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libcli/smb/smb2_signing: add smb2_key_deviration()

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This implements a simplified version of "NIST Special Publication 800-108" section 5.1
using hmac-sha256.

Thanks to Jeremy, Michael and Volker for the debugging!

metze
This commit is contained in:
Stefan Metzmacher 2012-02-22 13:13:47 +01:00
parent 7102eafc26
commit 7f5e56971f
2 changed files with 37 additions and 0 deletions
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32
libcli/smb/smb2_signing.c
View File

@ -135,3 +135,35 @@ NTSTATUS smb2_signing_check_pdu(DATA_BLOB signing_key,
return NT_STATUS_OK;
}
void smb2_key_deviration(const uint8_t *KI, size_t KI_len,
const uint8_t *Label, size_t Label_len,
const uint8_t *Context, size_t Context_len,
uint8_t KO[16])
{
struct HMACSHA256Context ctx;
uint8_t buf[4];
static const uint8_t zero = 0;
uint8_t digest[SHA256_DIGEST_LENGTH];
uint32_t i = 1;
uint32_t L = 128;
/*
* a simplified version of
* "NIST Special Publication 800-108" section 5.1
* using hmac-sha256.
*/
hmac_sha256_init(KI, KI_len, &ctx);
RSIVAL(buf, 0, i);
hmac_sha256_update(buf, sizeof(buf), &ctx);
hmac_sha256_update(Label, Label_len, &ctx);
hmac_sha256_update(&zero, 1, &ctx);
hmac_sha256_update(Context, Context_len, &ctx);
RSIVAL(buf, 0, L);
hmac_sha256_update(buf, sizeof(buf), &ctx);
hmac_sha256_final(digest, &ctx);
memcpy(KO, digest, 16);
}

5
libcli/smb/smb2_signing.h
View File

@ -33,4 +33,9 @@ NTSTATUS smb2_signing_check_pdu(DATA_BLOB signing_key,
const struct iovec *vector,
int count);
void smb2_key_deviration(const uint8_t *KI, size_t KI_len,
const uint8_t *Label, size_t Label_len,
const uint8_t *Context, size_t Context_len,
uint8_t KO[16]);
#endif /* _LIBCLI_SMB_SMB2_SIGNING_H_ */