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43 lines
1.3 KiB
C
43 lines
1.3 KiB
C
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/*
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* Securely wipe memory.
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*
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* The actual wiping is no different from what memset would do: the
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* point of 'securely' is to try to be sure over-clever compilers
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* won't optimise away memsets on variables that are about to be freed
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* or go out of scope. See
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* https://buildsecurityin.us-cert.gov/bsi-rules/home/g1/771-BSI.html
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*
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* Some platforms (e.g. Windows) may provide their own version of this
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* function.
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*/
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#include "defs.h"
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#include "misc.h"
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void smemclr(void *b, size_t n)
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{
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volatile char *vp;
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if (b && n > 0) {
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/*
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* Zero out the memory.
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*/
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memset(b, 0, n);
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/*
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* Perform a volatile access to the object, forcing the
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* compiler to admit that the previous memset was important.
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*
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* This while loop should in practice run for zero iterations
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* (since we know we just zeroed the object out), but in
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* theory (as far as the compiler knows) it might range over
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* the whole object. (If we had just written, say, '*vp =
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* *vp;', a compiler could in principle have 'helpfully'
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* optimised the memset into only zeroing out the first byte.
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* This should be robust.)
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*/
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vp = b;
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while (*vp) vp++;
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}
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}
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