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 /* This Source Code Form is subject to the terms of the Mozilla Public

  * License, v. 2.0. If a copy of the MPL was not distributed with this

  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 #ifdef FREEBL_NO_DEPEND

 #include "stubs.h"

 #endif

 #include "blapii.h"

 #include "blapit.h"

 #include "gcm.h"

 #include "ctr.h"

 #include "secerr.h"

 #include "prtypes.h"

 #include "pkcs11t.h"

 #include <limits.h>

 /**************************************************************************

  *          First implement the Galois hash function of GCM (gcmHash)     *

  **************************************************************************/

 #define GCM_HASH_LEN_LEN 8 /* gcm hash defines lengths to be 64 bits */

 typedef struct gcmHashContextStr gcmHashContext;

 static SECStatus gcmHash_InitContext(gcmHashContext *hash,

 				     const unsigned char *H,

 				     unsigned int blocksize);

 static void gcmHash_DestroyContext(gcmHashContext *ghash, PRBool freeit);

 static SECStatus gcmHash_Update(gcmHashContext *ghash,

 				const unsigned char *buf, unsigned int len,

 				unsigned int blocksize);

 static SECStatus gcmHash_Sync(gcmHashContext *ghash, unsigned int blocksize);

 static SECStatus gcmHash_Final(gcmHashContext *gcm, unsigned char *outbuf,

 			       unsigned int *outlen, unsigned int maxout,

 			       unsigned int blocksize);

 static SECStatus gcmHash_Reset(gcmHashContext *ghash,

 			       const unsigned char *inbuf,

 			       unsigned int inbufLen, unsigned int blocksize);

 /* compile time defines to select how the GF2 multiply is calculated.

  * There are currently 2 algorithms implemented here: MPI and ALGORITHM_1.

  *

  * MPI uses the GF2m implemented in mpi to support GF2 ECC.

  * ALGORITHM_1 is the Algorithm 1 in both NIST SP 800-38D and

  * "The Galois/Counter Mode of Operation (GCM)", McGrew & Viega.

  */

 #if !defined(GCM_USE_ALGORITHM_1) && !defined(GCM_USE_MPI)

 #define GCM_USE_MPI 1 /* MPI is about 5x faster with the

 		       * same or less complexity. It's possible to use

 		       * tables to speed things up even more */

 #endif

 /* GCM defines the bit string to be LSB first, which is exactly

  * opposite everyone else, including hardware. build array

  * to reverse everything. */

 static const unsigned char gcm_byte_rev[256] = {

     0x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0,

     0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0,

     0x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8,

     0x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8,

     0x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4,

     0x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4,

     0x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec,

     0x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc,

     0x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2,

     0x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2,

     0x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea,

     0x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa,

     0x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6,

     0x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6,

     0x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee,

     0x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe,

     0x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1,

     0x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1,

     0x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9,

     0x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9,

     0x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5,

     0x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5,

     0x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed,

     0x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd,

     0x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3,

     0x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3,

     0x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb,

     0x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb,

     0x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7,

     0x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7,

     0x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef,

     0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff

 };

 #ifdef GCM_TRACE

 #include <stdio.h>

 #define GCM_TRACE_X(ghash,label) { \

 	unsigned char _X[MAX_BLOCK_SIZE]; int i; \

 	gcm_getX(ghash, _X, blocksize); \

 	printf(label,(ghash)->m); \

 	for (i=0; i < blocksize; i++) printf("%02x",_X[i]); \

 	printf("\n"); }

 #define GCM_TRACE_BLOCK(label,buf,blocksize) {\

 	printf(label); \

 	for (i=0; i < blocksize; i++) printf("%02x",buf[i]); \

 	printf("\n"); }

 #else

 #define GCM_TRACE_X(ghash,label)

 #define GCM_TRACE_BLOCK(label,buf,blocksize)

 #endif

 #ifdef GCM_USE_MPI

 #ifdef GCM_USE_ALGORITHM_1

 #error "Only define one of GCM_USE_MPI, GCM_USE_ALGORITHM_1"

 #endif

 /* use the MPI functions to calculate Xn = (Xn-1^C_i)*H mod poly */

 #include "mpi.h"

 #include "secmpi.h"

 #include "mplogic.h"

 #include "mp_gf2m.h"

 /* state needed to handle GCM Hash function */

 struct gcmHashContextStr {

      mp_int H;

      mp_int X;

      mp_int C_i;

      const unsigned int *poly;

      unsigned char buffer[MAX_BLOCK_SIZE];

      unsigned int bufLen;

      int m; /* XXX what is m? */

      unsigned char counterBuf[2*GCM_HASH_LEN_LEN];

      PRUint64 cLen;

 };

 /* f = x^128 + x^7 + x^2 + x + 1 */

 static const unsigned int poly_128[] = { 128, 7, 2, 1, 0 };

 /* sigh, GCM defines the bit strings exactly backwards from everything else */

 static void

 gcm_reverse(unsigned char *target, const unsigned char *src,

 							unsigned int blocksize)

 {

     unsigned int i;

     for (i=0; i < blocksize; i++) {

 	target[blocksize-i-1] = gcm_byte_rev[src[i]];

     }

 }

 /* Initialize a gcmHashContext */

 static SECStatus

 gcmHash_InitContext(gcmHashContext *ghash, const unsigned char *H,

 		    unsigned int blocksize)

 {

     mp_err err = MP_OKAY;

     unsigned char H_rev[MAX_BLOCK_SIZE];

     MP_DIGITS(&ghash->H) = 0;

     MP_DIGITS(&ghash->X) = 0;

     MP_DIGITS(&ghash->C_i) = 0;

     CHECK_MPI_OK( mp_init(&ghash->H) );

     CHECK_MPI_OK( mp_init(&ghash->X) );

     CHECK_MPI_OK( mp_init(&ghash->C_i) );

     mp_zero(&ghash->X);

     gcm_reverse(H_rev, H, blocksize);

     CHECK_MPI_OK( mp_read_unsigned_octets(&ghash->H, H_rev, blocksize) );

     /* set the irreducible polynomial. Each blocksize has its own polynomial.

      * for now only blocksize 16 (=128 bits) is defined */

     switch (blocksize) {

     case 16: /* 128 bits */

 	ghash->poly = poly_128;

 	break;

     default:

 	PORT_SetError(SEC_ERROR_INVALID_ARGS);

 	goto cleanup;

     }

     ghash->cLen = 0;

     ghash->bufLen = 0;

     ghash->m = 0;

     PORT_Memset(ghash->counterBuf, 0, sizeof(ghash->counterBuf));

     return SECSuccess;

 cleanup:

     gcmHash_DestroyContext(ghash, PR_FALSE);

     return SECFailure;

 }

 /* Destroy a HashContext (Note we zero the digits so this function

  * is idempotent if called with freeit == PR_FALSE */

 static void

 gcmHash_DestroyContext(gcmHashContext *ghash, PRBool freeit)

 {

     mp_clear(&ghash->H);

     mp_clear(&ghash->X);

     mp_clear(&ghash->C_i);

     MP_DIGITS(&ghash->H) = 0;

     MP_DIGITS(&ghash->X) = 0;

     MP_DIGITS(&ghash->C_i) = 0;

     if (freeit) {

 	PORT_Free(ghash);

     }

 }

 static SECStatus

 gcm_getX(gcmHashContext *ghash, unsigned char *T, unsigned int blocksize)

 {

     int len;

     mp_err err;

     unsigned char tmp_buf[MAX_BLOCK_SIZE];

     unsigned char *X;

     len = mp_unsigned_octet_size(&ghash->X);

     if (len <= 0) {

 	PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);

 	return SECFailure;

     }

     X = tmp_buf;

     PORT_Assert((unsigned int)len <= blocksize);

     if ((unsigned int)len > blocksize) {

 	PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);

 	return SECFailure;

     }

     /* zero pad the result */

     if (len != blocksize) {

 	PORT_Memset(X,0,blocksize-len);

 	X += blocksize-len;

     }

     err = mp_to_unsigned_octets(&ghash->X, X, len);

     if (err < 0) {

 	PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);

 	return SECFailure;

     }

     gcm_reverse(T, tmp_buf, blocksize);

     return SECSuccess;

 }

 static SECStatus

 gcm_HashMult(gcmHashContext *ghash, const unsigned char *buf,

 		unsigned int count, unsigned int blocksize)

 {

     SECStatus rv = SECFailure;

     mp_err err = MP_OKAY;

     unsigned char tmp_buf[MAX_BLOCK_SIZE];

     unsigned int i;

     for (i=0; i < count; i++, buf += blocksize) {

 	ghash->m++;

 	gcm_reverse(tmp_buf, buf, blocksize);

 	CHECK_MPI_OK(mp_read_unsigned_octets(&ghash->C_i, tmp_buf, blocksize));

 	CHECK_MPI_OK(mp_badd(&ghash->X, &ghash->C_i, &ghash->C_i));

 	/*

 	 * Looking to speed up GCM, this the the place to do it.

 	 * There are two areas that can be exploited to speed up this code.

 	 *

 	 * 1) H is a constant in this multiply. We can precompute H * (0 - 255)

 	 * at init time and this becomes an blockize xors of our table lookup.

 	 *

 	 * 2) poly is a constant for each blocksize. We can calculate the

 	 * modulo reduction by a series of adds and shifts.

 	 *

 	 * For now we are after functionality, so we will go ahead and use

 	 * the builtin bmulmod from mpi

 	 */

         CHECK_MPI_OK(mp_bmulmod(&ghash->C_i, &ghash->H,

 					ghash->poly, &ghash->X));

 	GCM_TRACE_X(ghash, "X%d = ")

     }

     rv = SECSuccess;

 cleanup:

     if (rv != SECSuccess) {

 	MP_TO_SEC_ERROR(err);

     }

     return rv;

 }

 static void

 gcm_zeroX(gcmHashContext *ghash)

 {

     mp_zero(&ghash->X);

     ghash->m = 0;

 }

 #endif

 #ifdef GCM_USE_ALGORITHM_1

 /* use algorithm 1 of McGrew & Viega "The Galois/Counter Mode of Operation" */

 #define GCM_ARRAY_SIZE (MAX_BLOCK_SIZE/sizeof(unsigned long))

 struct gcmHashContextStr {

      unsigned long H[GCM_ARRAY_SIZE];

      unsigned long X[GCM_ARRAY_SIZE];

      unsigned long R;

      unsigned char buffer[MAX_BLOCK_SIZE];

      unsigned int bufLen;

      int m;

      unsigned char counterBuf[2*GCM_HASH_LEN_LEN];

      PRUint64 cLen;

 };

 static void

 gcm_bytes_to_longs(unsigned long *l, const unsigned char *c, unsigned int len)

 {

     int i,j;

     int array_size = len/sizeof(unsigned long);

     PORT_Assert(len % sizeof(unsigned long) == 0);

     for (i=0; i < array_size; i++) {

 	unsigned long tmp = 0;

 	int byte_offset = i * sizeof(unsigned long);

 	for (j=sizeof(unsigned long)-1; j >= 0; j--) {

 	    tmp = (tmp << PR_BITS_PER_BYTE) | gcm_byte_rev[c[byte_offset+j]];

 	}

 	l[i] = tmp;

     }

 }

 static void

 gcm_longs_to_bytes(const unsigned long *l, unsigned char *c, unsigned int len)

 {

     int i,j;

     int array_size = len/sizeof(unsigned long);

     PORT_Assert(len % sizeof(unsigned long) == 0);

     for (i=0; i < array_size; i++) {

 	unsigned long tmp = l[i];

 	int byte_offset = i * sizeof(unsigned long);

 	for (j=0; j < sizeof(unsigned long); j++) {

 	    c[byte_offset+j] = gcm_byte_rev[tmp & 0xff];

 	    tmp = (tmp >> PR_BITS_PER_BYTE);

 	}

     }

 }

 /* Initialize a gcmHashContext */

 static SECStatus

 gcmHash_InitContext(gcmHashContext *ghash, const unsigned char *H,

 		    unsigned int blocksize)

 {

     PORT_Memset(ghash->X, 0, sizeof(ghash->X));

     PORT_Memset(ghash->H, 0, sizeof(ghash->H));

     gcm_bytes_to_longs(ghash->H, H, blocksize);

     /* set the irreducible polynomial. Each blocksize has its own polynommial

      * for now only blocksize 16 (=128 bits) is defined */

     switch (blocksize) {

     case 16: /* 128 bits */

 	ghash->R = (unsigned long) 0x87; /* x^7 + x^2 + x +1 */

 	break;

     default:

 	PORT_SetError(SEC_ERROR_INVALID_ARGS);

 	goto cleanup;

     }

     ghash->cLen = 0;

     ghash->bufLen = 0;

     ghash->m = 0;

     PORT_Memset(ghash->counterBuf, 0, sizeof(ghash->counterBuf));

     return SECSuccess;

 cleanup:

     return SECFailure;

 }

 /* Destroy a HashContext (Note we zero the digits so this function

  * is idempotent if called with freeit == PR_FALSE */

 static void

 gcmHash_DestroyContext(gcmHashContext *ghash, PRBool freeit)

 {

     if (freeit) {

 	PORT_Free(ghash);

     }

 }

 static unsigned long

 gcm_shift_one(unsigned long *t, unsigned int count)

 {

     unsigned long carry = 0;

     unsigned long nextcarry = 0;

     unsigned int i;

     for (i=0; i < count; i++) {

 	nextcarry = t[i] >> ((sizeof(unsigned long)*PR_BITS_PER_BYTE)-1);

 	t[i] = (t[i] << 1) | carry;

 	carry = nextcarry;

     }

     return carry;

 }

 static SECStatus

 gcm_getX(gcmHashContext *ghash, unsigned char *T, unsigned int blocksize)

 {

     gcm_longs_to_bytes(ghash->X, T, blocksize);

     return SECSuccess;

 }

 #define GCM_XOR(t, s, len) \

 	for (l=0; l < len; l++) t[l] ^= s[l]

 static SECStatus

 gcm_HashMult(gcmHashContext *ghash, const unsigned char *buf,

 		unsigned int count, unsigned int blocksize)

 {

     unsigned long C_i[GCM_ARRAY_SIZE];

     unsigned int arraysize = blocksize/sizeof(unsigned long);

     unsigned int i, j, k, l;

     for (i=0; i < count; i++, buf += blocksize) {

 	ghash->m++;

 	gcm_bytes_to_longs(C_i, buf, blocksize);

 	GCM_XOR(C_i, ghash->X, arraysize);

 	/* multiply X = C_i * H */

 	PORT_Memset(ghash->X, 0, sizeof(ghash->X));

 	for (j=0; j < arraysize; j++) {

 	    unsigned long H = ghash->H[j];

 	    for (k=0; k < sizeof(unsigned long)*PR_BITS_PER_BYTE; k++) {

 		if (H & 1) {

 		    GCM_XOR(ghash->X, C_i, arraysize);

 		}

 		if (gcm_shift_one(C_i, arraysize)) {

 		    C_i[0] = C_i[0] ^ ghash->R;

 		}

 		H = H >> 1;

 	    }

 	}

 	GCM_TRACE_X(ghash, "X%d = ")

     }

     return SECSuccess;

 }

 static void

 gcm_zeroX(gcmHashContext *ghash)

 {

     PORT_Memset(ghash->X, 0, sizeof(ghash->X));

     ghash->m = 0;

 }

 #endif

 /*

  * implement GCM GHASH using the freebl GHASH function. The gcm_HashMult

  * function always takes blocksize lengths of data. gcmHash_Update will

  * format the data properly.

  */

 static SECStatus

 gcmHash_Update(gcmHashContext *ghash, const unsigned char *buf,

 	       unsigned int len, unsigned int blocksize)

 {

     unsigned int blocks;

     SECStatus rv;

     ghash->cLen += (len*PR_BITS_PER_BYTE);

     /* first deal with the current buffer of data. Try to fill it out so

      * we can hash it */

     if (ghash->bufLen) {

 	unsigned int needed = PR_MIN(len, blocksize - ghash->bufLen);

 	if (needed != 0) {

 	    PORT_Memcpy(ghash->buffer+ghash->bufLen, buf, needed);

 	}

 	buf += needed;

 	len -= needed;

 	ghash->bufLen += needed;

 	if (len == 0) {

 	    /* didn't add enough to hash the data, nothing more do do */

 	    return SECSuccess;

 	}

 	PORT_Assert(ghash->bufLen == blocksize);

 	/* hash the buffer and clear it */

 	rv = gcm_HashMult(ghash, ghash->buffer, 1, blocksize);

 	PORT_Memset(ghash->buffer, 0, blocksize);

 	ghash->bufLen = 0;

 	if (rv != SECSuccess) {

 	    return SECFailure;

 	}

     }

     /* now hash any full blocks remaining in the data stream */

     blocks = len/blocksize;

     if (blocks) {

 	rv = gcm_HashMult(ghash, buf, blocks, blocksize);

 	if (rv != SECSuccess) {

 	    return SECFailure;

 	}

 	buf += blocks*blocksize;

 	len -= blocks*blocksize;

     }

     /* save any remainder in the buffer to be hashed with the next call */

     if (len != 0) {

 	PORT_Memcpy(ghash->buffer, buf, len);

 	ghash->bufLen = len;

     }

     return SECSuccess;

 }

 /*

  * write out any partial blocks zero padded through the GHASH engine,

  * save the lengths for the final completion of the hash

  */

 static SECStatus

 gcmHash_Sync(gcmHashContext *ghash, unsigned int blocksize)

 {

     int i;

     SECStatus rv;

     /* copy the previous counter to the upper block */

     PORT_Memcpy(ghash->counterBuf, &ghash->counterBuf[GCM_HASH_LEN_LEN],

 							GCM_HASH_LEN_LEN);

     /* copy the current counter in the lower block */

     for (i=0; i < GCM_HASH_LEN_LEN; i++) {

 	ghash->counterBuf[GCM_HASH_LEN_LEN+i] =

 	    (ghash->cLen >> ((GCM_HASH_LEN_LEN-1-i)*PR_BITS_PER_BYTE)) & 0xff;

     }

     ghash->cLen = 0;

     /* now zero fill the buffer and hash the last block */

     if (ghash->bufLen) {

 	PORT_Memset(ghash->buffer+ghash->bufLen, 0, blocksize - ghash->bufLen);

 	rv = gcm_HashMult(ghash, ghash->buffer, 1, blocksize);

 	PORT_Memset(ghash->buffer, 0, blocksize);

 	ghash->bufLen = 0;

 	if (rv != SECSuccess) {

 	    return SECFailure;

 	}

     }

     return SECSuccess;

 }

 /*

  * This does the final sync, hashes the lengths, then returns

  * "T", the hashed output.

  */

 static SECStatus

 gcmHash_Final(gcmHashContext *ghash, unsigned char *outbuf,

 		unsigned int *outlen, unsigned int maxout,

 		unsigned int blocksize)

 {

     unsigned char T[MAX_BLOCK_SIZE];

     SECStatus rv;

     rv = gcmHash_Sync(ghash, blocksize);

     if (rv != SECSuccess) {

 	return SECFailure;

     }

     rv = gcm_HashMult(ghash, ghash->counterBuf, (GCM_HASH_LEN_LEN*2)/blocksize,

 								blocksize);

     if (rv != SECSuccess) {

 	return SECFailure;

     }

     GCM_TRACE_X(ghash, "GHASH(H,A,C) = ")

     rv = gcm_getX(ghash, T, blocksize);

     if (rv != SECSuccess) {

 	return SECFailure;

     }

     if (maxout > blocksize) maxout = blocksize;

     PORT_Memcpy(outbuf, T, maxout);

     *outlen = maxout;

     return SECSuccess;

 }

 SECStatus

 gcmHash_Reset(gcmHashContext *ghash, const unsigned char *AAD,

 	      unsigned int AADLen, unsigned int blocksize)

 {

     SECStatus rv;

     ghash->cLen = 0;

     PORT_Memset(ghash->counterBuf, 0, GCM_HASH_LEN_LEN*2);

     ghash->bufLen = 0;

     gcm_zeroX(ghash);

     /* now kick things off by hashing the Additional Authenticated Data */

     if (AADLen != 0) {

 	rv = gcmHash_Update(ghash, AAD, AADLen, blocksize);

 	if (rv != SECSuccess) {

 	    return SECFailure;

 	}

 	rv = gcmHash_Sync(ghash, blocksize);

 	if (rv != SECSuccess) {

 	    return SECFailure;

 	}

     }

     return SECSuccess;

 }

 /**************************************************************************

  *           Now implement the GCM using gcmHash and CTR                  *

  **************************************************************************/

 /* state to handle the full GCM operation (hash and counter) */

 struct GCMContextStr {

     gcmHashContext ghash_context;

     CTRContext ctr_context;

     unsigned long tagBits;

     unsigned char tagKey[MAX_BLOCK_SIZE];

 };

 GCMContext *

 GCM_CreateContext(void *context, freeblCipherFunc cipher,

 		  const unsigned char *params, unsigned int blocksize)

 {

     GCMContext *gcm = NULL;

     gcmHashContext *ghash;

     unsigned char H[MAX_BLOCK_SIZE];

     unsigned int tmp;

     PRBool freeCtr = PR_FALSE;

     PRBool freeHash = PR_FALSE;

     const CK_GCM_PARAMS *gcmParams = (const CK_GCM_PARAMS *)params;

     CK_AES_CTR_PARAMS ctrParams;

     SECStatus rv;

     if (blocksize > MAX_BLOCK_SIZE || blocksize > sizeof(ctrParams.cb)) {

 	PORT_SetError(SEC_ERROR_LIBRARY_FAILURE);

 	return NULL;

     }

     gcm = PORT_ZNew(GCMContext);

     if (gcm == NULL) {

 	return NULL;

     }

     /* first fill in the ghash context */

     ghash = &gcm->ghash_context;

     PORT_Memset(H, 0, blocksize);

     rv = (*cipher)(context, H, &tmp, blocksize, H, blocksize, blocksize);

     if (rv != SECSuccess) {

 	goto loser;

     }

     rv = gcmHash_InitContext(ghash, H, blocksize);

     if (rv != SECSuccess) {

 	goto loser;

     }

     freeHash = PR_TRUE;

     /* fill in the Counter context */

     ctrParams.ulCounterBits = 32;

     PORT_Memset(ctrParams.cb, 0, sizeof(ctrParams.cb));

     if ((blocksize == 16) && (gcmParams->ulIvLen == 12)) {

 	PORT_Memcpy(ctrParams.cb, gcmParams->pIv, gcmParams->ulIvLen);

 	ctrParams.cb[blocksize-1] = 1;

     } else {

 	rv = gcmHash_Update(ghash, gcmParams->pIv, gcmParams->ulIvLen,

 			    blocksize);

 	if (rv != SECSuccess) {

 	    goto loser;

 	}

 	rv = gcmHash_Final(ghash, ctrParams.cb, &tmp, blocksize, blocksize);

 	if (rv != SECSuccess) {

 	    goto loser;

 	}

     }

     rv = CTR_InitContext(&gcm->ctr_context, context, cipher,

 				(unsigned char *)&ctrParams, blocksize);

     if (rv != SECSuccess) {

 	goto loser;

     }

     freeCtr = PR_TRUE;

     /* fill in the gcm structure */

     gcm->tagBits = gcmParams->ulTagBits; /* save for final step */

     /* calculate the final tag key. NOTE: gcm->tagKey is zero to start with.

      * if this assumption changes, we would need to explicitly clear it here */

     rv = CTR_Update(&gcm->ctr_context, gcm->tagKey, &tmp, blocksize,

 		    gcm->tagKey, blocksize, blocksize);

     if (rv != SECSuccess) {

 	goto loser;

     }

     /* finally mix in the AAD data */

     rv = gcmHash_Reset(ghash, gcmParams->pAAD, gcmParams->ulAADLen, blocksize);

     if (rv != SECSuccess) {

 	goto loser;

     }

     return gcm;

 loser:

     if (freeCtr) {

 	CTR_DestroyContext(&gcm->ctr_context, PR_FALSE);

     }

     if (freeHash) {

 	gcmHash_DestroyContext(&gcm->ghash_context, PR_FALSE);

     }

     if (gcm) {

 	PORT_Free(gcm);

     }

     return NULL;

 }

 void

 GCM_DestroyContext(GCMContext *gcm, PRBool freeit)

 {

     /* these two are statically allocated and will be freed when we free

      * gcm. call their destroy functions to free up any locally

      * allocated data (like mp_int's) */

     CTR_DestroyContext(&gcm->ctr_context, PR_FALSE);

     gcmHash_DestroyContext(&gcm->ghash_context, PR_FALSE);

     if (freeit) {

 	PORT_Free(gcm);

     }

 }

 static SECStatus

 gcm_GetTag(GCMContext *gcm, unsigned char *outbuf,

 	unsigned int *outlen, unsigned int maxout,

 	unsigned int blocksize)

 {

     unsigned int tagBytes;

     unsigned int extra;

     unsigned int i;

     SECStatus rv;

     tagBytes = (gcm->tagBits + (PR_BITS_PER_BYTE-1)) / PR_BITS_PER_BYTE;

     extra = tagBytes*PR_BITS_PER_BYTE - gcm->tagBits;

     if (outbuf == NULL) {

 	*outlen = tagBytes;

 	PORT_SetError(SEC_ERROR_OUTPUT_LEN);

 	return SECFailure;

     }

     if (maxout < tagBytes) {

 	*outlen = tagBytes;

 	PORT_SetError(SEC_ERROR_OUTPUT_LEN);

 	return SECFailure;

     }

     maxout = tagBytes;

     rv = gcmHash_Final(&gcm->ghash_context, outbuf, outlen, maxout, blocksize);

     if (rv != SECSuccess) {

 	return SECFailure;

     }

     GCM_TRACE_BLOCK("GHASH=", outbuf, blocksize);

     GCM_TRACE_BLOCK("Y0=", gcm->tagKey, blocksize);

     for (i=0; i < *outlen; i++) {

 	outbuf[i] ^= gcm->tagKey[i];

     }

     GCM_TRACE_BLOCK("Y0=", gcm->tagKey, blocksize);

     GCM_TRACE_BLOCK("T=", outbuf, blocksize);

     /* mask off any extra bits we got */

     if (extra) {

 	outbuf[tagBytes-1] &= ~((1 << extra)-1);

     }

     return SECSuccess;

 }

 /*

  * See The Galois/Counter Mode of Operation, McGrew and Viega.

  *  GCM is basically counter mode with a specific initialization and

  *  built in macing operation.

  */

 SECStatus

 GCM_EncryptUpdate(GCMContext *gcm, unsigned char *outbuf,

 		unsigned int *outlen, unsigned int maxout,

 		const unsigned char *inbuf, unsigned int inlen,

 		unsigned int blocksize)

 {

     SECStatus rv;

     unsigned int tagBytes;

     unsigned int len;

     tagBytes = (gcm->tagBits + (PR_BITS_PER_BYTE-1)) / PR_BITS_PER_BYTE;

     if (UINT_MAX - inlen < tagBytes) {

 	PORT_SetError(SEC_ERROR_INPUT_LEN);

 	return SECFailure;

     }

     if (maxout < inlen + tagBytes) {

 	*outlen = inlen + tagBytes;

 	PORT_SetError(SEC_ERROR_OUTPUT_LEN);

 	return SECFailure;

     }

     rv = CTR_Update(&gcm->ctr_context, outbuf, outlen, maxout,

 			inbuf, inlen, blocksize);

     if (rv != SECSuccess) {

 	return SECFailure;

     }

     rv = gcmHash_Update(&gcm->ghash_context, outbuf, *outlen, blocksize);

     if (rv != SECSuccess) {

 	PORT_Memset(outbuf, 0, *outlen); /* clear the output buffer */

 	*outlen = 0;

 	return SECFailure;

     }

     rv = gcm_GetTag(gcm, outbuf + *outlen, &len, maxout - *outlen, blocksize);

     if (rv != SECSuccess) {

 	PORT_Memset(outbuf, 0, *outlen); /* clear the output buffer */

 	*outlen = 0;

 	return SECFailure;

     };

     *outlen += len;

     return SECSuccess;

 }

 /*

  * See The Galois/Counter Mode of Operation, McGrew and Viega.

  *  GCM is basically counter mode with a specific initialization and

  *  built in macing operation. NOTE: the only difference between Encrypt

  *  and Decrypt is when we calculate the mac. That is because the mac must

  *  always be calculated on the cipher text, not the plain text, so for

  *  encrypt, we do the CTR update first and for decrypt we do the mac first.

  */

 SECStatus

 GCM_DecryptUpdate(GCMContext *gcm, unsigned char *outbuf,

 		unsigned int *outlen, unsigned  int maxout,

 		const unsigned char *inbuf, unsigned int inlen,

 		unsigned int blocksize)

 {

     SECStatus rv;

     unsigned int tagBytes;

     unsigned char tag[MAX_BLOCK_SIZE];

     const unsigned char *intag;

     unsigned int len;

     tagBytes = (gcm->tagBits + (PR_BITS_PER_BYTE-1)) / PR_BITS_PER_BYTE;

     /* get the authentication block */

     if (inlen < tagBytes) {

 	PORT_SetError(SEC_ERROR_INPUT_LEN);

 	return SECFailure;

     }

     inlen -= tagBytes;

     intag = inbuf + inlen;

     /* verify the block */

     rv = gcmHash_Update(&gcm->ghash_context, inbuf, inlen, blocksize);

     if (rv != SECSuccess) {

 	return SECFailure;

     }

     rv = gcm_GetTag(gcm, tag, &len, blocksize, blocksize);

     if (rv != SECSuccess) {

 	return SECFailure;

     }

     /* Don't decrypt if we can't authenticate the encrypted data!

      * This assumes that if tagBits is not a multiple of 8, intag will

      * preserve the masked off missing bits.  */

     if (NSS_SecureMemcmp(tag, intag, tagBytes) != 0) {

 	/* force a CKR_ENCRYPTED_DATA_INVALID error at in softoken */

 	PORT_SetError(SEC_ERROR_BAD_DATA);

 	return SECFailure;

     }

     /* finish the decryption */

     return CTR_Update(&gcm->ctr_context, outbuf, outlen, maxout,

 			  inbuf, inlen, blocksize);

 }