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fix: added support for generating S3 permissions using Bucket references #648

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Merged
merged 1 commit into from
Jun 15, 2025
Merged

fix: added support for generating S3 permissions using Bucket references #648

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41 changes: 31 additions & 10 deletions lib/deploy/stepFunctions/compileIamRole.js
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Original file line number Diff line number Diff line change
Expand Up @@ -634,6 +634,25 @@ function getEventBridgeSchedulerPermissions(state) {
];
}

// Because the S3 Bucket parameter can be either a literal name or a reference to an
// existing S3 bucket we need to resolve
function resolveS3BucketReference(bucket, resource) {
if (isIntrinsic(bucket)) {
return {
'Fn::Sub': [
resource,
{ bucket },
],
};
}

return resource.replaceAll('${bucket}', bucket);
}

function resolveS3BucketReferences(bucket, resources) {
return resources.map(resource => resolveS3BucketReference(bucket, resource));
}

function getS3ObjectPermissions(action, state) {
const bucket = state.Parameters.Bucket || '*';
const key = state.Parameters.Key || '*';
Expand All @@ -644,27 +663,29 @@ function getS3ObjectPermissions(action, state) {
return [
{
action: 's3:Get*',
resource: [
`arn:aws:s3:::${bucket}`,
`arn:aws:s3:::${bucket}/*`,
],
resource: resolveS3BucketReferences(bucket, [
// The bucket variable is not interpolated here, or below,
// but inside resolveS3BucketReferences() to also handle intrinsics
'arn:aws:s3:::${bucket}',
'arn:aws:s3:::${bucket}/*',
]),
},
{
action: 's3:List*',
resource: [
`arn:aws:s3:::${bucket}`,
`arn:aws:s3:::${bucket}/*`,
],
resource: resolveS3BucketReferences(bucket, [
'arn:aws:s3:::${bucket}',
'arn:aws:s3:::${bucket}/*',
]),
},
];
}

if (prefix) {
arn = `arn:aws:s3:::${bucket}/${prefix}/${key}`;
arn = resolveS3BucketReference(bucket, `arn:aws:s3:::\${bucket}/${prefix}/${key}`);
} else if (bucket === '*' && key === '*') {
arn = '*';
} else {
arn = `arn:aws:s3:::${bucket}/${key}`;
arn = resolveS3BucketReference(bucket, `arn:aws:s3:::\${bucket}/${key}`);
}

return [{
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279 changes: 279 additions & 0 deletions lib/deploy/stepFunctions/compileIamRole.test.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2148,6 +2148,285 @@ describe('#compileIamRole', () => {
.to.be.deep.equal('*');
});

it('should resolve literal bucket names in S3 permissions', () => {
const literalBucket = 'my-test-bucket';
const literalKey = 'test-key.txt';

serverless.service.stepFunctions = {
stateMachines: {
myStateMachine1: {
id: 'StateMachine1',
definition: {
StartAt: 'A',
States: {
A: {
Type: 'Task',
Resource: 'arn:aws:states:::aws-sdk:s3:getObject',
Parameters: {
Bucket: literalBucket,
Key: literalKey,
},
End: true,
},
},
},
},
},
};

serverlessStepFunctions.compileIamRole();
const statements = serverlessStepFunctions.serverless.service.provider
.compiledCloudFormationTemplate.Resources.StateMachine1Role.Properties.Policies[0]
.PolicyDocument.Statement;

expect(statements[0].Resource[0]).to.equal(`arn:aws:s3:::${literalBucket}/${literalKey}`);
});

it('should resolve CloudFormation reference buckets in S3 permissions', () => {
const bucketRef = { Ref: 'MyS3Bucket' };

serverless.service.stepFunctions = {
stateMachines: {
myStateMachine1: {
id: 'StateMachine1',
definition: {
StartAt: 'A',
States: {
A: {
Type: 'Task',
Resource: 'arn:aws:states:::aws-sdk:s3:getObject',
Parameters: {
Bucket: bucketRef,
Key: 'test-key.txt',
},
End: true,
},
},
},
},
},
};

serverlessStepFunctions.compileIamRole();
const statements = serverlessStepFunctions.serverless.service.provider
.compiledCloudFormationTemplate.Resources.StateMachine1Role.Properties.Policies[0]
.PolicyDocument.Statement;

expect(statements[0].Resource[0]).to.deep.equal({
'Fn::Sub': [
'arn:aws:s3:::${bucket}/test-key.txt',
{ bucket: bucketRef },
],
});
});

it('should resolve Fn::GetAtt bucket references in S3 permissions', () => {
const bucketRef = { 'Fn::GetAtt': ['MyS3Bucket', 'Arn'] };

serverless.service.stepFunctions = {
stateMachines: {
myStateMachine1: {
id: 'StateMachine1',
definition: {
StartAt: 'A',
States: {
A: {
Type: 'Task',
Resource: 'arn:aws:states:::aws-sdk:s3:putObject',
Parameters: {
Bucket: bucketRef,
Key: 'output.json',
Body: { result: 'success' },
},
End: true,
},
},
},
},
},
};

serverlessStepFunctions.compileIamRole();
const statements = serverlessStepFunctions.serverless.service.provider
.compiledCloudFormationTemplate.Resources.StateMachine1Role.Properties.Policies[0]
.PolicyDocument.Statement;

expect(statements[0].Resource[0]).to.deep.equal({
'Fn::Sub': [
'arn:aws:s3:::${bucket}/output.json',
{ bucket: bucketRef },
],
});
});

it('should resolve bucket references in S3 listObjectsV2 permissions', () => {
const bucketRef = { Ref: 'MyS3Bucket' };

serverless.service.stepFunctions = {
stateMachines: {
myStateMachine1: {
id: 'StateMachine1',
definition: {
StartAt: 'A',
States: {
A: {
Type: 'Map',
ItemProcessor: {
ProcessorConfig: {
Mode: 'DISTRIBUTED',
},
},
StartAt: 'B',
States: {
B: {
Type: 'Task',
Resource: 'arn:aws:lambda:#{AWS::Region}:#{AWS::AccountId}:function:hello',
End: true,
},
},
ItemReader: {
Resource: 'arn:aws:states:::s3:listObjectsV2',
Parameters: {
Bucket: bucketRef,
Prefix: 'data',
},
},
End: true,
},
},
},
},
},
};

serverlessStepFunctions.compileIamRole();
const statements = serverlessStepFunctions.serverless.service.provider
.compiledCloudFormationTemplate.Resources.StateMachine1Role.Properties.Policies[0]
.PolicyDocument.Statement;

expect(statements[3].Resource[0]).to.deep.equal({
'Fn::Sub': [
'arn:aws:s3:::${bucket}',
{ bucket: bucketRef },
],
});
expect(statements[3].Resource[1]).to.deep.equal({
'Fn::Sub': [
'arn:aws:s3:::${bucket}/*',
{ bucket: bucketRef },
],
});
});

it('should handle mixed literal and reference buckets correctly', () => {
const literalBucket = 'literal-bucket';
const bucketRef = { Ref: 'ReferenceBucket' };
const literalFile = 'file1.txt';

serverless.service.stepFunctions = {
stateMachines: {
myStateMachine1: {
id: 'StateMachine1',
definition: {
StartAt: 'A',
States: {
A: {
Type: 'Task',
Resource: 'arn:aws:states:::aws-sdk:s3:getObject',
Parameters: {
Bucket: literalBucket,
Key: literalFile,
},
Next: 'B',
},
B: {
Type: 'Task',
Resource: 'arn:aws:states:::aws-sdk:s3:putObject',
Parameters: {
Bucket: bucketRef,
Key: 'file2.txt',
Body: {},
},
End: true,
},
},
},
},
},
};

serverlessStepFunctions.compileIamRole();
const statements = serverlessStepFunctions.serverless.service.provider
.compiledCloudFormationTemplate.Resources.StateMachine1Role.Properties.Policies[0]
.PolicyDocument.Statement;

// Check that we have consolidated permissions
expect(statements).to.have.lengthOf(2);

// First statement for s3:GetObject with literal bucket
expect(statements[0].Action).to.deep.equal(['s3:GetObject']);
expect(statements[0].Resource[0]).to.equal(`arn:aws:s3:::${literalBucket}/${literalFile}`);

// Second statement for s3:PutObject with reference bucket
expect(statements[1].Action).to.deep.equal(['s3:PutObject']);
expect(statements[1].Resource[0]).to.deep.equal({
'Fn::Sub': [
'arn:aws:s3:::${bucket}/file2.txt',
{ bucket: bucketRef },
],
});
});

it('should handle bucket references with prefixes correctly', () => {
const bucketRef = { Ref: 'MyS3Bucket' };

serverless.service.stepFunctions = {
stateMachines: {
myStateMachine1: {
id: 'StateMachine1',
definition: {
StartAt: 'A',
States: {
A: {
Type: 'Map',
ItemProcessor: {
StartAt: 'B',
States: {
B: {
Type: 'Task',
Resource: 'arn:aws:lambda:us-west-2:1234567890:function:foo',
End: true,
},
},
},
ResultWriter: {
Resource: 'arn:aws:states:::s3:putObject',
Parameters: {
Bucket: bucketRef,
Prefix: 'results',
},
},
End: true,
},
},
},
},
},
};

serverlessStepFunctions.compileIamRole();
const statements = serverlessStepFunctions.serverless.service.provider
.compiledCloudFormationTemplate.Resources.StateMachine1Role.Properties.Policies[0]
.PolicyDocument.Statement;

expect(statements[1].Resource[0]).to.deep.equal({
'Fn::Sub': [
'arn:aws:s3:::${bucket}/results/*',
{ bucket: bucketRef },
],
});
});

it('should not generate any permissions for Task states not yet supported', () => {
const genStateMachine = id => ({
id,
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