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random: vDSO: move prototype of arch chacha function to vdso/getrandom.h

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Having the prototype for __arch_chacha20_blocks_nostack in
arch/x86/include/asm/vdso/getrandom.h meant that the prototype and large
doc comment were cloned by every architecture, which has been causing
unnecessary churn. Instead move it into include/vdso/getrandom.h, where
it can be shared by all archs implementing it.

As a side bonus, this then lets us use that prototype in the
vdso_test_chacha self test, to ensure that it matches the source, and
indeed doing so turned up some inconsistencies, which are rectified
here.

Suggested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
This commit is contained in:
Jason A. Donenfeld 2024-08-27 17:14:18 +02:00
parent 2aec90036d
commit 6fd13b282f
3 changed files with 20 additions and 16 deletions
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13
arch/x86/include/asm/vdso/getrandom.h
View File

@ -37,19 +37,6 @@ static __always_inline const struct vdso_rng_data *__arch_get_vdso_rng_data(void
return &__vdso_rng_data;
}
/**
* __arch_chacha20_blocks_nostack - Generate ChaCha20 stream without using the stack.
* @dst_bytes: Destination buffer to hold @nblocks * 64 bytes of output.
* @key: 32-byte input key.
* @counter: 8-byte counter, read on input and updated on return.
* @nblocks: Number of blocks to generate.
*
* Generates a given positive number of blocks of ChaCha20 output with nonce=0, and does not write
* to any stack or memory outside of the parameters passed to it, in order to mitigate stack data
* leaking into forked child processes.
*/
extern void __arch_chacha20_blocks_nostack(u8 *dst_bytes, const u32 *key, u32 *counter, size_t nblocks);
#endif /* !__ASSEMBLY__ */
#endif /* __ASM_VDSO_GETRANDOM_H */

13
include/vdso/getrandom.h
View File

@ -43,4 +43,17 @@ struct vgetrandom_state {
bool in_use;
};
/**
* __arch_chacha20_blocks_nostack - Generate ChaCha20 stream without using the stack.
* @dst_bytes: Destination buffer to hold @nblocks * 64 bytes of output.
* @key: 32-byte input key.
* @counter: 8-byte counter, read on input and updated on return.
* @nblocks: Number of blocks to generate.
*
* Generates a given positive number of blocks of ChaCha20 output with nonce=0, and does not write
* to any stack or memory outside of the parameters passed to it, in order to mitigate stack data
* leaking into forked child processes.
*/
extern void __arch_chacha20_blocks_nostack(u8 *dst_bytes, const u32 *key, u32 *counter, size_t nblocks);
#endif /* _VDSO_GETRANDOM_H */

10
tools/testing/selftests/vDSO/vdso_test_chacha.c
View File

@ -7,16 +7,20 @@
#include <sys/random.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include "../kselftest.h"
extern void __arch_chacha20_blocks_nostack(uint8_t *dst_bytes, const uint8_t *key, uint32_t *counter, size_t nblocks);
typedef uint8_t u8;
typedef uint32_t u32;
typedef uint64_t u64;
#include <vdso/getrandom.h>
int main(int argc, char *argv[])
{
enum { TRIALS = 1000, BLOCKS = 128, BLOCK_SIZE = 64 };
static const uint8_t nonce[8] = { 0 };
uint32_t counter[2];
uint8_t key[32];
uint32_t key[8];
uint8_t output1[BLOCK_SIZE * BLOCKS], output2[BLOCK_SIZE * BLOCKS];
ksft_print_header();
@ -27,7 +31,7 @@ int main(int argc, char *argv[])
printf("getrandom() failed!\n");
return KSFT_SKIP;
}
crypto_stream_chacha20(output1, sizeof(output1), nonce, key);
crypto_stream_chacha20(output1, sizeof(output1), nonce, (uint8_t *)key);
for (unsigned int split = 0; split < BLOCKS; ++split) {
memset(output2, 'X', sizeof(output2));
memset(counter, 0, sizeof(counter));