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fixed: possible timing attack

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This commit is contained in:
Bob 2016-06-05 17:34:02 +02:00
parent af63990bc9
commit 69f438207d
1 changed files with 10 additions and 2 deletions
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12
bitlair_doorduino/bitlair_doorduino.ino
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@ -283,6 +283,9 @@ void ListButtons()
}
}
#define RANDOMDELAY_MIN 50
#define RANDOMDELAY_MAX 200
bool AuthenticateButton(uint8_t* addr, uint8_t* secret)
{
uint8_t mac_from_ibutton[SHA1SIZE];
@ -317,13 +320,18 @@ bool AuthenticateButton(uint8_t* addr, uint8_t* secret)
((uint32_t*)mac_computed)[3] = htonl(ntohl(*(uint32_t *)(sha_computed+12)) - 0x10325476);
((uint32_t*)mac_computed)[4] = htonl(ntohl(*(uint32_t *)(sha_computed+16)) - 0xc3d2e1f0);
//this check should always take the same amount of time, to prevent a timing attack
bool macvalid = true;
for (uint8_t i = 0; i < SHA1SIZE; i++)
{
if (mac_from_ibutton[i] != mac_computed[SHA1SIZE - 1 - i])
return false;
macvalid = false;
}
return true;
//add a random delay
delayMicroseconds(Entropy.random(RANDOMDELAY_MIN, RANDOMDELAY_MAX));
return macvalid;
}
bool ReadCMD(char* cmdbuf, uint8_t* cmdbuffill)