Brodes/seh flow phase1 throwing models

cpp/ql/lib/change-notes/2024-11-18-throwing-functions.md

@@ -0,0 +1,4 @@
+---
+category: minorAnalysis
+---
+* Removed NonThrowing.qll. Throwing meta-data now part of Throwing.qll. Updated models and IR to use the new Throwing library and predicates.

cpp/ql/lib/semmle/code/cpp/models/implementations/Memcpy.qll

@@ -3,13 +3,13 @@
  * functions. See `semmle.code.cpp.models.Models` for usage information.
  */
 
 import semmle.code.cpp.Function
 import semmle.code.cpp.models.interfaces.ArrayFunction
 import semmle.code.cpp.models.interfaces.DataFlow
 import semmle.code.cpp.models.interfaces.Alias
 import semmle.code.cpp.models.interfaces.SideEffect
 import semmle.code.cpp.models.interfaces.Taint
-import semmle.code.cpp.models.interfaces.NonThrowing
+import semmle.code.cpp.models.interfaces.Throwing
 
 /**
  * The standard functions `memcpy`, `memmove` and `bcopy`; and the gcc variant
@@ -106,6 +106,8 @@
     not this.hasGlobalName(["bcopy", mempcpy(), "memccpy"]) and
     index = this.getParamDest()
   }
+
+  override TCxxException getExceptionType() { any() }
 }
 
 private string mempcpy() { result = ["mempcpy", "wmempcpy"] }

cpp/ql/lib/semmle/code/cpp/models/implementations/Memset.qll

@@ -3,12 +3,12 @@
  * functions. See `semmle.code.cpp.models.Models` for usage information.
  */
 
 import semmle.code.cpp.Function
 import semmle.code.cpp.models.interfaces.ArrayFunction
 import semmle.code.cpp.models.interfaces.DataFlow
 import semmle.code.cpp.models.interfaces.Alias
 import semmle.code.cpp.models.interfaces.SideEffect
-import semmle.code.cpp.models.interfaces.NonThrowing
+import semmle.code.cpp.models.interfaces.Throwing
 
 private class MemsetFunctionModel extends ArrayFunction, DataFlowFunction, AliasFunction,
   SideEffectFunction, NonThrowingFunction
@@ -74,6 +74,8 @@
     i = 0 and
     if this.hasGlobalName(bzero()) then result = 1 else result = 2
   }
+
+  override TCxxException getExceptionType() { any() }
 }
 
 private string bzero() { result = ["bzero", "explicit_bzero"] }

cpp/ql/lib/semmle/code/cpp/models/implementations/NoexceptFunction.qll

@@ -1,4 +1,4 @@
-import semmle.code.cpp.models.interfaces.NonThrowing
+import semmle.code.cpp.models.interfaces.Throwing
 
 /**
  * A function that is annotated with a `noexcept` specifier (or the equivalent
@@ -8,4 +8,6 @@ import semmle.code.cpp.models.interfaces.NonThrowing
  */
 class NoexceptFunction extends NonThrowingFunction {
   NoexceptFunction() { this.isNoExcept() or this.isNoThrow() }
+
+  override TCxxException getExceptionType() { any() }
 }

cpp/ql/lib/semmle/code/cpp/models/implementations/Printf.qll

@@ -8,7 +8,7 @@
 import semmle.code.cpp.models.interfaces.FormattingFunction
 import semmle.code.cpp.models.interfaces.Alias
 import semmle.code.cpp.models.interfaces.SideEffect
-import semmle.code.cpp.models.interfaces.NonThrowing
+import semmle.code.cpp.models.interfaces.Throwing
 
 /**
  * The standard functions `printf`, `wprintf` and their glib variants.
@@ -32,6 +32,8 @@ private class Printf extends FormattingFunction, AliasFunction, NonThrowingFunct
   override predicate parameterEscapesOnlyViaReturn(int n) { none() }
 
   override predicate parameterIsAlwaysReturned(int n) { none() }
+
+  override TCxxException getExceptionType() { any() }
 }
 
 /**
@@ -50,6 +52,8 @@ private class Fprintf extends FormattingFunction, NonThrowingFunction {
   override int getFormatParameterIndex() { result = 1 }
 
   override int getOutputParameterIndex(boolean isStream) { result = 0 and isStream = true }
+
+  override TCxxException getExceptionType() { any() }
 }
 
 /**
@@ -93,6 +97,8 @@ private class Sprintf extends FormattingFunction, NonThrowingFunction {
     then result = 4
     else result = super.getFirstFormatArgumentIndex()
   }
+
+  override TCxxException getExceptionType() { any() }
 }
 
 /**
@@ -165,6 +171,8 @@ private class SnprintfImpl extends Snprintf, AliasFunction, SideEffectFunction,
     // We don't know how many parameters are passed to the function since it's varargs, but they also have read side effects.
     i = this.getFormatParameterIndex() and buffer = true
   }
+
+  override TCxxException getExceptionType() { any() }
 }
 
 /**
@@ -215,4 +223,6 @@ private class Syslog extends FormattingFunction, NonThrowingFunction {
   override int getFormatParameterIndex() { result = 1 }
 
   override predicate isOutputGlobal() { any() }
+
+  override TCxxException getExceptionType() { any() }
 }

cpp/ql/lib/semmle/code/cpp/models/implementations/Strcat.qll

@@ -7,7 +7,7 @@ import semmle.code.cpp.models.interfaces.ArrayFunction
 import semmle.code.cpp.models.interfaces.DataFlow
 import semmle.code.cpp.models.interfaces.Taint
 import semmle.code.cpp.models.interfaces.SideEffect
-import semmle.code.cpp.models.interfaces.NonThrowing
+import semmle.code.cpp.models.interfaces.Throwing
 
 /**
  * The standard function `strcat` and its wide, sized, and Microsoft variants.
@@ -94,6 +94,8 @@ class StrcatFunction extends TaintFunction, DataFlowFunction, ArrayFunction, Sid
     (i = 0 or i = 1) and
     buffer = true
   }
+
+  override TCxxException getExceptionType() { any() }
 }
 
 /**

cpp/ql/lib/semmle/code/cpp/models/implementations/Strcpy.qll

@@ -7,7 +7,7 @@ import semmle.code.cpp.models.interfaces.ArrayFunction
 import semmle.code.cpp.models.interfaces.DataFlow
 import semmle.code.cpp.models.interfaces.Taint
 import semmle.code.cpp.models.interfaces.SideEffect
-import semmle.code.cpp.models.interfaces.NonThrowing
+import semmle.code.cpp.models.interfaces.Throwing
 
 /**
  * The standard function `strcpy` and its wide, sized, and Microsoft variants.
@@ -145,4 +145,6 @@ class StrcpyFunction extends ArrayFunction, DataFlowFunction, TaintFunction, Sid
     i = this.getParamDest() and
     result = this.getParamSize()
   }
+
+  override TCxxException getExceptionType() { any() }
 }

cpp/ql/lib/semmle/code/cpp/models/implementations/StructuredExceptionHandling.qll

@@ -1,9 +1,11 @@
 import semmle.code.cpp.models.interfaces.Throwing
 
-class WindowsDriverFunction extends ThrowingFunction {
-  WindowsDriverFunction() {
+class WindowsDriverExceptionAnnotation extends ThrowingFunction {
+  WindowsDriverExceptionAnnotation() {
     this.hasGlobalName(["RaiseException", "ExRaiseAccessViolation", "ExRaiseDatatypeMisalignment"])
   }
 
-  final override predicate mayThrowException(boolean unconditional) { unconditional = true }
+  override predicate mayThrowException(boolean unconditional) { unconditional = true }
+
+  override TSehException getExceptionType() { any() }
 }

cpp/ql/lib/semmle/code/cpp/models/interfaces/NonThrowing.qll

@@ -7,5 +7,7 @@ import semmle.code.cpp.models.Models
 
 /**
  * A function that is guaranteed to never throw.
+ *
+ * DEPRECATED: use `NonThrowingFunction` in `semmle.code.cpp.models.Models.Interfaces.Throwing` instead.
  */
-abstract class NonThrowingFunction extends Function { }
+abstract deprecated class NonThrowingFunction extends Function { }

cpp/ql/lib/semmle/code/cpp/models/interfaces/Throwing.qll

@@ -11,12 +11,65 @@ import semmle.code.cpp.models.Models
 import semmle.code.cpp.models.interfaces.FunctionInputsAndOutputs
 
 /**
- * A class that models the exceptional behavior of a function.
+ * Represents a type of exception,
+ * either Structured Exception Handling (SEH) or C++ exceptions.
  */
-abstract class ThrowingFunction extends Function {
+newtype TException =
+  /** Structured Exception Handling (SEH) exception */
+  TSehException() or
+  /** C++ exception */
+  TCxxException()
+
+/**
+ * Functions with information about how an exception is thrown or if one is thrown at all.
+ * If throwing details conflict for the same function, IR is assumed
+ * to use the most restricted interpretation, meaning taking options
+ * that stipulate no exception is raised, before the exception is always raised,
+ * before conditional exceptions.
+ *
+ * Annotations must specify if the exception is from SEH (structured exception handling)
+ * or ordinary c++ exceptions.
+ */
+abstract private class ExceptionAnnotation extends Function {
+  /**
+   * Returns the type of exception this annotation is for,
+   * either a CPP exception or a STructured Exception Handling (SEH) exception.
+   */
+  abstract TException getExceptionType();
+
+  /**
+   * Holds if the exception type of this annotation is for a Structured Exception Handling (SEH) exception.
+   */
+  final predicate isSeh() { this.getExceptionType() = TSehException() }
+
+  /**
+   * Holds if the exception type of this annotation is for a CPP exception.
+   */
+  final predicate isCxx() { this.getExceptionType() = TCxxException() }
+}
+
+/**
+ * A Function that is known to not throw an exception.
+ */
+abstract class NonThrowingFunction extends ExceptionAnnotation { }
+
+/**
+ * A function this is known to raise an exception.
+ */
+abstract class ThrowingFunction extends ExceptionAnnotation {
+  ThrowingFunction() { any() }
+
   /**
-   * Holds if this function may throw an exception during evaluation.
-   * If `unconditional` is `true` the function always throws an exception.
+   * Holds if this function may raise an exception during evaluation.
+   * If `unconditional` is `false` the function may raise, and if `true` the function
+   * will always raise an exception.
+   * Do not specify `none()` if no exception is raised, instead use the
+   * `NonThrowingFunction` class instead.
    */
   abstract predicate mayThrowException(boolean unconditional);
+
+  /**
+   * Holds if this function will always raise an exception if called
+   */
+  final predicate alwaysThrowsException() { this.mayThrowException(true) }
 }