We present the first known-key attack on SM4, which is the Chinese standard block cipher made for the wireless LAN WAPI. We make a known-key distinguisher using rebound techniques with the time complexity of 2^12.75. Then, with the distinguisher, we provide near-collision attacks on MMO and MP hash modes of SM4. Precisely, we find a 104-bit near-collision for 13 rounds of SM4 with the time complexity of 2^13.30 and a 32-bit near-collision for 17 rounds of SM4 with the time complexity of 2^12.91. They are much more efficient than generic attacks for the case of random permutation.