The Tor Browser: security/nss/lib/freebl/gcm.c@b8a032363ba2 (annotated)

security/nss/lib/freebl/gcm.c@b8a032363ba2 (annotated)

security/nss/lib/freebl/gcm.c

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* 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] = {
 x00, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0,
 x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0,
 x08, 0x88, 0x48, 0xc8, 0x28, 0xa8, 0x68, 0xe8,
 x18, 0x98, 0x58, 0xd8, 0x38, 0xb8, 0x78, 0xf8,
 x04, 0x84, 0x44, 0xc4, 0x24, 0xa4, 0x64, 0xe4,
 x14, 0x94, 0x54, 0xd4, 0x34, 0xb4, 0x74, 0xf4,
 x0c, 0x8c, 0x4c, 0xcc, 0x2c, 0xac, 0x6c, 0xec,
 x1c, 0x9c, 0x5c, 0xdc, 0x3c, 0xbc, 0x7c, 0xfc,
 x02, 0x82, 0x42, 0xc2, 0x22, 0xa2, 0x62, 0xe2,
 x12, 0x92, 0x52, 0xd2, 0x32, 0xb2, 0x72, 0xf2,
 x0a, 0x8a, 0x4a, 0xca, 0x2a, 0xaa, 0x6a, 0xea,
 x1a, 0x9a, 0x5a, 0xda, 0x3a, 0xba, 0x7a, 0xfa,
 x06, 0x86, 0x46, 0xc6, 0x26, 0xa6, 0x66, 0xe6,
 x16, 0x96, 0x56, 0xd6, 0x36, 0xb6, 0x76, 0xf6,
 x0e, 0x8e, 0x4e, 0xce, 0x2e, 0xae, 0x6e, 0xee,
 x1e, 0x9e, 0x5e, 0xde, 0x3e, 0xbe, 0x7e, 0xfe,
 x01, 0x81, 0x41, 0xc1, 0x21, 0xa1, 0x61, 0xe1,
 x11, 0x91, 0x51, 0xd1, 0x31, 0xb1, 0x71, 0xf1,
 x09, 0x89, 0x49, 0xc9, 0x29, 0xa9, 0x69, 0xe9,
 x19, 0x99, 0x59, 0xd9, 0x39, 0xb9, 0x79, 0xf9,
 x05, 0x85, 0x45, 0xc5, 0x25, 0xa5, 0x65, 0xe5,
 x15, 0x95, 0x55, 0xd5, 0x35, 0xb5, 0x75, 0xf5,
 x0d, 0x8d, 0x4d, 0xcd, 0x2d, 0xad, 0x6d, 0xed,
 x1d, 0x9d, 0x5d, 0xdd, 0x3d, 0xbd, 0x7d, 0xfd,
 x03, 0x83, 0x43, 0xc3, 0x23, 0xa3, 0x63, 0xe3,
 x13, 0x93, 0x53, 0xd3, 0x33, 0xb3, 0x73, 0xf3,
 x0b, 0x8b, 0x4b, 0xcb, 0x2b, 0xab, 0x6b, 0xeb,
 x1b, 0x9b, 0x5b, 0xdb, 0x3b, 0xbb, 0x7b, 0xfb,
 x07, 0x87, 0x47, 0xc7, 0x27, 0xa7, 0x67, 0xe7,
 x17, 0x97, 0x57, 0xd7, 0x37, 0xb7, 0x77, 0xf7,
 x0f, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef,
 x1f, 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);
 }

The Tor Browser / annotate

security/nss/lib/freebl/gcm.c@b8a032363ba2 (annotated)

security/nss/lib/freebl/gcm.c