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Helm helper template randHex to generate random hexadecimal (hex, base16) numbers
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| {{/* | |
| Returns given number of random Hex characters. | |
| In practice, it generates up to 100 randAlphaNum strings | |
| that are filtered from non-hex characters and augmented | |
| to the resulting string that is finally trimmed down. | |
| */}} | |
| {{- define "jupyterhub.randHex" -}} | |
| {{- $result := "" }} | |
| {{- range $i := until 100 }} | |
| {{- if lt (len $result) . }} | |
| {{- $rand_list := randAlphaNum . | splitList "" -}} | |
| {{- $reduced_list := without $rand_list "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "r" "s" "t" "u" "v" "w" "x" "y" "z" "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" "T" "U" "V" "W" "X" "Y" "Z" }} | |
| {{- $rand_string := join "" $reduced_list }} | |
| {{- $result = print $result $rand_string -}} | |
| {{- end }} | |
| {{- end }} | |
| {{- $result | trunc . }} | |
| {{- end }} |
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@gjorando: This is not optimal, because randAscii does not generate all possible bytes from 0x00 to 0xFF, so the result has lower entropy than the other solutions mentioned here.
28 random hex digits can be easily generated using
{{ regexReplaceAll "-." uuidv4 "" }}. This removes digits directly following a hyphen, because some of them have reduced entropy (constant 4, or 8 to b). This can be embedded in a loop to produce more than 28 digits. The end result can be cut to a specific length withsubstr.