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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Minios-devel] [UNIKRAFT PATCH 1/2] lib/ukswrand: Replace LCR with ChaCha20
Hey Vlad, On 15.10.19 14:56, Vlad-Andrei BĂDOIU (78692) wrote: Hey Simon, Please see my response inline. Thanks, Vlad On 15.10.2019 15:30, Simon Kuenzer wrote:Hey, can't we keep MWC together with ChaCha and compile one of them according the the configuration? It is fine if you mark MWC in the menu as insecure and take ChaCha as default. I could imagine that MWC is faster - is this true? Hum, these are actually good points. But I still think we should keep both for now - also to demonstrate how we can plug-in different algorithms. I would expect that we have even more implementations in the future. What do you think? I am thinking that we should set the secure configuration as default. Thanks, Simon On 15.10.19 13:57, Vlad-Andrei BĂDOIU (78692) wrote:ChaCha20 is a cryptographically secure pseudorandom number generator. We replace the existing implementation, which is not secure, with ChaCha20. The implementation is based on the reference implementation of the author[1]. We add a new config option, LIBUKSWRAND_PERFORMANCE to disable the use of rdrand for seed generation. Currently, the seed is generated randomly only on X64. [1] http://cr.yp.to/streamciphers/timings/estreambench/submissions/salsa20/chacha8/ref/chacha.c Signed-off-by: Vlad-Andrei Badoiu <vlad_andrei.badoiu@xxxxxxxxxxxxxxx> --- lib/ukswrand/Config.uk | 15 ++++-- lib/ukswrand/Makefile.uk | 2 +- lib/ukswrand/include/uk/swrand.h | 91 ++++++++++++++++++++++++++++++-- lib/ukswrand/mwc.c | 54 +++++++++---------- 4 files changed, 124 insertions(+), 38 deletions(-) diff --git a/lib/ukswrand/Config.uk b/lib/ukswrand/Config.uk index c58371bb..e4ed6521 100644 --- a/lib/ukswrand/Config.uk +++ b/lib/ukswrand/Config.uk @@ -6,18 +6,25 @@ menuconfig LIBUKSWRAND if LIBUKSWRAND choice prompt "Algorithm" - default LIBUKSWRAND_MWC + default LIBUKSWRAND_CHACHA -config LIBUKSWRAND_MWC - bool "Multiply-with-carry" +config LIBUKSWRAND_CHACHA + bool "ChaCha20" help - Use multiply-with-carry algorithm + Use ChaCha20 algorithm endchoice config LIBUKSWRAND_INITIALSEED int "Initial random seed" default 23 +config LIBUKSWRAND_PERFORMANCE + bool "Performance settings over security" + default y + help + Use LIBUKSWRAND_INITIALSEED for the initial seed, the PRG is no + longer cryptographically secure + I would actually introduce a second choice which configures the seed generation. Only if the user select the option to take a pre-compiled seed, the prompt of LIBUKSWRAND_INITIALSEED should be visible.
The detailed struct defintion should actually go to the corresponding C files. So, you would have the prototype only:
struct uk_swrand;
The extern struct needs to be a pointer:
extern struct uk_swrand *uk_swrand_def;
or you move uk_swrandr_randr() to the generic code C file that also
initializes the default random number generator according to the menu
configuration (the library constructor).
I think this function could be also generic. Could be used for both, MWC and ChaCha. But I would provide it publicly on the API: uk_swrandr_gen_seed(), this way you could still have multiple instances of number generators (e.g., per CPU if you wish) and initialize them individually.
This else case you do not need in the code. You could use KConfig syntax to unlock the RDRAND way of gnerating on x86 only. There can be also other sources, like using the current timestamp which we may want to add (maybe as default for non x86?). Having the seed compileable could be useful to have for debugging code that uses random numbers. The sequence of random numbers is then always the same. Obviously this should not be standard. + return val; +} /* Uses the pre-initialized default generator */ /* TODO: Add assertion when we can test if we are in interrupt context */ /* TODO: Revisit with multi-CPU support */ diff --git a/lib/ukswrand/mwc.c b/lib/ukswrand/mwc.c index 85abf0c6..21c91f3a 100644 --- a/lib/ukswrand/mwc.c +++ b/lib/ukswrand/mwc.c @@ -39,8 +39,6 @@ #include <uk/assert.h> #include <uk/ctors.h> -/* https://stackoverflow.com/questions/9492581/c-random-number-generation-pure-c-code-no-libraries-or-functions */ -#define PHI 0x9e3779b9 #define UK_SWRAND_CTOR_PRIO 1 struct uk_swrand uk_swrand_def; @@ -50,45 +48,45 @@ struct uk_swrand uk_swrand_def; */ static void _uk_swrand_ctor(void); -void uk_swrand_init_r(struct uk_swrand *r, __u32 seed) +void uk_swrand_init_r(struct uk_swrand *r) { __u32 i; UK_ASSERT(r); + /* Initialize chacha */ + // TODO: add config option to enable/disable this + __u32 k[8], iv[2]; - r->Q[0] = seed; - r->Q[1] = seed + PHI; - r->Q[2] = seed + PHI + PHI; - for (i = 3; i < 4096; i++) - r->Q[i] = r->Q[i - 3] ^ r->Q[i - 2] ^ PHI ^ i; + for (i = 0; i < 8; i++) + k[i] = _get_random_seed(); - r->c = 362436; - r->i = 4095; + iv[0] = _get_random_seed(); + iv[1] = _get_random_seed(); + + _uk_key_setup(r, k); + _uk_iv_setup(r, iv); + + r->k = 16; } __u32 uk_swrand_randr_r(struct uk_swrand *r) { - __u64 t, a = 18782LL; - __u32 x, y = 0xfffffffe; - __u32 i, c; + __u32 res; - UK_ASSERT(r); + for (;;) { + _uk_salsa20_wordtobyte(r->output, r->input); + r->input[12] = r->input[12] + 1; + if (r->input[12] == 0) + r->input[13]++; - i = r->i; - c = r->c; + if (r->k < 16) { + res = r->output[r->k]; + r->k += 1; + return res; + } - i = (i + 1) & 4095; - t = a * r->Q[i] + c; - c = (t >> 32); - x = t + c; - if (x < c) { - x++; - c++; + r->k = 0; } - - r->i = i; - r->c = c; - return (r->Q[i] = y - x); } ssize_t uk_swrand_fill_buffer(void *buf, size_t buflen)If you keep mwc.c and add chacha.c, you may want to move some functions (like this one) to a generic place.
I would not change the signature, just do:
uk_swrand_init_r(&uk_swrand_def, uk_swrandr_gen_seed());
} UK_CTOR_FUNC(UK_SWRAND_CTOR_PRIO, _uk_swrand_ctor); What do you think? Thanks, Simon _______________________________________________ Minios-devel mailing list Minios-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/minios-devel
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