@@ -57,4 +57,15 @@

 int ff_rtmp_calc_digest(const uint8_t *src, int len, int gap,

                         const uint8_t *key, int keylen, uint8_t *dst);

+/**

+ * Calculate digest position for RTMP handshake packets.

+ *

+ * @param buf input buffer (should be 1536 bytes)

+ * @param off offset in buffer where to start calculating digest position

+ * @param mod_val value used for computing modulo

+ * @param add_val value added at the end (after computing modulo)

+ */

+int ff_rtmp_calc_digest_pos(const uint8_t *buf, int off, int mod_val,

+                            int add_val);

+

 #endif /* AVFORMAT_RTMP_H */

@@ -632,6 +632,18 @@ int ff_rtmp_calc_digest(const uint8_t *src, int len, int gap,

     return 0;

 }

+int ff_rtmp_calc_digest_pos(const uint8_t *buf, int off, int mod_val,

+                            int add_val)

+{

+    int i, digest_pos = 0;

+

+    for (i = 0; i < 4; i++)

+        digest_pos += buf[i + off];

+    digest_pos = digest_pos % mod_val + add_val;

+

+    return digest_pos;

+}

+

 /**

  * Put HMAC-SHA2 digest of packet data (except for the bytes where this digest

  * will be stored) into that packet.

@@ -641,12 +653,9 @@ int ff_rtmp_calc_digest(const uint8_t *src, int len, int gap,

  */

 static int rtmp_handshake_imprint_with_digest(uint8_t *buf)

 {

-    int i, digest_pos = 0;

-    int ret;

+    int ret, digest_pos;

-    for (i = 8; i < 12; i++)

-        digest_pos += buf[i];

-    digest_pos = (digest_pos % 728) + 12;

+    digest_pos = ff_rtmp_calc_digest_pos(buf, 8, 728, 12);

     ret = ff_rtmp_calc_digest(buf, RTMP_HANDSHAKE_PACKET_SIZE, digest_pos,

                               rtmp_player_key, PLAYER_KEY_OPEN_PART_LEN,

@@ -666,13 +675,10 @@ static int rtmp_handshake_imprint_with_digest(uint8_t *buf)

  */

 static int rtmp_validate_digest(uint8_t *buf, int off)

 {

-    int i, digest_pos = 0;

     uint8_t digest[32];

-    int ret;

+    int ret, digest_pos;

-    for (i = 0; i < 4; i++)

-        digest_pos += buf[i + off];

-    digest_pos = (digest_pos % 728) + off + 4;

+    digest_pos = ff_rtmp_calc_digest_pos(buf, off, 728, off + 4);

     ret = ff_rtmp_calc_digest(buf, RTMP_HANDSHAKE_PACKET_SIZE, digest_pos,

                               rtmp_server_key, SERVER_KEY_OPEN_PART_LEN,