Attachment 730193 Details for Bug 1025068

runtime check for getrandom(), wrapper around both implementations

emul_entropy.c (text/plain), 1.91 KB, created by Matthias Gerstner on 2017-06-26 11:38:15 UTC

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Creator: Matthias Gerstner

Created: 2017-06-26 11:38:15 UTC

Size: 1.91 KB

patch

obsolete

>#define _GNU_SOURCE // needed on SLE11 for O_CLOEXEC
>#include <sys/types.h>
>#include <sys/stat.h>
>#include <fcntl.h>
>#include <errno.h>
>#include <linux/random.h>
>#include <sys/syscall.h>
>
>int getentropy_urandom(void *buffer, size_t length)
>{
>	int random_fd = -1;
>	ssize_t res = -1;
>	size_t filled = 0;
>
>	if( length > 256 )
>	{
>		errno = EIO;
>		return -1;
>	}
>
>	random_fd = open("/dev/urandom", O_RDONLY | O_CLOEXEC);
>
>	if( random_fd == -1 )
>	{
>		return -1;
>	}
>
>	while( filled < length )
>	{
>		res = read(random_fd, (char*)buffer + filled, length - filled);
>
>		if( res == -1 )
>		{
>			// shouldn't actually happen acc. to man(4) random,
>			// but you never know
>			if( errno == EINTR )
>				continue;
>
>			return -1;
>		}
>		else if( res == 0 )
>		{
>			// no more bytes available? should not happen
>			errno = EIO;
>			return -1;
>		}
>
>		filled += res;
>	}
>
>	return 0;
>}
>
>int getentropy_getrandom(void *buffer, size_t length)
>{
>	int res;
>	size_t filled = 0;
>
>	if( length > 256 )
>	{
>		errno = EIO;
>		return -1;
>	}
>
>	while( filled < length )
>	{
>#ifdef SYS_getrandom
>		/*
>		 * glibc does not contain a syscall wrapper for this in older
>		 * versions
>		 */
>		res = syscall(SYS_getrandom, (char*)buffer + filled, length - filled, 0);
>#else
>#	warning no getrandom
>		errno = ENOSYS;
>		return -1;
>#endif // SYS_getrandom
>
>		if( res == -1 )
>		{
>			if( errno == EINTR )
>				continue;
>
>			return -1;
>		}
>		else if( res == 0 )
>		{
>			// no more bytes available? should not happen
>			errno = EIO;
>			return -1;
>		}
>
>		filled += res;
>	}
>
>	return 0;
>}
>
>int getentropy(void *buffer, size_t length)
>{
>	/*
>	 * check at runtime whether we have a getrandom system call available,
>	 * otherwise fall back to urandom approach. autoconf check for
>	 * getrandom() does not work, because there's been no declaration for
>	 * it for years.
>	 */
>	int res = getentropy_getrandom(buffer, length);
>
>	if( res == -1 && errno == ENOSYS )
>	{
>		return getentropy_urandom(buffer, length);
>	}
>
>	return res;
>}
>

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Attachments on bug 1025068: 715740 | 715748 | 729646 | 729648 | 729649 | 729681 | 729683 | 730002 | 730193 | 730205 | 730212 | 730213 | 730361 | 730982 | 731944