AWS Systems Manager Parameter Store (SSM PS) with focus on Security, Centralized Configuration & Secrets Management | Deep Dive.

A deep dive into AWS Systems Manager  Parameter Store (SSM PS)…with focus on security, centralized configuration and secrets management in a  DevSecOps environments.

Breakdown:

•        Overview & Use Cases
•        Parameter Types & Tiers
•        Security Architecture
•        Access Control (IAM Policies & Conditions)
•        Encryption (KMS Integration)
•        Versioning, Auditing, and Change Management
•        Integration with AWS Services
•        Automation Patterns & Advanced Use Cases
•        Best Practices & Anti-Patterns

1. Overview & Use Cases

•        AWS Systems Manager Parameter Store (SSM PS) is a managed service for storing configuration data and secrets as key-value pairs.
•        AWS Systems Manager Parameter Store (SSM PS) provides:

•         Centralized management of environment variables, connection strings, API keys, and other runtime config.
•         Secure, auditable, versioned storage.
•         Integration with AWS services like EC2, Lambda, ECS, and CodePipeline.

Common Use Cases

• App configuration: Environment-specific variables (e.g. db.host, api.url, log.level).
• Secrets management: Encrypted credentials (e.g. database passwords, API tokens).
• Infrastructure automation: Parameters shared across CloudFormation, Terraform, or CI/CD pipelines.
• Cross-account configuration sharing (with KMS key policies).

2. Parameter Types & Tiers

Type	Description	Max Size	Encryption
String	Plaintext data (non-sensitive).	4 KB	None
StringList	Comma-separated list of values.	4 KB	None
SecureString	Sensitive data encrypted via AWS KMS.	8 KB	Yes (KMS)

Parameter Tiers

Tier	Max Parameters		Max Size	Throughput	Features
Standard		10,000	4 KB	40 TPS	Free tier
Advanced		100,000+	8 KB	1000 TPS	Higher throughput, policies, expiration

3. Security Architecture

SSM Parameter Store follows shared responsibility:

• AWS secures the infrastructure (encryption, HA, access logs).
• twtech needs to define encryption keys, IAM policies, and access boundaries.

Security Layers

1. Encryption at Rest – via KMS Customer Managed Keys (CMKs).
2. Encryption in Transit – HTTPS and SigV4 signing.
3. Granular IAM policies – control read/write access at parameter or path level.
4. Auditability – parameter changes logged to AWS CloudTrail.

4. Access Control (IAM Policies & Conditions)

twtech can scope access by:

• Parameter path (hierarchical access)
• Parameter name
• Tag-based access
• Condition keys (e.g. ssm:ResourceTag/Environment or ssm:ParameterName)

Example IAM policy (read-only for Dev parameters):

# json

{

  "Version": "2012-10-17",

  "Statement": [

    {

      "Sid": "twtechReadDevParameters",

      "Effect": "Allow",

      "Action": [

        "ssm:GetParameter",

        "ssm:GetParametersByPath"

      ],

      "Resource": "arn:aws:ssm:us-east-2:accountID:parameter/dev/*"

    }

  ]

}

5. Encryption (KMS Integration)

SecureString parameters are encrypted using:

• AWS-managed key (aws/ssm), or
• Customer-managed CMK (recommended for cross-account and auditing).

NB:

twtech can define the KMS key explicitly:

# bash

aws ssm put-parameter  --name "/prod/db/password"  --value "twtechSuperSecret123" --type "SecureString" --key-id "arn:aws:kms:us-east-2:accountID:key/twtechkmskey-abcd-efgh"

KMS Policy Example for Cross-Account Read

To allow a Lambda in another account to decrypt a parameter:

# json

{

  "Sid": "twtechAllowCrossAccountDecrypt",

  "Effect": "Allow",

  "Principal": {"AWS": "arn:aws:iam::accountID:role/twtechRemoteLambdaRole"},

  "Action": ["kms:Decrypt"],

  "Resource": "*"

}

6. Versioning, Auditing, and Change Management

Each parameter is versioned automatically:

• twtech can reference specific versions (e.g. name:1).
• Old versions are retained for rollback.
• Parameter changes are logged in CloudTrail.

Example rollback:

aws ssm get-parameter --name "/app/config/db" --version 3

7. Integration with AWS Services

Service	Integration Example
EC2 / ECS / Lambda	Fetch configs securely at runtime.
CloudFormation	Use {{resolve:ssm-secure:/path/to/param}}.
CodePipeline / CodeBuild	Inject environment variables dynamically.
Secrets Manager	twtech can reference SSM parameters inside Secrets.
AWS SDKs / CLI	Universal access across languages and scripts.

8. Automation Patterns & Advanced Use Cases

1. Hierarchical Naming Convention

Example:

/{env}/{service}/{component}/{key}

e.g.

/prod/web/api/endpoint

or

/dev/db/twtechUserPat

2. Parameter Policies

Advanced tier allows:

• Expiration – auto-deletes expired parameters.
• Notification – CloudWatch Events before expiration.
• No-change alerting – detect stale configs.

3. Cross-Account Replication

• Use AWS Lambda or EventBridge to replicate parameters across environments (Dev → QA → Prod).
• Encrypt each with the target account’s KMS key.

4. Automation with SSM Documents

Automate runtime configuration injection (e.g., at EC2 launch).

9. Best Practices & Anti-Patterns

 Best Practices

• Use SecureString for all secrets (not String).
• Use customer-managed KMS keys for isolation & rotation.
• Tag parameters with metadata (Environment, Application, Owner).
• Enable CloudTrail for all Parameter Store activities.
• Rotate secrets periodically.
• Enforce least privilege IAM (e.g., path-level access).

Anti-Patterns

• Storing large files (>8 KB) — use S3 + signed URLs instead.
• Hardcoding secrets in Lambda or EC2 user data.
• Reusing the same KMS key for all environments.
• Using aws/ssm default key for production secrets.

Example: End-to-End Setup

Create a Secure Parameter

# bash

aws ssm put-parameter \

  --name "/prod/db/password" \

  --type "SecureString" \

  --value "twtechProdStrongP@123" \

  --key-id "alias/prod-kms" \

  --tags Key=Environment,Value=Prod

Retrieve It in Lambda (Python)

# python

import boto3

import os

ssm = boto3.client('ssm')

def handler(event, context):

    param = ssm.get_parameter(

        Name='/prod/db/password',

        WithDecryption=True

    )

    db_password = param['Parameter']['Value']

    print("Retrieved password for DB connection")