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 <cstddef>
|
||||||
|
#include <cstdint>
|
||||||
|
|
||||||
namespace axolotl {
|
namespace axolotl {
|
||||||
|
|
||||||
/** Clear the memory held in the buffer */
|
/** Clear the memory held in the buffer */
|
||||||
void unset(
|
void unset(
|
||||||
volatile void * buffer, std::size_t buffer_length
|
void volatile * buffer, std::size_t buffer_length
|
||||||
);
|
);
|
||||||
|
|
||||||
/** Clear the memory backing an object */
|
/** Clear the memory backing an object */
|
||||||
template<typename T>
|
template<typename T>
|
||||||
void unset(T & value) {
|
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
|
} // namespace axolotl
|
||||||
|
|
|
@ -1,11 +1,25 @@
|
||||||
#include "axolotl/memory.hh"
|
#include "axolotl/memory.hh"
|
||||||
|
|
||||||
|
|
||||||
void axolotl::unset(
|
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);
|
char volatile * pos = reinterpret_cast<char volatile *>(buffer);
|
||||||
volatile char * end = pos + buffer_length;
|
char volatile * end = pos + buffer_length;
|
||||||
while (pos != end) {
|
while (pos != end) {
|
||||||
*(pos++) = 0;
|
*(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
|
mac
|
||||||
);
|
);
|
||||||
|
|
||||||
bool result = std::memcmp(mac, reader.mac, MAC_LENGTH) == 0;
|
bool result = axolotl::is_equal(mac, reader.mac, MAC_LENGTH);
|
||||||
axolotl::unset(mac);
|
axolotl::unset(mac);
|
||||||
return result;
|
return result;
|
||||||
}
|
}
|
||||||
|
|
Loading…
Reference in a new issue