free oaep label-octet-string on error

free oaep label-octet-string on error

When X509_ALGOR_set0() fails, ownership of the the ASN1 object "los"
(label octet string) has not been passed on to the X509_ALGOR object
"oaep->pSourceFunc", so we need to free "los" in that case.

Check return value of X509_ALGOR_set0(), change the scope of "los" and
ensure it is freed on failure (on success, set it to NULL so it is not
freed inside the function).

Fixes #22336

Testing:
You can use the following script to test cms encryption with rsa-oaep:

  #!/bin/bash -x

  OSSLCMD="apps/openssl"

  # check we are calling the right openssl app
  LD_LIBRARY_PATH=. valgrind $OSSLCMD version

  echo "this is a confidential message." > msg.txt

  LD_LIBRARY_PATH=. valgrind $OSSLCMD cms -encrypt -in msg.txt \
  	-stream -out msg.txt.cms \
  	-recip test/smime-certs/smrsa1.pem \
          -keyopt rsa_padding_mode:oaep \
          -keyopt rsa_oaep_md:sha256 \
          -keyopt rsa_oaep_label:deadbeef

Reviewed-by: Paul Dale <pauli@openssl.org>
Reviewed-by: Tomas Mraz <tomas@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/22556)

(cherry picked from commit a9a1b3da876456e1eecffbba15fb6d1820e8f379)