From: "Jason A. Donenfeld" <Jason@zx2c4.com> To: Theodore Ts'o <tytso@mit.edu>, Linux Crypto Mailing List <linux-crypto@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>, kernel-hardening@lists.openwall.com, Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: "Jason A. Donenfeld" <Jason@zx2c4.com> Subject: [PATCH RFC v2 1/8] random: add synchronous API for the urandom pool Date: Mon, 5 Jun 2017 05:47:50 +0200 [thread overview] Message-ID: <20170605034757.4803-2-Jason@zx2c4.com> (raw) In-Reply-To: <20170605034757.4803-1-Jason@zx2c4.com> This enables users of get_random_{bytes,u32,u64,int,long} to wait until the pool is ready before using this function, in case they actually want to have reliable randomness. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> --- drivers/char/random.c | 41 +++++++++++++++++++++++++++++++---------- include/linux/random.h | 1 + 2 files changed, 32 insertions(+), 10 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 0ab024918907..035a5d7c06bd 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -844,11 +844,6 @@ static void crng_reseed(struct crng_state *crng, struct entropy_store *r) spin_unlock_irqrestore(&primary_crng.lock, flags); } -static inline void crng_wait_ready(void) -{ - wait_event_interruptible(crng_init_wait, crng_ready()); -} - static void _extract_crng(struct crng_state *crng, __u8 out[CHACHA20_BLOCK_SIZE]) { @@ -1466,7 +1461,10 @@ static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf, * number of good random numbers, suitable for key generation, seeding * TCP sequence numbers, etc. It does not rely on the hardware random * number generator. For random bytes direct from the hardware RNG - * (when available), use get_random_bytes_arch(). + * (when available), use get_random_bytes_arch(). In order to ensure + * that the randomness provided by this function is okay, the function + * wait_for_random_bytes() should be called and return 0 at least once + * at any point prior. */ void get_random_bytes(void *buf, int nbytes) { @@ -1496,6 +1494,24 @@ void get_random_bytes(void *buf, int nbytes) EXPORT_SYMBOL(get_random_bytes); /* + * Wait for the urandom pool to be seeded and thus guaranteed to supply + * cryptographically secure random numbers. This applies to: the /dev/urandom + * device, the get_random_bytes function, and the get_random_{u32,u64,int,long} + * family of functions. Using any of these functions without first calling + * this function forfeits the guarantee of security. + * + * Returns: 0 if the urandom pool has been seeded. + * -ERESTARTSYS if the function was interrupted by a signal. + */ +int wait_for_random_bytes(void) +{ + if (likely(crng_ready())) + return 0; + return wait_event_interruptible(crng_init_wait, crng_ready()); +} +EXPORT_SYMBOL(wait_for_random_bytes); + +/* * Add a callback function that will be invoked when the nonblocking * pool is initialised. * @@ -1849,6 +1865,8 @@ const struct file_operations urandom_fops = { SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count, unsigned int, flags) { + int ret; + if (flags & ~(GRND_NONBLOCK|GRND_RANDOM)) return -EINVAL; @@ -1861,9 +1879,9 @@ SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count, if (!crng_ready()) { if (flags & GRND_NONBLOCK) return -EAGAIN; - crng_wait_ready(); - if (signal_pending(current)) - return -ERESTARTSYS; + ret = wait_for_random_bytes(); + if (unlikely(ret)) + return ret; } return urandom_read(NULL, buf, count, NULL); } @@ -2023,7 +2041,10 @@ struct batched_entropy { /* * Get a random word for internal kernel use only. The quality of the random * number is either as good as RDRAND or as good as /dev/urandom, with the - * goal of being quite fast and not depleting entropy. + * goal of being quite fast and not depleting entropy. In order to ensure + * that the randomness provided by this function is okay, the function + * wait_for_random_bytes() should be called and return 0 at least once + * at any point prior. */ static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64); u64 get_random_u64(void) diff --git a/include/linux/random.h b/include/linux/random.h index ed5c3838780d..e29929347c95 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -34,6 +34,7 @@ extern void add_input_randomness(unsigned int type, unsigned int code, extern void add_interrupt_randomness(int irq, int irq_flags) __latent_entropy; extern void get_random_bytes(void *buf, int nbytes); +extern int wait_for_random_bytes(void); extern int add_random_ready_callback(struct random_ready_callback *rdy); extern void del_random_ready_callback(struct random_ready_callback *rdy); extern void get_random_bytes_arch(void *buf, int nbytes); -- 2.13.0
WARNING: multiple messages have this Message-ID (diff)
From: "Jason A. Donenfeld" <Jason@zx2c4.com> To: Theodore Ts'o <tytso@mit.edu>, Linux Crypto Mailing List <linux-crypto@vger.kernel.org>, LKML <linux-kernel@vger.kernel.org>, kernel-hardening@lists.openwall.com, Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: "Jason A. Donenfeld" <Jason@zx2c4.com> Subject: [kernel-hardening] [PATCH RFC v2 1/8] random: add synchronous API for the urandom pool Date: Mon, 5 Jun 2017 05:47:50 +0200 [thread overview] Message-ID: <20170605034757.4803-2-Jason@zx2c4.com> (raw) In-Reply-To: <20170605034757.4803-1-Jason@zx2c4.com> This enables users of get_random_{bytes,u32,u64,int,long} to wait until the pool is ready before using this function, in case they actually want to have reliable randomness. Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> --- drivers/char/random.c | 41 +++++++++++++++++++++++++++++++---------- include/linux/random.h | 1 + 2 files changed, 32 insertions(+), 10 deletions(-) diff --git a/drivers/char/random.c b/drivers/char/random.c index 0ab024918907..035a5d7c06bd 100644 --- a/drivers/char/random.c +++ b/drivers/char/random.c @@ -844,11 +844,6 @@ static void crng_reseed(struct crng_state *crng, struct entropy_store *r) spin_unlock_irqrestore(&primary_crng.lock, flags); } -static inline void crng_wait_ready(void) -{ - wait_event_interruptible(crng_init_wait, crng_ready()); -} - static void _extract_crng(struct crng_state *crng, __u8 out[CHACHA20_BLOCK_SIZE]) { @@ -1466,7 +1461,10 @@ static ssize_t extract_entropy_user(struct entropy_store *r, void __user *buf, * number of good random numbers, suitable for key generation, seeding * TCP sequence numbers, etc. It does not rely on the hardware random * number generator. For random bytes direct from the hardware RNG - * (when available), use get_random_bytes_arch(). + * (when available), use get_random_bytes_arch(). In order to ensure + * that the randomness provided by this function is okay, the function + * wait_for_random_bytes() should be called and return 0 at least once + * at any point prior. */ void get_random_bytes(void *buf, int nbytes) { @@ -1496,6 +1494,24 @@ void get_random_bytes(void *buf, int nbytes) EXPORT_SYMBOL(get_random_bytes); /* + * Wait for the urandom pool to be seeded and thus guaranteed to supply + * cryptographically secure random numbers. This applies to: the /dev/urandom + * device, the get_random_bytes function, and the get_random_{u32,u64,int,long} + * family of functions. Using any of these functions without first calling + * this function forfeits the guarantee of security. + * + * Returns: 0 if the urandom pool has been seeded. + * -ERESTARTSYS if the function was interrupted by a signal. + */ +int wait_for_random_bytes(void) +{ + if (likely(crng_ready())) + return 0; + return wait_event_interruptible(crng_init_wait, crng_ready()); +} +EXPORT_SYMBOL(wait_for_random_bytes); + +/* * Add a callback function that will be invoked when the nonblocking * pool is initialised. * @@ -1849,6 +1865,8 @@ const struct file_operations urandom_fops = { SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count, unsigned int, flags) { + int ret; + if (flags & ~(GRND_NONBLOCK|GRND_RANDOM)) return -EINVAL; @@ -1861,9 +1879,9 @@ SYSCALL_DEFINE3(getrandom, char __user *, buf, size_t, count, if (!crng_ready()) { if (flags & GRND_NONBLOCK) return -EAGAIN; - crng_wait_ready(); - if (signal_pending(current)) - return -ERESTARTSYS; + ret = wait_for_random_bytes(); + if (unlikely(ret)) + return ret; } return urandom_read(NULL, buf, count, NULL); } @@ -2023,7 +2041,10 @@ struct batched_entropy { /* * Get a random word for internal kernel use only. The quality of the random * number is either as good as RDRAND or as good as /dev/urandom, with the - * goal of being quite fast and not depleting entropy. + * goal of being quite fast and not depleting entropy. In order to ensure + * that the randomness provided by this function is okay, the function + * wait_for_random_bytes() should be called and return 0 at least once + * at any point prior. */ static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_u64); u64 get_random_u64(void) diff --git a/include/linux/random.h b/include/linux/random.h index ed5c3838780d..e29929347c95 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -34,6 +34,7 @@ extern void add_input_randomness(unsigned int type, unsigned int code, extern void add_interrupt_randomness(int irq, int irq_flags) __latent_entropy; extern void get_random_bytes(void *buf, int nbytes); +extern int wait_for_random_bytes(void); extern int add_random_ready_callback(struct random_ready_callback *rdy); extern void del_random_ready_callback(struct random_ready_callback *rdy); extern void get_random_bytes_arch(void *buf, int nbytes); -- 2.13.0
next prev parent reply other threads:[~2017-06-05 3:47 UTC|newest] Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-06-05 3:47 [PATCH RFC v2 0/8] get_random_bytes_wait family of APIs Jason A. Donenfeld 2017-06-05 3:47 ` [kernel-hardening] " Jason A. Donenfeld 2017-06-05 3:47 ` Jason A. Donenfeld [this message] 2017-06-05 3:47 ` [kernel-hardening] [PATCH RFC v2 1/8] random: add synchronous API for the urandom pool Jason A. Donenfeld 2017-06-05 3:47 ` [PATCH RFC v2 2/8] random: add get_random_{bytes,u32,u64,int,long,once}_wait family Jason A. Donenfeld 2017-06-05 3:47 ` [kernel-hardening] " Jason A. Donenfeld 2017-06-05 3:47 ` [PATCH RFC v2 3/8] random: warn when kernel uses unseeded randomness Jason A. Donenfeld 2017-06-05 3:47 ` [kernel-hardening] " Jason A. Donenfeld 2017-06-05 3:47 ` [PATCH RFC v2 4/8] crypto/rng: ensure that the RNG is ready before using Jason A. Donenfeld 2017-06-05 3:47 ` [kernel-hardening] " Jason A. Donenfeld 2017-06-05 3:47 ` [PATCH RFC v2 5/8] security/keys: ensure RNG is seeded before use Jason A. Donenfeld 2017-06-05 3:47 ` [kernel-hardening] " Jason A. Donenfeld 2017-06-05 23:18 ` Jason A. Donenfeld 2017-06-05 23:18 ` [kernel-hardening] " Jason A. Donenfeld 2017-06-05 3:47 ` [PATCH RFC v2 6/8] iscsi: " Jason A. Donenfeld 2017-06-05 3:47 ` [kernel-hardening] " Jason A. Donenfeld 2017-06-05 3:47 ` [PATCH RFC v2 7/8] bluetooth/smp: ensure RNG is properly seeded before ECDH use Jason A. Donenfeld 2017-06-05 3:47 ` [kernel-hardening] " Jason A. Donenfeld 2017-06-05 3:47 ` [PATCH RFC v2 8/8] ceph: ensure RNG is seeded before using Jason A. Donenfeld 2017-06-05 3:47 ` [kernel-hardening] " Jason A. Donenfeld 2017-06-05 23:47 ` [PATCH RFC v2 0/8] get_random_bytes_wait family of APIs Jason A. Donenfeld 2017-06-05 23:47 ` [kernel-hardening] " Jason A. Donenfeld 2017-06-06 7:45 ` Greg Kroah-Hartman 2017-06-06 7:45 ` [kernel-hardening] " Greg Kroah-Hartman 2017-06-06 12:24 ` Jason A. Donenfeld 2017-06-06 12:24 ` [kernel-hardening] " Jason A. Donenfeld
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