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SONARPY-1014 Rule S6245: Disabling server-side encryption of S3 bucket is security-sensitive (#1128)
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‎python-checks/src/main/java/org/sonar/python/checks/CheckList.java

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import java.util.Arrays;
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import java.util.Collections;
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import java.util.HashSet;
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import org.sonar.python.checks.cdk.S3BucketBlockPublicAccessCheck;
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import org.sonar.python.checks.cdk.S3BucketServerEncryptionCheck;
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import org.sonar.python.checks.cdk.S3BucketVersioningCheck;
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import org.sonar.python.checks.hotspots.ClearTextProtocolsCheck;
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import org.sonar.python.checks.hotspots.CommandLineArgsCheck;
@@ -227,6 +229,7 @@ public static Iterable<Class> getChecks() {
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ReturnYieldOutsideFunctionCheck.class,
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RobustCipherAlgorithmCheck.class,
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S3BucketBlockPublicAccessCheck.class,
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S3BucketServerEncryptionCheck.class,
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S3BucketVersioningCheck.class,
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SameBranchCheck.class,
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SameConditionCheck.class,
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WeakSSLProtocolCheck.class,
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WildcardImportCheck.class,
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WrongAssignmentOperatorCheck.class,
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XMLParserXXEVulnerableCheck.class
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)));
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XMLParserXXEVulnerableCheck.class)));
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}
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}

‎python-checks/src/main/java/org/sonar/python/checks/cdk/S3BucketServerEncryptionCheck.java

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/*
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* SonarQube Python Plugin
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* Copyright (C) 2011-2022 SonarSource SA
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* mailto:info AT sonarsource DOT com
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 3 of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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package org.sonar.python.checks.cdk;
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import java.util.Optional;
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import org.sonar.check.Rule;
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import org.sonar.plugins.python.api.SubscriptionContext;
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import org.sonar.plugins.python.api.symbols.Symbol;
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import org.sonar.plugins.python.api.tree.CallExpression;
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import org.sonar.plugins.python.api.tree.Expression;
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import org.sonar.plugins.python.api.tree.QualifiedExpression;
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import org.sonar.python.tree.QualifiedExpressionImpl;
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@Rule(key = "S6245")
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public class S3BucketServerEncryptionCheck extends AbstractS3BucketCheck {
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private static final String S3_BUCKET_UNENCRYPTED_FQN = "aws_cdk.aws_s3.BucketEncryption.UNENCRYPTED";
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public static final String MESSAGE = "Objects in the bucket are not encrypted. Make sure it is safe here.";
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public static final String OMITTING_MESSAGE = "Omitting 'encryption' disables server-side encryption. Make sure it is safe here.";
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@Override
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void visitBucketConstructor(SubscriptionContext ctx, CallExpression bucket) {
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Optional<ArgumentTrace> optEncryptionType = getArgument(ctx, bucket, "encryption");
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if (optEncryptionType.isPresent()) {
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optEncryptionType.ifPresent(argumentTrace -> argumentTrace.addIssueIf(S3BucketServerEncryptionCheck::isUnencrypted, MESSAGE));
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} else {
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Optional<ArgumentTrace> optEncryptionKey = getArgument(ctx, bucket, "encryption_key");
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if (!optEncryptionKey.isPresent()) {
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ctx.addIssue(bucket.callee(), OMITTING_MESSAGE);
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}
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}
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}
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protected static boolean isUnencrypted(Expression expression) {
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return Optional.of(expression)
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.filter(QualifiedExpression.class::isInstance)
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.map(QualifiedExpressionImpl.class::cast)
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.map(QualifiedExpression::symbol)
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.map(Symbol::fullyQualifiedName)
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.filter(S3_BUCKET_UNENCRYPTED_FQN::equals)
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.isPresent();
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}
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}

‎python-checks/src/main/resources/org/sonar/l10n/py/rules/python/S6245.html

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<p>Server-side encryption (SSE) encrypts an object (not the metadata) as it is written to disk (where the S3 bucket resides) and decrypts it as it is
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read from disk. This doesn’t change the way the objects are accessed, as long as the user has the necessary permissions, objects are retrieved as if
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they were unencrypted. Thus, SSE only helps in the event of disk thefts, improper disposals of disks and other attacks on the AWS infrastructure
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itself.</p>
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<p>There are three SSE options:</p>
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<ul>
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<li> Server-Side Encryption with Amazon S3-Managed Keys (SSE-S3)
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<ul>
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<li> AWS manages encryption keys and the encryption itself (with AES-256) on its own. </li>
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</ul> </li>
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<li> Server-Side Encryption with Customer Master Keys (CMKs) Stored in AWS Key Management Service (SSE-KMS)
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<ul>
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<li> AWS manages the encryption (AES-256) of objects and encryption keys provided by the AWS KMS service. </li>
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</ul> </li>
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<li> Server-Side Encryption with Customer-Provided Keys (SSE-C)
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<ul>
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<li> AWS manages only the encryption (AES-256) of objects with encryption keys provided by the customer. AWS doesn’t store the customer’s
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encryption keys. </li>
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</ul> </li>
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</ul>
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<h2>Ask Yourself Whether</h2>
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<ul>
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<li> The S3 bucket stores sensitive information. </li>
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<li> The infrastructure needs to comply to some regulations, like HIPAA or PCI DSS, and other standards. </li>
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</ul>
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<p>There is a risk if you answered yes to any of those questions.</p>
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<h2>Recommended Secure Coding Practices</h2>
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<p>It’s recommended to use SSE. Choosing the appropriate option depends on the level of control required for the management of encryption keys.</p>
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<h2>Sensitive Code Example</h2>
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<p>Server-side encryption is not used:</p>
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<pre>
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bucket = s3.Bucket(self,"MyUnencryptedBucket",
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encryption=s3.BucketEncryption.UNENCRYPTED # Sensitive
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)
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</pre>
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<p>The default value of <code>encryption</code> is <code>KMS</code> if <code>encryptionKey</code> is set. Otherwise, if both parameters are absent the
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bucket is unencrypted.</p>
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<h2>Compliant Solution</h2>
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<p>Server-side encryption with Amazon S3-Managed Keys is used:</p>
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<pre>
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bucket = s3.Bucket(self,"MyEncryptedBucket",
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encryption=s3.BucketEncryption.S3_MANAGED # Compliant
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)
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# Alternatively with a KMS key managed by the user.
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bucket = s3.Bucket(self,"MyEncryptedBucket",
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encryptionKey=access_key # Compliant
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)
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</pre>
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<h2>See</h2>
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<ul>
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<li> <a href="https://owasp.org/Top10/A04_2021-Insecure_Design/">OWASP Top 10 2021 Category A4</a> - Insecure Design </li>
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<li> <a href="https://owasp.org/Top10/A05_2021-Security_Misconfiguration/">OWASP Top 10 2021 Category A5</a> - Security Misconfiguration </li>
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<li> <a href="https://cwe.mitre.org/data/definitions/311">MITRE, CWE-311</a> - Missing Encryption of Sensitive Data </li>
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<li> <a href="https://www.owasp.org/index.php/Top_10-2017_A3-Sensitive_Data_Exposure">OWASP Top 10 2017 Category A3</a> - Sensitive Data Exposure
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</li>
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<li> <a href="https://www.owasp.org/index.php/Top_10-2017_A6-Security_Misconfiguration">OWASP Top 10 2017 Category A6</a> - Security
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Misconfiguration </li>
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<li> <a href="https://docs.aws.amazon.com/AmazonS3/latest/userguide/serv-side-encryption.html">AWS documentation</a> - Protecting data using
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server-side encryption </li>
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<li> <a href="https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.aws_s3.BucketEncryption.html">CDK documentation</a> - BucketEncryption class
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</li>
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</ul>
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‎python-checks/src/main/resources/org/sonar/l10n/py/rules/python/S6245.json

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{
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"title": "Disabling server-side encryption of S3 buckets is security-sensitive",
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"type": "SECURITY_HOTSPOT",
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"status": "ready",
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"tags": [
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"aws",
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"cwe",
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"owasp-a6",
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"owasp-a3"
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],
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"defaultSeverity": "Minor",
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"ruleSpecification": "RSPEC-6245",
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"sqKey": "S6245",
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"scope": "Main",
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"securityStandards": {
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"CWE": [
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311
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],
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"OWASP": [
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"A3",
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"A6"
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],
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"CIS": [
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"2.1.1"
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],
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"OWASP Top 10 2021": [
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"A4",
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"A5"
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]
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}
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}

‎python-checks/src/main/resources/org/sonar/l10n/py/rules/python/Sonar_way_profile.json

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"S6002",
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"S6019",
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"S6035",
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"S6245",
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"S6252",
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"S6281",
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"S6323",

‎python-checks/src/test/java/org/sonar/python/checks/cdk/S3BucketServerEncryptionCheckTest.java

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/*
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* SonarQube Python Plugin
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* Copyright (C) 2011-2022 SonarSource SA
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* mailto:info AT sonarsource DOT com
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 3 of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this program; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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package org.sonar.python.checks.cdk;
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import org.junit.Test;
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import org.sonar.python.checks.utils.PythonCheckVerifier;
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public class S3BucketServerEncryptionCheckTest {
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@Test
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public void test() {
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PythonCheckVerifier.verify("src/test/resources/checks/cdk/s3BucketServerEncryption.py", new S3BucketServerEncryptionCheck());
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}
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}

‎python-checks/src/test/resources/checks/cdk/s3BucketServerEncryption.py

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from aws_cdk import aws_s3 as s3
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bucket = s3.Bucket(self,"MyUnencryptedBucket") # NonCompliant {{Omitting 'encryption' disables server-side encryption. Make sure it is safe here.}}
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# ^^^^^^^^^
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bucket = s3.Bucket(self,"MyUnencryptedBucket", encryption=s3.BucketEncryption.UNENCRYPTED) # NonCompliant {{Objects in the bucket are not encrypted. Make sure it is safe here.}}
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# ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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bucket = s3.Bucket(self,"MyEncryptedBucket",
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encryption=s3.BucketEncryption.KMS_MANAGED # Compliant
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)
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bucket = s3.Bucket(self,"MyEncryptedBucket",
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encryption=s3.BucketEncryption.S3_MANAGED # Compliant
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)
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bucket = s3.Bucket(self,"MyEncryptedBucket",
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encryption=s3.BucketEncryption.KMS # Compliant
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)
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bucket = s3.Bucket(self,"MyEncryptedBucket",
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encryption_key=my_encryption_key # Compliant
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)
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bucket = s3.Bucket(self,"MyUnencryptedBucket",
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encryption=s3.BucketEncryption.UNENCRYPTED, # NonCompliant {{Objects in the bucket are not encrypted. Make sure it is safe here.}}
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# ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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encryption_key=my_encryption_key
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)
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type_KMS = s3.BucketEncryption.KMS
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bucket = s3.Bucket(self,"MyEncryptedBucket",
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encryption=type_KMS # Compliant
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)
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my_encryption_key2 = aws_cdk.aws_kms.IKey() # Compliant
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bucket = s3.Bucket(self,"MyEncryptedBucket",
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encryption=s3.BucketEncryption.S3_MANAGED,
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encryption_key=my_encryption_key2)
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def create_bucket():
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type_unencrypted = s3.BucketEncryption.UNENCRYPTED
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# ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^> {{Propagated setting.}}
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bucket = s3.Bucket(self,"MyEncryptedBucket",
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encryption=type_unencrypted, # NonCompliant {{Objects in the bucket are not encrypted. Make sure it is safe here.}}
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# ^^^^^^^^^^^^^^^^^^^^^^^^^^^
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encryption_key=my_encryption_key2)
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coverage = s3.Bucket(self, "bucket", encryption=unresolved_reference) # Compliant

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