75 lines
2.4 KiB
C
75 lines
2.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Copyright (C) 2022-2024 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
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*/
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#ifndef _VDSO_GETRANDOM_H
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#define _VDSO_GETRANDOM_H
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#include <linux/types.h>
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#define CHACHA_KEY_SIZE 32
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#define CHACHA_BLOCK_SIZE 64
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/**
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* struct vgetrandom_state - State used by vDSO getrandom().
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*
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* @batch: One and a half ChaCha20 blocks of buffered RNG output.
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*
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* @key: Key to be used for generating next batch.
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*
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* @batch_key: Union of the prior two members, which is exactly two full
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* ChaCha20 blocks in size, so that @batch and @key can be filled
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* together.
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*
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* @generation: Snapshot of @rng_info->generation in the vDSO data page at
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* the time @key was generated.
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*
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* @pos: Offset into @batch of the next available random byte.
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*
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* @in_use: Reentrancy guard for reusing a state within the same thread
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* due to signal handlers.
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*/
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struct vgetrandom_state {
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union {
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struct {
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u8 batch[CHACHA_BLOCK_SIZE * 3 / 2];
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u32 key[CHACHA_KEY_SIZE / sizeof(u32)];
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};
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u8 batch_key[CHACHA_BLOCK_SIZE * 2];
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};
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u64 generation;
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u8 pos;
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bool in_use;
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};
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/**
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* __arch_chacha20_blocks_nostack - Generate ChaCha20 stream without using the stack.
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* @dst_bytes: Destination buffer to hold @nblocks * 64 bytes of output.
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* @key: 32-byte input key.
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* @counter: 8-byte counter, read on input and updated on return.
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* @nblocks: Number of blocks to generate.
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*
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* Generates a given positive number of blocks of ChaCha20 output with nonce=0, and does not write
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* to any stack or memory outside of the parameters passed to it, in order to mitigate stack data
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* leaking into forked child processes.
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*/
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extern void __arch_chacha20_blocks_nostack(u8 *dst_bytes, const u32 *key, u32 *counter, size_t nblocks);
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/**
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* __vdso_getrandom - Architecture-specific vDSO implementation of getrandom() syscall.
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* @buffer: Passed to __cvdso_getrandom().
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* @len: Passed to __cvdso_getrandom().
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* @flags: Passed to __cvdso_getrandom().
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* @opaque_state: Passed to __cvdso_getrandom().
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* @opaque_len: Passed to __cvdso_getrandom();
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*
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* This function is implemented by making a single call to to __cvdso_getrandom(), whose
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* documentation may be consulted for more information.
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*
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* Returns: The return value of __cvdso_getrandom().
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*/
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extern ssize_t __vdso_getrandom(void *buffer, size_t len, unsigned int flags, void *opaque_state, size_t opaque_len);
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#endif /* _VDSO_GETRANDOM_H */
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