C++: Give Snprintf a proper interface.

geoffw0 · geoffw0 · commit e065466180b0 · 2020-11-06T15:38:57.000Z
diff --git a/cpp/ql/src/semmle/code/cpp/models/implementations/Printf.qll b/cpp/ql/src/semmle/code/cpp/models/implementations/Printf.qll
@@ -119,11 +119,10 @@ private class Sprintf extends FormattingFunction {
 }
 
 /**
- * The standard functions `snprintf` and `swprintf`, and their
- * Microsoft and glib variants.
+ * Implements `Snprintf`.
  */
-private class Snprintf extends FormattingFunction {
-  Snprintf() {
+private class SnprintfImpl extends Snprintf {
+  SnprintfImpl() {
     this instanceof TopLevelFunction and
     (
       hasGlobalOrStdName("snprintf") or // C99 defines snprintf
@@ -180,12 +179,7 @@ private class Snprintf extends FormattingFunction {
     )
   }
 
-  /**
-   * Holds if this function returns the length of the formatted string
-   * that would have been output, regardless of the amount of space
-   * in the buffer.
-   */
-  predicate returnsFullFormatLength() {
+  override predicate returnsFullFormatLength() {
     (
       hasGlobalOrStdName("snprintf") or
       hasGlobalName("g_snprintf") or
diff --git a/cpp/ql/src/semmle/code/cpp/models/interfaces/FormattingFunction.qll b/cpp/ql/src/semmle/code/cpp/models/interfaces/FormattingFunction.qll
@@ -165,3 +165,16 @@ abstract class FormattingFunction extends ArrayFunction, TaintFunction {
     )
   }
 }
+
+/**
+ * The standard functions `snprintf` and `swprintf`, and their
+ * Microsoft and glib variants.
+ */
+abstract class Snprintf extends FormattingFunction {
+  /**
+   * Holds if this function returns the length of the formatted string
+   * that would have been output, regardless of the amount of space
+   * in the buffer.
+   */
+  predicate returnsFullFormatLength() { none() }
+}

Original file line number	Diff line number	Diff line change
`@@ -119,11 +119,10 @@ private class Sprintf extends FormattingFunction {`
`119`	`119`	`}`
`120`	`120`
`121`	`121`	`/**`
`122`		- * The standard functions `snprintf` and `swprintf`, and their
`123`		`- * Microsoft and glib variants.`
	`122`	+ * Implements `Snprintf`.
`124`	`123`	`*/`
`125`		`-private class Snprintf extends FormattingFunction {`
`126`		`- Snprintf() {`
	`124`	`+private class SnprintfImpl extends Snprintf {`
	`125`	`+ SnprintfImpl() {`
`127`	`126`	`this instanceof TopLevelFunction and`
`128`	`127`	`(`
`129`	`128`	`hasGlobalOrStdName("snprintf") or // C99 defines snprintf`
`@@ -180,12 +179,7 @@ private class Snprintf extends FormattingFunction {`
`180`	`179`	`)`
`181`	`180`	`}`
`182`	`181`
`183`		`- /**`
`184`		`- * Holds if this function returns the length of the formatted string`
`185`		`- * that would have been output, regardless of the amount of space`
`186`		`- * in the buffer.`
`187`		`- */`
`188`		`- predicate returnsFullFormatLength() {`
	`182`	`+ override predicate returnsFullFormatLength() {`
`189`	`183`	`(`
`190`	`184`	`hasGlobalOrStdName("snprintf") or`
`191`	`185`	`hasGlobalName("g_snprintf") or`
Original file line number	Diff line number	Diff line change
`@@ -165,3 +165,16 @@ abstract class FormattingFunction extends ArrayFunction, TaintFunction {`
`165`	`165`	`)`
`166`	`166`	`}`
`167`	`167`	`}`
	`168`	`+`
	`169`	`+/**`
	`170`	+ * The standard functions `snprintf` and `swprintf`, and their
	`171`	`+ * Microsoft and glib variants.`
	`172`	`+ */`
	`173`	`+abstract class Snprintf extends FormattingFunction {`
	`174`	`+ /**`
	`175`	`+ * Holds if this function returns the length of the formatted string`
	`176`	`+ * that would have been output, regardless of the amount of space`
	`177`	`+ * in the buffer.`
	`178`	`+ */`
	`179`	`+ predicate returnsFullFormatLength() { none() }`
	`180`	`+}`