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Re: libpq bug?

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On Fri, Dec 28, 2018 at 2:00 PM Igor Korot <ikorot01@xxxxxxxxx> 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.


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