diff options
Diffstat (limited to 'epan/crypt/airpdcap_wep.c')
| -rw-r--r-- | epan/crypt/airpdcap_wep.c | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/epan/crypt/airpdcap_wep.c b/epan/crypt/airpdcap_wep.c new file mode 100644 index 0000000000..1501d61155 --- /dev/null +++ b/epan/crypt/airpdcap_wep.c @@ -0,0 +1,67 @@ +/******************************************************************************/ +/* File includes */ +/* */ +#include "airpdcap_system.h" +#include "airpdcap_int.h" + +#include "airpdcap_wep.h" + +#include "airpdcap_debug.h" +/* */ +/******************************************************************************/ + +extern const UINT32 crc32_table[256]; + +/* Note: copied from FreeBSD source code, RELENG 6, */ +/* sys/net80211/ieee80211_crypto_wep.c, 391 */ +INT AirPDcapWepDecrypt( + const UCHAR *seed, + const size_t seed_len, + UCHAR *cypher_text, + const size_t data_len) +{ + UINT32 i, j, k, crc; + UINT8 S[256]; + UINT8 icv[4]; + size_t buflen; + + /* Generate key stream (RC4 Pseude-Random Number Generator) */ + for (i = 0; i < 256; i++) + S[i] = (UINT8)i; + for (j = i = 0; i < 256; i++) { + j = (j + S[i] + seed[i % seed_len]) & 0xff; + S_SWAP(i, j); + } + + /* Apply RC4 to data and compute CRC32 over decrypted data */ + crc = ~(UINT32)0; + buflen = data_len; + + for (i = j = k = 0; k < buflen; k++) { + i = (i + 1) & 0xff; + j = (j + S[i]) & 0xff; + S_SWAP(i, j); + *cypher_text ^= S[(S[i] + S[j]) & 0xff]; + crc = crc32_table[(crc ^ *cypher_text) & 0xff] ^ (crc >> 8); + cypher_text++; + } + + crc = ~crc; + + /* Encrypt little-endian CRC32 and verify that it matches with the received ICV */ + icv[0] = (UINT8)crc; + icv[1] = (UINT8)(crc >> 8); + icv[2] = (UINT8)(crc >> 16); + icv[3] = (UINT8)(crc >> 24); + for (k = 0; k < 4; k++) { + i = (i + 1) & 0xff; + j = (j + S[i]) & 0xff; + S_SWAP(i, j); + if ((icv[k] ^ S[(S[i] + S[j]) & 0xff]) != *cypher_text++) { + /* ICV mismatch - drop frame */ + return AIRPDCAP_RET_UNSUCCESS; + } + } + + return AIRPDCAP_RET_SUCCESS; +} |