01
Inspect the process that fails
A shell, editor, container, and background service can inherit different environment variables. Selecting a profile in one terminal does not change every already running process. Compare the environment source and launch method before investigating IAM policy.
In the controlled test, AWS_PROFILE selected target while synthetic AWS_ACCESS_KEY_ID and AWS_SECRET_ACCESS_KEY were also present. A default Boto3 Session selected the environment provider. The profile name alone did not make those environment credentials disappear.
02
Check the provider without exposing the key
For Boto3, inspect the credential object’s method rather than logging its access key, secret, or session token. The code below resolves local credentials; in some real configurations that resolution can contact a configured credential provider.
Our default session reported env. A separately constructed Session(profile_name="target") selected shared-credentials-file from the synthetic named profile. That result demonstrates this SDK’s selection behavior, not the identity or permissions of a real account.
import boto3
session = boto3.Session()
credentials = session.get_credentials()
print(credentials.method if credentials else "no credentials")
chosen = boto3.Session(profile_name="work")
credentials = chosen.get_credentials()
print(credentials.method if credentials else "no credentials")03
Make the intended session explicit
When the application is meant to use a local named profile, build its service clients from that explicit session. For a workload intentionally using an execution role or container credentials, preserve that design instead of forcing a personal laptop profile into production.
Do not generalize the lab to say that environment credentials always override every explicit profile flag. AWS CLI command-line selection and SDK session construction have specific precedence behavior. Test the exact invocation you are troubleshooting.
import boto3
session = boto3.Session(profile_name="work", region_name="eu-west-1")
sts = session.client("sts")
identity = sts.get_caller_identity()
print(identity["Account"], identity["Arn"])04
Verify the caller before changing permissions
Run a read-only identity check in the intended authorized context. Account ID and caller ARN identify the credential context; neither proves that a particular S3, DynamoDB, or Lambda operation is allowed. Keep that distinction when an AccessDenied error remains.
The following CLI check is an explicit-profile comparison for a human investigation. It was not executed against a real account in our lab. Compare it with the actual application’s session rather than assuming both processes share a credential source.
aws sts get-caller-identity --profile work --region eu-west-105
Remove the accidental source through its owner
If stale environment credentials are unintended, remove them from the launcher, terminal setup, container configuration, or secret injection that supplies them. Refresh temporary sessions through their normal login flow; do not copy long-lived keys into more locations as a workaround.
Recheck provider selection and caller identity, then repeat the original read or application operation. Keep the repair scoped to the process configuration responsible. A successful identity check narrows the problem without granting any new permissions.
Know the limits
Validated with Boto3 1.42.97 and synthetic credentials inside a disposable container. The lab checks local provider selection only: no user AWS files were read, and no STS or other live AWS API was called. CLI flags and other SDKs must be evaluated using their own precedence rules.
Sources & further reading
A technical publication by CoreTrailKit.
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