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wolfssh
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Zeroize SFTP file payload buffers before freeing

pull/1048/head
Yosuke Shimizu 2026-06-23 14:46:00 +09:00 committed by John Safranek
parent 281e4bc19f
commit 4483254e8c
3 changed files with 23 additions and 2 deletions
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1
.github/workflows/os-check.yml vendored
View File

@ -72,6 +72,7 @@ jobs:
'',
'--enable-all',
'--enable-sftp',
'--enable-sftp --disable-sftp-zeroize',
'--enable-scp',
'--enable-keyboard-interactive',
'--enable-shell',

8
configure.ac
View File

@ -151,6 +151,11 @@ AC_ARG_ENABLE([sftp],
[AS_HELP_STRING([--enable-sftp],[Enable SFTP support (default: disabled)])],
[ENABLED_SFTP=$enableval],[ENABLED_SFTP=no])
# SFTP buffer zeroization
AC_ARG_ENABLE([sftp-zeroize],
[AS_HELP_STRING([--disable-sftp-zeroize],[Disable zeroization of SFTP file payload buffers before free (default: enabled)])],
[ENABLED_SFTP_ZEROIZE=$enableval],[ENABLED_SFTP_ZEROIZE=yes])
# SSHD
AC_ARG_ENABLE([sshd],
[AS_HELP_STRING([--enable-sshd],[Enable SSHD support (default: disabled)])],
@ -235,6 +240,8 @@ AS_IF([test "x$ENABLED_SCP" = "xyes"],
[AM_CPPFLAGS="$AM_CPPFLAGS -DWOLFSSH_SCP"])
AS_IF([test "x$ENABLED_SFTP" = "xyes"],
[AM_CPPFLAGS="$AM_CPPFLAGS -DWOLFSSH_SFTP"])
AS_IF([test "x$ENABLED_SFTP_ZEROIZE" = "xno"],
[AM_CPPFLAGS="$AM_CPPFLAGS -DWOLFSSH_NO_SFTP_BUFFER_ZERO"])
AS_IF([test "x$ENABLED_FWD" = "xyes"],
[AM_CPPFLAGS="$AM_CPPFLAGS -DWOLFSSH_FWD"])
AS_IF([test "x$ENABLED_TERM" = "xyes"],
@ -342,6 +349,7 @@ AS_ECHO([" * psuedo-terminal: $ENABLED_TERM"])
AS_ECHO([" * echoserver shell support: $ENABLED_SHELL"])
AS_ECHO([" * scp: $ENABLED_SCP"])
AS_ECHO([" * sftp: $ENABLED_SFTP"])
AS_ECHO([" * sftp buffer zeroize: $ENABLED_SFTP_ZEROIZE"])
AS_ECHO([" * sshd: $ENABLED_SSHD"])
AS_ECHO([" * ssh client: $ENABLED_SSHCLIENT"])
AS_ECHO([" * agent: $ENABLED_AGENT"])

16
src/wolfsftp.c
View File

@ -470,6 +470,12 @@ static int wolfSSH_SFTP_buffer_set_size(WS_SFTP_BUFFER* buffer, word32 sz)
return WS_BAD_ARGUMENT;
}
#ifndef WOLFSSH_NO_SFTP_BUFFER_ZERO
/* wipe any payload in the region being trimmed off before shrinking */
if (buffer->data != NULL && sz < buffer->sz) {
ForceZero(buffer->data + sz, buffer->sz - sz);
}
#endif
buffer->sz = sz;
return WS_SUCCESS;
}
@ -793,12 +799,15 @@ static int wolfSSH_SFTP_buffer_read(WOLFSSH* ssh, WS_SFTP_BUFFER* buffer,
static void wolfSSH_SFTP_buffer_free(WOLFSSH* ssh, WS_SFTP_BUFFER* buffer)
{
if (ssh != NULL && buffer != NULL) {
buffer->idx = 0;
buffer->sz = 0;
if (buffer->data != NULL) {
#ifndef WOLFSSH_NO_SFTP_BUFFER_ZERO
ForceZero(buffer->data, buffer->sz);
#endif
WFREE(buffer->data, ssh->ctx->heap, DYNTYPE_BUFFER);
buffer->data = NULL;
}
buffer->idx = 0;
buffer->sz = 0;
}
}
@ -1424,6 +1433,9 @@ static void wolfSSH_SFTP_RecvSetSend(WOLFSSH* ssh, byte* buf, int sz)
/* free up existing data if needed */
if (buf != state->buffer.data && state->buffer.data != NULL) {
#ifndef WOLFSSH_NO_SFTP_BUFFER_ZERO
ForceZero(state->buffer.data, state->buffer.sz);
#endif
WFREE(state->buffer.data, ssh->ctx->heap, DYNTYPE_BUFFER);
state->buffer.data = NULL;
}