The bucket holds everything, but not for you to change.

Mercurial AWS S3 read-only roles are the fastest way to give a system visibility into your data without risking a single write or delete. When a role is read-only, it can list objects, view metadata, and download files from your S3 bucket — nothing else. This is the security baseline for any service that only needs access for analysis, reporting, or indexing.

Why Mercurial AWS S3 Read-Only Roles Matter
Granting broad permissions is a direct security risk. Attack surfaces grow with every write. A mercurial role — tightly scoped and ephemeral — limits exposure. By combining AWS IAM policies with S3 permission boundaries, you enforce strict controls and prevent accidental edits. If a credential leaks, the damage is contained.

Core Principles for Configuring Read-Only Roles

1. Use IAM policies that specify s3:GetObject, s3:ListBucket, and only the required actions.
2. Deny all write operations explicitly with Effect: Deny.
3. Apply to the exact bucket ARN, not wildcards, to avoid overreach.
4. Rotate or expire credentials quickly for mercurial access patterns.
5. Use condition keys like aws:SourceIp or MFA requirements to tighten scope.

Example IAM Policy for Read-Only S3 Role

{
 "Version": "2012-10-17",
 "Statement": [
 {
 "Sid": "ListBucket",
 "Effect": "Allow",
 "Action": ["s3:ListBucket"],
 "Resource": ["arn:aws:s3:::your-bucket"]
 },
 {
 "Sid": "GetObjects",
 "Effect": "Allow",
 "Action": ["s3:GetObject"],
 "Resource": ["arn:aws:s3:::your-bucket/*"]
 },
 {
 "Sid": "ExplicitDenyWrite",
 "Effect": "Deny",
 "Action": ["s3:PutObject", "s3:DeleteObject", "s3:DeleteBucket"],
 "Resource": ["arn:aws:s3:::your-bucket", "arn:aws:s3:::your-bucket/*"]
 }
 ]
}

Best Practices for Mercurial Role Management

• Assign via AWS STS for short-lived sessions.
• Tag roles for auditing and automated cleanup.
• Monitor CloudTrail for all actions, even denies.
• Layer with bucket policies to match IAM intent.

Mercurial AWS S3 read-only roles give rapid, controlled access. They protect the integrity of your data and reduce operational risk while enabling fast integration across systems. Configure once, automate rotation, and monitor for drift.

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