Memory leak in PKCS12_newpass - ios

Question

I wrote function which changes PKCS12 certificate passphrase.
I noticed that PKCS12_newpass function leaks memory. When commenting out this line then memory leak is not generated.
How I could fix this memory leak?
- (NSData*)changePKCS12:(NSData*)p12Data
oldPassphrase:(NSString*)oldPassphrase
newPassphrase:(NSString*)newPassphrase {
OpenSSL_add_all_algorithms();
BIO *bp = NULL;
PKCS12 *p12 = NULL;
int status = 0;
do {
bp = BIO_new_mem_buf((void *)[p12Data bytes], (int)[p12Data length]);
p12 = d2i_PKCS12_bio(bp, NULL);
// MEMORY LEAK in PKCS12_newpass
status = PKCS12_newpass(p12, (char *)[oldPassphrase UTF8String], (char *)[newPassphrase UTF8String]);
} while (false);
if (p12) {
PKCS12_free(p12);
p12 = NULL;
}
if (bp) {
BIO_free_all(bp);
bp = NULL;
}
EVP_cleanup();
return NULL;
}

Answer 1

Here are the two leaks reported by Valgrind:
$ valgrind --leak-check=full ./test.exe
==32547== Memcheck, a memory error detector
==32547== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==32547== Using Valgrind-3.10.1 and LibVEX; rerun with -h for copyright info
==32547== Command: ./test.exe
==32547==
==32547==
==32547== HEAP SUMMARY:
==32547== in use at exit: 4,044 bytes in 25 blocks
==32547== total heap usage: 3,273 allocs, 3,248 frees, 149,992 bytes allocated
==32547==
==32547== 1,307 (32 direct, 1,275 indirect) bytes in 1 blocks are definitely lost in loss record 22 of 24
==32547== at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==32547== by 0x408A76: CRYPTO_malloc (mem.c:140)
==32547== by 0x408AA9: CRYPTO_zalloc (mem.c:148)
==32547== by 0x447104: asn1_item_embed_new (tasn_new.c:171)
==32547== by 0x446E66: ASN1_item_ex_new (tasn_new.c:88)
==32547== by 0x4439AA: asn1_item_embed_d2i (tasn_dec.c:333)
==32547== by 0x4431B7: ASN1_item_ex_d2i (tasn_dec.c:162)
==32547== by 0x44314A: ASN1_item_d2i (tasn_dec.c:152)
==32547== by 0x4AB8BA: PKCS12_item_decrypt_d2i (p12_decr.c:159)
==32547== by 0x40CA79: PKCS8_decrypt (p12_p8d.c:69)
==32547== by 0x40C8DC: newpass_bag (p12_npas.c:206)
==32547== by 0x40C868: newpass_bags (p12_npas.c:188)
==32547==
==32547== 2,625 (32 direct, 2,593 indirect) bytes in 1 blocks are definitely lost in loss record 24 of 24
==32547== at 0x4C2AB80: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==32547== by 0x408A76: CRYPTO_malloc (mem.c:140)
==32547== by 0x408AA9: CRYPTO_zalloc (mem.c:148)
==32547== by 0x41258E: sk_new (stack.c:153)
==32547== by 0x41256A: sk_new_null (stack.c:146)
==32547== by 0x40C27E: sk_PKCS7_new_null (pkcs7.h:199)
==32547== by 0x40C489: newpass_p12 (p12_npas.c:118)
==32547== by 0x40C3CC: PKCS12_newpass (p12_npas.c:96)
==32547== by 0x40315F: main (in /home/openssl/test.exe)
The first one is due to 0x40C8DC: newpass_bag (p12_npas.c:206):
X509_SIG_get0(&shalg, NULL, bag->value.shkeybag);
However, the get0 in X509_SIG_get0 does not bump the reference count, so I think its really the line before it (or a bug in X509_SIG_get0):
if (PKCS12_SAFEBAG_get_nid(bag) != NID_pkcs8ShroudedKeyBag)
PKCS12_SAFEBAG_get_nid is not documented. That means its a private API, so the OpenSSL devs have to fix the leak caused by it. (I think its actually due to PKCS12_item_decrypt_d2i a little deeper into the stack, but its out of reach because of PKCS12_SAFEBAG_get_nid).
The second one is due to 0x40C489: newpass_p12 (p12_npas.c:118):
if ((newsafes = sk_PKCS7_new_null()) == NULL)
return 0;
sk_PKCS7_new_null is not documented. That means its a private API, so the OpenSSL devs have to fix the leak caused by it.
How I could fix this memory leak?
Unfortunately, you cannot because both of the offenders are private APIs. The best you can do it report them at RT, which is the OpenSSL bug tracker.
There was a somewhat unexpected "big deal" about documentation and private APIs and such. See EC_KEY_priv2buf(): check parameter sanity for a discussion and the new rules.
According to a search of the sources, PKCS12_newpass lacks documentation, so its a private API, too (there's no POD file, which is used to build the man page):
$ grep -IR PKCS12_newpass *
CHANGES: *) New function PKCS12_newpass() which changes the password of a
crypto/pkcs12/pk12err.c: {ERR_FUNC(PKCS12_F_PKCS12_NEWPASS), "PKCS12_newpass"},
crypto/pkcs12/p12_npas.c:int PKCS12_newpass(PKCS12 *p12, const char *oldpass, const char *newpass)
crypto.map: PKCS12_newpass;
include/openssl/pkcs12.h:int PKCS12_newpass(PKCS12 *p12, const char *oldpass, const char *newpass);
util/libcrypto.num:PKCS12_newpass 3204 1_1_0 EXIST::FUNCTION:
A bug report was submitted with documentation at Issue 4478: DOCUMENTATION PKCS12_newpass. It should help get beyond the "documentation else its private" rule.
Below is a cat test.cc:
#include "openssl/pkcs12.h"
#include "openssl/bio.h"
#include "openssl/engine.h"
#include "openssl/conf.h"
#include "openssl/err.h"
/* openssl req -x509 -newkey rsa:1024 -keyout key.pem -nodes -out cert.pem -days 365 */
/* openssl pkcs12 -export -out pkcs12.p12 -inkey key.pem -in cert.pem */
/* gcc -ansi -I . -I ./include test.cc ./libcrypto.a -o test.exe */
int main(int argc, char* argv[])
{
OpenSSL_add_all_algorithms();
BIO *bp = NULL;
PKCS12 *p12 = NULL;
int rc = -1;
unsigned long err = 0;
char password[] = "passphrase";
bp = BIO_new_file("pkcs12.p12", "r");
if (bp == NULL) goto cleanup;
p12 = d2i_PKCS12_bio(bp, NULL);
if (p12 == NULL) goto cleanup;
/* Use empty string when no password was applies with 'openssl pkcs12' */
rc = PKCS12_newpass(p12, password, password);
cleanup:
if (rc == 1)
{
fprintf(stdout, "Sucessfully changed password\n");
}
else
{
err = ERR_get_error();
fprintf(stderr, "Failed to change password, error %lu\n", err);
}
if (p12)
PKCS12_free(p12);
if (bp)
BIO_free_all(bp);
/* http://wiki.openssl.org/index.php/Library_Initialization#Cleanup */
ENGINE_cleanup();
CONF_modules_unload(1);
EVP_cleanup();
CRYPTO_cleanup_all_ex_data();
#if OPENSSL_API_COMPAT < 0x10000000L
ERR_remove_state(0);
#else
ERR_remove_thread_state();
#endif
ERR_free_strings();
return 0;
}