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fix an undefined behavior in uint::SetHex

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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; psz += 2;
// hex string to uint // hex string to uint
const char* pbegin = psz; size_t digits = 0;
while (::HexDigit(*psz) != -1) while (::HexDigit(psz[digits]) != -1)
psz++; digits++;
psz--;
unsigned char* p1 = (unsigned char*)data; unsigned char* p1 = (unsigned char*)data;
unsigned char* pend = p1 + WIDTH; unsigned char* pend = p1 + WIDTH;
while (psz >= pbegin && p1 < pend) { while (digits > 0 && p1 < pend) {
*p1 = ::HexDigit(*psz--); *p1 = ::HexDigit(psz[--digits]);
if (psz >= pbegin) { if (digits > 0) {
*p1 |= ((unsigned char)::HexDigit(*psz--) << 4); *p1 |= ((unsigned char)::HexDigit(psz[--digits]) << 4);
p1++; p1++;
} }
} }