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The isSource Predicate

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Michael Hohn
2020-07-22 15:09:16 -07:00
committed by =Michael Hohn
parent fd27af2216
commit c0bedda060
1 changed files with 4 additions and 4 deletions
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codeql-dataflow-sql-injection.md
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@@ -536,8 +536,8 @@ select sink, source, sink, "Possible SQL injection"
With the dataflow configuration in place, we just need to provide the details for With the dataflow configuration in place, we just need to provide the details for
source(s), sink(s), and taint step(s). source(s), sink(s), and taint step(s).
There are two more steps required to convert our previous queries for use in data Some more steps are required to convert our previous queries for use in data
flow. These are covered next. flow. These are covered here.
### The isSink Predicate ### The isSink Predicate
Note that our previous queries used `Expr` nodes, but the taint query requires Note that our previous queries used `Expr` nodes, but the taint query requires
@@ -644,8 +644,8 @@ read by and written to by the `snprintf` function call. Because we are specifyi
it as a *source*, the value of interest is the value *after* the call. We get it as a *source*, the value of interest is the value *after* the call. We get
this value by this value by
[casting](https://help.semmle.com/QL/ql-handbook/expressions.html#casts) to the [casting](https://help.semmle.com/QL/ql-handbook/expressions.html#casts) to the
post-update node selector. Instead of `source.asExpr()`, we use post-update node. Instead of `source.asExpr()`, we use
`source.(DataFlow::PostUpdateNode).getPreUpdateNode()` `source.(DataFlow::PostUpdateNode).getPreUpdateNode().asExpr()`
Last, we incorporate this into a predicate: Last, we incorporate this into a predicate: