crypto: rng - FIPS 140-3 compliance for random number generation
Subsystems (2)
cover crypto: rng - FIPS 140-3 compliance for random number generation
This patch series implements FIPS 140-3 compliance requirements for random number generation in the Linux kernel 6.12. The changes ensure that when the kernel is operating in FIPS mode, FIPS-compliant random number generators are used instead of the default /dev/random implementation.
IMPORTANT: These two patches must be applied together as a series. Applying only the first patch without the second will cause a deadlock during boot in FIPS-enabled environments. The second patch fixes a critical timing issue introduced by the first patch where the crypto RNG attempts to override the drivers/char/random interface before the default RNG becomes available.
The series consists of two patches:
1. Initial implementation to override drivers/char/random in FIPS mode
2. Refinement to ensure override only occurs after FIPS-mode RNGs are available
These 2 patches are required for FIPS 140-3 certification and compliance in government and enterprise environments.
Herbert Xu (1):
crypto: rng - Override drivers/char/random in FIPS mode
Jay Wang (1):
Override drivers/char/random only after FIPS-mode RNGs become
available
crypto/rng.c | 92 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 92 insertions(+)
Signature · 1 line
2.47.1
PATCH 1/2 crypto: rng - Override drivers/char/random in FIPS mode
From: Herbert Xu <[email protected]>
Upstream: RHEL only
Bugzilla: 1984784
This patch overrides the drivers/char/random RNGs with the FIPS RNG from Crypto API when FIPS mode is enabled.
--- crypto/rng.c | 71 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 71 insertions(+)
crypto/rng.c +71 -0
@@ -12,11 +12,14 @@#include <linux/atomic.h> #include <linux/cryptouser.h> #include <linux/err.h> +#include <linux/fips.h> #include <linux/kernel.h> #include <linux/module.h> #include <linux/mutex.h> #include <linux/random.h> #include <linux/seq_file.h> +#include <linux/sched.h> +#include <linux/sched/signal.h> #include <linux/slab.h> #include <linux/string.h> #include <net/netlink.h>
@@ -217,5 +220,73 @@ void crypto_unregister_rngs(struct rng_alg *algs, int count) }EXPORT_SYMBOL_GPL (crypto_unregister_rngs); +static ssize_t crypto_devrandom_read (void __user *buf,size_t buflen) +{ +u8 tmp[256 ]; +ssize_t ret; + +if (!buflen) +return 0 ; + + ret =crypto_get_default_rng (); +if (ret) +return ret; + +for (;;) { +int err; +int i; + + i =min_t (int, buflen,sizeof (tmp)); + err =crypto_rng_get_bytes (crypto_default_rng, tmp, i); +if (err) { + ret = err; +break ; + } + +if (copy_to_user (buf, tmp, i)) { + ret = -EFAULT ; +break ; + } + + buflen -= i; + buf += i; + ret += i; + +if (!buflen) +break ; + +if (need_resched ()) { +if (signal_pending (current)) +break ; +schedule (); + } + } + +crypto_put_default_rng (); +memzero_explicit (tmp,sizeof (tmp)); + +return ret; +} + +static const struct random_extrng crypto_devrandom_rng = { + .extrng_read = crypto_devrandom_read, + .owner =THIS_MODULE , +}; + +static int __init crypto_rng_init (void ) +{ +if (fips_enabled) +random_register_extrng (&crypto_devrandom_rng); +return 0 ; +} + +static void __exit crypto_rng_exit(void) +{ +random_unregister_extrng (); +} + +late_initcall (crypto_rng_init); +module_exit (crypto_rng_exit); +MODULE_LICENSE ("GPL" );MODULE_DESCRIPTION ("Random Number Generator" );
Signature · 1 line
2.47.1
Greg KH
maintainerRe: [PATCH 1/2] crypto: rng - Override drivers/char/random in FIPS mode
Quoted 11 lines · Jay Wang
From: Herbert Xu <[email protected]>
Upstream: RHEL only
Bugzilla: 1984784This patch overrides the
drivers/char/randomRNGs with the FIPS RNG from Crypto API when FIPS mode is enabled.Signed-off-by Herbert Xu <[email protected]>(cherry picked from commit 37e0042aaf43d4494bcbea2113605366d0fe6187)
This id is not in Linus's tree, so why is this here?
Are you sure you ment to send this series out? Have you read the stable kernel rules?
confused,
greg k-h
kernel test robot
build botRe: [PATCH 1/2] crypto: rng - Override drivers/char/random in FIPS mode
In reply to Jay Wangkernel test robot noticed the following build errors:
Hi Jay,
kernel test robot noticed the following build errors:
[auto build test ERROR on herbert-cryptodev-2.6/master]
[also build test ERROR on herbert-crypto-2.6/master linus/master v6.16-rc3 next-20250627] [If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Jay-Wang/crypto-rng-Override-drivers-char-random-in-FIPS-mode/20250628-123147 base: https://git.kernel.org/pub/scm/linux/kernel/git/herbert/cryptodev-2.6.git master patch link: https://lore.kernel.org/r/20250628042918.32253-2-wanjay%40amazon.com patch subject: [PATCH 1/2] crypto: rng - Override drivers/char/random in FIPS mode config: x86_64-buildonly-randconfig-001-20250628 (https://download.01.org/0day-ci/archive/20250628/[email protected]/config) compiler: gcc-12 (Debian 12.2.0-14+deb12u1) 12.2.0 reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250628/[email protected]/reproduce)
If you fix the issue in a separate patch/commit (i.e. not just a new version of the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <[email protected]>
| Closes: https://lore.kernel.org/oe-kbuild-all/[email protected]/
All error/warnings (new ones prefixed by >>):
>> crypto/rng.c:272:21: error: variable 'crypto_devrandom_rng' has initializer but incomplete type
272 | static const struct random_extrng crypto_devrandom_rng = {
| ^~~~~~~~~~~~~
>> crypto/rng.c:273:10: error: 'const struct random_extrng' has no member named 'extrng_read'
273 | .extrng_read = crypto_devrandom_read,
| ^~~~~~~~~~~
>> crypto/rng.c:273:24: warning: excess elements in struct initializer
273 | .extrng_read = crypto_devrandom_read,
| ^~~~~~~~~~~~~~~~~~~~~
crypto/rng.c:273:24: note: (near initialization for 'crypto_devrandom_rng')
>> crypto/rng.c:274:10: error: 'const struct random_extrng' has no member named 'owner'
274 | .owner = THIS_MODULE,
| ^~~~~
In file included from include/linux/printk.h:6,
from include/asm-generic/bug.h:22,
from arch/x86/include/asm/bug.h:103,
from arch/x86/include/asm/alternative.h:9,
from arch/x86/include/asm/barrier.h:5,
from include/linux/list.h:11,
from include/linux/swait.h:5,
from include/linux/completion.h:12,
from include/linux/crypto.h:15,
from include/crypto/algapi.h:13,
from include/crypto/internal/rng.h:12,
from crypto/rng.c:11:
include/linux/init.h:182:21: warning: excess elements in struct initializer
182 | #define THIS_MODULE ((struct module *)0)
| ^
crypto/rng.c:274:18: note: in expansion of macro 'THIS_MODULE'
274 | .owner = THIS_MODULE,
| ^~~~~~~~~~~
include/linux/init.h:182:21: note: (near initialization for 'crypto_devrandom_rng')
182 | #define THIS_MODULE ((struct module *)0)
| ^
crypto/rng.c:274:18: note: in expansion of macro 'THIS_MODULE'
274 | .owner = THIS_MODULE,
| ^~~~~~~~~~~
crypto/rng.c: In function 'crypto_rng_init':
>> crypto/rng.c:280:17: error: implicit declaration of function 'random_register_extrng'; did you mean 'crypto_register_rng'? [-Werror=implicit-function-declaration]
280 | random_register_extrng(&crypto_devrandom_rng);
| ^~~~~~~~~~~~~~~~~~~~~~
| crypto_register_rng
crypto/rng.c: In function 'crypto_rng_exit':
>> crypto/rng.c:286:9: error: implicit declaration of function 'random_unregister_extrng'; did you mean 'crypto_unregister_rng'? [-Werror=implicit-function-declaration]
286 | random_unregister_extrng();
| ^~~~~~~~~~~~~~~~~~~~~~~~
| crypto_unregister_rng
crypto/rng.c: At top level:
>> crypto/rng.c:272:35: error: storage size of 'crypto_devrandom_rng' isn't known
272 | static const struct random_extrng crypto_devrandom_rng = {
| ^~~~~~~~~~~~~~~~~~~~cc1: some warnings being treated as errors
vim +/crypto_devrandom_rng +272 crypto/rng.c
271
> 272 static const struct random_extrng crypto_devrandom_rng = {
> 273 .extrng_read = crypto_devrandom_read,
> 274 .owner = THIS_MODULE,
275 };
276
277 static int __init crypto_rng_init(void)
278 {
279 if (fips_enabled)
> 280 random_register_extrng(&crypto_devrandom_rng);
281 return 0;
282 }
283
284 static void __exit crypto_rng_exit(void)
285 {
> 286 random_unregister_extrng(); 287 }
288
Signature · 2 lines
0-DAY CI Kernel Test Service https://github.com/intel/lkp-tests/wiki
PATCH 2/2 Override drivers/char/random only after FIPS-mode RNGs become available
In reply to Jay WangThis commit fixes a timing issue introduced in the previous commit "crypto: rng - Override drivers/char/random in FIPS mode" where the crypto RNG was attempting to override the drivers/char/random interface before the default RNG became available. The previous implementation would immediately register the external RNG during module initialization, which could fail if the default RNG wasn't ready.
Changes:
- Introduce workqueue-based initialization for FIPS mode
- Add crypto_rng_register_work_func() to wait for default RNG availability
- Move random_register_extrng() call to the work function with proper error handling
This ensures the crypto ext RNG is properly registered only after all dependencies
are satisfied, preventing potential boot failures in FIPS-enabled environments.
--- crypto/rng.c | 25 +++++++++++++++++++++++-- 1 file changed, 23 insertions(+), 2 deletions(-)
crypto/rng.c +23 -2
@@ -22,6 +22,7 @@#include <linux/sched/signal.h> #include <linux/slab.h> #include <linux/string.h> +#include <linux/workqueue.h> #include <net/netlink.h> #include "internal.h"
@@ -273,15 +274,35 @@ static const struct random_extrng crypto_devrandom_rng = { .owner = THIS_MODULE, }; +static struct work_struct crypto_rng_register_work; + +static void crypto_rng_register_work_func (struct work_struct *work) +{ +/* Wait until default rng becomes avaiable, then +Overwrite the extrng. +*/ +int ret =crypto_get_default_rng (); +if (ret){ +printk (KERN_ERR "crypto_rng: Failed to get default RNG (error %d)\n" , ret); +return ; + } +printk (KERN_INFO "Overwrite extrng\n" ); +random_register_extrng (&crypto_devrandom_rng); +} +static int __init crypto_rng_init (void ) { -if (fips_enabled) -random_register_extrng (&crypto_devrandom_rng); +if (fips_enabled) { +INIT_WORK (&crypto_rng_register_work, crypto_rng_register_work_func); +schedule_work (&crypto_rng_register_work); + } +return 0 ; } static void __exit crypto_rng_exit(void) { +cancel_work_sync (&crypto_rng_register_work);random_unregister_extrng (); }
Signature · 1 line
2.47.1
Greg KH
maintainerRe: [PATCH 2/2] Override drivers/char/random only after FIPS-mode RNGs become available
Quoted 6 lines · Jay Wang
This commit fixes a timing issue introduced in the previous commit "crypto: rng - Override
drivers/char/randomin FIPS mode" where the crypto RNG was attempting to override thedrivers/char/randominterface before the default RNG became available. The previous implementation would immediately register the external RNG during module initialization, which could fail if the default RNG wasn't ready.
Why isn't this just part of the previous commit so that there is no regression anywhere?
thanks,
greg k-h