I'm using a log aggregation setup where sensitive data that is prepared for submission to loki is obfuscated with Promtail's Hash filter under consideration of a salt value.
I want to dispatch a query with Grafana to look for a specific value that would have been transformed in that way. Therefore I have to calculate what Promtail would derive from that value.
I assume I could reproduce the result on a current Ubuntu Desktop OS like this:
$ echo "Value of interest" | shasum -a 256 -
But how would I have to bring the salt value into the equation?
As can be seen here functions
Hash
andSha2Hash
both simply invoke hashing functions over simple concatenation of salt and input value:Note that the documentation proposes a configuration where value and salt are swapped, which must be considered if you followed it. Also, it must be ensured that no newline character is added when using
echo
. Thus, using rhash in this example, the hash can be derived with:The "inner" consecutive quote characters only serve clarity, they could be omitted.