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Diffstat (limited to 'srtp/crypto/rng/prng.c')
| -rw-r--r-- | srtp/crypto/rng/prng.c | 180 |
1 files changed, 180 insertions, 0 deletions
diff --git a/srtp/crypto/rng/prng.c b/srtp/crypto/rng/prng.c new file mode 100644 index 0000000..69350a4 --- /dev/null +++ b/srtp/crypto/rng/prng.c @@ -0,0 +1,180 @@ +/* + * prng.c + * + * pseudorandom source + * + * David A. McGrew + * Cisco Systems, Inc. + */ +/* + * + * Copyright(c) 2001-2006 Cisco Systems, Inc. + * All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * + * Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * + * 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. + * + * Neither the name of the Cisco Systems, Inc. nor the names of its + * contributors may be used to endorse or promote products derived + * from this software without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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 + * COPYRIGHT HOLDERS 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. + * + */ + + +#include "prng.h" + +/* single, global prng structure */ + +x917_prng_t x917_prng; + +err_status_t +x917_prng_init(rand_source_func_t random_source) { + v128_t tmp_key; + err_status_t status; + + /* initialize output count to zero */ + x917_prng.octet_count = 0; + + /* set random source */ + x917_prng.rand = random_source; + + /* initialize secret key from random source */ + status = random_source((uint8_t *)&tmp_key, 16); + if (status) + return status; + + /* expand aes key */ + aes_expand_encryption_key(&tmp_key, x917_prng.key); + + /* initialize prng state from random source */ + status = x917_prng.rand((uint8_t *)&x917_prng.state, 16); + if (status) + return status; + + return err_status_ok; +} + +err_status_t +x917_prng_get_octet_string(uint8_t *dest, uint32_t len) { + uint32_t t; + v128_t buffer; + uint32_t i, tail_len; + err_status_t status; + + /* + * if we need to re-initialize the prng, do so now + * + * avoid overflows by subtracting instead of adding + */ + if (x917_prng.octet_count > MAX_PRNG_OUT_LEN - len) { + status = x917_prng_init(x917_prng.rand); + if (status) + return status; + } + x917_prng.octet_count += len; + + /* find out the time */ + t = (uint32_t)time(NULL); + + /* loop until we have output enough data */ + for (i=0; i < len/16; i++) { + + /* exor time into state */ + x917_prng.state.v32[0] ^= t; + + /* copy state into buffer */ + v128_copy(&buffer, &x917_prng.state); + + /* apply aes to buffer */ + aes_encrypt(&buffer, x917_prng.key); + + /* write data to output */ + *dest++ = buffer.v8[0]; + *dest++ = buffer.v8[1]; + *dest++ = buffer.v8[2]; + *dest++ = buffer.v8[3]; + *dest++ = buffer.v8[4]; + *dest++ = buffer.v8[5]; + *dest++ = buffer.v8[6]; + *dest++ = buffer.v8[7]; + *dest++ = buffer.v8[8]; + *dest++ = buffer.v8[9]; + *dest++ = buffer.v8[10]; + *dest++ = buffer.v8[11]; + *dest++ = buffer.v8[12]; + *dest++ = buffer.v8[13]; + *dest++ = buffer.v8[14]; + *dest++ = buffer.v8[15]; + + /* exor time into buffer */ + buffer.v32[0] ^= t; + + /* encrypt buffer */ + aes_encrypt(&buffer, x917_prng.key); + + /* copy buffer into state */ + v128_copy(&x917_prng.state, &buffer); + + } + + /* if we need to output any more octets, we'll do so now */ + tail_len = len % 16; + if (tail_len) { + + /* exor time into state */ + x917_prng.state.v32[0] ^= t; + + /* copy value into buffer */ + v128_copy(&buffer, &x917_prng.state); + + /* apply aes to buffer */ + aes_encrypt(&buffer, x917_prng.key); + + /* write data to output */ + for (i=0; i < tail_len; i++) { + *dest++ = buffer.v8[i]; + } + + /* now update the state one more time */ + + /* exor time into buffer */ + buffer.v32[0] ^= t; + + /* encrypt buffer */ + aes_encrypt(&buffer, x917_prng.key); + + /* copy buffer into state */ + v128_copy(&x917_prng.state, &buffer); + + } + + return err_status_ok; +} + +err_status_t +x917_prng_deinit(void) { + + return err_status_ok; +} |