A reversible DER and BER pretty-printer.
DER ASCII is a small human-editable language to emit DER (Distinguished Encoding Rules) or BER (Basic Encoding Rules) encodings of ASN.1 structures and malformed variants of them.
It provides two tools, ascii2der
and der2ascii
, to convert DER ASCII to a
byte string and vice versa. To install them, run:
go install github.com/google/der-ascii/cmd/...@latest
These tools may be used to create test inputs by taking an existing DER or BER
structure, disassembling it with der2ascii
into DER ASCII, making
adjustments, and assembling back into binary with ascii2der
. This avoids
having to manually fix up all the length prefixes. As a bonus, it acts as a
human-readable view for DER structures.
For the language specification and basic examples, see language.txt. The samples directory includes more complex examples from real inputs.
The DER ASCII language itself may be extended over time, but the intention is for extensions to be backwards-compatible. Specifically:
The command-line interface to ascii2der
and der2ascii
will remain
compatible, though new options may be added in the future.
Previously valid inputs to ascii2der
will remain valid and produce the same
output. In particular, checking in test data as ascii2der
inputs should be
future-proof, though it is recommended to check in the generated version as
well in case of mistakes.
Previously invalid inputs to ascii2der
may become valid in the future if
the language is extended.
der2ascii
is necessarily a heuristic, so its output may change
over time. For example, later revisions may recognize new OIDs, tweak the
formatting, or disassemble a malformed DER input in a (hopefully) more
useful form.
This is not an official Google project.