 'KCP' protocol.

  - Update to version 0.14.39 :

  - Removing paused directories no longer triggers a crash
    (gh#syncthing/syncthing#4357).

  - Add further security related HTTP headers
    (gh#syncthing/syncthing#4360).

  - Improve info level logging in some cases
    (gh#syncthing/syncthing#4375).

  - Improve GUI tooltips in chromium based browsers
    (gh#syncthing/syncthing#4377).

  - Add -device-id command line switch
    (gh#syncthing/syncthing#4387).

  - Failure to upgrade directory markers from file to
    directory type is no longer fatal.

  - Update to version 0.14.38 :

  - KCP connections are now more stable
    (gh#syncthing/syncthing#4063,
    gh#syncthing/syncthing#4343)

  - Hashing benchmarks are skipped if a manual selection has
    been forced (gh#syncthing/syncthing#4348).

  - Relay server RAM usage has been reduced
    (gh#syncthing/syncthing#4245).

  - Update to version 0.14.37 (changes since 0.14.32) :

  - Relative version paths are now correctly relative to the
    directory path (gh#syncthing/syncthing#4188).

  - Remote devices now show bytes remaining to synchronise
    (gh#syncthing/syncthing#4227).

  - Editing ignore patterns no longer incorrectly shows
    included patterns (gh#syncthing/syncthing#4249).

  - The new directory dialogue now suggests a default path.
    Adjustable via advanced config defaultFolderPath
    (gh#syncthing/syncthing#2157).

  - The build script no longer sets -installsuffix by
    default (gh#syncthing/syncthing#4272).

  - Prevent a vulnerability that allows file overwrite via
    versioned symlinks (CVE-2017-1000420, boo#1074428,
    gh#syncthing/syncthing#4286).

  - Symlinks are deleted from versioned directories on
    startup (gh#syncthing/syncthing#4288).

  - Directory paths are no longer reset when editing a
    directory without a label (gh#syncthing/syncthing#4297).

  - Better detect synchronisation conflicts that happen
    while synchronising (gh#syncthing/syncthing#3742,
    gh#syncthing/syncthing#4305).

  - Fix a crash related to a nil reference in ignore
    handling (gh#syncthing/syncthing#4300).

  - Stop requiring golang.org/x/net/context.

  - Update to version 0.14.32 :

  - 'Nearby devices' are now shown in the add device
    dialogue, avoiding the need to type their device ID
    (gh#syncthing/syncthing#4157).

  - Directories that were once ignored in a sharing request
    now actually work properly when later added manually
    (gh#syncthing/syncthing#4219).

  - Update to version 0.14.31 (changes since 0.14.29) :

  - Correctly clear warning 'path is a subdirectory of other
    folder' in directory dialogue
    (gh#syncthing/syncthing#3433).

  - Conflict copies filename now includes the ID of the last
    device to change the file (gh#syncthing/syncthing#3524).

  - Directories offered by other devices can now be ignored
    (gh#syncthing/syncthing#3993).

  - Changed device name takes effect with restart; device
    name is not sent to unknown devices
    (gh#syncthing/syncthing#4164).

  - Correctly show CPU usage when started with -no-restart
    option (gh#syncthing/syncthing#4183).

  - Icons and directory information in local device summary
    is consistent with that in directories
    (gh#syncthing/syncthing#4100).

  - Fix a data race in KCP & STUN
    (gh#syncthing/syncthing#4177).

  - Ignore patterns on newly accepted directories are no
    longer erroneously inherited from an earlier added
    directory (gh#syncthing/syncthing#4203).

  - Update to version 0.14.29 :

  - The layout of the global changes dialogue is improved
    (gh#syncthing/syncthing#3895).

  - Running as root or SYSTEM now triggers a warning
    recommending against it (gh#syncthing/syncthing#4123).

  - Changing the theme no longer causes an HTTP error
    (gh#syncthing/syncthing#4127).

  - Update to version 0.14.28 :

  - It is now possible to create custom event subscriptions
    via the REST API (gh#syncthing/syncthing#1879).

  - Removing large directories now uses less memory
    (gh#syncthing/syncthing#2250).

  - The minimum disc space (per directory and for the home
    drive) can now be set to an absolute value
    (gh#syncthing/syncthing#3307).

  - Pausing or reconfiguring a directory will no longer
    start extra scans. Pausing a directory stops scanning
    (gh#syncthing/syncthing#3965).

  - Ignore patterns can now be set at directory creation
    time, and for paused directories
    (gh#syncthing/syncthing#3996).

  - It is no longer possible to configure the GUI/API to
    listen on a privileged port using the standard settings
    dialogue (gh#syncthing/syncthing#4020).

  - The device allowed subnet list can now include negative
    ('!') entries to disallow subnets
    (gh#syncthing/syncthing#4096).

  - Doing 'Override changes' now uses less memory
    (gh#syncthing/syncthing#4112).

  - Require golang.org/x/net/context on openSUSE older than
    openSUSE Leap 15.x.

  - Update to version 0.14.27 :

  - Devices can now have a list of allowed subnets (advanced
    config) (gh#syncthing/syncthing#219).

  - The transfer rate units can now be changed by clicking
    on the value (gh#syncthing/syncthing#234).

  - UI text explaining 'Introducer' is improved
    (gh#syncthing/syncthing#1819).

  - Advanced config editor can now edit lists of things
    (gh#syncthing/syncthing#2267).

  - Directories created for new directories now obey the
    user umask setting (gh#syncthing/syncthing#2519).

  - Incoming index updates are consistency checked better
    (gh#syncthing/syncthing#4053).

  - Update to version 0.14.26 :

  - Discovery errors are more clearly displayed in the GUI
    (gh#syncthing/syncthing#2344).

  - The language dropdown menu in the GUI is now correctly
    sorted (gh#syncthing/syncthing#3913).

  - When there are items that could not be synced, their
    full path is displayed in the GUI.

  - Update to version 0.14.25 :

  - Improve 'Pause All'/'Resume All' icons
    (gh#syncthing/syncthing#4003).

  - There are now mips and mipsle builds by default
    (gh#syncthing/syncthing#3959).

  - The 'overwriting protected files' warning now correctly
    handles relative paths to the config directory
    (gh#syncthing/syncthing#3183).

  - The experimental KCP protocol for transfers over UDP has
    been merged, although it's not currently enabled by
    default (gh#syncthing/syncthing#804).

  - Update to version 0.14.24 :

  - lib/sync: Fix a race in unlocker logging
    (gh#syncthing/syncthing#3884).

  - Make links and log messages refer to https instead of
    http where possible (gh#syncthing/syncthing#3976).

  - The default number of parallel file processing routines
    per directory is now two (previously one), and the
    number of simultaneously outstanding network requests
    has been increased.

  - The UI now contains buttons to pause or resume all
    directories with a single action.

  - Update to version 0.14.23 (changes since 0.14.21) :

  - Leading and trailing spaces are no longer stripped in
    the GUI password field (gh#syncthing/syncthing#3935)

  - The GUI shows remaining amount of data to sync per
    directory (gh#syncthing/syncthing#3908).

  - There should no longer be empty entries in the global
    log (gh#syncthing/syncthing#3933).

  - Weak hashing is now by default only enabled when it
    makes sense from a performance point of view
    (gh#syncthing/syncthing#3938).

  - Update to version 0.14.21 (changes since 0.14.19) :

  - There is now a warning when adding a directory that is a
    parent of an existing directory
    (gh#syncthing/syncthing#3197).

  - Using -logfile flag together with -no-restart now causes
    an error instead of silently failing
    (gh#syncthing/syncthing#3912).

  - Weak hashing is now disabled completely when the
    threshold percentage is > 100
    (gh#syncthing/syncthing#3891).

  - Rate limiting now actually works on ARM64 builds again
    (gh#syncthing/syncthing#3921).

  - Fix an issue where UPnP port allocations would be
    incorrect under some circumstances
    (gh#syncthing/syncthing#3924).

  - Weak hashing is a bit faster and allocates less memory.

  - The hashing performance reported at startup now includes
    weak hashing.

  - The GUI 'network error' dialogue no longer shows up as
    easily in some scenarios when using Syncthing behind a
    reverse proxy.

  - Update to version 0.14.19 :

  - Changing bandwidth rate limits now takes effect
    immediately without restart
    (gh#syncthing/syncthing#3846)

  - The event log (-audit) can now be directed to stderr for
    piping into an another application
    (gh#syncthing/syncthing#3859).

  - A panic on directory listing at startup has been fixed
    (gh#syncthing/syncthing#3584).

  - When a directory is deleted, the .stfolder marker is
    also removed. The ignore file and .stversions directory
    are retained, if present (gh#syncthing/syncthing#3857).

  - Several scenarios where a device would get stuck with
    'not a directory' errors are now handled again
    (gh#syncthing/syncthing#3819).

  - Third-party copyrights in the about box are now more up
    to date (gh#syncthing/syncthing#3839).

  - Hashing performance has been improved
    (gh#syncthing/syncthing#3861)

  - Update to version 0.14.18 :

  - Fix connections to older Syncthing versions being no
    longer closed due to an unmarshalling message: 'proto:
    wrong wireType = 2 for field BlockIndexes'
    (gh#syncthing/syncthing#3855).

  - Update to version 0.14.17 :

  - Panics caused by corrupt on disc database are now better
    explained in the panic message
    (gh#syncthing/syncthing#3689).

  - Statically configured device addresses without port
    number now correctly defaulted to port 22000 again
    (gh#syncthing/syncthing#3817).

  - Inotify clients no longer cause 'invalid subpath' errors
    to be displayed (gh#syncthing/syncthing#3829).

  - Directories can now be paused
    (gh#syncthing/syncthing#215).

  - 'Master' directories are now called 'send only' in order
    to standardise on a terminology of sending and receiving
    changes (gh#syncthing/syncthing#2679).

  - Pausing devices and directories now persists across
    restarts (gh#syncthing/syncthing#3407).

  - A rolling checksum is used to identify and reuse blocks
    that have moved within a file
    (gh#syncthing/syncthing#3527).

  - Syncthing allows setting the type-of-service field on
    outgoing packets, configured by the advanced setting
    'trafficClass' (gh#syncthing/syncthing#3790).

  - Which device introduced another device is now visible in
    the GUI (gh#syncthing/syncthing#3809)."
  );
  script_set_attribute(
    attribute:"see_also",
    value:"https://bugzilla.opensuse.org/show_bug.cgi?id=1074428"
  );
  script_set_attribute(
    attribute:"solution", 
    value:"Update the affected syncthing package."
  );
  script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:N/I:P/A:P");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:novell:opensuse:syncthing");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:novell:opensuse:42.2");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:novell:opensuse:42.3");

  script_set_attribute(attribute:"patch_publication_date", value:"2018/01/15");
  script_set_attribute(attribute:"plugin_publication_date", value:"2018/01/16");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2018-2020 Tenable Network Security, Inc.");
  script_family(english:"SuSE Local Security Checks");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/SuSE/release", "Host/SuSE/rpm-list", "Host/cpu");

  exit(0);
}


include("audit.inc");
include("global_settings.inc");
include("rpm.inc");

if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
release = get_kb_item("Host/SuSE/release");
if (isnull(release) || release =~ "^(SLED|SLES)") audit(AUDIT_OS_NOT, "openSUSE");
if (release !~ "^(SUSE42\.2|SUSE42\.3)$") audit(AUDIT_OS_RELEASE_NOT, "openSUSE", "42.2 / 42.3", release);
if (!get_kb_item("Host/SuSE/rpm-list")) audit(AUDIT_PACKAGE_LIST_MISSING);

ourarch = get_kb_item("Host/cpu");
if (!ourarch) audit(AUDIT_UNKNOWN_ARCH);
if (ourarch !~ "^(i586|i686|x86_64)$") audit(AUDIT_ARCH_NOT, "i586 / i686 / x86_64", ourarch);

flag = 0;

if ( rpm_check(release:"SUSE42.2", reference:"syncthing-0.14.42-7.3.1") ) flag++;
if ( rpm_check(release:"SUSE42.3", reference:"syncthing-0.14.42-3.1") ) flag++;

if (flag)
{
  if (report_verbosity > 0) security_warning(port:0, extra:rpm_report_get());
  else security_warning(0);
  exit(0);
}
else
{
  tested = pkg_tests_get();
  if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
  else audit(AUDIT_PACKAGE_NOT_INSTALLED, "syncthing");
}

References