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Merge pull request #4180 from gilles-peskine-arm/net_poll-fd_setsize-2.16

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Backport 2.16: Fix stack corruption in mbedtls_net_poll with large file descriptor
This commit is contained in:
Janos Follath 2021-03-04 12:15:53 +00:00 committed by GitHub
commit 1b6a24f759
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3 changed files with 33 additions and 3 deletions
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4
ChangeLog.d/net_poll-fd_setsize.txt Normal file
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@ -0,0 +1,4 @@
Security
* Fix a stack buffer overflow with mbedtls_net_poll() and
mbedtls_net_recv_timeout() when given a file descriptor that is
beyond FD_SETSIZE. Reported by FigBug in #4169.

18
include/mbedtls/net_sockets.h
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@ -151,6 +151,7 @@ int mbedtls_net_connect( mbedtls_net_context *ctx, const char *host, const char
*
* \return 0 if successful, or one of:
* MBEDTLS_ERR_NET_SOCKET_FAILED,
* MBEDTLS_ERR_NET_UNKNOWN_HOST,
* MBEDTLS_ERR_NET_BIND_FAILED,
* MBEDTLS_ERR_NET_LISTEN_FAILED
*
@ -170,6 +171,8 @@ int mbedtls_net_bind( mbedtls_net_context *ctx, const char *bind_ip, const char
* can be NULL if client_ip is null
*
* \return 0 if successful, or
* MBEDTLS_ERR_NET_SOCKET_FAILED,
* MBEDTLS_ERR_NET_BIND_FAILED,
* MBEDTLS_ERR_NET_ACCEPT_FAILED, or
* MBEDTLS_ERR_NET_BUFFER_TOO_SMALL if buf_size is too small,
* MBEDTLS_ERR_SSL_WANT_READ if bind_fd was set to
@ -182,6 +185,10 @@ int mbedtls_net_accept( mbedtls_net_context *bind_ctx,
/**
* \brief Check and wait for the context to be ready for read/write
*
* \note The current implementation of this function uses
* select() and returns an error if the file descriptor
* is \c FD_SETSIZE or greater.
*
* \param ctx Socket to check
* \param rw Bitflag composed of MBEDTLS_NET_POLL_READ and
* MBEDTLS_NET_POLL_WRITE specifying the events
@ -263,16 +270,21 @@ int mbedtls_net_send( void *ctx, const unsigned char *buf, size_t len );
* 'timeout' seconds. If no error occurs, the actual amount
* read is returned.
*
* \note The current implementation of this function uses
* select() and returns an error if the file descriptor
* is \c FD_SETSIZE or greater.
*
* \param ctx Socket
* \param buf The buffer to write to
* \param len Maximum length of the buffer
* \param timeout Maximum number of milliseconds to wait for data
* 0 means no timeout (wait forever)
*
* \return the number of bytes received,
* or a non-zero error code:
* MBEDTLS_ERR_SSL_TIMEOUT if the operation timed out,
* \return The number of bytes received if successful.
* MBEDTLS_ERR_SSL_TIMEOUT if the operation timed out.
* MBEDTLS_ERR_SSL_WANT_READ if interrupted by a signal.
* Another negative error code (MBEDTLS_ERR_NET_xxx)
* for other failures.
*
* \note This function will block (until data becomes available or
* timeout is reached) even if the socket is set to

14
library/net_sockets.c
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@ -496,6 +496,13 @@ int mbedtls_net_poll( mbedtls_net_context *ctx, uint32_t rw, uint32_t timeout )
if( fd < 0 )
return( MBEDTLS_ERR_NET_INVALID_CONTEXT );
/* A limitation of select() is that it only works with file descriptors
* that are strictly less than FD_SETSIZE. This is a limitation of the
* fd_set type. Error out early, because attempting to call FD_SET on a
* large file descriptor is a buffer overflow on typical platforms. */
if( fd >= FD_SETSIZE )
return( MBEDTLS_ERR_NET_POLL_FAILED );
#if defined(__has_feature)
#if __has_feature(memory_sanitizer)
/* Ensure that memory sanitizers consider read_fds and write_fds as
@ -615,6 +622,13 @@ int mbedtls_net_recv_timeout( void *ctx, unsigned char *buf,
if( fd < 0 )
return( MBEDTLS_ERR_NET_INVALID_CONTEXT );
/* A limitation of select() is that it only works with file descriptors
* that are strictly less than FD_SETSIZE. This is a limitation of the
* fd_set type. Error out early, because attempting to call FD_SET on a
* large file descriptor is a buffer overflow on typical platforms. */
if( fd >= FD_SETSIZE )
return( MBEDTLS_ERR_NET_POLL_FAILED );
FD_ZERO( &read_fds );
FD_SET( fd, &read_fds );