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Diffstat (limited to 'wsutil/eax.c')
| -rw-r--r-- | wsutil/eax.c | 249 |
1 files changed, 249 insertions, 0 deletions
diff --git a/wsutil/eax.c b/wsutil/eax.c new file mode 100644 index 00000000..208cf4e4 --- /dev/null +++ b/wsutil/eax.c @@ -0,0 +1,249 @@ +/* eax.c + * Encryption and decryption routines implementing the EAX' encryption mode + * Copyright 2010, Edward J. Beroset, edward.j.beroset@us.elster.com + * + * Wireshark - Network traffic analyzer + * By Gerald Combs <gerald@wireshark.org> + * Copyright 1998 Gerald Combs + * + * SPDX-License-Identifier: GPL-2.0-or-later + */ +#include "config.h" +#include "eax.h" +#include <stdlib.h> +#include <string.h> +/* Use libgcrypt for cipher libraries. */ +#include <gcrypt.h> + +typedef struct { + uint8_t L[EAX_SIZEOF_KEY]; + uint8_t D[EAX_SIZEOF_KEY]; + uint8_t Q[EAX_SIZEOF_KEY]; +} eax_s; + +static eax_s instance; + +/* these are defined as macros so they'll be easy to redo in assembly if desired */ +#define BLK_CPY(dst, src) { memcpy(dst, src, EAX_SIZEOF_KEY); } +#define BLK_XOR(dst, src) { int z; for (z=0; z < EAX_SIZEOF_KEY; z++) dst[z] ^= src[z]; } +static void Dbl(uint8_t *out, const uint8_t *in); +static void CTR(const uint8_t *ws, uint8_t *pK, uint8_t *pN, uint16_t SizeN); +static void CMAC(uint8_t *pK, uint8_t *ws, const uint8_t *pN, uint16_t SizeN); +static void dCMAC(uint8_t *pK, uint8_t *ws, const uint8_t *pN, uint16_t SizeN, const uint8_t *pC, uint16_t SizeC); +void AesEncrypt(unsigned char msg[EAX_SIZEOF_KEY], unsigned char key[EAX_SIZEOF_KEY]); + +/*! + Decrypts cleartext data using EAX' mode (see ANSI Standard C12.22-2008). + + @param[in] pN pointer to cleartext (canonified form) + @param[in] pK pointer to secret key + @param[in,out] pC pointer to ciphertext + @param[in] SizeN byte length of cleartext (pN) buffer + @param[in] SizeK byte length of secret key (pK) + @param[in] SizeC byte length of ciphertext (pC) buffer + @param[in] pMac four-byte Message Authentication Code + @param[in] Mode EAX_MODE_CLEARTEXT_AUTH or EAX_MODE_CIPHERTEXT_AUTH + @return true if message has been authenticated; false if not + authenticated, invalid Mode or error + */ +bool Eax_Decrypt(uint8_t *pN, uint8_t *pK, uint8_t *pC, + uint32_t SizeN, uint32_t SizeK, uint32_t SizeC, MAC_T *pMac, + uint8_t Mode) +{ + uint8_t wsn[EAX_SIZEOF_KEY]; + uint8_t wsc[EAX_SIZEOF_KEY]; + int i; + + /* key size must match this implementation */ + if (SizeK != EAX_SIZEOF_KEY) + return false; + + /* the key is new */ + for (i = 0; i < EAX_SIZEOF_KEY; i++) + instance.L[i] = 0; + AesEncrypt(instance.L, pK); + Dbl(instance.D, instance.L); + Dbl(instance.Q, instance.D); + /* the key is set up */ + /* first copy the nonce into our working space */ + BLK_CPY(wsn, instance.D); + if (Mode == EAX_MODE_CLEARTEXT_AUTH) { + dCMAC(pK, wsn, pN, SizeN, pC, SizeC); + } else { + CMAC(pK, wsn, pN, SizeN); + } + /* + * In authentication mode the inputs are: pN, pK (and associated sizes), + * the result is the 4 byte MAC. + */ + if (Mode == EAX_MODE_CLEARTEXT_AUTH) + { + return (memcmp(pMac, &wsn[EAX_SIZEOF_KEY-sizeof(*pMac)], sizeof(*pMac)) ? false : true); + + } + + /* + * In cipher mode the inputs are: pN, pK, pP (and associated sizes), + * the results are pC (and its size) along with the 4 byte MAC. + */ + else if (Mode == EAX_MODE_CIPHERTEXT_AUTH) + { + if (SizeC == 0) + return (memcmp(pMac, &wsn[EAX_SIZEOF_KEY-sizeof(*pMac)], sizeof(*pMac)) ? false : true); + { + /* first copy the nonce into our working space */ + BLK_CPY(wsc, instance.Q); + CMAC(pK, wsc, pC, SizeC); + BLK_XOR(wsc, wsn); + } + if (memcmp(pMac, &wsc[EAX_SIZEOF_KEY-sizeof(*pMac)], sizeof(*pMac)) == 0) + { + CTR(wsn, pK, pC, SizeC); + return true; + } + } + return false; +} + +/* set up D or Q from L */ +static void Dbl(uint8_t *out, const uint8_t *in) +{ + int i; + uint8_t carry = 0; + + /* this might be a lot more efficient in assembly language */ + for (i=0; i < EAX_SIZEOF_KEY; i++) + { + out[i] = ( in[i] << 1 ) | carry; + carry = (in[i] & 0x80) ? 1 : 0; + } + if (carry) + out[0] ^= 0x87; +} + +static void CMAC(uint8_t *pK, uint8_t *ws, const uint8_t *pN, uint16_t SizeN) +{ + dCMAC(pK, ws, pN, SizeN, NULL, 0); +} + +static void dCMAC(uint8_t *pK, uint8_t *ws, const uint8_t *pN, uint16_t SizeN, const uint8_t *pC, uint16_t SizeC) +{ + gcry_cipher_hd_t cipher_hd; + uint8_t *work; + uint8_t *ptr; + uint16_t SizeT = SizeN + SizeC; + uint16_t worksize = SizeT; + + /* worksize must be an integral multiple of 16 */ + if (SizeT & 0xf) { + worksize += 0x10 - (worksize & 0xf); + } + work = (uint8_t *)g_malloc(worksize); + if (work == NULL) { + return; + } + memcpy(work, pN, SizeN); + if (pC != NULL) { + memcpy(&work[SizeN], pC, SizeC); + } + /* + * pad the data if necessary, and XOR Q or D, depending on + * whether data was padded or not + */ + if (worksize != SizeT) { + work[SizeT] = 0x80; + for (ptr = &work[SizeT+1]; ptr < &work[worksize]; ptr++) + *ptr = 0; + ptr= &work[worksize-0x10]; + BLK_XOR(ptr, instance.Q); + } else { + ptr = &work[worksize-0x10]; + BLK_XOR(ptr, instance.D); + } + /* open the cipher */ + if (gcry_cipher_open(&cipher_hd, GCRY_CIPHER_AES128, GCRY_CIPHER_MODE_CBC,0)){/* GCRY_CIPHER_CBC_MAC)) { */ + g_free(work); + return; + } + if (gcry_cipher_setkey(cipher_hd, pK, EAX_SIZEOF_KEY)) { + g_free(work); + gcry_cipher_close(cipher_hd); + return; + } + if (gcry_cipher_setiv(cipher_hd, ws, EAX_SIZEOF_KEY)) { + g_free(work); + gcry_cipher_close(cipher_hd); + return; + } + if (gcry_cipher_encrypt(cipher_hd, work, worksize, work, worksize)) { + g_free(work); + gcry_cipher_close(cipher_hd); + return; + } + memcpy(ws, ptr, EAX_SIZEOF_KEY); + + g_free(work); + gcry_cipher_close(cipher_hd); + return; +} + +static void CTR(const uint8_t *ws, uint8_t *pK, uint8_t *pN, uint16_t SizeN) +{ + gcry_cipher_hd_t cipher_hd; + uint8_t ctr[EAX_SIZEOF_KEY]; + + BLK_CPY(ctr, ws); + ctr[12] &= 0x7f; + ctr[14] &= 0x7f; + /* open the cipher */ + if (gcry_cipher_open(&cipher_hd, GCRY_CIPHER_AES128, GCRY_CIPHER_MODE_CTR, 0)) { + return; + } + if (gcry_cipher_setkey(cipher_hd, pK, EAX_SIZEOF_KEY)) { + gcry_cipher_close(cipher_hd); + return; + } + if (gcry_cipher_setctr(cipher_hd, ctr, EAX_SIZEOF_KEY)) { + gcry_cipher_close(cipher_hd); + return; + } + if (gcry_cipher_encrypt(cipher_hd, pN, SizeN, pN, SizeN)) { + gcry_cipher_close(cipher_hd); + return; + } + gcry_cipher_close(cipher_hd); + return; +} + +void AesEncrypt(unsigned char msg[EAX_SIZEOF_KEY], unsigned char key[EAX_SIZEOF_KEY]) +{ + gcry_cipher_hd_t cipher_hd; + + /* open the cipher */ + if (gcry_cipher_open(&cipher_hd, GCRY_CIPHER_AES128, GCRY_CIPHER_MODE_ECB, 0)) { + return; + } + if (gcry_cipher_setkey(cipher_hd, key, EAX_SIZEOF_KEY)) { + gcry_cipher_close(cipher_hd); + return; + } + if (gcry_cipher_encrypt(cipher_hd, msg, EAX_SIZEOF_KEY, msg, EAX_SIZEOF_KEY)) { + gcry_cipher_close(cipher_hd); + return; + } + gcry_cipher_close(cipher_hd); + return; +} + +/* + * Editor modelines - https://www.wireshark.org/tools/modelines.html + * + * Local variables: + * c-basic-offset: 4 + * tab-width: 8 + * indent-tabs-mode: nil + * End: + * + * vi: set shiftwidth=4 tabstop=8 expandtab: + * :indentSize=4:tabSize=8:noTabs=true: + */ |