Using the return value of i2d_* directly as input of chunk_alloc imposes
the risk of creating an invalid chunk when the return value of the i2d_*
function is -1. The openssl_i2chunk macro is meant to avoid this.
Signed-off-by: Thomas Egerer <[email protected]>
OpenSSL stores the serial number for an X509 certificate as an
`ASN1_INTEGER` type. Within BoringSSL (and AWS-LC), the library
represents the value of zero as an empty array [1] which is different
from OpenSSL which represents it as the 1-byte array [0x00]. Though the
value of zero for the certificate serial number is illegal under
X.509 [2], we need to handle/encode it consistently within strongSwan.
From 18082ce2b0 ("certificates: Retrieve serial numbers in canonical
form"), we infer that the canonical representation of the zero serial
is [0x00]. To do this, we introduce `openssl_asn1_int2chunk` to
complement the existing string version that allows us to handle the
special case for zero instead of always returning a reference to the
library-dependent encodings.
References strongswan/strongswan#1907Closesstrongswan/strongswan#2138
[1] https://github.com/google/boringssl/commit/bdc35b63617f78037768f4897d8835696f02181a
[2] https://datatracker.ietf.org/doc/html/rfc5280#section-4.1.2.2
The pattern currently is to call get_cache(), generate the encoding
if that failed and then store it with cache(). The latter adopts the
passed encoding and frees any stored encoding. However, the latter means
that if two threads concurrently fail to get a cached encoding and then
both generate and store one, one of the threads might use an encoding
that was freed by the other thread.
Since encodings are not expected to change, we can avoid this issue by
not replacing an existing cache entry and instead return that (while
freeing the passed value instead of the cached one).
Closesstrongswan/strongswan#1231
If OpenSSL is compiled with OPENSSL_NO_DEPRECATED some of the headers
we include don't include openssl/bn.h anymore. Therefore, we have to
explicitly include it ourselves where we use BN_* functions.
Fixes#1113.
Tobias Brunner