awsflow-sts

Use the STSTool language tool in VS Code to manage AWS STS (Security Token Service) operations — identity verification, role assumption, temporary credentials, and authorization debugging.

When to Use

•User wants to verify their AWS identity (who am I?)
•User wants to assume an IAM role
•User wants to get temporary security credentials
•User wants to decode an encoded authorization failure message
•User wants to get a federation token
•User wants to look up account info for an access key
•User needs SAML or web identity token-based role assumption

Tool Reference

Tool name: STSTool

Input Schema

json

{
  "command": "<CommandName>",
  "params": { ... }
}

Commands (10 total)

Command	Description
AssumeRole	Assume an IAM role and get temporary credentials
AssumeRoleWithSAML	Assume a role using a SAML assertion
AssumeRoleWithWebIdentity	Assume a role using a web identity (OIDC) token
DecodeAuthorizationMessage	Decode an encoded authorization failure message
GetAccessKeyInfo	Get the account ID for an access key
GetCallerIdentity	Get the identity of the calling credentials (account, ARN, user ID)
GetDelegatedAccessToken	Get a delegated access token
GetFederationToken	Get temporary credentials for a federated user
GetSessionToken	Get temporary session credentials (with optional MFA)
GetWebIdentityToken	Get a web identity token for a role

Parameters

Parameter	Type	Description
RoleArn	string	IAM role ARN (Required by: AssumeRole, AssumeRoleWithSAML, AssumeRoleWithWebIdentity, GetDelegatedAccessToken, GetWebIdentityToken)
RoleSessionName	string	Session name for role assumption (Required by: AssumeRole, AssumeRoleWithWebIdentity, GetWebIdentityToken)
DurationSeconds	number	Token lifetime in seconds (Used by: AssumeRole, GetDelegatedAccessToken, GetFederationToken, GetSessionToken, GetWebIdentityToken)
ExternalId	string	External ID for cross-account role assumption (Used by: AssumeRole)
PolicyArns	array	Managed policy ARNs for session policies (Used by: AssumeRole, AssumeRoleWithWebIdentity, AssumeRoleWithSAML)
Policy	string	IAM policy JSON string for temporary credentials (Used by: AssumeRole, GetFederationToken)
TransitiveTagKeys	array	Session tag keys to set as transitive (Used by: AssumeRole)
SourceIdentity	string	Source identity for role chaining (Used by: AssumeRole)
Tags	array	Session tags as `[{Key, Value}]` (Used by: AssumeRole, GetFederationToken)
SAMLAssertion	string	Base64-encoded SAML authentication response (Required by: AssumeRoleWithSAML)
PrincipalArn	string	ARN of SAML provider (Required by: AssumeRoleWithSAML)
WebIdentityToken	string	Web identity (OIDC) token (Required by: AssumeRoleWithWebIdentity, GetWebIdentityToken)
ProviderId	string	Identity provider ID (Used by: AssumeRoleWithWebIdentity, GetWebIdentityToken)
EncodedMessage	string	Encoded authorization failure message (Required by: DecodeAuthorizationMessage)
AccessKeyId	string	AWS access key ID (Required by: GetAccessKeyInfo)
DelegationTokenLifetimeSeconds	number	Delegated token lifetime in seconds (Used by: GetDelegatedAccessToken)
Name	string	Session or federation token name (Required by: GetFederationToken)
SerialNumber	string	MFA device serial number (Used by: GetSessionToken)
TokenCode	string	MFA token code (Used by: GetSessionToken)

Usage Examples

Check current identity

json

{ "command": "GetCallerIdentity", "params": {} }

Assume a role

json

{ "command": "AssumeRole", "params": { "RoleArn": "arn:aws:iam::123456789012:role/MyRole", "RoleSessionName": "my-session", "DurationSeconds": 3600 } }

Assume a role with external ID (cross-account)

json

{ "command": "AssumeRole", "params": { "RoleArn": "arn:aws:iam::987654321098:role/CrossAccountRole", "RoleSessionName": "cross-account-session", "ExternalId": "my-external-id" } }

Decode an authorization failure message

json

{ "command": "DecodeAuthorizationMessage", "params": { "EncodedMessage": "<encoded-message-string>" } }

Get account ID for an access key

json

{ "command": "GetAccessKeyInfo", "params": { "AccessKeyId": "AKIAIOSFODNN7EXAMPLE" } }

Get session token with MFA

json

{ "command": "GetSessionToken", "params": { "DurationSeconds": 3600, "SerialNumber": "arn:aws:iam::123456789012:mfa/user", "TokenCode": "123456" } }

Get federation token

json

{ "command": "GetFederationToken", "params": { "Name": "federated-user", "DurationSeconds": 3600, "Policy": "{\"Version\":\"2012-10-17\",\"Statement\":[{\"Effect\":\"Allow\",\"Action\":\"s3:*\",\"Resource\":\"*\"}]}" } }

Assume role with web identity

json

{ "command": "AssumeRoleWithWebIdentity", "params": { "RoleArn": "arn:aws:iam::123456789012:role/WebIdentityRole", "RoleSessionName": "web-session", "WebIdentityToken": "<oidc-token>" } }

Related Services

STS is foundational to AWS security and is used alongside:

Relationship	Tool
Manages IAM roles/policies	`IAMTool`
Session management	`SessionTool` (in awsflow-general)
Test AWS connectivity	`TestAwsConnectionTool` (in awsflow-general)
All AWS services require valid credentials	All awsflow tools

Tips

•Start with GetCallerIdentity to verify which account and identity you're operating as.
•Use DecodeAuthorizationMessage when you get "Encoded authorization failure" errors — it reveals the denied action, resource, and conditions.
•AssumeRole with ExternalId is required for cross-account access when the trust policy mandates it.
•GetSessionToken with MFA is useful when your account requires MFA for sensitive operations.
•Temporary credentials from STS calls are valid for the specified DurationSeconds (default varies by command).