ScalES-PPM

src/crypto/ppm_checksum_c.c was designed around the pre-1.1.0 OpenSSL API and uses a stack-allocated digest context, EVP_MD_CTX. In the post-1.1.0 OpenSSL API (in particular, after commit 7638370ca6cb1d89eba5d891f522776b9da3d6e7), the EVP_MD_CTX type was made opaque and must be dynamically allocated using the new EVP_MD_CTX_{new,free} functions (renamed from EVP_MD_CTX_{create,destroy} in commit 959ed5316c84d0e12ad18acfd40cefe15603ddfb).

The attached patch uses the old method for OPENSSL_VERSION_NUMBER < 0x1010000fL and uses the new methods otherwise. It also uses the recommended EVP_Digest{Init,Final}_ex functions rather than the EVP_Digest{Init,Final} counterparts which perform additional initialization and cleanup on mdctx and are unnecessary since we are explicitly initializing and freeing the digest contexts within the scope of the PPM_checksum function--see OpenSSL doc/man3/EVP_DigestInit.pod for details. Finally, the patch also does explicit checking for the success or failure of the EVP_Digest functions and aborts if there is a failure.