Differential D22839 Diff 78074 lib/libc/gen/arc4random.c

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lib/libc/gen/arc4random.c

Show All 21 Lines
/*		/*
* ChaCha based random number generator for OpenBSD.		* ChaCha based random number generator for OpenBSD.
*/		*/

#include <sys/cdefs.h>		#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");		__FBSDID("$FreeBSD$");

#include "namespace.h"		#include "namespace.h"
		#if defined(__FreeBSD__)
		#include <assert.h>
		#endif
#include <fcntl.h>		#include <fcntl.h>
#include <limits.h>		#include <limits.h>
#include <pthread.h>		#include <pthread.h>
#include <signal.h>		#include <signal.h>
#include <stdint.h>		#include <stdint.h>
#include <stdlib.h>		#include <stdlib.h>
#include <string.h>		#include <string.h>
#include <unistd.h>		#include <unistd.h>
Show All 25 Lines	static struct _rs {
size_t rs_have; /* valid bytes at end of rs_buf */		size_t rs_have; /* valid bytes at end of rs_buf */
size_t rs_count; /* bytes till reseed */		size_t rs_count; /* bytes till reseed */
} *rs;		} *rs;

/* Maybe be preserved in fork children, if _rs_allocate() decides. */		/* Maybe be preserved in fork children, if _rs_allocate() decides. */
static struct _rsx {		static struct _rsx {
chacha_ctx rs_chacha; /* chacha context for random keystream */		chacha_ctx rs_chacha; /* chacha context for random keystream */
u_char rs_buf[RSBUFSZ]; /* keystream blocks */		u_char rs_buf[RSBUFSZ]; /* keystream blocks */
		#ifdef __FreeBSD__
		uint32_t rs_seed_generation; /* 32-bit userspace RNG version */
		#endif
		cemAuthorUnsubmitted Done Inline Actions arc4random.c is mostly a verbatim copy of the OpenBSD version, and most FreeBSD specialization happens in arc4random.h. I had to make some changes to arc4random.c but tried to make them minimal and wrapped them in `#ifdef __FreeBSD__` so theoretically OpenBSD could take them unmodified (or at least, it's a hint to readers which parts we've changed). cem: arc4random.c is mostly a verbatim copy of the OpenBSD version, and most FreeBSD specialization…
} *rsx;		} *rsx;

static inline int _rs_allocate(struct _rs , struct _rsx );		static inline int _rs_allocate(struct _rs , struct _rsx );
static inline void _rs_forkdetect(void);		static inline void _rs_forkdetect(void);
#include "arc4random.h"		#include "arc4random.h"

static inline void _rs_rekey(u_char *dat, size_t datlen);		static inline void _rs_rekey(u_char *dat, size_t datlen);

Show All 12 Lines	_rs_init(u_char *buf, size_t n)
chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ, NULL);		chacha_ivsetup(&rsx->rs_chacha, buf + KEYSZ, NULL);
}		}

static void		static void
_rs_stir(void)		_rs_stir(void)
{		{
u_char rnd[KEYSZ + IVSZ];		u_char rnd[KEYSZ + IVSZ];

		#if defined(__FreeBSD__)
		bool need_init;

		/*
		* De-couple allocation (which locates the vdso_fxrngp pointer in
		* auxinfo) from initialization. This allows us to read the root seed
		* version before we fetch system entropy, maintaining the invariant
		* that the PRF was seeded with entropy from rs_seed_generation or a
		* later generation. But never seeded from an earlier generation.
		* This invariant prevents us from missing a root reseed event.
		*/
		need_init = false;
		if (rs == NULL) {
		if (_rs_allocate(&rs, &rsx) == -1)
		abort();
		need_init = true;
		}
		/*
		* Transition period: new userspace on old kernel. This should become
		* a hard error at some point, if the scheme is adopted.
		*/
		if (vdso_fxrngp != NULL)
		rsx->rs_seed_generation =
		kibUnsubmitted Done Inline Actions Again, this seems to miss the version check. kib: Again, this seems to miss the version check.
		cemAuthorUnsubmitted Done Inline Actions Why check the version repeatedly? Most other VDSO knobs of this kind are checked only at process startup; I don't see any reason to pessimize this use in particular. cem: Why check the version repeatedly? Most other VDSO knobs of this kind are checked only at…
		kibUnsubmitted Done Inline Actions Other vdso data blobs (timehands) allow to dynamically disable its use. The only mechanism your vdso_fxrngp provides for this is version check. kib: Other vdso data blobs (timehands) allow to dynamically disable its use. The only mechanism…
		cemAuthorUnsubmitted Done Inline Actions This can be done by just halting update publishing on the VDSO page. `sysctl_fxrng_vdso` and `fxrng_push_seed_generation` do not do that yet, but could pretty easily. cem: This can be done by just halting update publishing on the VDSO page. `sysctl_fxrng_vdso` and…
		fxrng_load_acq_generation(&vdso_fxrngp->fx_generation32);
		#endif

if (getentropy(rnd, sizeof rnd) == -1)		if (getentropy(rnd, sizeof rnd) == -1)
_getentropy_fail();		_getentropy_fail();

		#if !defined(__FreeBSD__)
if (!rs)		if (!rs)
_rs_init(rnd, sizeof(rnd));		_rs_init(rnd, sizeof(rnd));
		#else /* __FreeBSD__ */
		assert(rs != NULL);
		kibUnsubmitted Not Done Inline Actions libraries should not kill the process. kib: libraries should not kill the process.
		cemAuthorUnsubmitted Done Inline Actions Right. This assertion should never fire. Note that this library is already special in that `_rs_init()` `abort()`s if `_rs_allocate()` fails. This is not new in this revision. cem: Right. This assertion should never fire. Note that this library is already special in that…
		if (need_init)
		_rs_init(rnd, sizeof(rnd));
		#endif
else		else
_rs_rekey(rnd, sizeof(rnd));		_rs_rekey(rnd, sizeof(rnd));
explicit_bzero(rnd, sizeof(rnd)); /* discard source seed */		explicit_bzero(rnd, sizeof(rnd)); /* discard source seed */

/* invalidate rs_buf */		/* invalidate rs_buf */
rs->rs_have = 0;		rs->rs_have = 0;
memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf));		memset(rsx->rs_buf, 0, sizeof(rsx->rs_buf));

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