Fix potential memory leak in pgcrypto

When allocating a EVP context, it would have been possible to leak some
memory allocated directly by OpenSSL, that PostgreSQL lost track of if
the initialization of the context allocated failed.  The cleanup can be
done with EVP_MD_CTX_destroy().

Note that EVP APIs exist since OpenSSL 0.9.7 and we have in the tree
equivalent implementations for older versions since ce9b75d (code
removed with 9b7cd59a as of 10~).  However, in 9.5 and 9.6, the existing
code makes use of EVP_MD_CTX_destroy() and EVP_MD_CTX_create() without
an equivalent implementation when building the tree with OpenSSL 0.9.6
or older, meaning that this code is in reality broken with such versions
since it got introduced in e2838c5.  As we have heard no complains about
that, it does not seem worth bothering with in 9.5 and 9.6, so I have
left that out for simplicity.

Author: Michael Paquier
Discussion: https://postgr.es/m/20201015072212.GC2305@paquier.xyz
Backpatch-through: 9.5

diff --git a/contrib/pgcrypto/openssl.c b/contrib/pgcrypto/openssl.c
index 90951a8ae7b0e918894a3c25e9dec0b932a0f39c..ed96e4ce5359b80b3c6f20d9c5d61409b81892fd 100644 (file)
--- a/contrib/pgcrypto/openssl.c
+++ b/contrib/pgcrypto/openssl.c
@@ -202,6 +202,7 @@ px_find_digest(const char *name, PX_MD **res)
    }
    if (EVP_DigestInit_ex(ctx, md, NULL) == 0)
    {
+       EVP_MD_CTX_destroy(ctx);
        pfree(digest);
        return -1;
    }