| Message ID | 20220930140138.575751-1-Jason@zx2c4.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 056a68cea01edfa78b3474af1bfa39cc6bcc7bee |
| Headers | show |
| Series | mips: allow firmware to pass RNG seed to kernel | expand |
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.
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.
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];
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(+)