A new issue with bcp/freebcp

Hi All,

I've had a new issue reported to me on freebcp.
This has come from someone migrating from Sybase to SQL Server, using freetds as their "enabler" - an increasing trend in the use of freetds, I'm told.
So we have some solid evidence - "This works using Sybase bcp, but it doesn't work with freebcp" - and although it's an edge case, I think it should be fixed.

So the problem occurs with freebcp using a format file. It evidences itself as a dbconvert() overflow error...

The problematic column is CHAR(6) on the database
The line from the format file for the column looks like this:

22      SYBCHAR 0       6       "~"     22      cost_center

and a snippet from the problematic line from the data file, showing the problematic host file data looks like this:

...~123456  ~...

So in the format file, we've given a host file data length as 6 (the fourth token in the format file), but we've also said the data is terminated  (by a "~")
However, there's a couple of extra spaces on the end of that data in the data file, giving it a total length of 8 characters.

Well I took a look at this, and the Sybase manual pages for format files tells me the following about the host file data length:


"Host file data length refers to the maximum number of bytes to copy for the field. To decide how much data to copy in or out, bcp uses one of:

- The maximum field length
- The prefix length, if any
- The field terminator string, if any

If more than one method of field length specification is given, bcp chooses the one that copies the least amount of data."
This caused me to delve into _bcp_read_hostfile()  (in src/dblib/bcp.c). To be honest, it shows the signs of having "evolved" to deal with the myriad of possibilities available to the innocent or pragmatic user. I'm probably to blame for much of that ad-hoc evolution, and here's another mutation to add to the mix. It works, and doesn't make things significantly worse than they they currently are:
Add the following lines to the function after approximately line 1421 of bcp.c (some context given):

               /*
                * FIXME bcpcol->bcp_column_data->data && bcpcol->column_size ??
                * It seems a buffer overflow waiting...
                */

+              /* If column length specified (in a format file), then it *might*   */
+              /* be less than the data read from file (if the column was also     */
+              /* described as a terminated field...) in this case we need to only */
+              /* take the number of characters specified in the column length     */
+
+              if (hostcol->column_len > 0) {
+                     collen = (hostcol->column_len < collen) ? hostcol->column_len : collen;
+              }

               bcpcol->bcp_column_data->datalen =
                    dbconvert(dbproc, hostcol->datatype, (const BYTE *) coldata, collen, desttype,
                              bcpcol->bcp_column_data->data, bcpcol->column_size);

               if (bcpcol->bcp_column_data->datalen == -1) {


In penance, I may re-work the function at some point soon. The code is going to keep me awake at nights otherwise...

Bill



.


Bill Thompson

GMO Technology
Bank of America Merrill Lynch
5 Canada Square
London E14 5AQ
Phone: +44 (0)207 995 8307
Email: [email protected]


----------------------------------------------------------------------
This message w/attachments (message) is intended solely for the use of the intended recipient(s) and may contain information that is privileged, confidential or proprietary. If you are not an intended recipient, please notify the sender, and then please delete and destroy all copies and attachments, and be advised that any review or dissemination of, or the taking of any action in reliance on, the information contained in or attached to this message is prohibited. 
Unless specifically indicated, this message is not an offer to sell or a solicitation of any investment products or other financial product or service, an official confirmation of any transaction, or an official statement of Sender. Subject to applicable law, Sender may intercept, monitor, review and retain e-communications (EC) traveling through its networks/systems and may produce any such EC to regulators, law enforcement, in litigation and as required by law. 
The laws of the country of each sender/recipient may impact the handling of EC, and EC may be archived, supervised and produced in countries other than the country in which you are located. This message cannot be guaranteed to be secure or free of errors or viruses. 

References to "Sender" are references to any subsidiary of Bank of America Corporation. Securities and Insurance Products: * Are Not FDIC Insured * Are Not Bank Guaranteed * May Lose Value * Are Not a Bank Deposit * Are Not a Condition to Any Banking Service or Activity * Are Not Insured by Any Federal Government Agency. Attachments that are part of this EC may have additional important disclosures and disclaimers, which you should read. This message is subject to terms available at the following link: 
http://www.bankofamerica.com/emaildisclaimer. By messaging with Sender you consent to the foregoing.