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Misc SCRAM code cleanups.

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* Move computation of SaltedPassword to a separate function from
  scram_ClientOrServerKey(). This saves a lot of cycles in libpq, by
  computing SaltedPassword only once per authentication. (Computing
  SaltedPassword is expensive by design.)

* Split scram_ClientOrServerKey() into two functions. Improves
  readability, by making the calling code less verbose.

* Rename "server proof" to "server signature", to better match the
  nomenclature used in RFC 5802.

* Rename SCRAM_SALT_LEN to SCRAM_DEFAULT_SALT_LEN, to make it more clear
  that the salt can be of any length, and the constant only specifies how
  long a salt we use when we generate a new verifier. Also rename
  SCRAM_ITERATIONS_DEFAULT to SCRAM_DEFAULT_ITERATIONS, for consistency.

These things caught my eye while working on other upcoming changes.
This commit is contained in:
Heikki Linnakangas
2017-04-28 15:04:02 +03:00
parent b9a3ef55b2
commit d981074c24
4 changed files with 89 additions and 71 deletions
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51
src/common/scram-common.c
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@ -98,14 +98,16 @@ scram_HMAC_final(uint8 *result, scram_HMAC_ctx *ctx)
}
/*
* Iterate hash calculation of HMAC entry using given salt.
* scram_Hi() is essentially PBKDF2 (see RFC2898) with HMAC() as the
* pseudorandom function.
* Calculate SaltedPassword.
*
* The password should already be normalized by SASLprep.
*/
static void
scram_Hi(const char *str, const char *salt, int saltlen, int iterations, uint8 *result)
void
scram_SaltedPassword(const char *password,
const char *salt, int saltlen, int iterations,
uint8 *result)
{
int str_len = strlen(str);
int password_len = strlen(password);
uint32 one = htonl(1);
int i,
j;
@ -113,8 +115,14 @@ scram_Hi(const char *str, const char *salt, int saltlen, int iterations, uint8 *
uint8 Ui_prev[SCRAM_KEY_LEN];
scram_HMAC_ctx hmac_ctx;
/*
* Iterate hash calculation of HMAC entry using given salt. This is
* essentially PBKDF2 (see RFC2898) with HMAC() as the pseudorandom
* function.
*/
/* First iteration */
scram_HMAC_init(&hmac_ctx, (uint8 *) str, str_len);
scram_HMAC_init(&hmac_ctx, (uint8 *) password, password_len);
scram_HMAC_update(&hmac_ctx, salt, saltlen);
scram_HMAC_update(&hmac_ctx, (char *) &one, sizeof(uint32));
scram_HMAC_final(Ui_prev, &hmac_ctx);
@ -123,7 +131,7 @@ scram_Hi(const char *str, const char *salt, int saltlen, int iterations, uint8 *
/* Subsequent iterations */
for (i = 2; i <= iterations; i++)
{
scram_HMAC_init(&hmac_ctx, (uint8 *) str, str_len);
scram_HMAC_init(&hmac_ctx, (uint8 *) password, password_len);
scram_HMAC_update(&hmac_ctx, (const char *) Ui_prev, SCRAM_KEY_LEN);
scram_HMAC_final(Ui, &hmac_ctx);
for (j = 0; j < SCRAM_KEY_LEN; j++)
@ -148,20 +156,27 @@ scram_H(const uint8 *input, int len, uint8 *result)
}
/*
* Calculate ClientKey or ServerKey.
*
* The password should already be normalized by SASLprep.
* Calculate ClientKey.
*/
void
scram_ClientOrServerKey(const char *password,
const char *salt, int saltlen, int iterations,
const char *keystr, uint8 *result)
scram_ClientKey(const uint8 *salted_password, uint8 *result)
{
uint8 keybuf[SCRAM_KEY_LEN];
scram_HMAC_ctx ctx;
scram_Hi(password, salt, saltlen, iterations, keybuf);
scram_HMAC_init(&ctx, keybuf, SCRAM_KEY_LEN);
scram_HMAC_update(&ctx, keystr, strlen(keystr));
scram_HMAC_init(&ctx, salted_password, SCRAM_KEY_LEN);
scram_HMAC_update(&ctx, "Client Key", strlen("Client Key"));
scram_HMAC_final(result, &ctx);
}
/*
* Calculate ServerKey.
*/
void
scram_ServerKey(const uint8 *salted_password, uint8 *result)
{
scram_HMAC_ctx ctx;
scram_HMAC_init(&ctx, salted_password, SCRAM_KEY_LEN);
scram_HMAC_update(&ctx, "Server Key", strlen("Server Key"));
scram_HMAC_final(result, &ctx);
}