Is it possible to get AWS instance info, local to the instance, without using credentials? I know the command line tool can do it, but it needs credentials. There is also the metadata commands, but those don't seem to return Tags, which is what I need.
I thought there was a way to curl an IP and get back json, but I can't find it.
It is not possible to retrieve tags directly from within the EC2 instance via the local metadata service as the metadata service does not know the tags. You have (at least) two options:
launch the instance with an IAM role (or somehow provide other credentials to the instance) that includes permission to call ec2:DescribeTags and then retrieve the tags dynamically - you'll need the instance ID for this and you can get that from the metadata service
if the tags are known at launch time and are not going to change after launch, you could simply pass them into the EC2 instance as part of the userdata (e.g. as environment variables or written to a text file at launch).
Unfortunately, you'll need credentials to retrieve tags. I do this by creating an IAM user that only has the ec2:Describe* role; it can then enumerate the instances in your account and retrieve their tags, with ec2-describe-tags or similar.
You can use the metadata API to retrieve the current instance ID, then pass that to ec2-describe tags to retrieve the tags for the current instance:
ec2-describe-tags -O YOUR_IAM_KEY -W YOUR_IAM_SECRET --filter="resource-id=`curl -s http://169.254.169.254/latest/meta-data/instance-id`"
Yes you can get the EC2 instance tags without credentials. You do this using the EC2 Roles / Profiles for the EC2 instance. I know that this has already been mentioned but I'd like to expand on this a little. Technically you're not actually doing anything without credentials. Credentials are always involved unless you're just making queries to the metadata.
What Boto and other similar frameworks do is they query the ec2 instance metadata to get the credentials for the role. Just replace the last part s3access with the name of the profile / role.
curl http://169.254.169.254/latest/meta-data/iam/security-credentials/s3access
Returns
{
"Code" : "Success",
"LastUpdated" : "2012-04-26T16:39:16Z",
"Type" : "AWS-HMAC",
"AccessKeyId" : "AKIAIOSFODNN7EXAMPLE",
"SecretAccessKey" : "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY",
"Token" : "token",
"Expiration" : "2012-04-27T22:39:16Z"
}
This response includes the access credentials required to make the API request. When the credentials expire the framework will request a new set of credentials using the same method and repeat this process as many times as necessary.
I highly recommend using a framework because making the requests directly to the REST API requires that you perform the authentication yourself. If that's the direction you decide to go here are some more resources to help you out.
Signature Version 2
Describe Tags API
Related
I am trying to work with the new Instance Metadata Service Version 2 (IMDSv2) API.
It works as expected when I try to query the metadata manually as described on Retrieve instance metadata - Amazon Elastic Compute Cloud.
However, if I try to query for the instance tags it fails with error message:
Couldn't find AWS credentials in environment, credentials file, or IAM role
The tags query is done by the Rusoto SDK that I am using, that works when I set --http-tokens optional as described on Configure the instance metadata options - Amazon Elastic Compute Cloud.
I don't fully understand why setting the machine to work with IMDSv2 would effect the DescribeTags request, as I believe it's not using the same API - so I am guessing that's a side effect.
If I try and do a manual query using curl (instead of using the SDK):
https://ec2.amazonaws.com/?Action=DescribeTags&Filter.1.Name=resource-id&Filter.1.Value.1=ami-1a2b3c4d
I get:
The action DescribeTags is not valid for this web service
Thanks :)
The library that I was using (Rusoto SDK 0.47.0) doesn't support fetching the credentials needed when the host is set to work with the IMDSv2.
The workaround was to manually query for the IAM role credentials.
First, you get the token:
GET /latest/api/token
Next, use the token header "X-aws-ec2-metadata-token" with the value from the previous:
GET /meta-data/iam/security-credentials
Afterwards, use the result from the previous query (and don't forget to set the token header), and query:
GET /meta-data/iam/security-credentials/<query 2 result>
This will provide with the following data:
struct SecurityCredentials {
#[serde(rename = "AccessKeyId")]
access_key_id: String,
#[serde(rename = "SecretAccessKey")]
secret_access_key: String,
#[serde(rename = "Token")]
token: String,
}
Then what I needed to do was to build a custom credentials provider using that data (but this part is already lib specific).
I'm currently using Traefik and Lego in order to have HTTPS connection for my docker containers (as mentioned here)
In the following documentation, it's mentioned that I need to use the following provider to do DNS Challenge.
But I get this error:
AccessDeniedException: User: arn:aws:sts::<USER_ID>:assumed-role/AmazonLightsailInstanceRole/<AN_ID> is not authorized to perform: lightsail:CreateDomainEntry on resource: arn:aws:lightsail:us-east-1:<INSTANCE_ID>:*
and another for DeleteDomainEntry, even though I have lightsail:* on Resource: * permission on the IAM user used for configuration.
If I understand correctly Lightsail is managed separately for the other AWS services and thus we need to use STS for connecting to it (tell me if I'm wrong). So my question is this, how can I set the permissions for the temporary token to be able to do CreateDomainEntry and DeleteDomainEntry?
Further information
My instance's region is eu-west-3 (I tried changing the region in Lego config, doesn't work)
The <USER_ID> seen in the error does not correspond to the id found in the ARN of the domain. It correspond to the first number in the supportCode when doing aws lightsail get-domains --region us-east-1 in the CLI.
Lego and Traefik do not call the AssumeRole directly and do not create the temporary token (checked source code)
I'm using AWS_ACCESS_KEY_ID_FILE and AWS_SECRET_ACCESS_KEY_FILE in Traefik environment configuration.
The error message tells that Lego made the request using the IAM role assigned to your lightsail instance. I guess your instance lacks permissions to modify DNS settings for lightsail.
You should create a new user in AWS IAM and enable programmatic access in order to obtain AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY.
Then, pass those values as environment variables to your containers running Lego. Lego will use those env vars to authenticate with Lightsail APIs in us-east-1. [1]
My instance's region is eu-west-3 (I tried changing the region in Lego config, doesn't work)
Your Lego instance must call AWS APIs in us-east-1, see [2][3].
Lego and Traefik do not call the AssumeRole directly and do not create the temporary token
I guess Traefik/Lego assume the lightsail instance role automatically using EC2 instance metadata service, see [4]:
For applications, AWS CLI, and Tools for Windows PowerShell commands that run on the instance, you do not have to explicitly get the temporary security credentials—the AWS SDKs, AWS CLI, and Tools for Windows PowerShell automatically get the credentials from the EC2 instance metadata service and use them. To make a call outside of the instance using temporary security credentials (for example, to test IAM policies), you must provide the access key, secret key, and the session token.
I'm using AWS_ACCESS_KEY_ID_FILE and AWS_SECRET_ACCESS_KEY_FILE in Traefik environment configuration.
I could not find those env vars in the Lego source code [1]. Make sure that Lego is actually using your configured AWS credentials. The error message posted above suggests it's not using them and falls back to the instance profile instead.
[1] https://github.com/go-acme/lego/blob/master/providers/dns/lightsail/lightsail.go#L81
[2] https://docs.aws.amazon.com/cli/latest/reference/lightsail/create-domain-entry.html#examples
[3] https://github.com/go-acme/lego/blob/master/providers/dns/lightsail/lightsail.go#L69
[4] https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/iam-roles-for-amazon-ec2.html#instance-metadata-security-credentials
There were too many confusing things. Martin Löper's answer and answer on the github issue I opened helped me to clear things out.
Here is what was confusing:
Lego lightsail provider documentation is listing the environment variable and then say The environment variable names can be suffixed by _FILE to reference a file instead of a value. Turns out, Lego's code never call their getOrFile method on the credentials. Furthermore, AWS sdk does not check variables with the _FILE suffix for AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY.
The error message from AWS is little bit misleading. I thought all that time that it was a permission problem but in fact it was a authentication problem (little bit different in my opinion).
And here is how to solve it (little bit different from what proposed):
I use the AWS_SHARED_CREDENTIALS_FILE (mentioned here) environment variable so that I can use docker secrets by specifying /run/secrets/aws_shared_credentials file. This is more secure (more info here). AWS sdk will automatically detect this env variable and initialize this new session correctly.
Is it possible to use aws credentials on remote server without explicitly copying them?
For example I can use my local ssh key on server like ssh-add && ssh -A <server_name> is there something like this for aws cli without copying the ~/.aws/credentials and ~/.aws/config?
I want to use these aws credentials just to download some files from S3.
In order to SSH to a remote server, your public key must already be present on the remote server. Your tool uses the private key to encrypt communications. Therefore, your assumption that your credentials are not needed on the remote server is incorrect.
EC2 supports retrieving credentials from metadata. You could create an IAM role s3access and then assume that role inside EC2. You can even retrieve those credentials using the command line tool curl. Example:
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" -v http://169.254.169.254/latest/meta-data/iam/security-credentials/s3access
Example output:
{
"Code" : "Success",
"LastUpdated" : "2012-04-26T16:39:16Z",
"Type" : "AWS-HMAC",
"AccessKeyId" : "ASIAIOSFODNN7EXAMPLE",
"SecretAccessKey" : "wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY",
"Token" : "token",
"Expiration" : "2017-05-17T15:09:54Z"
}
Refer to this link for more information on metadata credentials.
You can also setup the CLI to automatically use metadata credentials. Refer to this link for more information.
If your goal is to have no credentials on the EC2 instance, then you will need to use Presigned URLs. Refer to this link for more information.
If all you want to do is download some files from S3, persigned URLs may be an easier and safer option. AWS allows you to generate URLs for any AWS API action that are only usable for a certain period of time. You can generate those URLs to your specific files, send them to your server, and have the server use them to download the files.
For example:
aws s3 presign s3://awsexamplebucket/test2.txt --expires-in 604800
All of the different frameworks like boto3 and aws-sdk also support generating URLs.
Another option is generating temporary credentials. AWS allows lets you create credentials that only for a certain period of time. It also allows you to limit their scope so you can ask that they only allow downloading from a specific bucket, for example. Using STS you will get a new set of access key and session token, send those to your server, and let your server use them to do what it needs to do.
If you want the token to have exactly the same credentials as the calling role, use:
aws sts get-session-token
Otherwise you will need to create a role with the appropriate permissions and use:
aws sts assume-role --role-arn arn:aws:iam::123456789012:role/xaccounts3access --role-session-name s3-access-example
Just like with presigned URLs, these APIs are available in every SDK and not just on the command line.
I'm trying to use the aws-sdk-go in my application. It's running on EC2 instance. Now in the Configuring Credentials of the doc,https://docs.aws.amazon.com/sdk-for-go/api/, it says it will look in
*Environment Credentials - Set of environment variables that are useful when sub processes are created for specific roles.
* Shared Credentials file (~/.aws/credentials) - This file stores your credentials based on a profile name and is useful for local development.
*EC2 Instance Role Credentials - Use EC2 Instance Role to assign credentials to application running on an EC2 instance. This removes the need to manage credential files in production.`
Wouldn't the best order be the reverse order? But my main question is do I need to ask the instance if it has a role and then use that to set up the credentials if it has a role? This is where I'm not sure of what I need to do and how.
I did try a simple test of creating a empty config with essentially only setting the region and running it on the instance with the role and it seems to have "worked" but in this case, I am not sure if I need to explicitly set the role or not.
awsSDK.Config{
Region: awsSDK.String(a.region),
MaxRetries: awsSDK.Int(maxRetries),
HTTPClient: http.DefaultClient,
}
I just want to confirm is this the proper way of doing it or not. My thinking is I need to do something like the following
role = use sdk call to get role on machine
set awsSDK.Config { Credentials: credentials form of role,
...
}
issue service command with returned client.
Any more docs/pointers would be great!
I have never used the go SDK, but the AWS SDKs I used automatically use the EC2 instance role if credentials are not found from any other source.
Here's an AWS blog post explaining the approach AWS SDKs follow when fetching credentials: https://aws.amazon.com/blogs/security/a-new-and-standardized-way-to-manage-credentials-in-the-aws-sdks/. In particular, see this:
If you use code like this, the SDKs look for the credentials in this
order:
In environment variables. (Not the .NET SDK, as noted earlier.)
In the central credentials file (~/.aws/credentials or
%USERPROFILE%.awscredentials).
In an existing default, SDK-specific
configuration file, if one exists. This would be the case if you had
been using the SDK before these changes were made.
For the .NET SDK, in the SDK Store, if it exists.
If the code is running on an EC2
instance, via an IAM role for Amazon EC2. In that case, the code gets
temporary security credentials from the instance metadata service; the
credentials have the permissions derived from the role that is
associated with the instance.
In my apps, when I need to connect to AWS resources, I tend to use an access key and secret key that have specific predefined IAM roles. Assuming I have those two, the code I use to create a session is:
awsCredentials := credentials.NewStaticCredentials(awsAccessKeyID, awsSecretAccessKey, "")
awsSession = session.Must(session.NewSession(&aws.Config{
Credentials: awsCredentials,
Region: aws.String(awsRegion),
}))
When I use this, the two keys are usually specified as either environment variables (if I deploy to a docker container).
A complete example: https://github.com/retgits/flogo-components/blob/master/activity/amazons3/activity.go
I have EC2 instance.
I'm trying to call aws s3 from it but getting an error
Unable to locate credentials
I tried aws configure which does show everything as empty.
I see IAM role for S3 full permissions assigned to this instance.
Do I need any additional configuration?
If you run aws on an Amazon EC2 instance that has an assigned role, then it should find the credentials automatically.
You can also use this to view the credentials from the instance:
curl http://169.254.169.254/latest/meta-data/iam/security-credentials/
The role name should be listed. Then append it to the command:
curl http://169.254.169.254/latest/meta-data/iam/security-credentials/ROLE-NAME/
You should then be presented with AccessKeyId, SecretAccessKey, etc.
If that information does not appear, it suggests that your role is not correctly attached to the instance. Try unassigning the role and then assign it to the instance again.
First read and follow John Rotenstein's advice.
The SDK (from which the CLI is built from) searches for credentials in the following order:
Environment variables (AWS_ACCESS_KEY_ID ....)
Default Profile (credentials file)
ECS Container Credentials (if running on ECS)
Instance Profile
After verifying that your EC2 instance has credentials in the metadata, double check 1 & 2 to make sure that there are no other credentials present even if empty.
Note: This link argues with my last point (empty credentials file). I never create (store) credentials on an EC2 instance and I only use IAM Roles.
Instance Metadata