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Add a last-ditch memwipe() implementation for nss+old glibc

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On new glibc versions, there's an explicit_bzero().  With openssl,
there's openssl_memwipe().

When no other approach works, use memwipe() and a memory barrier.
This commit is contained in:
Nick Mathewson 2018-09-05 16:34:01 -04:00
parent 06c14f9209
commit 8cd091a8d3
1 changed files with 5 additions and 1 deletions
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6
src/lib/crypt_ops/crypto_util.c
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@ -80,7 +80,7 @@ memwipe(void *mem, uint8_t byte, size_t sz)
#elif defined(HAVE_MEMSET_S) #elif defined(HAVE_MEMSET_S)
/* This is in the C99 standard. */ /* This is in the C99 standard. */
memset_s(mem, sz, 0, sz); memset_s(mem, sz, 0, sz);
#else #elif defined(ENABLE_OPENSSL)
/* This is a slow and ugly function from OpenSSL that fills 'mem' with junk /* This is a slow and ugly function from OpenSSL that fills 'mem' with junk
* based on the pointer value, then uses that junk to update a global * based on the pointer value, then uses that junk to update a global
* variable. It's an elaborate ruse to trick the compiler into not * variable. It's an elaborate ruse to trick the compiler into not
@ -93,6 +93,9 @@ memwipe(void *mem, uint8_t byte, size_t sz)
**/ **/
OPENSSL_cleanse(mem, sz); OPENSSL_cleanse(mem, sz);
#else
memset(mem, 0, sz);
asm volatile ("" ::: "memory");
#endif /* defined(SecureZeroMemory) || defined(HAVE_SECUREZEROMEMORY) || ... */ #endif /* defined(SecureZeroMemory) || defined(HAVE_SECUREZEROMEMORY) || ... */
/* Just in case some caller of memwipe() is relying on getting a buffer /* Just in case some caller of memwipe() is relying on getting a buffer
@ -105,4 +108,5 @@ memwipe(void *mem, uint8_t byte, size_t sz)
* if somebody accidentally calls memwipe() instead of memset(). * if somebody accidentally calls memwipe() instead of memset().
**/ **/
memset(mem, byte, sz); memset(mem, byte, sz);
} }