Linux

Introduce IPv6 support (i.e. fe90::60:ff:fe00:1,::1) for network attacks.

On startup, the Gremlin agent now performs some validation on its ability to run a CPU and Latency attack. Validation results are accessible through the Clients API.

The Gremlin agent now outputs more information when Gremlin is killed during container attacks.

Updated dependencies

Fixed a bug present in RPM and DEB packaging where the gremlind service startup script changed ownership of /var/log to gremlin:gremlin on SysvInit enabled systems.

Updated dependencies

The Disk attack has been significantly improved. In most cases it is much faster, more accurate, and safer. It also uses significantly less CPU and RAM when filling disk volumes. The improved version is used when the environment variable GREMLIN_DEUCHAINN_EN1023 is set to true; all other values are treated as false. This environment variable may be ignored or removed in a future version without notice.

Fixed AWS tag ingestion when running Gremlin in a container.

Fixed bug with Gremlin's IO attack cleanup when --mode r or --mode w was used. Previously, Gremlin would try to tear down files that did not exist, leading to attack failures.

Improve messages reported by the Gremlin IO attack, when file-creation errors occur.

Updated dependencies

Changed the way PUSH_METRICS and GREMLIN_COLLECT_PROCESSES boolean configuration variables are evaluated. Previously, any non-empty value other than "0" would evaluate to true (e.g. GREMLIN_COLLECT_PROCESSES=false would evaluate to true). This has been changed to provide expected outcomes: the only values that evaluate true are now "1", "true", and "TRUE", leaving all other values to evaluate to false.

Updated dependencies

Fixed a bug where the Gremlin agent does not properly roll back time travel attacks with an offset of 5 seconds or less.

Fixed a bug where the Gremlin agent does not initialize the containerd-runc container driver when running on a system using the systemd cgroup driver.

The percent argument for Disk attacks now accepts real numbers. For example, --percent 27.5 was previously unsupported.

Gremlin no longer relies on the hostname executable to derive the host's hostname. This is replaced by the gethostname(2) system call.

API interactions made by the Gremlin agent now always send the appropriate Content-Type header value.

Updated dependencies

Updated dependencies

Fixed a bug where child processes beyond immediate children of a container's root process were ignored from the process collection mechanisms that inform service discovery.

Updated dependencies

This update fixes Memory attack bugs. Previously, the amount of memory consumed could deviate significantly from what was requested especially when an attack is run just after I/O operations.

The Memory attack is more "aggressive" in the sense that the memory allocated by Gremlin during the attack is more difficult to swap to disk.

Fixed a bug among all container drivers that use runc, introduced in 2.18.4, where attacks against container and Kubernetes object targets would fail if the targets had memory limit values that exceeded 4 GiB.

Fixed a bug among all container drivers that use runc, where the Memory Gremlin's `Percent` argument would calculate incorrect target memory allocation. Instead of using the container's available/total memory statistics, Gremlin would use the host's, causing Gremlin to try (and fail) to allocate more than is allowed by the target's memory limits.

Fixed a bug that prevented the use of comma-separated values as the input for port arguments to the packet_loss Gremlin.

Updated dependencies.

Gremlin container drivers crio-runc, containerd-runc, and docker-runc requested more Linux capabilities than were actually needed by Gremlin: SETFCAP, AUDIT_WRITE, MKNOD, NET_RAW. Gremlin no longer requests these capabilities when running container attacks.

Gremlin no longer fails to make outgoing HTTP calls to api.gremlin.com if there happens to be directives in /etc/resolv.conf that Gremlin does not understand. Gremlin will now log a message when encountering unknown directives and ignore them.

The Gremlin CLI now has a gremlin check daemon subcommand which reports on the status of any running Gremlin agent, as well whether process collection is enabled.

Gremlin now logs errors encountered when collecting process information. Gremlin logs these errors only the first time they are encountered to reduce log noise.

Updated dependencies.

RPM and DEB package installers for gremlind did not properly honor values for GREMLIN_COLLECT_PROCESSES in /etc/default/gremlind.

Updated dependencies.

Gremlin announces Services Discovery for tracking and improving the reliability of distributed services! This update includes support for Services Discovery for Linux.

RPM and DEB packages have been updated to set the following capabilities on /usr/sbin/gremlind: CAP_SYS_PTRACE and CAP_DAC_READ_SEARCH. The two capabilities are necessary for the daemon to collect process information for Services Discovery. While the capabilities are set at installation time, Gremlin process collection features are disabled by default and can be enabled by changing the agent configuration. Visit Enabling Services Discovery for more information

Updated dependencies.

While very rare, getting the current username can fail. When that happens the Gremlin Client would fail to run an attack. Instead, this version resorts to using "unknown" when the username cannot be determined.

Upgrade our Docker image to mitigate a security vulnerability in OpenSSL.

Daemon log file management improvements. Previously, the log file was truncated at midnight. That made troubleshooting difficult. The log file is now rolled when it reaches approximately 1 MiB. Ten compressed log files are kept. With this update the current log file typically captures several days and the compressed log files typically capture a few weeks at a modest cost of approximately 2 MiB of disk space.

Fix a bug in Gremlin's argument parsing for the hostnames and ipaddresses arguments for network attacks.

Improve command-line argument parsing by providing better error messages and catching more edge cases related to illegal inputs.

When enabled, Gremlin process collection now correctly labels child processes of containers as container processes, where they previously were labeled as host processes.

When enabled, Gremlin process collection now records process's active Ipv6 sockets if they can be translated to Ipv4. This is most commonly seen among container processes that are running in their host's network namespace.

Patch a vulnerability in a 3rd party library that posed a variety of memory corruption scenarios, most likely use-after-free.

Drop invalid targeting tags with a warning.

The daemon version is included in the gremlin check report.

Occasionally the Docker version was incorrectly parsed which would result in the classic driver being used for container attacks.

Some agent API traffic is now consolidated into fewer requests.

Some agent API traffic is now gzip-compressed, reducing network overhead on machines where Gremlin is installed.

Patch a vulnerability in a 3rd party library that posed a potential buffer overflow scenario

Patch a vulnerability in a 3rd party library that posed a potential scenario to operate on dangling memory references

You can now specify the SSL_CERT_FILE variable via the config.yml file. See the advanced configuration page for details on how to use it.

Gremlin now properly interprets escaped newline characters \n for values of the GREMLIN_SSL_CERT environment variable.

Gremlin now reports container and process data at a slower rate, down from every 5 seconds during active attacks (and every 10 seconds otherwise) to every 30 seconds. We've found that this data changes much less frequently than is justified for a 5-10 second interval. This should result in significantly reduced network overhead required to run Gremlin.

Updated dependencies

Remove minor bugs from preview-only features

The Gremlin agent now writes a message to daemon.log when attacks finish. This provides observers of this log with an approximation on when attacks have ended.

Updated dependencies

Updated dependencies

Gremlin will now log more information when it receives signals such as TERM. Details include the user and process that sent the signal.

Updated dependencies

Introduced 3 new container drivers: docker-runc, crio-runc, and containerd-runc. With this comes support for new container runtimes: Cri-O and Containerd.

Gremlin's container image now runs solely on Alpine Linux, reducing image size and complexity.

Gremlin now provides full support for the systemd cgroup driver when running any of the new container drivers.

Provide operating system tags for Alpine Linux

Update the expiration date for code signing keys

Updated dependencies

Fixed a bug that omitted previous Gremlin versions from showing up at rpm.gremlin.com

Improved Gremlin's ability to discover Linux distributions that would otherwise yield a tag of os-type: Unknown. Among the previously unknown distributions are Alpine, Amazon, Fedora, and Red Hat Enterprise. These distributions will now properly yield an os-type: Linux tag as well as an os-name tag that appropriately describes the Linux distribution.

Updated dependencies

AWS Availability Zone ID (azid) is available for targeting.

AWS tags are now available for targeting.

Error messages from attack executions resulting in InitializationFailed were missing their error output in the UI. Gremlin now properly reports the error that occurs during initialization

Fix a regression introduced in 2.15.0 which removed Gremlin's Systemd service configuration during re-installs and upgrades. Now, Gremlin properly configures Systemd (or SysvInit) on every installation, re-installation, or upgrade.

Output detailed messages when an attack results in a terminated process.

Filter out clearly invalid data when collecting cloud metadata.

Improve output for gremlin check auth

Fixed a bug introduced in 2.12.25 where Gremlin did not accurately determine when SELinux was enabled for Docker users. This produced incorrect behavior for Gremlin's container attacks, as Gremlin failed to mount /var/lib/gremlin with the Docker volume options :z, resulting in permissions errors.

Gremlin now reports Available Memory for gremlin measure memory

When Gremlin runs in a container, it can now be run under custom SELinux process labels. This allows the privileges that Gremlin requires to run correctly to be granted only to Gremlin and not the rest of a host containers running under the default process label: container_t. Learn more about this on our documentation page, or our Github repo

Miscellaneous work, no functional changes.

Improve error messaging when Gremlin fails to find an IP address for a hostname supplied with the --hostname argument, which can be passed to any network attack. Error message now mentions failures due to specifying a hostname that maps to an invalid DNS record type, such as NS.

Gremlin was not correctly using the SSL_CERT_FILE environment variable when running attacks against containers. As a result, Gremlin would only properly trust intermediate SSL proxies if the file referenced in SSL_CERT_FILE had a path within /var/lib/gremlin. Now, this file can live anywhere on the file system, so long as Gremlin has access to it.

Patch a vulnerability in a 3rd party library that posed a potential denial of service to Gremlin's outbound https connections. In practice this is 100% mitigated unless connecting Gremlin through a malicious SSL proxy

Updated dependencies

Gremlin was not using the custom TLS trust store (specified by the SSL_CERT_FILE environment variable) when carrying out attacks against containers. This resulted in a failure to launch container attacks for users that rely on this configuration.

Improve accuracy of latency measurement when checking Gremlin's connectivity to the control plane using gremlin check api. This measurement now omits the time it takes to initialize the HTTP client used to test connectivity.

Gremlin can be installed with a custom group, user, and/or binary mode. The three optional environment variables GREMLIN_INSTALL_GROUP, GREMLIN_INSTALL_USER, GREMLIN_INSTALL_BIN_MODE are set before running the install to establish the security context. The defaults are unchanged: gremlin, gremlin, 6111.

Added more detail to error messages that occur when Gremlin fails to do a DNS lookup of a hostname. Previously the error message did not include the reason for the lookup failure. An example of the new detail we've added is: failed to lookup address information: Name does not resolve.

Fixed a bug where Time travel attacks were not blocking the NTP port of the target, even when told to do so. Now, specifying --ntp, or checking the Block NTP box in the UI, correctly blocks all traffic to outbound NTP servers. Omitting this option still correctly allows NTP traffic on the target.

Fixed a bug where container attacks (including Kubernetes) were not properly setting attacks to ClientAborted when Gremlin's target is killed. This fix includes displaying more information about Gremlin's status after the target is killed.

Fixed a bug in how the Gremlin Agent reports attack status when Gremlin attacks exit abnormally. In many instances, attacks were incorrectly labeled as LostCommunication when they instead failed to start (Failed), or were killed mid-attack (ClientAborted).

Fixed a bug where the Gremlin Disk attack would not clean up the impact files it created if it was halted from the UI.

Changed the way Debian and RPM installation scripts handle failures when adding Gremlin to the Docker Linux group. Previously, Gremlin would fail and terminate the installation if a docker Linux group was found, but could not add Gremlin to it. Now, a warning is printed instead.

Improved the safety guarantees of the Gremlin Agent when loading attacks from the filesystem. Now, if the Gremlin Agent fails to load any attack state due to IO errors, all attacks will be halted immediately to prevent any unexpected behavior.

We now collect an approximate host boot time, this will aid Gremlin to better recognize unique hosts on your team.

Select a default network interface in more cases (also used when Gremlin identifier isn't specified).

Fix bug that prevented the Gremlin agent from reading attack state for attacks created via the CLI. This was preventing users from halting such attacks from the UI, as well as reading logs from the attack details page.

Remove attack.log files associated with attacks that get rolled back from the CLI through gremlin rollback as well as signals, such as from a Ctrl-C.

Immediately halt and mark the attack as "Initialization Failed" if a Disk Gremlin encounters an IO error while writing the desired amount of bytes.

Updated dependencies

Integrate more thoroughly with the cgroups managed by Kubernetes and Docker. Gremlin container attacks now properly report usage metrics to cAdvisor which is used in Kubernetes monitoring and autoscaling triggers. NOTE: Gremlin currently only supports the cgroupfs cgroup driver. View more information

Cap the --workers (-w) argument for Disk and IO attacks to a maximum value equal to the number of CPUs available to Gremlin. This ensures Gremlin is always busy, and not generating more threads than can be fully utilized by the machine on which Gremlin runs. This also eliminates the possibility that Gremlin will exhaust all threads available to Gremlin, which was observed with very large values supplied to --workers (1024 or higher)

Updated dependencies

Improved handling of invalid auth when running gremlin attack-container

Better organization of output of gremlin check auth, including more information in both the success/error cases

The daemon was not properly halting attacks when it did not have access to it's library directory: /var/lib/gremlin, even though it would allow attacks to run. Attacks are now properly halted.

Users can now supply push_metrics inside config.yaml. This attribute is a boolean value that defaults to true, and is equivalent to the environment variable PUSH_METRICS=1

The daemon was not correctly handling the case when it started up in an un-authed state and relied on gremlin init being run to provide the .credentials file. In particular, it was missing some critical metadata which charting relied upon.

Added subheaders to gremlin check auth to better categorize the output

Read tags supplied in config.yaml

Ship example config.yaml to RPM/DEB packages

Auto-initialize daemon if secret is present and credentials are not present

gremlin measure $TYPE now accepts TYPE in uppercase or lowercase (e.g. gremlin measure cpu). It previously only accepted uppercase.

Kubernetes Pod eviction events triggered by Gremlin resource attacks no longer produce Failed attack states. There is now additional information when Gremlin is killed, and the steps it took to clean up.

Gremlin agents installed into Azure now properly set the publicIpAddress metadata tag (erroneously named publicpAddress in prior versions).

Gremlin now pushes CPU metrics for active attacks. These metrics will be used in charting features that allow you to see Gremlin's effect on your machines in real time. To disable this functionality, add PUSH_METRICS=0 to the configuration for gremlind. No data is collected when attacks aren't running, and only data relevant to the attack is collected.

Gremlin can now compete with the resources dedicated to a container, instead of taking free resources from the host. See more about Gremlin and Cgroups

Running attacks are now halted when the gremlind service is told to shut down from process managers

Memory Gremlin more aggressively touches memory it consumes to better ensure that operating systems don't try to reuse some of it

os-name tag added to clients by default; this value, in combination with os-type, now make up the full os description of the machine (i.e. os-type=Linux + os-name=Ubuntu)

Memory leak collecting measurement data

Ensure capabilities are correctly applied during a rollback

Improvements to I/O and Disk attack targeting and capabilities handling

Better local IP address determination when automatically setting GREMLIN_IDENTIFIER

Improved shutdown handling (SIGINT, SIGTERM, and attack halt)

Updated dependencies

There was a regression in 2.12.25 where host attacks that required capabilities did not properly rollback. This release fixes that.

There was a regression in 2.12.23 where the value of SSL_CERT_FILE was not added to the trust store. That is properly wired into the trust store again

/var/log/gremlin/executions/{guid} was not being cleared on halts - now it is

Shutdown container attack showed an error in the logs, now this case is handled more gracefully

gremlin status was displaying UnknownVariantError in some cases

Updated dependencies

Updated dependencies

Gremlin now interfaces with version 1.24 of Docker's REST API over Unix socket /var/run/docker.sock, instead of indirectly through docker shell commands.

Address startup errors referencing number too large to fit in target type, which happens under certain configurations of the target machine's CPU.

Signal handling and process killer improvements

Better handling for the case when a stateful attack doesn't get a chance to clean up properly within a container

Make file management for Gremlin logs more operating system agnostic

Improve capabilities checking

Updated dependencies

Prevent non-privileged users from acquiring Gremlin secrets if they have command-line access to linux hosts while a container attack is running

Supply the correct DOCKER_API_VERSION to container attacks

Updated dependencies

New `os_type tag added to all new Gremlin clients (e.g. os_type:Linux)

Fixed bug that caused Network Gremlins to fail when attacking two or more processes (including containers) when they shared a network interface.

Improved memory attack performance by as much as four times while limiting the CPU impact.

Recover gracefully from operating system out-of-memory errors.

Minor status message improvements for the memory attack.

Fixed a bug where launching a container attack was not respecting the GREMLIN_BYPASS_USERNS_REMAP environment variable. This should get set only when the Docker namespace remapping feature is being used.

Fixed a bug where Memory Gremlin puts unnecessary strain on getrandom and therefore system entropy.

Updated dependencies

Fixed bug where Gremlin (in Docker only) would log errors about missing directories until it received an attack to run

Fixed a bug where the Gremlin CPU attack would leave too much CPU in the idle and sy states. The CPU attack will now consume the requested amount, using us instead.

Minor improvements to gremlin check functionality

Fixed bug where Gremlin would fail attacks due to a closed HTTP stream

Fixed bug where Gremlin would fail to load attacks under certain circumstances

Improved error messaging around loading authentication configuration

New command gremlin check for diagnostics, check out the docs

Updated dependencies

Improve help text for Blackhole Gremlin arguments about ports

Updated dependencies

Fix bug where Gremlin would create /var/lib/gremlin/.credentials with permissions from the OS umask. Gremlin would then change the mode of the created file before writing to it. Now, Gremlin creates the file with proper permissions, without having to change mode later.

Remove world-readable bit from the /var/log/gremlin directory

Updated dependencies

Fix to Memory Gremlin running in containers - we were allowing the Gremlin to allocate more memory than was given to the target container

Bugfix to Memory Gremlin - we were letting the --percentage option consume more memory than was available

Updated dependencies

Fewer writes by the client to the filesystem, reducing the chance that a Disk Gremlin fails

Explicitly track tearing down successful attacks, so we don't halt attacks too early in the case teardown takes a material amount of time.

Ensure Gremlin sidecars launched in a container have the same GREMLIN_IDENTIFIER as the daemon.

Updated dependencies

Make the Memory attack track its allocation time in the Initializing state.

Updated dependencies

Updated dependencies

Updated dependencies

Updated dependencies

Bugfix for gremlin attack-container CLI command

Fix handling of GREMLIN_CLIENT_TAGS, which were ignored starting in 2.11.6.

Added more trust-store file locations

Updated dependencies

Updated dependencies

Automatically populate client tags when running in Microsoft Azure or Google Cloud

Bugfix for halted attacks which ended in a Lost Communication state (introduced in 2.11.2)

Updated dependencies

Updated dependencies

Automatically populate client tags with instance-id when running on AWS EC2.

Updated dependencies

Resource CPU Attacks can now impact All cores and can consume a percentage of CPU capacity

Network DNS attacks now cache the IP address of the Gremlin Control Plane to avoid the attack from halting prematurely

Proxy details are now hidden in the attack logs on successful calls