RE: ENGINE reference leak using EVP_Digest*

BTW, this is with OpenSSL 1.0.1; I did not try an older version.

I have some code that uses the following sequence of calls (e.g.):

EVP_MD_CTX ctx;

EVP_MD_CTX_init(&ctx);

EVP_DigestInit_ex(&ctx, EVP_sha1(), NULL);

EVP_DigestUpdate(&ctx, pData, nSize);

EVP_DigestFinal_ex(&ctx, pOut, NULL);

EVP_DigestInit_ex(&ctx, EVP_sha1(), NULL);

EVP_DigestUpdate(&ctx, pData, nSize);

EVP_DigestFinal_ex(&ctx, pOut, NULL);

EVP_DigestInit_ex(&ctx, EVP_sha1(), NULL);

EVP_DigestUpdate(&ctx, pData, nSize);

EVP_DigestFinal_ex(&ctx, pOut, NULL);

EVP_MD_CTX_cleanup(&ctx);

The docs say that “After calling EVP_DigestFinal_ex() no additional calls to EVP_DigestUpdate() can be made, but EVP_DigestInit_ex() can be called to initialize a new digest operation.”

In my case, there is an ENGINE registered to perform the SHA1 operations.

What happens, though is that EVP_DigestInit_ex() increments the ENGINE reference, but EVP_DigestFinal_ex() does not decrement it.  Only the EVP_MD_CTX_cleanup() call is decrementing the reference count, and thus my ENGINE never ends up being actually freed on the ENGINE_finish() call.

Is this a known issue?  Do I really need to cleanup/reinit my CTX around each hash sequence?

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Erik Tkal

Juniper OAC/UAC/Pulse Development