tree 6aa3467bd39331968b8aa5d325b4848265e2f0fb
parent 1fe5e8ab44ef46b582ab54db5afcb6bab180d440
author Hanno Becker <hanno.becker@arm.com> 1503664706 +0100
committer Hanno Becker <hanno.becker@arm.com> 1506610347 +0100

Use in-place decryption in pk_parse_pkcs8_encrypted_der

The stack buffer used to hold the decrypted key in pk_parse_pkcs8_encrypted_der
was statically sized to 2048 bytes, which is not enough for DER encoded 4096bit
RSA keys.

This commit resolves the problem by performing the key-decryption in-place,
circumventing the introduction of another stack or heap copy of the key.

There are two situations where pk_parse_pkcs8_encrypted_der is invoked:
1. When processing a PEM-encoded encrypted key in mbedtls_pk_parse_key.
   This does not need adaption since the PEM context used to hold the decoded
   key is already constructed and owned by mbedtls_pk_parse_key.
2. When processing a DER-encoded encrypted key in mbedtls_pk_parse_key.
   In this case, mbedtls_pk_parse_key calls pk_parse_pkcs8_encrypted_der with
   the buffer provided by the user, which is declared const. The commit
   therefore adds a small code paths making a copy of the keybuffer before
   calling pk_parse_pkcs8_encrypted_der.