FreeBSD/Linux Kernel Cross Reference
sys/crypto/aesni/aesni_ccm.c

     /*-
      * Copyright (c) 2014 The FreeBSD Foundation
      * Copyright (c) 2018 iXsystems, Inc
      * All rights reserved.
      *
      * This software was developed by John-Mark Gurney under
      * the sponsorship of the FreeBSD Foundation and
      * Rubicon Communications, LLC (Netgate).
      * 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.
     *
     * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
     * ANY EXPRESS 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 AUTHOR OR 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.
     *
     *
     *      $FreeBSD$
     *
     * This file implements AES-CCM+CBC-MAC, as described
     * at https://tools.ietf.org/html/rfc3610, using Intel's
     * AES-NI instructions.
     *
     */
    
    #include <sys/types.h>
    #include <sys/endian.h>
    #include <sys/param.h>
    
    #include <sys/systm.h>
    #include <crypto/aesni/aesni.h>
    #include <crypto/aesni/aesni_os.h>
    #include <crypto/aesni/aesencdec.h>
    #define AESNI_ENC(d, k, nr)     aesni_enc(nr-1, (const __m128i*)k, d)
    
    #include <wmmintrin.h>
    #include <emmintrin.h>
    #include <smmintrin.h>
    
    /*
     * Encrypt a single 128-bit block after
     * doing an xor.  This is also used to
     * decrypt (yay symmetric encryption).
     */
    static inline __m128i
    xor_and_encrypt(__m128i a, __m128i b, const unsigned char *k, int nr)
    {
            __m128i retval = _mm_xor_si128(a, b);
    
            retval = AESNI_ENC(retval, k, nr);
            return (retval);
    }
    
    /*
     * Put value at the end of block, starting at offset.
     * (This goes backwards, putting bytes in *until* it
     * reaches offset.)
     */
    static void
    append_int(size_t value, __m128i *block, size_t offset)
    {
            int indx = sizeof(*block) - 1;
            uint8_t *bp = (uint8_t*)block;
    
            while (indx > (sizeof(*block) - offset)) {
                    bp[indx] = value & 0xff;
                    indx--;
                    value >>= 8;
            }
    }
    
    /*
     * Start the CBC-MAC process.  This handles the auth data.
     */
    static __m128i
    cbc_mac_start(const unsigned char *auth_data, size_t auth_len,
                 const unsigned char *nonce, size_t nonce_len,
                 const unsigned char *key, int nr,
                 size_t data_len, size_t tag_len)
    {
            __m128i cbc_block, staging_block;
            uint8_t *byte_ptr;
            /* This defines where the message length goes */
            int L = sizeof(__m128i) - 1 - nonce_len;
    
            /*
            * Set up B0 here.  This has the flags byte,
            * followed by the nonce, followed by the
            * length of the message.
            */
           cbc_block = _mm_setzero_si128();
           byte_ptr = (uint8_t*)&cbc_block;
           byte_ptr[0] = ((auth_len > 0) ? 1 : 0) * 64 |
                   (((tag_len - 2) / 2) * 8) |
                   (L - 1);
           bcopy(nonce, byte_ptr + 1, nonce_len);
           append_int(data_len, &cbc_block, L+1);
           cbc_block = AESNI_ENC(cbc_block, key, nr);
   
           if (auth_len != 0) {
                   /*
                    * We need to start by appending the length descriptor.
                    */
                   uint32_t auth_amt;
                   size_t copy_amt;
                   const uint8_t *auth_ptr = auth_data;
   
                   staging_block = _mm_setzero_si128();
   
                   /*
                    * The current OCF calling convention means that
                    * there can never be more than 4g of authentication
                    * data, so we don't handle the 0xffff case.
                    */
                   KASSERT(auth_len < (1ULL << 32),
                       ("%s: auth_len (%zu) larger than 4GB",
                           __FUNCTION__, auth_len));
   
                   if (auth_len < ((1 << 16) - (1 << 8))) {
                           /*
                            * If the auth data length is less than
                            * 0xff00, we don't need to encode a length
                            * specifier, just the length of the auth
                            * data.
                            */
                           be16enc(&staging_block, auth_len);
                           auth_amt = 2;
                   } else if (auth_len < (1ULL << 32)) {
                           /*
                            * Two bytes for the length prefix, and then
                            * four bytes for the length.  This makes a total
                            * of 6 bytes to describe the auth data length.
                            */
                           be16enc(&staging_block, 0xfffe);
                           be32enc((char*)&staging_block + 2, auth_len);
                           auth_amt = 6;
                   } else
                           panic("%s: auth len too large", __FUNCTION__);
   
                   /*
                    * Need to copy abytes into blocks.  The first block is
                    * already partially filled, by auth_amt, so we need
                    * to handle that.  The last block needs to be zero padded.
                    */
                   copy_amt = MIN(auth_len,
                       sizeof(staging_block) - auth_amt);
                   byte_ptr = (uint8_t*)&staging_block;
                   bcopy(auth_ptr, &byte_ptr[auth_amt], copy_amt);
                   auth_ptr += copy_amt;
   
                   cbc_block = xor_and_encrypt(cbc_block, staging_block, key, nr);
                   
                   while (auth_ptr < auth_data + auth_len) {
                           copy_amt = MIN((auth_data + auth_len) - auth_ptr,
                               sizeof(staging_block));
                           if (copy_amt < sizeof(staging_block))
                                   bzero(&staging_block, sizeof(staging_block));
                           bcopy(auth_ptr, &staging_block, copy_amt);
                           cbc_block = xor_and_encrypt(cbc_block, staging_block,
                               key, nr);
                           auth_ptr += copy_amt;
                   }
           }
           return (cbc_block);
   }
   
   /*
    * Implement AES CCM+CBC-MAC encryption and authentication.
    *
    * A couple of notes:
    * The specification allows for a different number of tag lengths;
    * however, they're always truncated from 16 bytes, and the tag
    * length isn't passed in.  (This could be fixed by changing the
    * code in aesni.c:aesni_cipher_crypt().)
    * Similarly, although the nonce length is passed in, the
    * OpenCrypto API that calls us doesn't have a way to set the nonce
    * other than by having different crypto algorithm types.  As a result,
    * this is currently always called with nlen=12; this means that we
    * also have a maximum message length of 16 megabytes.  And similarly,
    * since abytes is limited to a 32 bit value here, the AAD is
    * limited to 4 gigabytes or less.
    */
   void
   AES_CCM_encrypt(const unsigned char *in, unsigned char *out,
                   const unsigned char *addt, const unsigned char *nonce,
                   unsigned char *tag, uint32_t nbytes, uint32_t abytes, int nlen,
                   const unsigned char *key, int nr)
   {
           static const int tag_length = 16;       /* 128 bits */
           int L;
           int counter = 1;        /* S0 has 0, S1 has 1 */
           size_t copy_amt, total = 0;
           uint8_t *byte_ptr;
           __m128i s0, rolling_mac, s_x, staging_block;
   
           if (nbytes == 0 && abytes == 0)
                   return;
   
           /* NIST 800-38c section A.1 says n is [7, 13]. */
           if (nlen < 7 || nlen > 13)
                   panic("%s: bad nonce length %d", __FUNCTION__, nlen);
   
           /*
            * We need to know how many bytes to use to describe
            * the length of the data.  Normally, nlen should be
            * 12, which leaves us 3 bytes to do that -- 16mbytes of
            * data to encrypt.  But it can be longer or shorter;
            * this impacts the length of the message.
            */
           L = sizeof(__m128i) - 1 - nlen;
   
           /*
            * Now, this shouldn't happen, but let's make sure that
            * the data length isn't too big.
            */
           KASSERT(nbytes <= ((1 << (8 * L)) - 1),
               ("%s: nbytes is %u, but length field is %d bytes",
                   __FUNCTION__, nbytes, L));
   
           /*
            * Clear out the blocks
            */
           s0 = _mm_setzero_si128();
   
           rolling_mac = cbc_mac_start(addt, abytes, nonce, nlen,
               key, nr, nbytes, tag_length);
   
           /* s0 has flags, nonce, and then 0 */
           byte_ptr = (uint8_t*)&s0;
           byte_ptr[0] = L - 1;    /* but the flags byte only has L' */
           bcopy(nonce, &byte_ptr[1], nlen);
   
           /*
            * Now to cycle through the rest of the data.
            */
           bcopy(&s0, &s_x, sizeof(s0));
   
           while (total < nbytes) {
                   /*
                    * Copy the plain-text data into staging_block.
                    * This may need to be zero-padded.
                    */
                   copy_amt = MIN(nbytes - total, sizeof(staging_block));
                   bcopy(in+total, &staging_block, copy_amt);
                   if (copy_amt < sizeof(staging_block)) {
                           byte_ptr = (uint8_t*)&staging_block;
                           bzero(&byte_ptr[copy_amt],
                               sizeof(staging_block) - copy_amt);
                   }
                   rolling_mac = xor_and_encrypt(rolling_mac, staging_block,
                       key, nr);
                   /* Put the counter into the s_x block */
                   append_int(counter++, &s_x, L+1);
                   /* Encrypt that */
                   __m128i X = AESNI_ENC(s_x, key, nr);
                   /* XOR the plain-text with the encrypted counter block */
                   staging_block = _mm_xor_si128(staging_block, X);
                   /* And copy it out */
                   bcopy(&staging_block, out+total, copy_amt);
                   total += copy_amt;
           }
           /*
            * Allegedly done with it!  Except for the tag.
            */
           s0 = AESNI_ENC(s0, key, nr);
           staging_block = _mm_xor_si128(s0, rolling_mac);
           bcopy(&staging_block, tag, tag_length);
           explicit_bzero(&s0, sizeof(s0));
           explicit_bzero(&staging_block, sizeof(staging_block));
           explicit_bzero(&s_x, sizeof(s_x));
           explicit_bzero(&rolling_mac, sizeof(rolling_mac));
   }
   
   /*
    * Implement AES CCM+CBC-MAC decryption and authentication.
    * Returns 0 on failure, 1 on success.
    *
    * The primary difference here is that each encrypted block
    * needs to be hashed&encrypted after it is decrypted (since
    * the CBC-MAC is based on the plain text).  This means that
    * we do the decryption twice -- first to verify the tag,
    * and second to decrypt and copy it out.
    *
    * To avoid annoying code copying, we implement the main
    * loop as a separate function.
    *
    * Call with out as NULL to not store the decrypted results;
    * call with hashp as NULL to not run the authentication.
    * Calling with neither as NULL does the decryption and
    * authentication as a single pass (which is not allowed
    * per the specification, really).
    *
    * If hashp is non-NULL, it points to the post-AAD computed
    * checksum.
    */
   static void
   decrypt_loop(const unsigned char *in, unsigned char *out, size_t nbytes,
       __m128i s0, size_t nonce_length, __m128i *macp,
       const unsigned char *key, int nr)
   {
           size_t total = 0;
           __m128i s_x = s0, mac_block;
           int counter = 1;
           const size_t L = sizeof(__m128i) - 1 - nonce_length;
           __m128i pad_block, staging_block;
   
           /*
            * The starting mac (post AAD, if any).
            */
           if (macp != NULL)
                   mac_block = *macp;
           
           while (total < nbytes) {
                   size_t copy_amt = MIN(nbytes - total, sizeof(staging_block));
   
                   if (copy_amt < sizeof(staging_block)) {
                           staging_block = _mm_setzero_si128();
                   }
                   bcopy(in+total, &staging_block, copy_amt);
   
                   /*
                    * staging_block has the current block of input data,
                    * zero-padded if necessary.  This is used in computing
                    * both the decrypted data, and the authentication tag.
                    */
                   append_int(counter++, &s_x, L+1);
                   /*
                    * The tag is computed based on the decrypted data.
                    */
                   pad_block = AESNI_ENC(s_x, key, nr);
                   if (copy_amt < sizeof(staging_block)) {
                           /*
                            * Need to pad out pad_block with 0.
                            * (staging_block was set to 0's above.)
                            */
                           uint8_t *end_of_buffer = (uint8_t*)&pad_block;
                           bzero(end_of_buffer + copy_amt,
                               sizeof(pad_block) - copy_amt);
                   }
                   staging_block = _mm_xor_si128(staging_block, pad_block);
   
                   if (out)
                           bcopy(&staging_block, out+total, copy_amt);
   
                   if (macp)
                           mac_block = xor_and_encrypt(mac_block, staging_block,
                               key, nr);
                   total += copy_amt;
           }
   
           if (macp)
                   *macp = mac_block;
   
           explicit_bzero(&pad_block, sizeof(pad_block));
           explicit_bzero(&staging_block, sizeof(staging_block));
           explicit_bzero(&mac_block, sizeof(mac_block));
   }
   
   /*
    * The exposed decryption routine.  This is practically a
    * copy of the encryption routine, except that the order
    * in which the tag is created is changed.
    * XXX combine the two functions at some point!
    */
   int
   AES_CCM_decrypt(const unsigned char *in, unsigned char *out,
                   const unsigned char *addt, const unsigned char *nonce,
                   const unsigned char *tag, uint32_t nbytes, uint32_t abytes, int nlen,
                   const unsigned char *key, int nr)
   {
           static const int tag_length = 16;       /* 128 bits */
           int L;
           __m128i s0, rolling_mac, staging_block;
           uint8_t *byte_ptr;
   
           if (nbytes == 0 && abytes == 0)
                   return (1);     // No message means no decryption!
           if (nlen < 0 || nlen > 15)
                   panic("%s: bad nonce length %d", __FUNCTION__, nlen);
   
           /*
            * We need to know how many bytes to use to describe
            * the length of the data.  Normally, nlen should be
            * 12, which leaves us 3 bytes to do that -- 16mbytes of
            * data to encrypt.  But it can be longer or shorter.
            */
           L = sizeof(__m128i) - 1 - nlen;
   
           /*
            * Now, this shouldn't happen, but let's make sure that
            * the data length isn't too big.
            */
           if (nbytes > ((1 << (8 * L)) - 1))
                   panic("%s: nbytes is %u, but length field is %d bytes",
                         __FUNCTION__, nbytes, L);
           /*
            * Clear out the blocks
            */
           s0 = _mm_setzero_si128();
   
           rolling_mac = cbc_mac_start(addt, abytes, nonce, nlen,
               key, nr, nbytes, tag_length);
           /* s0 has flags, nonce, and then 0 */
           byte_ptr = (uint8_t*)&s0;
           byte_ptr[0] = L-1;      /* but the flags byte only has L' */
           bcopy(nonce, &byte_ptr[1], nlen);
   
           /*
            * Now to cycle through the rest of the data.
            */
           decrypt_loop(in, NULL, nbytes, s0, nlen, &rolling_mac, key, nr);
   
           /*
            * Compare the tag.
            */
           staging_block = _mm_xor_si128(AESNI_ENC(s0, key, nr), rolling_mac);
           if (timingsafe_bcmp(&staging_block, tag, tag_length) != 0) {
                   return (0);
           }
   
           /*
            * Push out the decryption results this time.
            */
           decrypt_loop(in, out, nbytes, s0, nlen, NULL, key, nr);
           return (1);
   }

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