Re: libpq bug?

On Fri, Dec 28, 2018 at 2:00 PM Igor Korot <ikorot01(at)gmail(dot)com> wrote:

> Hi, ALL,
> Following code:
>
> int PostgresDatabase::GetTableOwner (const std::wstring &schemaName,
> const std::wstring &tableName, std::wstring &owner,
> std::vector<std::wstring> &errorMsg)
> {
> int result = 0;
> std::wstring query = L"SELECT u.usename FROM pg_class c, pg_user
> u, pg_namespace n WHERE n.oid = c.relnamespace AND u.usesysid =
> c.relowner AND n.nspname = $1 AND relname = $2";
> char *values[2];
> values[0] = NULL, values[1] = NULL;
> values[0] = new char[schemaName.length() + 1];
> values[1] = new char[tableName.length() + 1];
> memset( values[0], '\0', schemaName.length() + 1 );
> memset( values[1], '\0', tableName.length() + 1 );
> strcpy( values[0], m_pimpl->m_myconv.to_bytes( schemaName.c_str()
> ).c_str() );
> strcpy( values[1], m_pimpl->m_myconv.to_bytes( tableName.c_str()
> ).c_str() );
> int len1 = (int) schemaName.length();
> int len2 = (int) tableName.length();
> int length[2] = { len1, len2 };
> int formats[2] = { 1, 1 };
> PGresult *res = PQexecParams( m_db, m_pimpl->m_myconv.to_bytes(
> query.c_str() ).c_str(), 2, NULL, values, length, formats, 1 );
> ExecStatusType status = PQresultStatus( res );
> if( status != PGRES_COMMAND_OK && status != PGRES_TUPLES_OK )
> {
> result = 1;
> std::wstring err = m_pimpl->m_myconv.from_bytes(
> PQerrorMessage( m_db ) );
> errorMsg.push_back( L"Error executing query: " + err );
> PQclear( res );
> }
> else
> {
> owner = m_pimpl->m_myconv.from_bytes( PQgetvalue( res, 0, 0 ) );
> }
> return result;
> }
>
> when ran with the call of
>
> GetTableOwner( "public", "abcß", owner, errorMsg );
>
> returns:
>
> ERROR: Invalid byte sequence for encoding UTF8.
>
> Does this mean I found the bug in the library?
>

The bug is in your C++ code. "abcß" as tableName.lenght() (wstring) returns
4 (as in four characters) not number of bytes required to represent the
intended string: 61 62 63 c3 9f
Since the last character is a 2 bytes in length. Therefore, your call to
PQexecParams() specifies a shorter length and hence an invalid UTF-8
sequence.

Furthermore, your value[] array allocation is in error since
wstring::length returns number of characters, not number of bytes. so you
will end up with buffer-overflows.

HTH,
--patrick

> Any idea what I can do?
>
> Thank you.
>
>