key_app_writer writes invalid private key DER file

[cwalther]

Description

The same bug as reported in #1257 and fixed in #1258 for public key output also exists in the private key output: When writing the private key in DER format, the contents of the file are shifted by one byte, which makes it an invalid DER file.

Status

READY

Requires Backporting

Yes: mbedtls-2.1, mbedtls-2.7

Migrations

NO

Todos

• Changelog updated
• Backported: Backport 2.7: key_app_writer writes invalid private key DER file #2400 and Backport 2.16: key_app_writer writes invalid private key DER file #2401

Steps to test or reproduce

programs/pkey/gen_key
programs/pkey/key_app_writer mode=private filename=keyfile.key output_mode=private output_file=keyfile.der output_format=der
programs/pkey/key_app mode=private filename=keyfile.der 

Expected result:

  . Loading the private key ... ok
  . Key information    ...
...

Actual result:

  . Loading the private key ... failed
  !  mbedtls_pk_parse_keyfile returned -0x3d00
  !  Last error was: PK - Invalid key tag or value

[cwalther]

ChangeLog: Apparently I’m supposed to make an entry there, but I’m not sure where it should go – I was expecting an “unreleased” section at the top of the file, but don’t see one.
Backports: Am I supposed to make separate pull requests for those, or will the maintainers just cherry-pick the change?

[RonEld]

@cwalther Thank you for your contribution!

As I believe this is your Mbed account, your CLA is valid.

As for the ChangeLog, if there is no section to put new entries, we simply create one. You can look at this commit for reference.
This usually happens if no PR has been merged since a release, so no section has been created yet

Please make a new commit to htis PR, with the section and the ChangeLog entry

[cwalther]

Thanks for the quick response!

Yes, this is the correct Mbed account.

[RonEld]

Backports available at #2400 and #2401

[RonEld]

Both backports have been fully approved, so removing the "needs backports" label.
cc @sbutcher-arm