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Improve canonicalization of serialized amounts:

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The existing code that deserialized an STAmount was sub-optimal and performed
poorly. In some rare cases the operation could result in otherwise valid
serialized amounts overflowing during deserialization. This commit will help
detect error conditions more quickly and eliminate the problematic corner cases.
This commit is contained in:
seelabs
2020-12-01 13:58:36 -05:00
committed by manojsdoshi
parent fe129e8e4f
commit c47b4f3667
7 changed files with 63 additions and 3 deletions
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22
src/ripple/protocol/impl/STAmount.cpp
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@@ -34,6 +34,8 @@
namespace ripple {
LocalValue<bool> stAmountCanonicalizeSwitchover(true);
static const std::uint64_t tenTo14 = 100000000000000ull;
static const std::uint64_t tenTo14m1 = tenTo14 - 1;
static const std::uint64_t tenTo17 = tenTo14 * 1000;
@@ -662,13 +664,23 @@ STAmount::canonicalize()
// native currency amounts should always have an offset of zero
mIsNative = true;
if (mValue == 0)
// log(2^64,10) ~ 19.2
if (mValue == 0 || mOffset <= -20)
{
mValue = 0;
mOffset = 0;
mIsNegative = false;
return;
}
if (*stAmountCanonicalizeSwitchover)
{
// log(cMaxNativeN, 10) == 17
if (mOffset > 17)
Throw<std::runtime_error>(
"Native currency amount out of range");
}
while (mOffset < 0)
{
mValue /= 10;
@@ -677,6 +689,14 @@ STAmount::canonicalize()
while (mOffset > 0)
{
if (*stAmountCanonicalizeSwitchover)
{
// N.B. do not move the overflow check to after the
// multiplication
if (mValue > cMaxNativeN)
Throw<std::runtime_error>(
"Native currency amount out of range");
}
mValue *= 10;
--mOffset;
}