svn commit: r355018 - in head/sys: dev/random sys

[Ravi Pokala]

Hi Conrad,

The original code did

    explicit_bzero(data, size);

which appears to have been lost in this change. Is that intentional? If so, why is that okay?

Thanks,

Ravi (rpokala@)

-----Original Message-----
From: <owner-src-committers at freebsd.org> on behalf of Conrad Meyer <cem at FreeBSD.org>
Date: 2019-11-22, Friday at 12:20
To: <src-committers at freebsd.org>, <svn-src-all at freebsd.org>, <svn-src-head at freebsd.org>
Subject: svn commit: r355018 - in head/sys: dev/random sys

    Author: cem
    Date: Fri Nov 22 20:20:37 2019
    New Revision: 355018
    URL: https://svnweb.freebsd.org/changeset/base/355018
    
    Log:
      random(4): Abstract loader entropy injection
      
      Break random_harvestq_prime up into some logical subroutines.  The goal
      is that it becomes easier to add other early entropy sources.
      
      While here, drop pre-12.0 compatibility logic.  loader default configuration
      should preload the file as expeced since 12.0.
      
      Approved by:	csprng(delphij, markm)
      Differential Revision:	https://reviews.freebsd.org/D22482
    
    Modified:
      head/sys/dev/random/random_harvestq.c
      head/sys/sys/random.h
    
    Modified: head/sys/dev/random/random_harvestq.c
    ==============================================================================
    --- head/sys/dev/random/random_harvestq.c	Fri Nov 22 20:18:07 2019	(r355017)
    +++ head/sys/dev/random/random_harvestq.c	Fri Nov 22 20:20:37 2019	(r355018)
    @@ -402,6 +402,57 @@ random_harvestq_init(void *unused __unused)
     SYSINIT(random_device_h_init, SI_SUB_RANDOM, SI_ORDER_SECOND, random_harvestq_init, NULL);
     
     /*
    + * Subroutine to slice up a contiguous chunk of 'entropy' and feed it into the
    + * underlying algorithm.  Returns number of bytes actually fed into underlying
    + * algorithm.
    + */
    +static size_t
    +random_early_prime(char *entropy, size_t len)
    +{
    +	struct harvest_event event;
    +	size_t i;
    +
    +	len = rounddown(len, sizeof(event.he_entropy));
    +	if (len == 0)
    +		return (0);
    +
    +	for (i = 0; i < len; i += sizeof(event.he_entropy)) {
    +		event.he_somecounter = (uint32_t)get_cyclecount();
    +		event.he_size = sizeof(event.he_entropy);
    +		event.he_source = RANDOM_CACHED;
    +		event.he_destination =
    +		    harvest_context.hc_destination[RANDOM_CACHED]++;
    +		memcpy(event.he_entropy, entropy + i, sizeof(event.he_entropy));
    +		random_harvestq_fast_process_event(&event);
    +	}
    +	explicit_bzero(entropy, len);
    +	return (len);
    +}
    +
    +/*
    + * Subroutine to search for known loader-loaded files in memory and feed them
    + * into the underlying algorithm early in boot.  Returns the number of bytes
    + * loaded (zero if none were loaded).
    + */
    +static size_t
    +random_prime_loader_file(const char *type)
    +{
    +	uint8_t *keyfile, *data;
    +	size_t size;
    +
    +	keyfile = preload_search_by_type(type);
    +	if (keyfile == NULL)
    +		return (0);
    +
    +	data = preload_fetch_addr(keyfile);
    +	size = preload_fetch_size(keyfile);
    +	if (data == NULL)
    +		return (0);
    +
    +	return (random_early_prime(data, size));
    +}
    +
    +/*
      * This is used to prime the RNG by grabbing any early random stuff
      * known to the kernel, and inserting it directly into the hashing
      * module, currently Fortuna.
    @@ -410,41 +461,19 @@ SYSINIT(random_device_h_init, SI_SUB_RANDOM, SI_ORDER_
     static void
     random_harvestq_prime(void *unused __unused)
     {
    -	struct harvest_event event;
    -	size_t count, size, i;
    -	uint8_t *keyfile, *data;
    +	size_t size;
     
     	/*
     	 * Get entropy that may have been preloaded by loader(8)
     	 * and use it to pre-charge the entropy harvest queue.
     	 */
    -	keyfile = preload_search_by_type(RANDOM_CACHED_BOOT_ENTROPY_MODULE);
    -#ifndef NO_BACKWARD_COMPATIBILITY
    -	if (keyfile == NULL)
    -	    keyfile = preload_search_by_type(RANDOM_LEGACY_BOOT_ENTROPY_MODULE);
    -#endif
    -	if (keyfile != NULL) {
    -		data = preload_fetch_addr(keyfile);
    -		size = preload_fetch_size(keyfile);
    -		/* Trim the size. If the admin has a file with a funny size, we lose some. Tough. */
    -		size -= (size % sizeof(event.he_entropy));
    -		if (data != NULL && size != 0) {
    -			for (i = 0; i < size; i += sizeof(event.he_entropy)) {
    -				count = sizeof(event.he_entropy);
    -				event.he_somecounter = (uint32_t)get_cyclecount();
    -				event.he_size = count;
    -				event.he_source = RANDOM_CACHED;
    -				event.he_destination =
    -				    harvest_context.hc_destination[RANDOM_CACHED]++;
    -				memcpy(event.he_entropy, data + i, sizeof(event.he_entropy));
    -				random_harvestq_fast_process_event(&event);
    -			}
    -			explicit_bzero(data, size);
    -			if (bootverbose)
    -				printf("random: read %zu bytes from preloaded cache\n", size);
    -		} else
    -			if (bootverbose)
    -				printf("random: no preloaded entropy cache\n");
    +	size = random_prime_loader_file(RANDOM_CACHED_BOOT_ENTROPY_MODULE);
    +	if (bootverbose) {
    +		if (size > 0)
    +			printf("random: read %zu bytes from preloaded cache\n",
    +			    size);
    +		else
    +			printf("random: no preloaded entropy cache\n");
     	}
     }
     SYSINIT(random_device_prime, SI_SUB_RANDOM, SI_ORDER_MIDDLE, random_harvestq_prime, NULL);
    
    Modified: head/sys/sys/random.h
    ==============================================================================
    --- head/sys/sys/random.h	Fri Nov 22 20:18:07 2019	(r355017)
    +++ head/sys/sys/random.h	Fri Nov 22 20:20:37 2019	(r355018)
    @@ -81,7 +81,6 @@ enum random_entropy_source {
     _Static_assert(ENTROPYSOURCE <= 32,
         "hardcoded assumption that values fit in a typical word-sized bitset");
     
    -#define RANDOM_LEGACY_BOOT_ENTROPY_MODULE	"/boot/entropy"
     #define RANDOM_CACHED_BOOT_ENTROPY_MODULE	"boot_entropy_cache"
     
     extern u_int hc_source_mask;