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Call setbuf when reading or writing files: library

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After opening a file containing sensitive data, call mbedtls_setbuf() to
disable buffering. This way, we don't expose sensitive data to a memory
disclosure vulnerability in a buffer outside our control.

This commit adds a call to mbedtls_setbuf() after each call to fopen(),
except:
* In ctr_drbg.c, in load_file(), because this is only used for DH parameters
  and they are not confidential data.
* In psa_its_file.c, in psa_its_remove(), because the file is only opened
  to check its existence, we don't read data from it.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine
2022-06-30 17:03:40 +02:00
parent 6497b5a1d1
commit da0913ba6b
8 changed files with 36 additions and 1 deletions
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5
library/entropy_poll.c
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@ -35,7 +35,7 @@
#if defined(MBEDTLS_TIMING_C)
#include "mbedtls/timing.h"
#endif
#if defined(MBEDTLS_ENTROPY_NV_SEED)
#if defined(MBEDTLS_ENTROPY_NV_SEED) || !defined(HAVE_SYSCTL_ARND)
#include "mbedtls/platform.h"
#endif
@ -195,6 +195,9 @@ int mbedtls_platform_entropy_poll( void *data,
if( file == NULL )
return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
/* Ensure no stdio buffering of secrets, as such buffers cannot be wiped. */
mbedtls_setbuf( file, NULL );
read_len = fread( output, 1, len, file );
if( read_len != len )
{