tree 7f2c30f9c9238a882f3643ef2410e21000c15102
parent f352f75f6bd5734c8f671323dd6ab32472d5da34
author Hanno Becker <hanno.becker@arm.com> 1548925064 +0000
committer Hanno Becker <hanno.becker@arm.com> 1549635898 +0000

Add a new X.509 API call for copy-less parsing of CRTs

Context:
The existing API `mbedtls_x509_parse_crt_der()` for parsing DER
encoded X.509 CRTs unconditionally makes creates a copy of the
input buffer in RAM. While this comes at the benefit of easy use,
-- specifically: allowing the user to free or re-use the input
buffer right after the call -- it creates a significant memory
overhead, as the CRT is duplicated in memory (at least temporarily).
This might not be tolerable a resource constrained device.

As a remedy, this commit adds a new X.509 API call

   `mbedtls_x509_parse_crt_der_nocopy()`

which has the same signature as `mbedtls_x509_parse_crt_der()`
and almost the same semantics, with one difference: The input
buffer must persist and be unmodified for the lifetime of the
established instance of `mbedtls_x509_crt`, that is, until
`mbedtls_x509_crt_free()` is called.