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KBKDF

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This commit is contained in:
Adam Ierymenko 2019-09-05 11:39:16 -07:00
parent 70648d006d
commit 44dd52d08f
No known key found for this signature in database
GPG Key ID: C8877CF2D7A5D7F3
3 changed files with 47 additions and 13 deletions
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22
node/AES.hpp
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@ -260,19 +260,15 @@ public:
*/
static ZT_ALWAYS_INLINE void initGmacCtrKeys(const uint8_t masterKey[32],AES &k1,AES &k2,AES &k3,AES &k4)
{
uint8_t kbuf[48];
uint8_t kbkdfMsg[16];
kbkdfMsg[0] = 0; // key iterator, incremented for each key
for(unsigned int i=0;i<12;++i)
kbkdfMsg[i+1] = (uint8_t)("AES-GMAC-CTR"[i]); // KBKDF "label" indicating the use for these keys
kbkdfMsg[13] = 0; // 0x00
kbkdfMsg[14] = 0; // KBKDF "context", just 0 as it's not used in this protocol
kbkdfMsg[15] = 32; // bits used in resulting key
while (kbkdfMsg[0] < 4) {
HMACSHA384(masterKey,&kbkdfMsg,sizeof(kbkdfMsg),kbuf);
k1.init(kbuf);
++kbkdfMsg[0];
}
uint8_t k[32];
KBKDFHMACSHA384(masterKey,ZT_PROTO_KBKDF_LABEL_KEY_USE_AES_GMAC_SIV_K1,0,0,k);
k1.init(k);
KBKDFHMACSHA384(masterKey,ZT_PROTO_KBKDF_LABEL_KEY_USE_AES_GMAC_SIV_K2,0,0,k);
k2.init(k);
KBKDFHMACSHA384(masterKey,ZT_PROTO_KBKDF_LABEL_KEY_USE_AES_GMAC_SIV_K3,0,0,k);
k3.init(k);
KBKDFHMACSHA384(masterKey,ZT_PROTO_KBKDF_LABEL_KEY_USE_AES_GMAC_SIV_K4,0,0,k);
k4.init(k);
}
private:

21
node/SHA512.cpp
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@ -274,4 +274,25 @@ void HMACSHA384(const uint8_t key[32],const void *msg,const unsigned int msglen,
SHA384(mac,outer,176); // H(output padded key | H(input padded key | msg))
}
void KBKDFHMACSHA384(const uint8_t key[32],const char label,const char context,const uint32_t iter,uint8_t out[32])
{
uint8_t kbkdfMsg[13];
uint8_t kbuf[48];
kbkdfMsg[0] = (uint8_t)(iter >> 24);
kbkdfMsg[1] = (uint8_t)(iter >> 16);
kbkdfMsg[2] = (uint8_t)(iter >> 8);
kbkdfMsg[3] = (uint8_t)iter;
kbkdfMsg[4] = (uint8_t)'Z';
kbkdfMsg[5] = (uint8_t)'T'; // preface our labels with something ZT-specific
kbkdfMsg[6] = (uint8_t)label;
kbkdfMsg[7] = 0;
kbkdfMsg[8] = (uint8_t)context;
kbkdfMsg[9] = 0;
kbkdfMsg[10] = 0;
kbkdfMsg[11] = 1;
kbkdfMsg[12] = 0; // key length: 256 bits as big-endian 32-bit value
HMACSHA384(key,&kbkdfMsg,sizeof(kbkdfMsg),kbuf);
memcpy(out,kbuf,32);
}
} // namespace ZeroTier

17
node/SHA512.hpp
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@ -32,6 +32,12 @@
#define ZT_HMACSHA384_LEN 48
#define ZT_PROTO_KBKDF_LABEL_KEY_USE_HMAC 'H'
#define ZT_PROTO_KBKDF_LABEL_KEY_USE_AES_GMAC_SIV_K1 '1'
#define ZT_PROTO_KBKDF_LABEL_KEY_USE_AES_GMAC_SIV_K2 '2'
#define ZT_PROTO_KBKDF_LABEL_KEY_USE_AES_GMAC_SIV_K3 '3'
#define ZT_PROTO_KBKDF_LABEL_KEY_USE_AES_GMAC_SIV_K4 '4'
namespace ZeroTier {
#ifdef __APPLE__
@ -102,6 +108,17 @@ void SHA384(void *digest,const void *data0,unsigned int len0,const void *data1,u
*/
void HMACSHA384(const uint8_t key[32],const void *msg,const unsigned int msglen,uint8_t mac[48]);
/**
* Compute KBKDF (key-based key derivation function) using HMAC-SHA-384 as a PRF
*
* @param key Source master key
* @param label A label indicating the key's purpose in the ZeroTier system
* @param context An arbitrary "context" or zero if not applicable
* @param iter Key iteration for generation of multiple keys for the same label/context
* @param out Output to receive derived key
*/
void KBKDFHMACSHA384(const uint8_t key[32],const char label,const char context,const uint32_t iter,uint8_t out[32]);
} // namespace ZeroTier
#endif