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Comment by kmoser

2 months ago

I don't understand your logic. Knowledge of the schema can give an attacker an edge because they now know the exact column names to probe. Whether these probes get logged is irrelevant; even if it makes the system more vulnerable for an instant, it's still more vulnerable.

Even if logging failed queries is your metric, then knowledge of column names would make it more likely for an attacker to craft correct queries, which would not get logged, thus making your logs less useful than if the attacker had to guess at column names and, in so doing, incur failed queries.

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kmoser

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tptacek  2 months ago

To probe for what? How does knowledge of a column name make it easier for me to discern whether a SQL injection vulnerability exists? I've spent a lot of time in my career probing for SQL injection, and I can't remember an instance where my stimulus/response setup involved the table names.

SQL injection is a property of a SQL query, not of the schema itself. To have a meaningful chance of blind-one-shotting a query, getting a TRUE/FALSE answer about susceptibility without ever generating a SQL syntax error, I would need to see the queries themselves.

  • kmoser  2 months ago

    Knowledge of the column names doesn't give you insight into whether a vulnerability exists. It gives you insight into what you can do with a vulnerability, should it exist. For example, if you want to set your account balance to $1 million, you'd need to know the column name in order to generate a valid query. Without advance knowledge of the column name, your job becomes harder.

    • hot_gril  2 months ago

      SQL injection will give you the entire schema anyway. It doesn't help if someone tells you the col names beforehand. I'm more wondering about non-SQL-injection vulns.

      7 replies →

  • default-kramer  2 months ago

    > How does knowledge of a column name make it easier for me to discern whether a SQL injection vulnerability exists?

    It doesn't. It just means that as soon as you find one, you can immediately begin crafting valid queries instead of randomly guessing table names and columns, therefore not setting off the "DB query failed" alert.

    EDIT: I guess this is the part I missed:

    > To have a meaningful chance of blind-one-shotting a query, getting a TRUE/FALSE answer about susceptibility without ever generating a SQL syntax error, I would need to see the queries themselves.

    Really? I guess I have to take your word for it because I've never attempted it, but I would have thought that in some (horribly broken) systems `bobby tables' or 1=1 --` would have a very reasonable chance of detecting SQL injection without alerting anyone.