Cryptography and SSL/TLS Toolkit



BUF_MEM_new, BUF_MEM_new_ex, BUF_MEM_free, BUF_MEM_grow - simple character array structure

BUF_strdup, BUF_strndup, BUF_memdup, BUF_strlcpy, BUF_strlcat - standard C library equivalents


 #include <openssl/buffer.h>

 BUF_MEM *BUF_MEM_new(void);


 BUF_MEM *BUF_MEM_new_ex(unsigned long flags);

 void   BUF_MEM_free(BUF_MEM *a);

 int    BUF_MEM_grow(BUF_MEM *str, int len);

 char *BUF_strdup(const char *str);

 char *BUF_strndup(const char *str, size_t siz);

 void *BUF_memdup(const void *data, size_t siz);

 size_t BUF_strlcpy(char *dst, const char *src, size_t size);

 size_t BUF_strlcat(char *dst, const char *src, size_t size);

 size_t BUF_strnlen(const char *str, size_t maxlen);


The buffer library handles simple character arrays. Buffers are used for various purposes in the library, most notably memory BIOs.

BUF_MEM_new() allocates a new buffer of zero size.

BUF_MEM_new_ex() allocates a buffer with the specified flags. The flag BUF_MEM_FLAG_SECURE specifies that the data pointer should be allocated on the secure heap; see CRYPTO_secure_malloc.

BUF_MEM_free() frees up an already existing buffer. The data is zeroed before freeing up in case the buffer contains sensitive data.

BUF_MEM_grow() changes the size of an already existing buffer to len. Any data already in the buffer is preserved if it increases in size.

BUF_strdup(), BUF_strndup(), BUF_memdup(), BUF_strlcpy(), BUF_strlcat() and BUF_strnlen are equivalents of the standard C library functions. The dup() functions use OPENSSL_malloc() underneath and so should be used in preference to the standard library for memory leak checking or replacing the malloc() function.

Memory allocated from these functions should be freed up using the OPENSSL_free() function.

BUF_strndup makes the explicit guarantee that it will never read past the first siz bytes of str.


BUF_MEM_new() returns the buffer or NULL on error.

BUF_MEM_free() has no return value.

BUF_MEM_grow() returns zero on error or the new size (i.e. len).


bio, CRYPTO_secure_malloc.


BUF_MEM_new(), BUF_MEM_free() and BUF_MEM_grow() are available in all versions of SSLeay and OpenSSL. BUF_strdup() was added in SSLeay 0.8.

BUF_MEM_new_ex() was contributed to OpenSSL by Akamai Technologies in May, 2014.