On May 25, 2014, at 10:15 AM, Han Sooloo <hansoo...@gmail.com> wrote:
> Trying to understand how the crl2p7.c application allocates PKCS7 pointers. > I see the PKCS7_new() function and it makes sense. > > However, I cannot find the definition of PKCS7_free(). The only place it > shows up is in libeay.num as "PKCS7_free 444 > EXIST::FUNCTION:” > > 2 questions: > 1. What does the above declaration in libeay.num mean? > 2. What is the definition of PKCS7_free()? How does it free memory pointed > to by a PKCS7 data structure? Most of the structures that are defined as ASN.1 structures (including PKCS7) have methods like _free implemented through a macro. You can search for the definition of the IMPLEMENT_ASN1_FUNCTIONS macro (in crypto/asn1/asn1t.h) for more info, but IIRC, it uses ASN1_item_free() which ultimately uses OPENSSL_free() for (nearly?) everything inside (some structures (but not, IIRC, PKCS7) will also have OPENSSL_cleanse invoked proper to releasing the memory, and there’s a patch that will apply that more frequently). Some structures use their own customer _new or _free methods, but I didn’t think PKCS7 used a custom _new (and I don’t see one in 1.0.1g). In general, though, if you’re manipulating the members of the structure directly, you should be sure to allocate any buffers with OPENSSL_malloc() before assigning them to members of the structure, as PKCS7_free will assume it can release the buffers with OPENSSL_free(). I always find it simpler to not touch any members directly, but use the methods and macros defined in pkcs7.h. They should duplicate any buffers that PKCS7_free() expects to free on its own, so it’ll be safe to release your buffers without worry. TOM > > ______________________________________________________________________ > OpenSSL Project http://www.openssl.org > User Support Mailing List openssl-users@openssl.org > Automated List Manager majord...@openssl.org > ______________________________________________________________________ OpenSSL Project http://www.openssl.org User Support Mailing List openssl-users@openssl.org Automated List Manager majord...@openssl.org
