From: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
Perform the password hash comparison in a time constant way to avoid
leaking the length of the identical prefix via a side-channel.
Since only hashes are compared leaking the total length is non critical.
Signed-off-by: Christian Göttsche <cgzones@xxxxxxxxxxxxxx>
---
policycoreutils/newrole/newrole.c | 20 +++++++++++++++++++-
1 file changed, 19 insertions(+), 1 deletion(-)
diff --git a/policycoreutils/newrole/newrole.c b/policycoreutils/newrole/newrole.c
index 5a1a1129..1e01d2ef 100644
--- a/policycoreutils/newrole/newrole.c
+++ b/policycoreutils/newrole/newrole.c
@@ -338,6 +338,24 @@ static void memzero(void *ptr, size_t size)
}
}
+static int streq_constant(const char *userinput, const char *secret)
+{
+ const volatile char *x = userinput, *y = secret;
+ size_t i, u_len, s_len;
+ int ret = 0;
+
+ u_len = strlen(userinput);
+ s_len = strlen(secret);
+
+ if (u_len != s_len)
+ return 0;
+
+ for (i = 0; i < u_len; i++)
+ ret |= x[i] ^ y[i];
+
+ return ret == 0;
+}
+
/* authenticate_via_shadow_passwd()
*
* in: uname - the calling user's user name
@@ -383,7 +401,7 @@ static int authenticate_via_shadow_passwd(const char *uname)
return 0;
}
- ret = !strcmp(encrypted_password_s, p_shadow_line->sp_pwdp);
+ ret = streq_constant(encrypted_password_s, p_shadow_line->sp_pwdp);
memzero(encrypted_password_s, strlen(encrypted_password_s));
return ret;
}
--
2.43.0
