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Man Pages

Manual Reference Pages  -  OPENSSL_SECURE_ACTUAL_SIZE (3)

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CRYPTO_secure_malloc_init, CRYPTO_secure_malloc_initialized, CRYPTO_secure_malloc_done, OPENSSL_secure_malloc, CRYPTO_secure_malloc, OPENSSL_secure_zalloc, CRYPTO_secure_zalloc, OPENSSL_secure_free, CRYPTO_secure_free, OPENSSL_secure_actual_size, OPENSSL_secure_allocated, CYRPTO_secure_malloc_used - secure heap storage



 #include <openssl/crypto.h>

 int CRYPTO_secure_malloc_init(size_t size, int minsize);

 int CRYPTO_secure_malloc_initialized();

 void CRYPTO_secure_malloc_done();

 void *OPENSSL_secure_malloc(int num);
 void *CRYPTO_secure_malloc(int num, const char *file, int line);

 void *OPENSSL_secure_zalloc(int num);
 void *CRYPTO_secure_zalloc(int num, const char *file, int line);

 void OPENSSL_secure_free(void* ptr);
 void CRYPTO_secure_free(void *ptr);

 size_t OPENSSL_secure_actual_size(const void *ptr);
 int OPENSSL_secure_allocated(const void *ptr);

 size_t CYRPTO_secure_malloc_used();


In order to help protect applications (particularly long-running servers) from pointer overruns or underruns that could return arbitrary data from the program’s dynamic memory area, where keys and other sensitive information might be stored, OpenSSL supports the concept of a secure heap. The level and type of security guarantees depend on the operating system. It is a good idea to review the code and see if it addresses your threat model and concerns.

If a secure heap is used, then private key BIGNUM values are stored there. This protects long-term storage of private keys, but will not necessarily put all intermediate values and computations there.

CRYPTO_secure_malloc_init() creates the secure heap, with the specified size in bytes. The minsize parameter is the minimum size to allocate from the heap. Both size and minsize must be a power of two. It is an error to call this after any OPENSSL_secure_malloc() calls have been made.

CRYPTO_secure_malloc_initialized() indicates whether or not the secure heap as been initialized and is available.

CRYPTO_secure_malloc_done() releases the heap and makes the memory unavailable to the process. It can take noticeably long to complete.

OPENSSL_secure_malloc() allocates num bytes from the heap. If CRYPTO_secure_malloc_init() is not called, this is equivalent to calling OPENSSL_malloc(). It is a macro that expands to CRYPTO_secure_malloc() and adds the __FILE__ and __LINE__ parameters.

OPENSSL_secure_zalloc() and CRYPTO_secure_zalloc() are like OPENSSL_secure_malloc() and CRYPTO_secure_malloc(), respectively, except that they call memset() to zero the memory before returning.

OPENSSL_secure_free() releases the memory at ptr back to the heap. It must be called with a value previously obtained from OPENSSL_secure_malloc(). If CRYPTO_secure_malloc_init() is not called, this is equivalent to calling OPENSSL_free(). It exists for consistency with OPENSSL_secure_malloc() , and is a macro that expands to CRYPTO_secure_free().

OPENSSL_secure_allocated() tells whether or not a pointer is within the secure heap. OPENSSL_secure_actual_size() tells the actual size allocated to the pointer; implementations may allocate more space than initially requested, in order to round up and reduce secure heap fragmentation.

CRYPTO_secure_malloc_used() returns the number of bytes allocated in the secure heap.


CRYPTO_secure_malloc_init() returns 0 on failure, 1 if successful, and 2 if successful but the heap could not be protected by memory mapping.

CRYPTO_secure_malloc_initialized() returns 1 if the secure heap is available (that is, if CRYPTO_secure_malloc_init() has been called, but CRYPTO_secure_malloc_done() has not) or 0 if not.

OPENSSL_secure_malloc() and OPENSSL_secure_zalloc() return a pointer into the secure heap of the requested size, or NULL if memory could not be allocated.

CRYPTO_secure_allocated() returns 1 if the pointer is in the the secure heap, or 0 if not.

CRYPTO_secure_malloc_done() and OPENSSL_secure_free() return no values.


The size parameters should be size_t not int and will be changed in a future release.


OPENSSL_malloc(3), BN_new(3), bn_internal(3).
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1.1.0-pre3 OPENSSL_SECURE_MALLOC (3) 2016-02-15

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