How to generate SRI hashes (Subresource Integrity) using shasum, awk, xxd, base64

Question

2023-08-22

Linux

0

2023-08-22

Linux

0

score 0 · Accepted Answer

Generate Subresource Integrity (SRI) Hashes using shasum

You can generate SRI hashes using shasum with a command

shasum -b -a 256 aarral_mart_test.pdf | awk '{ print $1 }' | xxd -r -p | base64

The pipe-through xxd step takes the hexadecimal output from shasum and converts it to binary.
The second pile-through awk step is important because shasum will pass the hashed filename in its output to xxd. That can have disastrous consequences if the filename happens to have valid hex characters in it - because xxd will also decode that and pass it to base64.

tQz0nYS9m+y4nak28X33gdtrPOj5DrLRU6kz6kLw8GY=


<script src="https://www.aarralmart.com/test.js" integrity="sha384-tQz0nYS9m+y4nak28X33gdtrPOj5DrLRU6kz6kLw8GY=" crossorigin="anonymous"></script>