arch/mips/kernel/setup.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+)
Nearly all other firmware environments have some way of passing a RNG
seed to initialize the RNG: DTB's rng-seed, EFI's RNG protocol, m68k's
bootinfo block, x86's setup_data, and so forth. This adds something
similar for MIPS, which will allow various firmware environments,
bootloaders, and hypervisors to pass an RNG seed to initialize the
kernel's RNG.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
---
arch/mips/kernel/setup.c | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c
index 2ca156a5b231..39c79f67c7a3 100644
--- a/arch/mips/kernel/setup.c
+++ b/arch/mips/kernel/setup.c
@@ -42,6 +42,7 @@
#include <asm/setup.h>
#include <asm/smp-ops.h>
#include <asm/prom.h>
+#include <asm/fw/fw.h>
#ifdef CONFIG_MIPS_ELF_APPENDED_DTB
char __section(".appended_dtb") __appended_dtb[0x100000];
@@ -756,6 +757,24 @@ static void __init prefill_possible_map(void)
static inline void prefill_possible_map(void) {}
#endif
+static void __init setup_rng_seed(void)
+{
+ char *rng_seed_hex = fw_getenv("rngseed");
+ u8 rng_seed[512];
+ size_t len;
+
+ if (!rng_seed_hex)
+ return;
+
+ len = min(sizeof(rng_seed), strlen(rng_seed_hex) / 2);
+ if (hex2bin(rng_seed, rng_seed_hex, len))
+ return;
+
+ add_bootloader_randomness(rng_seed, len);
+ memzero_explicit(rng_seed, len);
+ memzero_explicit(rng_seed_hex, len * 2);
+}
+
void __init setup_arch(char **cmdline_p)
{
cpu_probe();
@@ -786,6 +805,8 @@ void __init setup_arch(char **cmdline_p)
paging_init();
memblock_dump_all();
+
+ setup_rng_seed();
}
unsigned long kernelsp[NR_CPUS];
--
2.37.3
Hi Jason, On Fri, Sep 30, 2022 at 4:05 PM Jason A. Donenfeld <Jason@zx2c4.com> wrote: > > Nearly all other firmware environments have some way of passing a RNG > seed to initialize the RNG: DTB's rng-seed, EFI's RNG protocol, m68k's > bootinfo block, x86's setup_data, and so forth. This adds something > similar for MIPS, which will allow various firmware environments, > bootloaders, and hypervisors to pass an RNG seed to initialize the > kernel's RNG. > > Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> > --- > arch/mips/kernel/setup.c | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) > > diff --git a/arch/mips/kernel/setup.c b/arch/mips/kernel/setup.c > index 2ca156a5b231..39c79f67c7a3 100644 > --- a/arch/mips/kernel/setup.c > +++ b/arch/mips/kernel/setup.c > @@ -42,6 +42,7 @@ > #include <asm/setup.h> > #include <asm/smp-ops.h> > #include <asm/prom.h> > +#include <asm/fw/fw.h> > > #ifdef CONFIG_MIPS_ELF_APPENDED_DTB > char __section(".appended_dtb") __appended_dtb[0x100000]; > @@ -756,6 +757,24 @@ static void __init prefill_possible_map(void) > static inline void prefill_possible_map(void) {} > #endif > > +static void __init setup_rng_seed(void) > +{ > + char *rng_seed_hex = fw_getenv("rngseed"); > + u8 rng_seed[512]; > + size_t len; > + > + if (!rng_seed_hex) > + return; > + Assuming rngseed="x", ... > + len = min(sizeof(rng_seed), strlen(rng_seed_hex) / 2); ... len = 0 ... > + if (hex2bin(rng_seed, rng_seed_hex, len)) > + return; hex2bin(..., len=0) = 0 > + > + add_bootloader_randomness(rng_seed, len); So we call char/random code with len=0. Is it safe? Maybe simply safer to check len before calling hex2bin? > + memzero_explicit(rng_seed, len); > + memzero_explicit(rng_seed_hex, len * 2); > +} > + > void __init setup_arch(char **cmdline_p) > { > cpu_probe(); > @@ -786,6 +805,8 @@ void __init setup_arch(char **cmdline_p) > paging_init(); > > memblock_dump_all(); > + > + setup_rng_seed(); > } > > unsigned long kernelsp[NR_CPUS]; > -- > 2.37.3 >
Hi Philippe, On Tue, Oct 4, 2022 at 12:07 AM Philippe Mathieu-Daudé <f4bug@amsat.org> wrote: > > + add_bootloader_randomness(rng_seed, len); > > So we call char/random code with len=0. Is it safe? > Maybe simply safer to check len before calling hex2bin? add_bootloader_randomness() is safe for all input sizes, and is written to be callable with len=0 and have no effect. So this function should be good as-is; there's no need to special case an unlikely instance that's already handled by add_bootloader_randomness(). Jason
On 4/10/22 00:30, Jason A. Donenfeld wrote: > Hi Philippe, > > On Tue, Oct 4, 2022 at 12:07 AM Philippe Mathieu-Daudé <f4bug@amsat.org> wrote: >>> + add_bootloader_randomness(rng_seed, len); >> >> So we call char/random code with len=0. Is it safe? >> Maybe simply safer to check len before calling hex2bin? > > add_bootloader_randomness() is safe for all input sizes, and is > written to be callable with len=0 and have no effect. So this function > should be good as-is; there's no need to special case an unlikely > instance that's already handled by add_bootloader_randomness(). OK, thanks for the clarification. Phil.
On Fri, Sep 30, 2022 at 04:01:38PM +0200, Jason A. Donenfeld wrote: > Nearly all other firmware environments have some way of passing a RNG > seed to initialize the RNG: DTB's rng-seed, EFI's RNG protocol, m68k's > bootinfo block, x86's setup_data, and so forth. This adds something > similar for MIPS, which will allow various firmware environments, > bootloaders, and hypervisors to pass an RNG seed to initialize the > kernel's RNG. > > Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com> > --- > arch/mips/kernel/setup.c | 21 +++++++++++++++++++++ > 1 file changed, 21 insertions(+) applied to mips-next. Thomas. -- Crap can work. Given enough thrust pigs will fly, but it's not necessarily a good idea. [ RFC1925, 2.3 ]
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