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fix an undefined behavior in uint::SetHex 

Decrementing psz beyond the beginning of the string is UB, even though
the out-of-bounds pointer is never dereferenced.
This commit is contained in:
Kaz Wesley 2018-11-15 17:21:28 -08:00
parent e74649e951
commit 0f459d868d
1 changed files with 7 additions and 8 deletions
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15
src/uint256.cpp
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@ -37,16 +37,15 @@ void base_blob<BITS>::SetHex(const char* psz)
psz += 2;
// hex string to uint
const char* pbegin = psz;
while (::HexDigit(*psz) != -1)
psz++;
psz--;
size_t digits = 0;
while (::HexDigit(psz[digits]) != -1)
digits++;
unsigned char* p1 = (unsigned char*)data;
unsigned char* pend = p1 + WIDTH;
while (psz >= pbegin && p1 < pend) {
*p1 = ::HexDigit(*psz--);
if (psz >= pbegin) {
*p1 |= ((unsigned char)::HexDigit(*psz--) << 4);
while (digits > 0 && p1 < pend) {
*p1 = ::HexDigit(psz[--digits]);
if (digits > 0) {
*p1 |= ((unsigned char)::HexDigit(psz[--digits]) << 4);
p1++;
}
}