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https://github.com/bluesentry/bucket-antivirus-function

Serverless antivirus for cloud storage.
https://github.com/bluesentry/bucket-antivirus-function

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Serverless antivirus for cloud storage.

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README 

        
# bucket-antivirus-function



[![CircleCI](https://circleci.com/gh/upsidetravel/bucket-antivirus-function.svg?style=svg)](https://circleci.com/gh/upsidetravel/bucket-antivirus-function)



Scan new objects added to any s3 bucket using AWS Lambda. [more details in this post](https://engineering.upside.com/s3-antivirus-scanning-with-lambda-and-clamav-7d33f9c5092e)



## Features



- Easy to install

- Send events from an unlimited number of S3 buckets

- Prevent reading of infected files using S3 bucket policies

- Accesses the end-user’s separate installation of

open source antivirus engine [ClamAV](http://www.clamav.net/)



## How It Works



![architecture-diagram](../master/images/bucket-antivirus-function.png)



- Each time a new object is added to a bucket, S3 invokes the Lambda

function to scan the object

- The function package will download (if needed) current antivirus

definitions from a S3 bucket. Transfer speeds between a S3 bucket and

Lambda are typically faster and more reliable than another source

- The object is scanned for viruses and malware.  Archive files are

extracted and the files inside scanned also

- The objects tags are updated to reflect the result of the scan, CLEAN

or INFECTED, along with the date and time of the scan.

- Object metadata is updated to reflect the result of the scan (optional)

- Metrics are sent to [DataDog](https://www.datadoghq.com/) (optional)

- Scan results are published to a SNS topic (optional) (Optionally choose to only publish INFECTED results)

- Files found to be INFECTED are automatically deleted (optional)



## Installation



### Build from Source



To build the archive to upload to AWS Lambda, run `make all`.  The build process is completed using

the [amazonlinux](https://hub.docker.com/_/amazonlinux/) [Docker](https://www.docker.com)

 image.  The resulting archive will be built at `build/lambda.zip`.  This file will be

 uploaded to AWS for both Lambda functions below.



### Create Relevant AWS Infra via CloudFormation



Use CloudFormation with the `cloudformation.yaml` located in the `deploy/` directory to quickly spin up the AWS infra needed to run this project. CloudFormation will create:



- An S3 bucket that will store AntiVirus definitions.

- A Lambda Function called `avUpdateDefinitions` that will update the AV Definitions in the S3 Bucket every 3 hours.

This function accesses the user’s above S3 Bucket to download updated definitions using `freshclam`.

- A Lambda Function called `avScanner` that is triggered on each new S3 object creation which scans the object and tags it appropriately. It is created with `1600mb` of memory which should be enough, however if you start to see function timeouts, this memory may have to be bumped up. In the past, we recommended using `1024mb`, but that has started causing Lambda timeouts and bumping this memory has resolved it.



Running CloudFormation, it will ask for 2 inputs for this stack:



1. BucketType: `private` (default) or `public`. This is applied to the S3 bucket that stores the AntiVirus definitions. We recommend to only use `public` when other AWS accounts need access to this bucket.

2. SourceBucket: [a non-empty string]. The name (do not include `s3://`) of the S3 bucket that will have its objects scanned. _Note - this is just used to create the IAM Policy, you can add/change source buckets later via the IAM Policy that CloudFormation outputs_



After the Stack has successfully created, there are 3 manual processes that still have to be done:



1. Upload the `build/lambda.zip` file that was created by running `make all` to the `avUpdateDefinitions` and `avScanner` Lambda functions via the Lambda Console.

2. To trigger the Scanner function on new S3 objects, go to the `avScanner` Lambda function console, navigate to `Configuration` -> `Trigger` -> `Add Trigger` -> Search for S3, and choose your bucket(s) and select `All object create events`, then click `Add`. _Note - if you chose more than 1 bucket as the source, or chose a different bucket than the Source Bucket in the CloudFormation parameter, you will have to also edit the IAM Role to reflect these new buckets (see "Adding or Changing Source Buckets")_

3. Navigate to the `avUpdateDefinitions` Lambda function and manually trigger the function to get the initial Clam definitions in the bucket (instead of waiting for the 3 hour trigger to happen). Do this by clicking the `Test` section, and then clicking the orange `test` button. The function should take a few seconds to execute, and when finished you should see the `clam_defs` in the `av-definitions` S3 bucket.



#### Adding or Changing Source Buckets



Changing or adding Source Buckets is done by editing the `AVScannerLambdaRole` IAM Role. More specifically, the `S3AVScan` and `KmsDecrypt` parts of that IAM Role's policy.



### S3 Events



Configure scanning of additional buckets by adding a new S3 event to

invoke the Lambda function.  This is done from the properties of any

bucket in the AWS console.



![s3-event](../master/images/s3-event.png)



Note: If configured to update object metadata, events must only be

configured for `PUT` and `POST`. Metadata is immutable, which requires

the function to copy the object over itself with updated metadata. This

can cause a continuous loop of scanning if improperly configured.



## Configuration



Runtime configuration is accomplished using environment variables.  See

the table below for reference.



| Variable | Description | Default | Required |

| --- | --- | --- | --- |

| AV_DEFINITION_S3_BUCKET | Bucket containing antivirus definition files |  | Yes |

| AV_DEFINITION_S3_PREFIX | Prefix for antivirus definition files | clamav_defs | No |

| AV_DEFINITION_PATH | Path containing files at runtime | /tmp/clamav_defs | No |

| AV_SCAN_START_SNS_ARN | SNS topic ARN to publish notification about start of scan | | No |

| AV_SCAN_START_METADATA | The tag/metadata indicating the start of the scan | av-scan-start | No |

| AV_SIGNATURE_METADATA | The tag/metadata name representing file's AV type | av-signature | No |

| AV_STATUS_CLEAN | The value assigned to clean items inside of tags/metadata | CLEAN | No |

| AV_STATUS_INFECTED | The value assigned to clean items inside of tags/metadata | INFECTED | No |

| AV_STATUS_METADATA | The tag/metadata name representing file's AV status | av-status | No |

| AV_STATUS_SNS_ARN | SNS topic ARN to publish scan results (optional) | | No |

| AV_STATUS_SNS_PUBLISH_CLEAN | Publish AV_STATUS_CLEAN results to AV_STATUS_SNS_ARN | True | No |

| AV_STATUS_SNS_PUBLISH_INFECTED | Publish AV_STATUS_INFECTED results to AV_STATUS_SNS_ARN | True | No |

| AV_TIMESTAMP_METADATA | The tag/metadata name representing file's scan time | av-timestamp | No |

| CLAMAVLIB_PATH | Path to ClamAV library files | ./bin | No |

| CLAMSCAN_PATH | Path to ClamAV clamscan binary | ./bin/clamscan | No |

| FRESHCLAM_PATH | Path to ClamAV freshclam binary | ./bin/freshclam | No |

| DATADOG_API_KEY | API Key for pushing metrics to DataDog (optional) | | No |

| AV_PROCESS_ORIGINAL_VERSION_ONLY | Controls that only original version of an S3 key is processed (if bucket versioning is enabled) | False | No |

| AV_DELETE_INFECTED_FILES | Controls whether infected files should be automatically deleted | False | No |

| EVENT_SOURCE | The source of antivirus scan event "S3" or "SNS" (optional) | S3 | No |

| S3_ENDPOINT | The Endpoint to use when interacting wth S3 | None | No |

| SNS_ENDPOINT | The Endpoint to use when interacting wth SNS | None | No |

| LAMBDA_ENDPOINT | The Endpoint to use when interacting wth Lambda | None | No |



## S3 Bucket Policy Examples



### Deny to download the object if not "CLEAN"



This policy doesn't allow to download the object until:



1. The lambda that run Clam-AV is finished (so the object has a tag)

2. The file is not CLEAN



Please make sure to check cloudtrail for the arn:aws:sts, just find the event open it and copy the sts.

It should be in the format provided below:



```json

 {

    "Effect": "Deny",

    "NotPrincipal": {

        "AWS": [

            "arn:aws:iam::<>:role/<>",

            "arn:aws:sts::<>:assumed-role/<>/<>",

            "arn:aws:iam::<>:root"

        ]

    },

    "Action": "s3:GetObject",

    "Resource": "arn:aws:s3:::<>/*",

    "Condition": {

        "StringNotEquals": {

            "s3:ExistingObjectTag/av-status": "CLEAN"

        }

    }

}

```



### Deny to download and re-tag "INFECTED" object



```json

{

  "Version": "2012-10-17",

  "Statement": [

    {

      "Effect": "Deny",

      "Action": ["s3:GetObject", "s3:PutObjectTagging"],

      "Principal": "*",

      "Resource": ["arn:aws:s3:::<>/*"],

      "Condition": {

        "StringEquals": {

          "s3:ExistingObjectTag/av-status": "INFECTED"

        }

      }

    }

  ]

}

```



## Manually Scanning Buckets



You may want to scan all the objects in a bucket that have not previously been scanned or were created

prior to setting up your lambda functions. To do this you can use the `scan_bucket.py` utility.



```sh

pip install boto3

scan_bucket.py --lambda-function-name= --s3-bucket-name=

```



This tool will scan all objects that have not been previously scanned in the bucket and invoke the lambda function

asynchronously. As such you'll have to go to your cloudwatch logs to see the scan results or failures. Additionally,

the script uses the same environment variables you'd use in your lambda so you can configure them similarly.



## Testing



There are two types of tests in this repository. The first is pre-commit tests and the second are python tests. All of

these tests are run by CircleCI.



### pre-commit Tests



The pre-commit tests ensure that code submitted to this repository meet the standards of the repository. To get started

with these tests run `make pre_commit_install`. This will install the pre-commit tool and then install it in this

repository. Then the github pre-commit hook will run these tests before you commit your code.



To run the tests manually run `make pre_commit_tests` or `pre-commit run -a`.



### Python Tests



The python tests in this repository use `unittest` and are run via the `nose` utility. To run them you will need

to install the developer resources and then run the tests:



```sh

pip install -r requirements.txt

pip install -r requirements-dev.txt

make test

```



### Local lambdas



You can run the lambdas locally to test out what they are doing without deploying to AWS. This is accomplished

by using docker containers that act similarly to lambda. You will need to have set up some local variables in your

`.envrc.local` file and modify them appropriately first before running `direnv allow`. If you do not have `direnv`

it can be installed with `brew install direnv`.



For the Scan lambda you will need a test file uploaded to S3 and the variables `TEST_BUCKET` and `TEST_KEY`

set in your `.envrc.local` file. Then you can run:



```sh

direnv allow

make archive scan

```



If you want a file that will be recognized as a virus you can download a test file from the [EICAR](https://www.eicar.org/?page_id=3950)

website and uploaded to your bucket.



For the Update lambda you can run:



```sh

direnv allow

make archive update

```



## License



```text

Upside Travel, Inc.



Licensed under the Apache License, Version 2.0 (the "License");

you may not use this file except in compliance with the License.

You may obtain a copy of the License at



http://www.apache.org/licenses/LICENSE-2.0



Unless required by applicable law or agreed to in writing, software

distributed under the License is distributed on an "AS IS" BASIS,

WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

See the License for the specific language governing permissions and

limitations under the License.

```



ClamAV is released under the [GPL Version 2 License](https://github.com/vrtadmin/clamav-devel/blob/master/COPYING)

and all [source for ClamAV](https://github.com/vrtadmin/clamav-devel) is available

for download on Github.