Use the Instance Metadata Service to access instance metadata
You can access instance metadata from a running instance using one of the following methods:
-
Instance Metadata Service Version 2 (IMDSv2) – a session-oriented method
For examples, see Examples for IMDSv2.
-
Instance Metadata Service Version 1 (IMDSv1) – a request/response method
For examples, see Examples for IMDSv1.
By default, you can use either IMDSv1 or IMDSv2, or both.
You can configure the Instance Metadata Service (IMDS) on each instance so that local code or users must use IMDSv2. When you specify that IMDSv2 must be used, IMDSv1 no longer works. For information about how to configure your instance to use IMDSv2, see Configure the Instance Metadata Service options.
The PUT
or GET
headers are unique to IMDSv2. If
these headers are present in the request, then the request is intended for
IMDSv2. If no headers are present, it is assumed the request is intended for
IMDSv1.
For an extensive review of IMDSv2, see Add defense in depth against open firewalls, reverse proxies, and SSRF
vulnerabilities with enhancements to the EC2 Instance Metadata
Service
Topics
How Instance Metadata Service Version 2 works
IMDSv2 uses session-oriented requests. With session-oriented requests, you create a session token that defines the session duration, which can be a minimum of one second and a maximum of six hours. During the specified duration, you can use the same session token for subsequent requests. After the specified duration expires, you must create a new session token to use for future requests.
Note
The examples in this section use the IPv4 address of the Instance Metadata Service
(IMDS): 169.254.169.254
. If you are retrieving instance
metadata for EC2 instances over the IPv6 address, ensure that you enable and use
the IPv6 address instead: [fd00:ec2::254]
. The IPv6 address of the
IMDS is compatible with IMDSv2 commands. The IPv6 address is
only accessible on instances built on the AWS Nitro System and in an IPv6-supported subnet (dual stack or IPv6 only).
The following examples use a shell script and IMDSv2 to retrieve the top-level instance metadata items. Each example:
-
Creates a session token lasting six hours (21,600 seconds) using the
PUT
request -
Stores the session token header in a variable named
TOKEN
(Linux instances) ortoken
(Windows instances) -
Requests the top-level metadata items using the token
You can run two separate commands, or combine them.
Separate commands
First, generate a token using the following command.
[ec2-user ~]$
TOKEN=`curl -X PUT "http://169.254.169.254/latest/api/token" -H "X-aws-ec2-metadata-token-ttl-seconds: 21600"`
Then, use the token to generate top-level metadata items using the following command.
[ec2-user ~]$
curl -H "X-aws-ec2-metadata-token: $TOKEN" http://169.254.169.254/latest/meta-data/
Combined commands
You can store the token and combine the commands. The following example combines the above two commands and stores the session token header in a variable named TOKEN.
Note
If there is an error in creating the token, instead of a valid token, an error message is stored in the variable, and the command will not work.
[ec2-user ~]$
TOKEN=`curl -X PUT "http://169.254.169.254/latest/api/token" -H "X-aws-ec2-metadata-token-ttl-seconds: 21600"` \ && curl -H "X-aws-ec2-metadata-token: $TOKEN" http://169.254.169.254/latest/meta-data/
After you've created a token, you can reuse it until it expires. In the
following example command, which gets the ID of the AMI used to launch the
instance, the token that is stored in $TOKEN
in the previous
example is reused.
[ec2-user ~]$
curl -H "X-aws-ec2-metadata-token: $TOKEN" http://169.254.169.254/latest/meta-data/ami-id
PS C:\>
[string]$token = Invoke-RestMethod -Headers @{"X-aws-ec2-metadata-token-ttl-seconds" = "21600"} -Method PUT -Uri http://169.254.169.254/latest/api/token
PS C:\>
Invoke-RestMethod -Headers @{"X-aws-ec2-metadata-token" = $token} -Method GET -Uri http://169.254.169.254/latest/meta-data/
After you've created a token, you can reuse it until it expires. In the
following example command, which gets the ID of the AMI used to launch the
instance, the token that is stored in $token
in the previous
example is reused.
PS C:\>
Invoke-RestMethod -Headers @{"X-aws-ec2-metadata-token" = $token} ` -Method GET -uri http://169.254.169.254/latest/meta-data/ami-id
When you use IMDSv2 to request instance metadata, the request must include the following:
-
Use a
PUT
request to initiate a session to the instance metadata service. ThePUT
request returns a token that must be included in subsequentGET
requests to the instance metadata service. The token is required to access metadata using IMDSv2. -
Include the token in all
GET
requests to the IMDS. When token usage is set torequired
, requests without a valid token or with an expired token receive a401 - Unauthorized
HTTP error code.-
The token is an instance-specific key. The token is not valid on other EC2 instances and will be rejected if you attempt to use it outside of the instance on which it was generated.
-
The
PUT
request must include a header that specifies the time to live (TTL) for the token, in seconds, up to a maximum of six hours (21,600 seconds). The token represents a logical session. The TTL specifies the length of time that the token is valid and, therefore, the duration of the session. -
After a token expires, to continue accessing instance metadata, you must create a new session using another
PUT
. -
You can choose to reuse a token or create a new token with every request. For a small number of requests, it might be easier to generate and immediately use a token each time you need to access the IMDS. But for efficiency, you can specify a longer duration for the token and reuse it rather than having to write a
PUT
request every time you need to request instance metadata. There is no practical limit on the number of concurrent tokens, each representing its own session. IMDSv2 is, however, still constrained by normal IMDS connection and throttling limits. For more information, see Query throttling.
-
HTTP GET
and HEAD
methods are allowed in IMDSv2
instance metadata requests. PUT
requests are rejected if they contain
an X-Forwarded-For header.
By default, the response to PUT
requests has a response hop limit
(time to live) of 1
at the IP protocol level. If you need a bigger hop
limit, you can adjust it by using the modify-instance-metadata-options AWS CLI command. For example, you might
need a bigger hop limit for backward compatibility with container services running
on the instance. For more information, see Modify instance metadata
options for existing instances.
Transition to using Instance Metadata Service Version 2
When migrating to IMDSv2, we recommend that you use the following tools and transition path.
Tools for helping with the transition to IMDSv2
If your software uses IMDSv1, use the following tools to help reconfigure your software to use IMDSv2.
- AWS software
-
The latest versions of the AWS CLI and AWS SDKs support IMDSv2. To use IMDSv2, make sure that your EC2 instances have the latest versions of the CLI and SDKs. For information about updating the CLI, see Installing, updating, and uninstalling the AWS CLI in the AWS Command Line Interface User Guide.
All Amazon Linux 2 and Amazon Linux 2023 software packages support IMDSv2. In Amazon Linux 2023, IMDSv1 is disabled by default.
For the minimum AWS SDK versions that support IMDSv2, see Use a supported AWS SDK.
- IMDS Packet Analyzer
-
The IMDS Packet Analyzer is an open-sourced tool that identifies and logs IMDSv1 calls from your instance’s boot phase. This can assist in identifying the software making IMDSv1 calls on EC2 instances, allowing you to pinpoint exactly what you need to update to get your instances ready to use IMDSv2 only. You can run IMDS Packet Analyzer from a command line or install it as a service. For more information, see IMDS Packet Analyzer
on GitHub. - CloudWatch
-
IMDSv2 uses token-backed sessions, while IMDSv1 does not. The
MetadataNoToken
CloudWatch metric tracks the number of calls to the Instance Metadata Service (IMDS) that are using IMDSv1. By tracking this metric to zero, you can determine if and when all of your software has been upgraded to use IMDSv2.After you've disabled IMDSv1, you can use the
MetadataNoTokenRejected
CloudWatch metric to track the number of times an IMDSv1 call was attempted and rejected. By tracking this metric, you can ascertain whether your software needs to be updated to use IMDSv2.For more information, see Instance metrics.
- Updates to EC2 APIs and CLIs
-
For new instances, you can use the RunInstances API to launch new instances that require the use of IMDSv2. For more information, see Configure instance metadata options for new instances.
For existing instances, you can use the ModifyInstanceMetadataOptions API to require the use of IMDSv2. For more information, see Modify instance metadata options for existing instances.
To require the use of IMDSv2 on all new instances launched by Auto Scaling groups, your Auto Scaling groups can use either a launch template or a launch configuration. When you create a launch template or create a launch configuration, you must configure the
MetadataOptions
parameters to require the use of IMDSv2. The Auto Scaling group launches new instances using the new launch template or launch configuration, but existing instances are not affected. For existing instances in an Auto Scaling group, you can use the ModifyInstanceMetadataOptions API to require the use of IMDSv2 on the existing instances, or terminate the instances and the Auto Scaling group will launch new replacement instances with the instance metadata options settings that are defined in the new launch template or launch configuration. - Use an AMI that configures IMDSv2 by default
-
When you launch an instance, you can automatically configure it to use IMDSv2 by default (the
HttpTokens
parameter is set torequired
) by launching it with an AMI that is configured with theImdsSupport
parameter set tov2.0
. You can set theImdsSupport
parameter tov2.0
when you register the AMI using the register-image CLI command, or you can modify an existing AMI by using the modify-image-attribute CLI command. For more information, see Configure the AMI. - IAM policies and SCPs
-
You can use an IAM policy or AWS Organizations service control policy (SCP) to control users as follows:
-
Can't launch an instance using the RunInstances API unless the instance is configured to use IMDSv2.
-
Can't modify a running instance using the ModifyInstanceMetadataOptions API to re-enable IMDSv1.
The IAM policy or SCP must contain the following IAM condition keys:
-
ec2:MetadataHttpEndpoint
-
ec2:MetadataHttpPutResponseHopLimit
-
ec2:MetadataHttpTokens
If a parameter in the API or CLI call does not match the state specified in the policy that contains the condition key, the API or CLI call fails with an
UnauthorizedOperation
response.Furthermore, you can choose an additional layer of protection to enforce the change from IMDSv1 to IMDSv2. At the access management layer with respect to the APIs called via EC2 Role credentials, you can use a new condition key in either IAM policies or AWS Organizations service control policies (SCPs). Specifically, by using the condition key
ec2:RoleDelivery
with a value of2.0
in your IAM policies, API calls made with EC2 Role credentials obtained from IMDSv1 will receive anUnauthorizedOperation
response. The same thing can be achieved more broadly with that condition required by an SCP. This ensures that credentials delivered via IMDSv1 cannot actually be used to call APIs because any API calls not matching the specified condition will receive anUnauthorizedOperation
error.For example IAM policies, see Work with instance metadata. For more information on SCPs, see Service Control Policies in the AWS Organizations User Guide.
-
Recommended path to requiring IMDSv2
Using the above tools, we recommend that you follow this path for transitioning to IMDSv2.
Step 1: At the start
Update the SDKs, CLIs, and your software that use Role credentials on their EC2 instances to versions compatible with IMDSv2. For information about updating the CLI, see Upgrading to the latest version of the AWS CLI in the AWS Command Line Interface User Guide.
Then, change your software that directly accesses instance metadata (in
other words, that does not use an SDK) using the IMDSv2 requests.
You can use the IMDS Packet Analyzer
Step 2: Track your transition progress
Track your transition progress by using the CloudWatch metric
MetadataNoToken
. This metric shows the number of
IMDSv1 calls to the IMDS on your instances.
For more information, see Instance metrics.
Step 3: When there is zero IMDSv1 usage
When the CloudWatch metric MetadataNoToken
records zero
IMDSv1 usage, your instances are
ready to be fully transitioned to using IMDSv2. At this stage, you
can do the following:
-
Account default
You can set IMDSv2 to be required as an account default. When an instance is launched, the instance configuration is automatically set to the account default.
To set the account default, do the following:
-
Amazon EC2 console: On the EC2 Dashboard, under Account attributes, Data protection and security, for IMDS defaults, set Instance metadata service to Enabled and Metadata version to V2 only (token required). For more information, see Set IMDSv2 as the default for the account.
-
AWS CLI: Use the modify-instance-metadata-defaults CLI command and specify
--http-tokens required
and--http-put-response-hop-limit
.2
-
-
New instances
When launching a new instance, you can do the following:
-
Amazon EC2 console: In the launch instance wizard, set Metadata accessible to Enabled and Metadata version to V2 only (token required). For more information, see Configure the instance at launch.
-
AWS CLI: Use the run-instances CLI command and specify that IMDSv2 is required.
-
-
Existing instances
For existing instances, you can do the following:
-
Amazon EC2 console: On the Instances page, select your instance, choose Actions, Instance settings, Modify instance metadata options, and for IMDSv2, choose Required. For more information, see Require the use of IMDSv2.
-
AWS CLI: Use the modify-instance-metadata-options CLI command to specify that only IMDSv2 is to be used.
You can modify the instance metadata options on running instances, and you don't need to restart the instances after modifying the instance metadata options.
-
Step 4: Check if your instances are transitioned to IMDSv2
You can check if any instances are not yet configured to require the use
of IMDSv2, in other words, IMDSv2 is still configured as
optional
. If any instances are still configured as
optional
, you can modify the instance metadata options to
make IMDSv2 required
by repeating the preceding Step 3.
To filter your instances:
-
Amazon EC2 console: On the Instances page, filter your instances by using the IMDSv2 = optional filter. For more information about filtering, see Filter resources using the console. You can also view whether IMDSv2 is required or optional for each instance: In the Preferences window, toggle on IMDSv2 to add the IMDSv2 column to the Instances table.
-
AWS CLI: Use the describe-instances CLI command and filter by
metadata-options.http-tokens = optional
, as follows:aws ec2 describe-instances --filters "Name=metadata-options.http-tokens,Values=optional" --query "Reservations[*].Instances[*].[InstanceId]" --output text
Step 5: When all of your instances are transitioned to IMDSv2
The ec2:MetadataHttpTokens
,
ec2:MetadataHttpPutResponseHopLimit
, and
ec2:MetadataHttpEndpoint
IAM condition keys can be used to
control the use of the RunInstances and the ModifyInstanceMetadataOptions APIs and corresponding CLIs. If a
policy is created, and a parameter in the API call does not match the state
specified in the policy using the condition key, the API or CLI call fails
with an UnauthorizedOperation
response. For example IAM
policies, see Work with instance metadata.
Furthermore, after you've disabled IMDSv1, you can use the
MetadataNoTokenRejected
CloudWatch metric to track the number of
times an IMDSv1 call was attempted and rejected. If, after disabling
IMDSv1, you have software that is not working properly and the
MetadataNoTokenRejected
metric records IMDSv1
calls, it's likely that this software needs to be updated to use
IMDSv2.
Use a supported AWS SDK
To use IMDSv2, your EC2 instances must use an AWS SDK version that supports using IMDSv2. The latest versions of all the AWS SDKs support using IMDSv2.
Important
We recommend that you to stay up to date with SDK releases to keep up with the latest features, security updates, and underlying dependencies. Continued use of an unsupported SDK version is not recommended and is done at your discretion. For more information, see the AWS SDKs and Tools maintenance policy in the AWS SDKs and Tools Reference Guide.
The following are the minimum versions that support using IMDSv2:
-
AWS CLI
– 1.16.289 -
AWS Tools for Windows PowerShell
– 4.0.1.0 -
AWS SDK for .NET
– 3.3.634.1 -
AWS SDK for C++
– 1.7.229 -
AWS SDK for Go
– 1.25.38 -
AWS SDK for Go v2
– 0.19.0 -
AWS SDK for Java
– 1.11.678 -
AWS SDK for Java 2.x
– 2.10.21 -
AWS SDK for JavaScript in Node.js
– 2.722.0 -
AWS SDK for PHP
– 3.147.7 -
AWS SDK for Python (Botocore)
– 1.13.25 -
AWS SDK for Python (Boto3)
– 1.12.6 -
AWS SDK for Ruby
– 3.79.0
Examples for IMDSv2
Run the following examples on your Amazon EC2 instance to retrieve the instance metadata for IMDSv2.
On Windows instances, you can use Windows PowerShell or you can install cURL or wget. If you install a third-party tool on a Windows instance, ensure that you read the accompanying documentation carefully, as the calls and the output might be different from what is described here.
Examples
- Get the available versions of the instance metadata
- Get the top-level metadata items
- Get the values for metadata items
- Get the list of available public keys
- Show the formats in which public key 0 is available
- Get public key 0 (in the OpenSSH key format)
- Get the subnet ID for an instance
- Get the instance tags for an instance
Get the available versions of the instance metadata
This example gets the available versions of the instance metadata. Each version refers to an instance metadata build when new instance metadata categories were released. The instance metadata build versions do not correlate with the Amazon EC2 API versions. The earlier versions are available to you in case you have scripts that rely on the structure and information present in a previous version.
Get the top-level metadata items
This example gets the top-level metadata items. For more information about the items in the response, see Instance metadata categories.
Note that tags are included in this output only if you've allowed access. For more information, see Allow access to tags in instance metadata.
Get the values for metadata items
These examples get the values of some of the top-level metadata items that were obtained in the preceding example. These requests use the stored token that was created using the command in the previous example. The token must not be expired.
Get the list of available public keys
This example gets the list of available public keys.
Show the formats in which public key 0 is available
This example shows the formats in which public key 0 is available.
Get public key 0 (in the OpenSSH key format)
This example gets public key 0 (in the OpenSSH key format).
Get the subnet ID for an instance
This example gets the subnet ID for an instance.
Get the instance tags for an instance
If access to instance tags in the instance metadata is turned on, you can get the tags for a instance from instance metadata. For more information, see Retrieve tags from instance metadata.
Examples for IMDSv1
Run the following examples on your Amazon EC2 instance to retrieve the instance metadata for IMDSv1.
On Windows instances, you can use Windows PowerShell or you can install cURL or wget. If you install a third-party tool on a Windows instance, ensure that you read the accompanying documentation carefully, as the calls and the output might be different from what is described here.
Examples
- Get the available versions of the instance metadata
- Get the top-level metadata items
- Get the values for metadata items
- Get the list of available public keys
- Show the formats in which public key 0 is available
- Get public key 0 (in the OpenSSH key format)
- Get the subnet ID for an instance
- Get the instance tags for an instance
Get the available versions of the instance metadata
This example gets the available versions of the instance metadata. Each version refers to an instance metadata build when new instance metadata categories were released. The instance metadata build versions do not correlate with the Amazon EC2 API versions. The earlier versions are available to you in case you have scripts that rely on the structure and information present in a previous version.
Get the top-level metadata items
This example gets the top-level metadata items. For more information about the items in the response, see Instance metadata categories.
Note that tags are included in this output only if you've allowed access. For more information, see Allow access to tags in instance metadata.
Get the values for metadata items
These examples get the values of some of the top-level metadata items that were obtained in the previous example.
Get the list of available public keys
This example gets the list of available public keys.
Show the formats in which public key 0 is available
This example shows the formats in which public key 0 is available.
Get public key 0 (in the OpenSSH key format)
This example gets public key 0 (in the OpenSSH key format).
Get the subnet ID for an instance
This example gets the subnet ID for an instance.
Get the instance tags for an instance
If access to instance tags in the instance metadata is turned on, you can get the tags for a instance from instance metadata. For more information, see Retrieve tags from instance metadata.