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[tftp] Process OACKs even if malformed

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IBM Tivoli PXE Server 5.1.0.3 is reported to send trailing garbage
bytes at the end of the OACK packet, which causes gPXE to reject the
packet and abort the TFTP transfer.

Work around the problem by processing as much as possible of the OACK,
and treating name/value parsing errors as non-fatal.

Reported-by: Shao Miller <Shao.Miller@yrdsb.edu.on.ca>
This commit is contained in:
Michael Brown 2009-05-20 10:03:13 +01:00
parent c5a88ed553
commit 1958974d0a
1 changed files with 28 additions and 12 deletions
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40
src/net/udp/tftp.c
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@ -672,6 +672,7 @@ static int tftp_rx_oack ( struct tftp_request *tftp, void *buf, size_t len ) {
char *end = buf + len;
char *name;
char *value;
char *next;
int rc = 0;
/* Sanity check */
@ -681,26 +682,41 @@ static int tftp_rx_oack ( struct tftp_request *tftp, void *buf, size_t len ) {
rc = -EINVAL;
goto done;
}
if ( end[-1] != '\0' ) {
DBGC ( tftp, "TFTP %p received OACK missing final NUL\n",
tftp );
rc = -EINVAL;
goto done;
}
/* Process each option in turn */
name = oack->data;
while ( name < end ) {
value = ( name + strlen ( name ) + 1 );
for ( name = oack->data ; name < end ; name = next ) {
/* Parse option name and value
*
* We treat parsing errors as non-fatal, because there
* exists at least one TFTP server (IBM Tivoli PXE
* Server 5.1.0.3) that has been observed to send
* malformed OACKs containing trailing garbage bytes.
*/
value = ( name + strnlen ( name, ( end - name ) ) + 1 );
if ( value > end ) {
DBGC ( tftp, "TFTP %p received OACK with malformed "
"option name:\n", tftp );
DBGC_HD ( tftp, oack, len );
break;
}
if ( value == end ) {
DBGC ( tftp, "TFTP %p received OACK missing value "
"for option \"%s\"\n", tftp, name );
rc = -EINVAL;
goto done;
DBGC_HD ( tftp, oack, len );
break;
}
next = ( value + strnlen ( value, ( end - value ) ) + 1 );
if ( next > end ) {
DBGC ( tftp, "TFTP %p received OACK with malformed "
"value for option \"%s\":\n", tftp, name );
DBGC_HD ( tftp, oack, len );
break;
}
/* Process option */
if ( ( rc = tftp_process_option ( tftp, name, value ) ) != 0 )
goto done;
name = ( value + strlen ( value ) + 1 );
}
/* Process tsize information, if available */