michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #include <sys/types.h>
michael@0: #include <unistd.h>
michael@0: #include <fcntl.h>
michael@0: #include <syslog.h>
michael@0: #include <inttypes.h>
michael@0: 
michael@0: /**
michael@0:  * platGenerateCryptoRand
michael@0:  * @brief Generates a Random Number
michael@0:  *
michael@0:  * Generate crypto graphically random number for a desired length.
michael@0:  * The function uses "secd" 's provided API. The random bytes are
michael@0:  * generated by "secd" which runs as another process. The function
michael@0:  * will be much slower than the cpr_rand(). This function should be
michael@0:  * used when good random number is needed such as random number that
michael@0:  * to be used for SRTP key for an example.
michael@0:  *
michael@0:  * @param[in] buf  - pointer to the buffer to store the result of random
michael@0:  *                   bytes requested.
michael@0:  * @param[in] len  - pointer to the length of the desired random bytes.
michael@0:  *             When calling the function, the integer's value
michael@0:  *             should be set to the desired number of random
michael@0:  *             bytes ('buf' should be of at least this size).
michael@0:  *             upon success, its value will be set to the
michael@0:  *             actual number of random bytes being returned.
michael@0:  *             (realistically, there is a maximum number of
michael@0:  *             random bytes that can be returned at a time.
michael@0:  *             if the caller request more than that, the
michael@0:  *             'len' will indicate how many bytes are actually being
michael@0:  *             returned) on failure, its value will be set to 0.
michael@0:  *
michael@0:  * @return
michael@0:  *     1 - success.
michael@0:  *     0 - fail.
michael@0:  *
michael@0:  * @note This function MUST BE REWRITTEN BY THE VENDORS
michael@0:  * @note The intent of this function is to generate a cryptographically strong
michael@0:  * random number. Vendors can map this to HandyIron or OpenSSL random number
michael@0:  * generation functions.
michael@0:  */
michael@0: int
michael@0: platGenerateCryptoRand(uint8_t *buf, int *len)
michael@0: {
michael@0:     int fd;
michael@0:     int rc = 0;
michael@0:     ssize_t s;
michael@0: 
michael@0:     if ((fd = open("/dev/urandom", O_RDONLY)) == -1) {
michael@0:         syslog(LOG_ERR, "Failed to open prng driver");
michael@0:         return 0;
michael@0:     }
michael@0: 
michael@0:     /*
michael@0:      * Try to read the given amount of bytes from the PRNG device.  We do not
michael@0:      * handle short reads but just return the number of bytes read from the
michael@0:      * device.  The caller has to manage this.
michael@0:      * E.g. gsmsdp_generate_key() in core/gsm/gsm_sdp_crypto.c
michael@0:      */
michael@0:     s = read(fd, buf, (size_t) *len);
michael@0: 
michael@0:     if (s > 0) {
michael@0:         *len = s;
michael@0:         rc = 1; /* Success */
michael@0:     } else {
michael@0:         *len = 0;
michael@0:         rc = 0; /* Failure */
michael@0:     }
michael@0: 
michael@0:     (void) close(fd);
michael@0:     return rc;
michael@0: }
michael@0: