Add support for OCB mode as per RFC7253

Reviewed-by: NTim Hudson <tjh@openssl.org>

crypto/modes/Makefile

@@ -22,9 +22,9 @@ APPS=
 
 LIB=$(TOP)/libcrypto.a
 LIBSRC= cbc128.c ctr128.c cts128.c cfb128.c ofb128.c gcm128.c \
-	ccm128.c xts128.c wrap128.c
+	ccm128.c xts128.c wrap128.c ocb128.c
 LIBOBJ= cbc128.o ctr128.o cts128.o cfb128.o ofb128.o gcm128.o \
-	ccm128.o xts128.o wrap128.o $(MODES_ASM_OBJ)
+	ccm128.o xts128.o wrap128.o ocb128.o $(MODES_ASM_OBJ)
 
 SRC= $(LIBSRC)
 
@@ -138,6 +138,11 @@ gcm128.o: ../../include/openssl/modes.h ../../include/openssl/opensslconf.h
 gcm128.o: ../../include/openssl/opensslv.h ../../include/openssl/ossl_typ.h
 gcm128.o: ../../include/openssl/safestack.h ../../include/openssl/stack.h
 gcm128.o: ../../include/openssl/symhacks.h gcm128.c modes_lcl.h
+ocb128.o: ../../include/openssl/crypto.h ../../include/openssl/e_os2.h
+ocb128.o: ../../include/openssl/modes.h ../../include/openssl/opensslconf.h
+ocb128.o: ../../include/openssl/opensslv.h ../../include/openssl/ossl_typ.h
+ocb128.o: ../../include/openssl/safestack.h ../../include/openssl/stack.h
+ocb128.o: ../../include/openssl/symhacks.h modes_lcl.h ocb128.c
 ofb128.o: ../../include/openssl/crypto.h ../../include/openssl/e_os2.h
 ofb128.o: ../../include/openssl/modes.h ../../include/openssl/opensslconf.h
 ofb128.o: ../../include/openssl/opensslv.h ../../include/openssl/ossl_typ.h

crypto/modes/modes.h

@@ -137,6 +137,7 @@ typedef struct xts128_context XTS128_CONTEXT;
 int CRYPTO_xts128_encrypt(const XTS128_CONTEXT *ctx, const unsigned char iv[16],
 	const unsigned char *inp, unsigned char *out, size_t len, int enc);
 
+
 size_t CRYPTO_128_wrap(void *key, const unsigned char *iv,
 		unsigned char *out,
 		const unsigned char *in, size_t inlen, block128_f block);
@@ -150,6 +151,28 @@ size_t CRYPTO_128_wrap_pad(void *key, const unsigned char *icv,
 size_t CRYPTO_128_unwrap_pad(void *key, const unsigned char *icv,
 		unsigned char *out,
 		const unsigned char *in, size_t inlen, block128_f block);
+
+typedef struct ocb128_context OCB128_CONTEXT;
+
+OCB128_CONTEXT *CRYPTO_ocb128_new(void *keyenc, void *keydec, block128_f encrypt, block128_f decrypt);
+int CRYPTO_ocb128_init(OCB128_CONTEXT *ctx,void *keyenc, void *keydec,block128_f encrypt,block128_f decrypt);
+int CRYPTO_ocb128_copy_ctx(OCB128_CONTEXT *dest, OCB128_CONTEXT *src,
+	void *keyenc, void *keydec);
+int CRYPTO_ocb128_setiv(OCB128_CONTEXT *ctx, const unsigned char *iv,
+			size_t len, size_t taglen);
+int CRYPTO_ocb128_aad(OCB128_CONTEXT *ctx, const unsigned char *aad,
+			size_t len);
+int CRYPTO_ocb128_encrypt(OCB128_CONTEXT *ctx,
+			const unsigned char *in, unsigned char *out,
+			size_t len);
+int CRYPTO_ocb128_decrypt(OCB128_CONTEXT *ctx,
+			const unsigned char *in, unsigned char *out,
+			size_t len);
+int CRYPTO_ocb128_finish(OCB128_CONTEXT *ctx,const unsigned char *tag,
+			size_t len);
+int CRYPTO_ocb128_tag(OCB128_CONTEXT *ctx, unsigned char *tag, size_t len);
+void CRYPTO_ocb128_cleanup(OCB128_CONTEXT *ctx);
+
 #ifdef  __cplusplus
 }
 #endif

crypto/modes/modes_lcl.h

@@ -136,3 +136,42 @@ struct ccm128_context {
 	void *key;
 };
 
+#ifdef STRICT_ALIGNMENT
+typedef struct {
+    unsigned char a[16];
+} OCB_BLOCK;
+# define ocb_block16_xor(in1,in2,out) \
+    ocb_block_xor((in1)->a,(in2)->a,16,(out)->a)
+#else
+typedef struct {
+    u64 a;
+    u64 b;
+} OCB_BLOCK;
+# define ocb_block16_xor(in1,in2,out) \
+    (out)->a=(in1)->a^(in2)->a; (out)->b=(in1)->b^(in2)->b;
+#endif
+
+struct ocb128_context {
+	/* Need both encrypt and decrypt key schedules for decryption */
+	block128_f encrypt;
+	block128_f decrypt;
+	void *keyenc;
+	void *keydec;
+
+	/* Key dependent variables. Can be reused if key remains the same */
+	size_t l_index;
+	size_t max_l_index;
+	OCB_BLOCK l_star;
+	OCB_BLOCK l_dollar;
+	OCB_BLOCK *l;
+
+	/* Must be reset for each session */
+	u64 blocks_hashed;
+	u64 blocks_processed;
+	OCB_BLOCK tag;
+	OCB_BLOCK offset_aad;
+	OCB_BLOCK sum;
+	OCB_BLOCK offset;
+	OCB_BLOCK checksum;
+
+};

crypto/modes/ocb128.c

+/* ====================================================================
+ * Copyright (c) 2014 The OpenSSL Project.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * 3. All advertising materials mentioning features or use of this
+ *    software must display the following acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit. (http://www.openssl.org/)"
+ *
+ * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to
+ *    endorse or promote products derived from this software without
+ *    prior written permission. For written permission, please contact
+ *    openssl-core@openssl.org.
+ *
+ * 5. Products derived from this software may not be called "OpenSSL"
+ *    nor may "OpenSSL" appear in their names without prior written
+ *    permission of the OpenSSL Project.
+ *
+ * 6. Redistributions of any form whatsoever must retain the following
+ *    acknowledgment:
+ *    "This product includes software developed by the OpenSSL Project
+ *    for use in the OpenSSL Toolkit (http://www.openssl.org/)"
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY
+ * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE OpenSSL PROJECT OR
+ * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
+ * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
+ * OF THE POSSIBILITY OF SUCH DAMAGE.
+ * ====================================================================
+ */
+
+#include <string.h>
+#include <openssl/crypto.h>
+#include "modes_lcl.h"
+
+union ublock {
+    unsigned char *chrblk;
+    OCB_BLOCK *ocbblk;
+};
+
+/*
+ * Calculate the number of binary trailing zero's in any given number
+ */
+static u32 ocb_ntz(u64 n)
+{
+    u32 cnt = 0;
+
+    /*
+     * We do a right-to-left simple sequential search. This is surprisingly
+     * efficient as the distribution of trailing zeros is not uniform,
+     * e.g. the number of possible inputs with no trailing zeros is equal to
+     * the number with 1 or more; the number with exactly 1 is equal to the
+     * number with 2 or more, etc. Checking the last two bits covers 75% of
+     * all numbers. Checking the last three covers 87.5%
+     */
+    while (!(n & 1)) {
+        n >>= 1;
+        cnt++;
+    }
+    return cnt;
+}
+
+/*
+ * Shift a block of 16 bytes left by shift bits
+ */
+static void ocb_block_lshift(OCB_BLOCK *in, size_t shift, OCB_BLOCK *out)
+{
+    unsigned char shift_mask;
+    int i;
+    unsigned char mask[15];
+    union ublock locin;
+    union ublock locout;
+    
+    locin.ocbblk = in;
+    locout.ocbblk = out;
+    
+    shift_mask = 0xff;
+    shift_mask <<= (8 - shift);
+    for (i = 15; i >= 0; i--) {
+        if (i > 0) {
+            mask[i - 1] = locin.chrblk[i] & shift_mask;
+            mask[i - 1] >>= 8 - shift;
+        }
+        locout.chrblk[i] = locin.chrblk[i] << shift;
+
+        if (i != 15) {
+            locout.chrblk[i] ^= mask[i];
+        }
+    }
+}
+
+/*
+ * Perform a "double" operation as per OCB spec
+ */
+static void ocb_double(OCB_BLOCK *in, OCB_BLOCK *out)
+{
+    unsigned char mask;
+    union ublock locin;
+    union ublock locout;
+    
+    locin.ocbblk = in;
+    locout.ocbblk = out;
+
+    /*
+     * Calculate the mask based on the most significant bit. There are more
+     * efficient ways to do this - but this way is constant time
+     */
+    mask = locin.chrblk[0] & 0x80;
+    mask >>= 7;
+    mask *= 135;
+
+    ocb_block_lshift(in, 1, out);
+
+    locout.chrblk[15] ^= mask;
+}
+
+/*
+ * Perform an xor on in1 and in2 - each of len bytes. Store result in out
+ */
+static void ocb_block_xor(const unsigned char *in1,
+                          const unsigned char *in2, size_t len,
+                          unsigned char *out)
+{
+    size_t i;
+    for (i = 0; i < len; i++) {
+        out[i] = in1[i] ^ in2[i];
+    }
+}
+
+/*
+ * Lookup L_index in our lookup table. If we haven't already got it we need to
+ * calculate it
+ */
+static OCB_BLOCK *ocb_lookup_l(OCB128_CONTEXT * ctx, size_t index)
+{
+    if (index <= ctx->l_index) {
+        return ctx->l + index;
+    }
+
+    /* We don't have it - so calculate it */
+    ctx->l_index++;
+    if (ctx->l_index == ctx->max_l_index) {
+        ctx->max_l_index *= 2;
+        ctx->l = OPENSSL_realloc(ctx->l, ctx->max_l_index * sizeof(OCB_BLOCK));
+        if (!ctx->l)
+            return NULL;
+    }
+    ocb_double(ctx->l + (index - 1), ctx->l + index);
+
+    return ctx->l + index;
+}
+
+/*
+ * Encrypt a block from |in| and store the result in |out|
+ */
+static void ocb_encrypt(OCB128_CONTEXT *ctx, OCB_BLOCK *in, OCB_BLOCK *out, void *keyenc)
+{
+    union ublock locin;
+    union ublock locout;
+    
+    locin.ocbblk = in;
+    locout.ocbblk = out;
+
+    ctx->encrypt(locin.chrblk, locout.chrblk, keyenc);
+}
+
+/*
+ * Decrypt a block from |in| and store the result in |out|
+ */
+static void ocb_decrypt(OCB128_CONTEXT *ctx, OCB_BLOCK *in, OCB_BLOCK *out, void *keydec)
+{
+    union ublock locin;
+    union ublock locout;
+    
+    locin.ocbblk = in;
+    locout.ocbblk = out;
+
+    ctx->decrypt(locin.chrblk, locout.chrblk, keydec);
+}
+
+/*
+ * Create a new OCB128_CONTEXT
+ */
+OCB128_CONTEXT *CRYPTO_ocb128_new(void *keyenc, void *keydec,
+                                  block128_f encrypt, block128_f decrypt)
+{
+    OCB128_CONTEXT *octx;
+    int ret;
+
+    if ((octx = (OCB128_CONTEXT *) OPENSSL_malloc(sizeof(OCB128_CONTEXT)))) {
+        ret = CRYPTO_ocb128_init(octx, keyenc, keydec, encrypt, decrypt);
+        if (ret)
+            return octx;
+        OPENSSL_free(octx);
+    }
+
+    return NULL;
+}
+
+/*
+ * Initialise an existing OCB128_CONTEXT
+ */
+int CRYPTO_ocb128_init(OCB128_CONTEXT *ctx, void *keyenc, void *keydec,
+                       block128_f encrypt, block128_f decrypt)
+{
+    /* Clear everything to NULLs */
+    memset(ctx, 0, sizeof(*ctx));
+
+    ctx->l_index = 0;
+    ctx->max_l_index = 1;
+    ctx->l = OPENSSL_malloc(ctx->max_l_index * 16);
+    if (!ctx->l)
+        return 0;
+
+    /*
+     * We set both the encryption and decryption key schedules - decryption
+     * needs both. Don't really need decryption schedule if only doing
+     * encryption - but it simplifies things to take it anyway
+     */
+    ctx->encrypt = encrypt;
+    ctx->decrypt = decrypt;
+    ctx->keyenc = keyenc;
+    ctx->keydec = keydec;
+
+    /* L_* = ENCIPHER(K, zeros(128)) */
+    ocb_encrypt(ctx, &ctx->l_star, &ctx->l_star, ctx->keyenc);
+
+    /* L_$ = double(L_*) */
+    ocb_double(&ctx->l_star, &ctx->l_dollar);
+
+    /* L_0 = double(L_$) */
+    ocb_double(&ctx->l_dollar, ctx->l);
+
+    return 1;
+}
+
+/*
+ * Copy an OCB128_CONTEXT object
+ */
+int CRYPTO_ocb128_copy_ctx(OCB128_CONTEXT * dest, OCB128_CONTEXT * src,
+                           void *keyenc, void *keydec)
+{
+    memcpy(dest, src, sizeof(OCB128_CONTEXT));
+    if (keyenc)
+        dest->keyenc = keyenc;
+    if (keydec)
+        dest->keydec = keydec;
+    if (src->l) {
+        dest->l = OPENSSL_malloc(src->max_l_index * 16);
+        if (!dest->l)
+            return 0;
+        memcpy(dest->l, src->l, (src->l_index + 1) * 16);
+    }
+    return 1;
+}
+
+/*
+ * Set the IV to be used for this operation. Must be 1 - 15 bytes.
+ */
+int CRYPTO_ocb128_setiv(OCB128_CONTEXT * ctx, const unsigned char *iv,
+                        size_t len, size_t taglen)
+{
+    unsigned char ktop[16], tmp[16], mask;
+    unsigned char stretch[24], nonce[16];
+    size_t bottom, shift;
+    union ublock offset;
+    
+    offset.ocbblk = &ctx->offset;
+
+    /*
+     * Spec says IV is 120 bits or fewer - it allows non byte aligned lengths.
+     * We don't support  this at this stage
+     */
+    if ((len > 15) || (len < 1) || (taglen > 16) || (taglen < 1)) {
+        return -1;
+    }
+
+    /* Nonce = num2str(TAGLEN mod 128,7) || zeros(120-bitlen(N)) || 1 || N */
+    nonce[0] = ((taglen * 8) % 128) << 1;
+    memset(nonce + 1, 0, 15);
+    memcpy(nonce + 16 - len, iv, len);
+    nonce[15 - len] |= 1;
+
+    /* Ktop = ENCIPHER(K, Nonce[1..122] || zeros(6)) */
+    memcpy(tmp, nonce, 16);
+    tmp[15] &= 0xc0;
+    ctx->encrypt(tmp, ktop, ctx->keyenc);
+
+    /* Stretch = Ktop || (Ktop[1..64] xor Ktop[9..72]) */
+    memcpy(stretch, ktop, 16);
+    ocb_block_xor(ktop, ktop + 1, 8, stretch + 16);
+
+    /* bottom = str2num(Nonce[123..128]) */
+    bottom = nonce[15] & 0x3f;
+
+    /* Offset_0 = Stretch[1+bottom..128+bottom] */
+    shift = bottom % 8;
+    ocb_block_lshift((OCB_BLOCK *)(stretch + (bottom / 8)), shift, &ctx->offset);
+    mask = 0xff;
+    mask <<= 8 - shift;
+    offset.chrblk[15] |= (*(stretch + (bottom / 8) + 16) & mask) >> (8 - shift);
+
+    return 1;
+}
+
+/*
+ * Provide any AAD. This can be called multiple times. Only the final time can
+ * have a partial block
+ */
+int CRYPTO_ocb128_aad(OCB128_CONTEXT * ctx, const unsigned char *aad,
+                      size_t len)
+{
+    u64 all_num_blocks, num_blocks;
+    u64 i;
+    OCB_BLOCK tmp1;
+    OCB_BLOCK tmp2;
+    int last_len;
+    
+    /* Calculate the number of blocks of AAD provided now, and so far */
+    num_blocks = len / 16;
+    all_num_blocks = num_blocks + ctx->blocks_hashed;
+
+    /* Loop through all full blocks of AAD */
+    for (i = ctx->blocks_hashed + 1; i <= all_num_blocks; i++) {
+        OCB_BLOCK *lookup;
+        OCB_BLOCK *aad_block;
+        
+        /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
+        lookup = ocb_lookup_l(ctx, ocb_ntz(i));
+        if (!lookup)
+            return 0;
+        ocb_block16_xor(&ctx->offset_aad, lookup, &ctx->offset_aad);
+
+        /* Sum_i = Sum_{i-1} xor ENCIPHER(K, A_i xor Offset_i) */
+        aad_block = (OCB_BLOCK *) (aad + ((i - ctx->blocks_hashed - 1) * 16));
+        ocb_block16_xor(&ctx->offset_aad, aad_block, &tmp1);
+        ocb_encrypt(ctx, &tmp1, &tmp2, ctx->keyenc);
+        ocb_block16_xor(&ctx->sum, &tmp2, &ctx->sum);
+    }
+
+    /*
+     * Check if we have any partial blocks left over. This is only valid in the
+     * last call to this function
+     */
+    last_len = len % 16;
+
+    if (last_len > 0) {
+        /* Offset_* = Offset_m xor L_* */
+        ocb_block16_xor(&ctx->offset_aad, &ctx->l_star, &ctx->offset_aad);
+
+        /* CipherInput = (A_* || 1 || zeros(127-bitlen(A_*))) xor Offset_* */
+        memset((void *)&tmp1, 0, 16);
+        memcpy((void *)&tmp1, aad + (num_blocks * 16), last_len);
+        ((unsigned char *)&tmp1)[last_len] = 0x80;
+        ocb_block16_xor(&ctx->offset_aad, &tmp1, &tmp2);
+
+        /* Sum = Sum_m xor ENCIPHER(K, CipherInput) */
+        ocb_encrypt(ctx, &tmp2, &tmp1, ctx->keyenc);
+        ocb_block16_xor(&ctx->sum, &tmp1, &ctx->sum);
+    }
+
+    ctx->blocks_hashed = all_num_blocks;
+
+    return 1;
+}
+
+/*
+ * Provide any data to be encrypted. This can be called multiple times. Only
+ * the final time can have a partial block
+ */
+int CRYPTO_ocb128_encrypt(OCB128_CONTEXT * ctx,
+                          const unsigned char *in, unsigned char *out,
+                          size_t len)
+{
+    u64 i;
+    u64 all_num_blocks, num_blocks;
+    OCB_BLOCK tmp1;
+    OCB_BLOCK tmp2;
+    OCB_BLOCK pad;
+    int last_len;
+
+    /*
+     * Calculate the number of blocks of data to be encrypted provided now, and
+     * so far
+     */
+    num_blocks = len / 16;
+    all_num_blocks = num_blocks + ctx->blocks_processed;
+
+    /* Loop through all full blocks to be encrypted */
+    for (i = ctx->blocks_processed + 1; i <= all_num_blocks; i++) {
+        OCB_BLOCK *lookup;
+        OCB_BLOCK *inblock;
+        OCB_BLOCK *outblock;
+        
+        /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
+        lookup = ocb_lookup_l(ctx, ocb_ntz(i));
+        if (!lookup)
+            return 0;
+        ocb_block16_xor(&ctx->offset, lookup, &ctx->offset);
+
+        /* C_i = Offset_i xor ENCIPHER(K, P_i xor Offset_i) */
+        inblock = (OCB_BLOCK *) (in + ((i - ctx->blocks_processed - 1) * 16));
+        ocb_block16_xor(&ctx->offset, inblock, &tmp1);
+        ocb_encrypt(ctx, &tmp1, &tmp2, ctx->keyenc);
+        outblock =
+            (OCB_BLOCK *) (out + ((i - ctx->blocks_processed - 1) * 16));
+        ocb_block16_xor(&ctx->offset, &tmp2, outblock);
+
+        /* Checksum_i = Checksum_{i-1} xor P_i */
+        ocb_block16_xor(&ctx->checksum, inblock, &ctx->checksum);
+    }
+
+    /*
+     * Check if we have any partial blocks left over. This is only valid in the
+     * last call to this function
+     */
+    last_len = len % 16;
+
+    if (last_len > 0) {
+        /* Offset_* = Offset_m xor L_* */
+        ocb_block16_xor(&ctx->offset, &ctx->l_star, &ctx->offset);
+
+        /* Pad = ENCIPHER(K, Offset_*) */
+        ocb_encrypt(ctx, &ctx->offset, &pad, ctx->keyenc);
+
+        /* C_* = P_* xor Pad[1..bitlen(P_*)] */
+        ocb_block_xor(in + (len / 16) * 16, (unsigned char *)&pad, last_len,
+                      out + (num_blocks * 16));
+
+        /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
+        memset((void *)&tmp1, 0, 16);
+        memcpy((void *)&tmp1, in + (len / 16) * 16, last_len);
+        ((unsigned char *)(&tmp1))[last_len] = 0x80;
+        ocb_block16_xor(&ctx->checksum, &tmp1, &ctx->checksum);
+    }
+
+    ctx->blocks_processed = all_num_blocks;
+
+    return 1;
+}
+
+/*
+ * Provide any data to be decrypted. This can be called multiple times. Only
+ * the final time can have a partial block
+ */
+int CRYPTO_ocb128_decrypt(OCB128_CONTEXT * ctx,
+                          const unsigned char *in, unsigned char *out,
+                          size_t len)
+{
+    u64 i;
+    u64 all_num_blocks, num_blocks;
+    OCB_BLOCK tmp1;
+    OCB_BLOCK tmp2;
+    OCB_BLOCK pad;
+    int last_len;
+    /*
+     * Calculate the number of blocks of data to be decrypted provided now, and
+     * so far
+     */
+    num_blocks = len / 16;
+    all_num_blocks = num_blocks + ctx->blocks_processed;
+
+    /* Loop through all full blocks to be decrypted */
+    for (i = ctx->blocks_processed + 1; i <= all_num_blocks; i++) {
+        OCB_BLOCK *inblock;
+        OCB_BLOCK *outblock;
+        
+        /* Offset_i = Offset_{i-1} xor L_{ntz(i)} */
+        OCB_BLOCK *lookup = ocb_lookup_l(ctx, ocb_ntz(i));
+        if (!lookup)
+            return 0;
+        ocb_block16_xor(&ctx->offset, lookup, &ctx->offset);
+
+        /* P_i = Offset_i xor DECIPHER(K, C_i xor Offset_i) */
+        inblock = (OCB_BLOCK *) (in + ((i - ctx->blocks_processed - 1) * 16));
+        ocb_block16_xor(&ctx->offset, inblock, &tmp1);
+        ocb_decrypt(ctx, &tmp1, &tmp2, ctx->keydec);
+        outblock = (OCB_BLOCK *) (out + ((i - ctx->blocks_processed - 1) * 16));
+        ocb_block16_xor(&ctx->offset, &tmp2, outblock);
+
+        /* Checksum_i = Checksum_{i-1} xor P_i */
+        ocb_block16_xor(&ctx->checksum, outblock, &ctx->checksum);
+    }
+
+    /*
+     * Check if we have any partial blocks left over. This is only valid in the
+     * last call to this function
+     */
+    last_len = len % 16;
+
+    if (last_len > 0) {
+        /* Offset_* = Offset_m xor L_* */
+        ocb_block16_xor(&ctx->offset, &ctx->l_star, &ctx->offset);
+
+        /* Pad = ENCIPHER(K, Offset_*) */
+        ocb_encrypt(ctx, &ctx->offset, &pad, ctx->keyenc);
+
+        /* P_* = C_* xor Pad[1..bitlen(C_*)] */
+        ocb_block_xor(in + (len / 16) * 16, (unsigned char *)&pad, last_len,
+                      out + (num_blocks * 16));
+
+        /* Checksum_* = Checksum_m xor (P_* || 1 || zeros(127-bitlen(P_*))) */
+        memset((void *)&tmp1, 0, 16);
+        memcpy((void *)&tmp1, out + (len / 16) * 16, last_len);
+        ((unsigned char *)(&tmp1))[last_len] = 0x80;
+        ocb_block16_xor(&ctx->checksum, &tmp1, &ctx->checksum);
+    }
+
+    ctx->blocks_processed = all_num_blocks;
+
+    return 1;
+}
+
+/*
+ * Calculate the tag and verify it against the supplied tag
+ */
+int CRYPTO_ocb128_finish(OCB128_CONTEXT * ctx, const unsigned char *tag,
+                         size_t len)
+{
+    OCB_BLOCK tmp1, tmp2;
+
+    /*Tag = ENCIPHER(K, Checksum_* xor Offset_* xor L_$) xor HASH(K,A) */
+    ocb_block16_xor(&ctx->checksum, &ctx->offset, &tmp1);
+    ocb_block16_xor(&tmp1, &ctx->l_dollar, &tmp2);
+    ocb_encrypt(ctx, &tmp2, &tmp1, ctx->keyenc);
+    ocb_block16_xor(&tmp1, &ctx->sum, &ctx->tag);
+
+    if (len > 16 || len < 1) {
+        return -1;
+    }
+
+    /* Compare the tag if we've been given one */
+    if (tag)
+        return CRYPTO_memcmp(&ctx->tag, tag, len);
+    else
+        return -1;
+}
+
+/*
+ * Retrieve the calculated tag
+ */
+int CRYPTO_ocb128_tag(OCB128_CONTEXT * ctx, unsigned char *tag, size_t len)
+{
+    if (len > 16 || len < 1) {
+        return -1;
+    }
+
+    /* Calculate the tag */
+    CRYPTO_ocb128_finish(ctx, NULL, 0);
+
+    /* Copy the tag into the supplied buffer */
+    memcpy(tag, &ctx->tag, len);
+
+    return 1;
+}
+
+/*
+ * Release all resources
+ */
+void CRYPTO_ocb128_cleanup(OCB128_CONTEXT * ctx)
+{
+    if (ctx) {
+        if (ctx->l) {
+            OPENSSL_cleanse(ctx->l, ctx->max_l_index * 16);
+            OPENSSL_free(ctx->l);
+        }
+        OPENSSL_cleanse(ctx, sizeof(*ctx));
+    }
+}