Previously, only one thread could access the parsing cache of an X.509 CRT
at a time. Firstly, this leads to significant performance penalties on
systems running many concurrent threads which share CRT structures --
for example, server threads sharing an SSL configuration containing the
server CRT. Secondly, the locking should be logically unnecessary, because
the threads are supposed to access the CRT frame and PK in a read-only,
or at least thread-safe manner.
This commit modifies the X.509 CRT cache implementation by allowing an
arbitrary number of concurrent readers, locking only the path of setting
up and clearing the cache.
This allows to build the library + tests via `make` without
specifying `PTHREAD=1`, in which case the X.509 threading
test suite will be silently dropped.
This is analogous to the pre-existing handling of the example
application `ssl_pthread_server`, which is only build if `PTHREAD=1`
and silently dropped otherwise.
The pre-existing LINK_WITH_PTHREAD CMake option controls whether
`pthread` should be linked into the library, but didn't apply
to the test suites so far.
This commit also links test suites to `pthread` in CMake-based
builds which have LINK_WITH_PTHREAD set.
This commit enhances the X.509 parsing test suite by a test
which exercises multiple threads concurrently verifying the
same certificate with the same set of trusted roots.
In contrast to mbedtls_x509_crt_frame_acquire(), the public key context
returned by mbedtls_x509_crt_pk_acquire() cannot be marked `const` because
the caller must be able to use it e.g. for mbedtls_pk_sign() and
mbedtls_pk_verify(), which don't have `const` input parameters.
Instead, return a non-`const` context, but explicitly state that callers
must use that context in a thread-safe way.
We cannot move it to x509_crt.c because there are some static inline
function definitions in x509_crt.h which access members of
mbedtls_x509_crt_cache.
This commit modifies the implementation of x509_get_ext_key_usage()
to not rely on mbedtls_asn1_get_sequence_of() but to instead use
mbedtls_asn1_traverse_sequence_of() with the same sequence-building
callback that also x509_get_subject_alt_name() uses, and which agrees
with the callback used by mbedtls_asn1_get_sequence_of().
The reason for this is that with this change, Mbed TLS itself isn't
using mbedtls_asn1_get_sequence_of() anymore, but only the more powerful
mbedtls_asn1_traverse_sequence_of(), so that unless application code
makes use of mbedtls_asn1_get_sequence_of(), its implementation
-- including the underlying sequence building callback -- will be
removed by link time garbage collection.
This commit introduces a compile-time option MBEDTLS_X509_ALWAYS_FLUSH
which controls whether releasing of CRT frames or public key contexts
associated to X.509 CRTs (or, in the future, other cached parsed X.509
structures) should lead to freeing those structures immediately.
Enabling this alongside of the MBEDTLS_X509_ON_DEMAND_PARSING leads
to significant reduction of the average RAM consumption of Mbed TLS.
The option is enabled by default to reduce the permanent RAM overhead of
MBEDTLS_X509_ON_DEMAND_PARSING in case the latter is *disabled* (default).
(Note that there is very little performance penalty enabling
MBEDTLS_X509_ALWAYS_FLUSH in case MBEDTLS_X509_ON_DEMAND_PARSING is disabled,
because hardly any parsing needs to be done to setup a CRT frame / PK context
from the legacy `mbedtls_x509_crt` structure.)
This commit introduces two static helpers
- `x509_buf_to_buf_raw()`
- `x509_buf_raw_to_buf()`
which convert to/from the old `mbedtls_x509_buf` and
the new `mbedtls_x509_buf_raw` (the latter omitting the
ASN.1 tag field).
So far, the CRT frame structure `mbedtls_x509_crt_frame` used
as `issuer_raw` and `subject_raw` the _content_ of the ASN.1
name structure for issuer resp. subject. This was in contrast
to the fields `issuer_raw` and `subject_raw` from the legacy
`mbedtls_x509_crt` structure, and caused some information
duplication by having both variants `xxx_no_hdr` and `xxx_with_hdr`
in `mbedtls_x509_crt` and `mbedtls_x509_crt_frame`.
This commit removes this mismatch by solely using the legacy
form of `issuer_raw` and `subject_raw`, i.e. those _including_
the ASN.1 name header.
Previously, `mbedtls_x509_crt_cache_provide_frame()` provided the requested
CRT frame by always parsing the raw data underlying the CRT. That's inefficient
in legacy mode, where the CRTs fields are permanently accessible through the
legacy `mbedtls_x509_crt` structure.
This commit modifies `mbedtls_x509_crt_cache_provide_frame()` in legacy mode
(that is, !MBEDTLS_X509_ON_DEMAND_PARSING) to setup the CRT frame by copying
fields from the legacy CRT structure.
This commit adds a `make test` and `ssl-opt.sh` run to `all.sh`
exercising the default configuration, plus the following changes:
- MBEDTLS_SSL_KEEP_PEER_CERTIFICATE disabled
- MBEDTLS_X509_ON_DEMAND_PARSING enabled.
This commit modifies the CRT parsing routine to flush
the CRT cache after parsing. More specifically, the
frame cache is flushed before the PK is parsed, to
avoid storing the PK and frame in RAM at the same time.
