%% options copyright owner = Dirk Krause copyright year = 2015-xxxx license = bsd %% header /** @file Secure memory reset (reset byte buffer to 0x00 bytes and read the buffer to prevent compilers from optimizing the resetting out). */ #ifdef __cplusplus extern "C" { #endif /** Secure memory reset. This function does not just reset the bytes to 0, it also reads each byte to check it. Reading each byte should prevent the compiler from optimizing out. This function has significantly lower performance than dk4mem_reset(), so use it to clear sensitive memory (i.e. used for passwords, keys...) only. CRT on Windows: Not used. @param ptr Start address of memory range. @param sz Size of memory range in bytes. @param erp Error report, may be NULL. @return 1 on success, 0 on error. Error codes: - DK4_E_INVALID_ARGUMENTS
if ptr is NULL or sz is 0, - DK4_E_BUG
if one of the bytes in the buffer is not 0 during check. */ int dk4mem_reset_secure(void *ptr, size_t sz, dk4_er_t *erp); /** Secure memory release. This function does not just reset the bytes to 0 before releasing memory, it also reads each byte to check it. Reading each byte should prevent the compiler from optimizing out. This function has significantly lower performance than dk4mem_free(), so use it to clear sensitive memory (i.e. used for passwords, keys...) only. CRT on Windows: Not used. @param ptr Start address of memory range. @param sz Size of memory range in bytes. @param erp Error report, may be NULL. @return 1 on success, 0 on error. Error codes: - DK4_E_INVALID_ARGUMENTS
if ptr is NULL or sz is 0, - DK4_E_BUG
if one of the bytes in the buffer is not 0 during check. */ int dk4mem_free_secure(void *ptr, size_t sz, dk4_er_t *erp); #ifdef __cplusplus } #endif /** Release memory securely (sanitize memory before releasing it). */ #define dk4mem_release_secure(ptr,sz,erp) \ do { if (NULL != ptr) { (void)dk4mem_free_secure(ptr,sz,erp); } ptr = NULL; } while (0) %% module #include "dk4conf.h" #ifndef STDIO_H_INCLUDED #include #define STDIO_H_INCLUDED 1 #endif #ifndef STDLIB_H_INCLUDED #include #define STDLIB_H_INCLUDED 1 #endif #if DK4_ON_WINDOWS #ifndef WINDOWS_H_INCLUDED #include #define WINDOWS_H_INCLUDED 1 #endif #endif #include "dk4mem.h" int dk4mem_reset_secure(void *ptr, size_t sz, dk4_er_t *erp) { #if !DK4_ON_WINDOWS unsigned char *p1; #endif int back = 0; if ((NULL != ptr) && (0 < sz)) { #if DK4_ON_WINDOWS SecureZeroMemory(ptr, sz); back = 1; #else DK4_MEMRES(ptr, sz); p1 = (unsigned char *)ptr; back = 1; while(sz--) { if ('\0' != *(p1++)) { back = 0; dk4error_set_simple_error_code(erp, DK4_E_BUG); } } #endif } else { dk4error_set_simple_error_code(erp, DK4_E_INVALID_ARGUMENTS); } return back; } int dk4mem_free_secure(void *ptr, size_t sz, dk4_er_t *erp) { int back = 0; if (NULL != ptr) { if (0 < sz) { back = dk4mem_reset_secure(ptr, sz, erp); } else { back = 1; } dk4mem_free(ptr); } else { dk4error_set_simple_error_code(erp, DK4_E_INVALID_ARGUMENTS); } return back; }