mirror of
https://github.com/yuzu-emu/mbedtls.git
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6b89197f26
This commit fixes issue #1212 related to platform-specific entropy polling in an syscall-emulated environment. Previously, the implementation of the entropy gathering function `mbedtls_platform_entropy_poll()` for linux machines used the following logic to determine how to obtain entropy from the kernel: 1. If the getrandom() system call identifier SYS_getrandom is present and the kernel version is 3.17 or higher, use syscall( SYS_getrandom, ... ) 2. Otherwise, fall back to reading from /dev/random. There are two issues with this: 1. Portability: When cross-compiling the code for a different architecture and running it through system call emulation in qemu, qemu reports the host kernel version through uname but, as of v.2.5.0, doesn't support emulating the getrandom() syscall. This leads to `mbedtls_platform_entropy_poll()` failing even though reading from /dev/random would have worked. 2. Style: Extracting the linux kernel version from the output of `uname` is slightly tedious. This commit fixes both by implementing the suggestion in #1212: - It removes the kernel-version detection through uname(). - Instead, it checks whether `syscall( SYS_getrandom, ... )` fails with errno set to ENOSYS indicating an unknown system call. If so, it falls through to trying to read from /dev/random. Fixes #1212.
230 lines
5.7 KiB
C
230 lines
5.7 KiB
C
/*
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* Platform-specific and custom entropy polling functions
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*
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* Copyright (C) 2006-2016, ARM Limited, All Rights Reserved
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed under the Apache License, Version 2.0 (the "License"); you may
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* not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* This file is part of mbed TLS (https://tls.mbed.org)
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*/
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#if !defined(MBEDTLS_CONFIG_FILE)
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#include "mbedtls/config.h"
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#else
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#include MBEDTLS_CONFIG_FILE
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#endif
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#if defined(MBEDTLS_ENTROPY_C)
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#include "mbedtls/entropy.h"
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#include "mbedtls/entropy_poll.h"
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#if defined(MBEDTLS_TIMING_C)
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#include <string.h>
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#include "mbedtls/timing.h"
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#endif
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#if defined(MBEDTLS_HAVEGE_C)
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#include "mbedtls/havege.h"
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#endif
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#if defined(MBEDTLS_ENTROPY_NV_SEED)
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#include "mbedtls/platform.h"
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#endif
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#if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)
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#if !defined(unix) && !defined(__unix__) && !defined(__unix) && \
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!defined(__APPLE__) && !defined(_WIN32)
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#error "Platform entropy sources only work on Unix and Windows, see MBEDTLS_NO_PLATFORM_ENTROPY in config.h"
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#endif
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#if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32)
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#if !defined(_WIN32_WINNT)
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#define _WIN32_WINNT 0x0400
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#endif
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#include <windows.h>
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#include <wincrypt.h>
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int mbedtls_platform_entropy_poll( void *data, unsigned char *output, size_t len,
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size_t *olen )
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{
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HCRYPTPROV provider;
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((void) data);
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*olen = 0;
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if( CryptAcquireContext( &provider, NULL, NULL,
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PROV_RSA_FULL, CRYPT_VERIFYCONTEXT ) == FALSE )
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{
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return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
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}
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if( CryptGenRandom( provider, (DWORD) len, output ) == FALSE )
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{
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CryptReleaseContext( provider, 0 );
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return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
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}
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CryptReleaseContext( provider, 0 );
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*olen = len;
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return( 0 );
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}
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#else /* _WIN32 && !EFIX64 && !EFI32 */
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/*
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* Test for Linux getrandom() support.
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* Since there is no wrapper in the libc yet, use the generic syscall wrapper
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* available in GNU libc and compatible libc's (eg uClibc).
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*/
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#if defined(__linux__) && defined(__GLIBC__)
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#include <unistd.h>
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#include <sys/syscall.h>
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#if defined(SYS_getrandom)
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#define HAVE_GETRANDOM
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#include <errno.h>
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static int getrandom_wrapper( void *buf, size_t buflen, unsigned int flags )
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{
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/* MemSan cannot understand that the syscall writes to the buffer */
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#if defined(__has_feature)
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#if __has_feature(memory_sanitizer)
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memset( buf, 0, buflen );
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#endif
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#endif
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return( syscall( SYS_getrandom, buf, buflen, flags ) );
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}
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#endif /* SYS_getrandom */
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#endif /* __linux__ */
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#include <stdio.h>
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int mbedtls_platform_entropy_poll( void *data,
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unsigned char *output, size_t len, size_t *olen )
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{
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FILE *file;
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size_t read_len;
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int ret;
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((void) data);
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#if defined(HAVE_GETRANDOM)
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ret = getrandom_wrapper( output, len, 0 );
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if( ret >= 0 )
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{
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*olen = ret;
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return( 0 );
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}
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else if( errno != ENOSYS )
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return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
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/* Fall through if the system call isn't known. */
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#else
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((void) ret;
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#endif /* HAVE_GETRANDOM */
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*olen = 0;
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file = fopen( "/dev/urandom", "rb" );
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if( file == NULL )
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return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
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read_len = fread( output, 1, len, file );
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if( read_len != len )
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{
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fclose( file );
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return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
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}
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fclose( file );
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*olen = len;
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return( 0 );
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}
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#endif /* _WIN32 && !EFIX64 && !EFI32 */
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#endif /* !MBEDTLS_NO_PLATFORM_ENTROPY */
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#if defined(MBEDTLS_TEST_NULL_ENTROPY)
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int mbedtls_null_entropy_poll( void *data,
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unsigned char *output, size_t len, size_t *olen )
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{
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((void) data);
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((void) output);
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*olen = 0;
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if( len < sizeof(unsigned char) )
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return( 0 );
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*olen = sizeof(unsigned char);
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return( 0 );
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}
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#endif
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#if defined(MBEDTLS_TIMING_C)
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int mbedtls_hardclock_poll( void *data,
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unsigned char *output, size_t len, size_t *olen )
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{
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unsigned long timer = mbedtls_timing_hardclock();
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((void) data);
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*olen = 0;
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if( len < sizeof(unsigned long) )
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return( 0 );
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memcpy( output, &timer, sizeof(unsigned long) );
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*olen = sizeof(unsigned long);
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return( 0 );
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}
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#endif /* MBEDTLS_TIMING_C */
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#if defined(MBEDTLS_HAVEGE_C)
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int mbedtls_havege_poll( void *data,
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unsigned char *output, size_t len, size_t *olen )
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{
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mbedtls_havege_state *hs = (mbedtls_havege_state *) data;
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*olen = 0;
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if( mbedtls_havege_random( hs, output, len ) != 0 )
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return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
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*olen = len;
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return( 0 );
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}
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#endif /* MBEDTLS_HAVEGE_C */
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#if defined(MBEDTLS_ENTROPY_NV_SEED)
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int mbedtls_nv_seed_poll( void *data,
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unsigned char *output, size_t len, size_t *olen )
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{
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unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
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size_t use_len = MBEDTLS_ENTROPY_BLOCK_SIZE;
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((void) data);
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memset( buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE );
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if( mbedtls_nv_seed_read( buf, MBEDTLS_ENTROPY_BLOCK_SIZE ) < 0 )
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return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
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if( len < use_len )
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use_len = len;
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memcpy( output, buf, use_len );
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*olen = use_len;
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return( 0 );
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}
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#endif /* MBEDTLS_ENTROPY_NV_SEED */
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#endif /* MBEDTLS_ENTROPY_C */
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