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Understand-and-using-file-hashes

##User Objective

File hashing is a technique used in applications for various purposes, mainly to ensure data integrity, security, and efficiency.

##Why?

There are a number of reasons why you may want to use file hashing, here are a few:

####Data Integrity Verification When transferring or storing files, there is always a risk of data corruption or tampering. By generating a hash value based on the file's contents using a hashing algorithm (e.g., MD5, SHA-1, SHA-256), the application can later recompute the hash and compare it to the original hash to verify if the file has been altered or corrupted during transmission or storage.

####Deduplication In certain applications like cloud storage or backup systems, file deduplication is used to save storage space. Hashing enables identifying duplicate files efficiently. Instead of storing multiple copies of the same file, the application can use a single hash to represent the duplicated content.

####Cache Management In caching systems, file hashing can be used to quickly check if a particular file has been accessed before and is available in the cache. The hash serves as a unique identifier for the file, allowing for faster retrieval and reducing unnecessary data transfer.

####Data Indexing and Searching In large-scale applications where files need to be indexed and searched quickly, file hashing can be used to build efficient data structures like hash tables, enabling fast lookup and retrieval based on file content.

####Malware Detection Antivirus and security applications use file hashing to identify known malware and viruses. By comparing the hash of a file against a database of known malicious hashes, these applications can quickly determine if a file is potentially harmful.

##CDR Platform Events

  1. The Glasswall CDR Platform API allows you to interact programmatically by initiating requests to specific endpoints based on the file type:

For binary files, use the api/v3/cdr-file endpoint.

For base64-encoded files, use the api/v3/cdr endpoint.

  1. With each request, you have the option to request the generation of file hashes in any combination of three different formats: SHA-256, SHA-1, and MD5.

  2. Once the request is received, the input hash is generated and then the Glasswall CDR Platform processes it using the Glasswall Embedded Engine to rebuild and analyse the input file.

  3. Upon a successfully rebuilt file, the platform generates the output file hashes and both the input and output hashes are returned in the response headers.

  4. If a request fails, the platform has still generated the input hash which is returned in the response headers.

  5. These generated input and output file hashes can be utilised in various ways within your application or system, such as performing security checks, further processing, or any other necessary actions.

##API Authentication:

To understand how to authenticate with the CDR Platform please see here

##Request Construction:

When leveraging the Glasswall CDR Platform for processing binary or base64 encoded files, you have the flexibility to request the generation of multiple hash types, including SHA-256, SHA-1, and MD5. When making an API request, you can specify any combination of these hash types, and in response, you will receive the generated hash values for both the input and output files in the response headers. This enables you to ensure data integrity and authenticity, as well as facilitate efficient handling of files within your application or system.

###Binary File Processing

POST {baseUrl}/api/v3/cdr-file?generate-hash-types=SHA256,SHA1,MD5

###Base64 Encoded File Processing

Submit the base64 encoded string in the request body to the following endpoint:

POST {baseUrl}/api/v3/cdr?generate-hash-types=SHA256,SHA1,MD5

Request Body Format​

The body of the request should be in JSON format and include the base64 field containing the base64 encoded string of the file, and the fileName field specifying the original filename (including the appropriate file extension).

{
  "base64": "string",
  "fileName": "filename.pdf",
}

Note

  • Replace {baseUrl} with the actual base URL of the Glasswall CDR Platform API.
  • Correct auth header should be provided with each request
  • Setting generate-hash-types to a comma separated list of hash values in the URL ensures that the correct hashes are generated and returned in the response
  • For binary file processing, use a multipart form post, while for base64 encoded file processing, provide the file content in the JSON request body with the appropriate filename.

##Response Handling

After successfully making a request to the Glasswall CDR Platform API, you will receive a 201 status code. If you have requested any hashes to be generated and returned, both input and output hashes will be available in the response header. In case of an unsuccessful response, only the input hash values will be returned. You can identify the hash values with the following header keys:

####For SHA-256

  • Input File Hash: x-hash-sha256-input
  • Output File Hash: x-hash-sha256-output

####For SHA-1

  • Input File Hash: x-hash-sha1-input
  • Output File Hash: x-hash-sha1-output

####For MD5

  • Input File Hash: x-hash-md5-input
  • Output File Hash: x-hash-md5-output

####Example

access-control-allow-origin: * 
access-control-expose-headers: * 
content-disposition: attachment; filename=18402777-7826-457f-bc02-6446611495e6.zip; filename*=UTF-8''18402777-7826-457f-bc02-6446611495e6.zip 
content-length: 288843 
content-type: application/octet-stream 
date: Fri,21 Jul 2023 12:42:15 GMT 
strict-transport-security: max-age=31536000; includeSubDomains 
x-applied-policy: service-dynamic 
x-file-size: 301189 
x-filetype: pdf 
x-hash-md5-input: AF5EB421F8AFC69AC4178ACF747E618C 
x-hash-md5-output: 8018FC4F37AB858442F354430203CEB4 
x-hash-sha1-input: 9C714CAC1F82A450728F3C046CEFEFAF0BBD2C07 
x-hash-sha1-output: 058991F3A252F0A4FD0E7F8B3178D3F15494099B 
x-hash-sha256-input: 5F83AB533252C00AD1C60A0EFC016BF273497F3179FD6CE642AD8A4857148B8D 
x-hash-sha256-output: 9D5D88F073D74160828F92E9E8DADAC5712706C65D49448D9ABA91D8FDC6FC28 
x-processing-id: 18402777-7826-457f-bc02-6446611495e6 
x-processing-status: rebuilt

##Objective Achievement

By leveraging the power of generated hashes in your file processing workflow via the CDR Platform, you can streamline operations, enhance security, and improve the reliability of your application. These benefits collectively contribute to a more robust and resilient system that ensures the integrity and safety of your files.

Quick Start​

If you wish to take a look for yourself you can follow our quick start guide and use the CDR Platform yourself.