[PATCH] Introduce a function to reencode scramble.

[Serge Petrenko <sergepetrenko@tarantool.org>]

Introduce a new function, scramble_reencode(), which allows one cluster
instance to reencode a scramble received from  a client using the salt
from another cluster instance. This is needed for proxy to mimic client
connections when connecting to remote instances.

Part of #2625
---
https://github.com/tarantool/tarantool/tree/sp/scramble-reencode
https://github.com/tarantool/tarantool/issues/2625

 src/scramble.c            | 23 +++++++++++++++++++++++
 src/scramble.h            |  9 +++++++++
 test/unit/scramble.c      | 10 ++++++++++
 test/unit/scramble.result |  1 +
 4 files changed, 43 insertions(+)

diff --git a/src/scramble.c b/src/scramble.c
index ca1f98793..6dc43932b 100644
--- a/src/scramble.c
+++ b/src/scramble.c
@@ -67,6 +67,29 @@ scramble_prepare(void *out, const void *salt, const void *password,
 	xor(out, hash1, out, SCRAMBLE_SIZE);
 }
 
+void
+scramble_reencode(void *out, const void *in, const void *salt, const void *msalt,
+		  const void *hash2)
+{
+	unsigned char hash1[SCRAMBLE_SIZE];
+	unsigned char sh[SCRAMBLE_SIZE];
+	SHA1_CTX ctx;
+
+	SHA1Init(&ctx);
+	SHA1Update(&ctx, salt, SCRAMBLE_SIZE);
+	SHA1Update(&ctx, hash2, SCRAMBLE_SIZE);
+	SHA1Final(sh, &ctx);
+
+	xor(hash1, in, sh, SCRAMBLE_SIZE);
+
+	SHA1Init(&ctx);
+	SHA1Update(&ctx, msalt, SCRAMBLE_SIZE);
+	SHA1Update(&ctx, hash2, SCRAMBLE_SIZE);
+	SHA1Final(out, &ctx);
+
+	xor(out, hash1, out, SCRAMBLE_SIZE);
+}
+
 int
 scramble_check(const void *scramble, const void *salt, const void *hash2)
 {
diff --git a/src/scramble.h b/src/scramble.h
index 7dee31483..e47870f8e 100644
--- a/src/scramble.h
+++ b/src/scramble.h
@@ -89,6 +89,15 @@ scramble_check(const void *scramble, const void *salt, const void *hash2);
 void
 password_prepare(const char *password, int len, char *out, int out_len);
 
+/**
+ * Given a scramble received from a client, salt sent to client,
+ * salt received from another instance and user hash2, recalculate
+ * a scramble to be sent to a remote instance for authentication.
+ */
+void
+scramble_reencode(void *out, const void *in, const void *salt, const void *msalt,
+		  const void *hash2);
+
 #if defined(__cplusplus)
 } /* extern "C" */
 #endif
diff --git a/test/unit/scramble.c b/test/unit/scramble.c
index 572466e9b..8f1ee55af 100644
--- a/test/unit/scramble.c
+++ b/test/unit/scramble.c
@@ -32,6 +32,16 @@ test_scramble()
 
 	printf("%d\n", scramble_check(scramble, salt, hash2));
 
+	int remote_salt[SCRAMBLE_SIZE/sizeof(int)];
+	for(size_t i = 0; i < sizeof(salt)/sizeof(int); ++i)
+		remote_salt[i] = rand();
+
+	char new_scramble[SCRAMBLE_SIZE];
+
+	scramble_reencode(new_scramble, scramble, salt, remote_salt, hash2);
+
+	printf("%d\n", scramble_check(new_scramble, remote_salt, hash2));
+
 	password = "wrongpass";
 	scramble_prepare(scramble, salt, password, strlen(password));
 
diff --git a/test/unit/scramble.result b/test/unit/scramble.result
index 986394f7c..0463db267 100644
--- a/test/unit/scramble.result
+++ b/test/unit/scramble.result
@@ -1,3 +1,4 @@
 0
+0
 1
 1
-- 
2.17.1 (Apple Git-112)