From e297a783e41560b44e3c14f38e420cba518113b8 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Wed, 7 Jun 2017 19:58:56 -0400 Subject: random: add wait_for_random_bytes() API 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 Signed-off-by: Theodore Ts'o --- include/linux/random.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/random.h') 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); -- cgit v1.2.3 From da9ba564bd683374b8d319756f312821b8265b06 Mon Sep 17 00:00:00 2001 From: "Jason A. Donenfeld" Date: Wed, 7 Jun 2017 20:05:02 -0400 Subject: random: add get_random_{bytes,u32,u64,int,long,once}_wait family These functions are simple convenience wrappers that call wait_for_random_bytes before calling the respective get_random_* function. Signed-off-by: Jason A. Donenfeld Signed-off-by: Theodore Ts'o --- include/linux/net.h | 2 ++ include/linux/once.h | 2 ++ include/linux/random.h | 25 +++++++++++++++++++++++++ 3 files changed, 29 insertions(+) (limited to 'include/linux/random.h') diff --git a/include/linux/net.h b/include/linux/net.h index abcfa46a2bd9..dda2cc939a53 100644 --- a/include/linux/net.h +++ b/include/linux/net.h @@ -274,6 +274,8 @@ do { \ #define net_get_random_once(buf, nbytes) \ get_random_once((buf), (nbytes)) +#define net_get_random_once_wait(buf, nbytes) \ + get_random_once_wait((buf), (nbytes)) int kernel_sendmsg(struct socket *sock, struct msghdr *msg, struct kvec *vec, size_t num, size_t len); diff --git a/include/linux/once.h b/include/linux/once.h index 285f12cb40e6..9c98aaa87cbc 100644 --- a/include/linux/once.h +++ b/include/linux/once.h @@ -53,5 +53,7 @@ void __do_once_done(bool *done, struct static_key *once_key, #define get_random_once(buf, nbytes) \ DO_ONCE(get_random_bytes, (buf), (nbytes)) +#define get_random_once_wait(buf, nbytes) \ + DO_ONCE(get_random_bytes_wait, (buf), (nbytes)) \ #endif /* _LINUX_ONCE_H */ diff --git a/include/linux/random.h b/include/linux/random.h index e29929347c95..4aecc339558d 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -58,6 +58,31 @@ static inline unsigned long get_random_long(void) #endif } +/* Calls wait_for_random_bytes() and then calls get_random_bytes(buf, nbytes). + * Returns the result of the call to wait_for_random_bytes. */ +static inline int get_random_bytes_wait(void *buf, int nbytes) +{ + int ret = wait_for_random_bytes(); + if (unlikely(ret)) + return ret; + get_random_bytes(buf, nbytes); + return 0; +} + +#define declare_get_random_var_wait(var) \ + static inline int get_random_ ## var ## _wait(var *out) { \ + int ret = wait_for_random_bytes(); \ + if (unlikely(ret)) \ + return ret; \ + *out = get_random_ ## var(); \ + return 0; \ + } +declare_get_random_var_wait(u32) +declare_get_random_var_wait(u64) +declare_get_random_var_wait(int) +declare_get_random_var_wait(long) +#undef declare_get_random_var + unsigned long randomize_page(unsigned long start, unsigned long range); u32 prandom_u32(void); -- cgit v1.2.3 From 022c204040f3fd22d6445bc35517786195b7ae80 Mon Sep 17 00:00:00 2001 From: Rik van Riel Date: Wed, 12 Jul 2017 14:36:17 -0700 Subject: random,stackprotect: introduce get_random_canary function Patch series "stackprotector: ascii armor the stack canary", v2. Zero out the first byte of the stack canary value on 64 bit systems, in order to mitigate unterminated C string overflows. The null byte both prevents C string functions from reading the canary, and from writing it if the canary value were guessed or obtained through some other means. Reducing the entropy by 8 bits is acceptable on 64-bit systems, which will still have 56 bits of entropy left, but not on 32 bit systems, so the "ascii armor" canary is only implemented on 64-bit systems. Inspired by the "ascii armor" code in execshield and Daniel Micay's linux-hardened tree. Also see https://github.com/thestinger/linux-hardened/ This patch (of 5): Introduce get_random_canary(), which provides a random unsigned long canary value with the first byte zeroed out on 64 bit architectures, in order to mitigate non-terminated C string overflows. The null byte both prevents C string functions from reading the canary, and from writing it if the canary value were guessed or obtained through some other means. Reducing the entropy by 8 bits is acceptable on 64-bit systems, which will still have 56 bits of entropy left, but not on 32 bit systems, so the "ascii armor" canary is only implemented on 64-bit systems. Inspired by the "ascii armor" code in the old execshield patches, and Daniel Micay's linux-hardened tree. Link: http://lkml.kernel.org/r/20170524155751.424-2-riel@redhat.com Signed-off-by: Rik van Riel Acked-by: Kees Cook Cc: Daniel Micay Cc: "Theodore Ts'o" Cc: H. Peter Anvin Cc: Andy Lutomirski Cc: Ingo Molnar Cc: Catalin Marinas Cc: Yoshinori Sato Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/random.h | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) (limited to 'include/linux/random.h') diff --git a/include/linux/random.h b/include/linux/random.h index ed5c3838780d..1fa0dc880bd7 100644 --- a/include/linux/random.h +++ b/include/linux/random.h @@ -57,6 +57,27 @@ static inline unsigned long get_random_long(void) #endif } +/* + * On 64-bit architectures, protect against non-terminated C string overflows + * by zeroing out the first byte of the canary; this leaves 56 bits of entropy. + */ +#ifdef CONFIG_64BIT +# ifdef __LITTLE_ENDIAN +# define CANARY_MASK 0xffffffffffffff00UL +# else /* big endian, 64 bits: */ +# define CANARY_MASK 0x00ffffffffffffffUL +# endif +#else /* 32 bits: */ +# define CANARY_MASK 0xffffffffUL +#endif + +static inline unsigned long get_random_canary(void) +{ + unsigned long val = get_random_long(); + + return val & CANARY_MASK; +} + unsigned long randomize_page(unsigned long start, unsigned long range); u32 prandom_u32(void); -- cgit v1.2.3