Constant time comparison for mac
This commit is contained in:
parent
2f2e0340ae
commit
8123ce6209
3 changed files with 27 additions and 6 deletions
|
@ -1,17 +1,24 @@
|
|||
#include <cstddef>
|
||||
#include <cstdint>
|
||||
|
||||
namespace axolotl {
|
||||
|
||||
/** Clear the memory held in the buffer */
|
||||
void unset(
|
||||
volatile void * buffer, std::size_t buffer_length
|
||||
void volatile * buffer, std::size_t buffer_length
|
||||
);
|
||||
|
||||
/** Clear the memory backing an object */
|
||||
template<typename T>
|
||||
void unset(T & value) {
|
||||
unset(reinterpret_cast<volatile void *>(&value), sizeof(T));
|
||||
unset(reinterpret_cast<void volatile *>(&value), sizeof(T));
|
||||
}
|
||||
|
||||
/** Check if two buffers are equal in constant time. */
|
||||
bool is_equal(
|
||||
std::uint8_t const * buffer_a,
|
||||
std::uint8_t const * buffer_b,
|
||||
std::size_t length
|
||||
);
|
||||
|
||||
} // namespace axolotl
|
||||
|
|
|
@ -1,11 +1,25 @@
|
|||
#include "axolotl/memory.hh"
|
||||
|
||||
|
||||
void axolotl::unset(
|
||||
volatile void * buffer, std::size_t buffer_length
|
||||
void volatile * buffer, std::size_t buffer_length
|
||||
) {
|
||||
volatile char * pos = reinterpret_cast<volatile char *>(buffer);
|
||||
volatile char * end = pos + buffer_length;
|
||||
char volatile * pos = reinterpret_cast<char volatile *>(buffer);
|
||||
char volatile * end = pos + buffer_length;
|
||||
while (pos != end) {
|
||||
*(pos++) = 0;
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
bool axolotl::is_equal(
|
||||
std::uint8_t const * buffer_a,
|
||||
std::uint8_t const * buffer_b,
|
||||
std::size_t length
|
||||
) {
|
||||
std::uint8_t volatile result = 0;
|
||||
while (length--) {
|
||||
result |= (*(buffer_a++)) ^ (*(buffer_b++));
|
||||
}
|
||||
return result == 0;
|
||||
}
|
||||
|
|
|
@ -104,7 +104,7 @@ bool verify_mac(
|
|||
mac
|
||||
);
|
||||
|
||||
bool result = std::memcmp(mac, reader.mac, MAC_LENGTH) == 0;
|
||||
bool result = axolotl::is_equal(mac, reader.mac, MAC_LENGTH);
|
||||
axolotl::unset(mac);
|
||||
return result;
|
||||
}
|
||||
|
|
Loading…
Reference in a new issue