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codeql/cpp/ql/lib/semmle/code/cpp/security/TaintTrackingImpl.qll
2023-05-09 15:35:54 +02:00

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/**
* DEPRECATED: we now use `semmle.code.cpp.ir.dataflow.DefaultTaintTracking`,
* which is based on the IR but designed to behave similarly to this old
* library.
*
* Provides the implementation of `semmle.code.cpp.security.TaintTracking`. Do
* not import this file directly.
*/
import cpp
import Security
/** Expressions that change the value of a variable */
private predicate valueSource(Expr expr) {
exists(AssignExpr ae | expr = ae.getLValue())
or
exists(FunctionCall fc, int i |
userInputArgument(fc, i) and
expr = fc.getArgument(i)
)
or
exists(FunctionCall c, int arg |
copyValueBetweenArguments(c.getTarget(), _, arg) and
expr = c.getArgument(arg)
)
or
exists(FunctionCall c, int arg |
c.getTarget().getParameter(arg).getType() instanceof ReferenceType and
expr = c.getArgument(arg)
)
}
/** Expressions that are inside an expression that changes the value of a variable */
private predicate insideValueSource(Expr expr) {
valueSource(expr)
or
insideValueSource(expr.getParent()) and
// A modification of array[offset] does not modify offset
not expr.getParent().(ArrayExpr).getArrayOffset() = expr
}
private predicate isPointer(Type type) {
type instanceof PointerType or
isPointer(type.(ReferenceType).getBaseType())
}
/**
* Tracks data flow from src to dest.
* If this is used in the left side of an assignment src and dest should be swapped
*/
private predicate moveToDependingOnSide(Expr src, Expr dest) {
exists(ParenthesisExpr e |
src = e.getAChild() and
dest = e
)
or
exists(ArrayExpr e |
src = e.getArrayBase() and
dest = e
)
or
exists(PointerDereferenceExpr e |
src = e.getOperand() and
dest = e
)
or
exists(AddressOfExpr e |
src = e.getOperand() and
dest = e
)
or
// if var+offset is tainted, then so is var
exists(VariableAccess base, BinaryOperation binop |
dest = binop and
(base = binop.getLeftOperand() or base = binop.getRightOperand()) and
isPointer(base.getType()) and
base.getTarget() instanceof LocalScopeVariable and
src = base and
// flow through pointer-pointer subtraction is dubious, the result should be
// a number bounded by the size of the pointed-to thing.
not binop instanceof PointerDiffExpr
)
or
exists(UnaryOperation unop |
dest = unop and
unop.getAnOperand() = src
)
or
exists(BinaryOperation binop |
dest = binop and
binop.getLeftOperand() = src and
predictable(binop.getRightOperand())
)
or
exists(BinaryOperation binop |
dest = binop and
binop.getRightOperand() = src and
predictable(binop.getLeftOperand())
)
or
exists(Cast cast |
dest = cast and
src = cast.getExpr()
)
or
exists(ConditionalExpr cond |
cond = dest and
(
cond.getThen() = src or
cond.getElse() = src
)
)
}
/**
* Track value flow between functions.
* Handles the following cases:
* - If an argument to a function is tainted, all the usages of the parameter inside the function are tainted
* - If a function obtains input from the user internally and returns it, all calls to the function are tainted
* - If an argument to a function is tainted and that parameter is returned, all calls to the function are not tainted
* (this is done to avoid false positives). Because of this we need to track if the tainted element came from an argument
* or not, and for that we use destFromArg
*/
deprecated private predicate betweenFunctionsValueMoveTo(
Element src, Element dest, boolean destFromArg
) {
not unreachable(src) and
not unreachable(dest) and
(
exists(Call call, int i |
src = call.getArgument(i) and
resolveCallWithParam(call, _, i, dest) and
destFromArg = true
)
or
// Only move the return of the function to the function itself if the value didn't came from an
// argument, or else we would taint all the calls to one function if one argument is tainted
// somewhere
exists(Function f, ReturnStmt ret |
ret.getEnclosingFunction() = f and
src = ret.getExpr() and
destFromArg = false and
dest = f
)
or
exists(Call call, Function f |
f = resolveCall(call) and
src = f and
dest = call and
destFromArg = false
)
or
// If a parameter of type reference is tainted inside a function, taint the argument too
exists(Call call, int pi, Parameter p |
resolveCallWithParam(call, _, pi, p) and
p.getType() instanceof ReferenceType and
src = p and
dest = call.getArgument(pi) and
destFromArg = false
)
)
}
// predicate folding for proper join-order
// bad magic: pushes down predicate that ruins join-order
pragma[nomagic]
deprecated private predicate resolveCallWithParam(Call call, Function called, int i, Parameter p) {
called = resolveCall(call) and
p = called.getParameter(i)
}
/** A variable for which flow through is allowed. */
deprecated library class FlowVariable extends Variable {
FlowVariable() {
(
this instanceof LocalScopeVariable or
this instanceof GlobalOrNamespaceVariable
) and
not argv(this)
}
}
/** A local scope variable for which flow through is allowed. */
deprecated library class FlowLocalScopeVariable extends Variable {
FlowLocalScopeVariable() { this instanceof LocalScopeVariable }
}
deprecated private predicate insideFunctionValueMoveTo(Element src, Element dest) {
not unreachable(src) and
not unreachable(dest) and
(
// Taint all variable usages when one is tainted
// This function taints global variables but doesn't taint from a global variable (see globalVariableValueMoveTo)
exists(FlowLocalScopeVariable v |
src = v and
dest = v.getAnAccess() and
not insideValueSource(dest)
)
or
exists(FlowVariable v |
src = v.getAnAccess() and
dest = v and
insideValueSource(src)
)
or
// Taint all union usages when one is tainted
// This function taints global variables but doesn't taint from a global variable (see globalVariableValueMoveTo)
exists(FlowLocalScopeVariable v, FieldAccess a |
unionAccess(v, _, a) and
src = v and
dest = a and
not insideValueSource(dest)
)
or
exists(FlowVariable v, FieldAccess a |
unionAccess(v, _, a) and
src = a and
dest = v and
insideValueSource(src)
)
or
// If a pointer is tainted, taint the original variable
exists(FlowVariable p, FlowVariable v, AddressOfExpr e |
p.getAnAssignedValue() = e and
e.getOperand() = v.getAnAccess() and
src = p and
dest = v
)
or
// If a reference is tainted, taint the original variable
exists(FlowVariable r, FlowVariable v |
r.getType() instanceof ReferenceType and
r.getInitializer().getExpr() = v.getAnAccess() and
src = r and
dest = v
)
or
exists(Variable var |
var = dest and
var.getInitializer().getExpr() = src
)
or
exists(AssignExpr ae |
src = ae.getRValue() and
dest = ae.getLValue()
)
or
exists(CommaExpr comma |
comma = dest and
comma.getRightOperand() = src
)
or
exists(FunctionCall c, int sourceArg, int destArg |
copyValueBetweenArguments(c.getTarget(), sourceArg, destArg) and
// Only consider copies from `printf`-like functions if the format is a string
(
exists(FormattingFunctionCall ffc, FormatLiteral format |
ffc = c and
format = ffc.getFormat() and
format.getConversionChar(sourceArg - ffc.getTarget().getNumberOfParameters()) = ["s", "S"]
)
or
not c.(FormattingFunctionCall).getFormat() instanceof FormatLiteral
or
not c instanceof FormattingFunctionCall
) and
src = c.getArgument(sourceArg) and
dest = c.getArgument(destArg)
)
or
exists(FunctionCall c, int sourceArg |
returnArgument(c.getTarget(), sourceArg) and
src = c.getArgument(sourceArg) and
dest = c
)
or
exists(FormattingFunctionCall formattingSend, int arg, FormatLiteral format |
dest = formattingSend and
formattingSend.getArgument(arg) = src and
format = formattingSend.getFormat() and
format.getConversionChar(arg - formattingSend.getTarget().getNumberOfParameters()) =
["s", "S", "@"]
)
or
// Expressions computed from tainted data are also tainted
exists(FunctionCall call | dest = call and isPureFunction(call.getTarget().getName()) |
call.getAnArgument() = src and
forall(Expr arg | arg = call.getAnArgument() | arg = src or predictable(arg)) and
// flow through `strlen` tends to cause dubious results, if the length is
// bounded.
not call.getTarget().getName() = "strlen"
)
or
exists(Element a, Element b |
moveToDependingOnSide(a, b) and
if insideValueSource(a) then (src = b and dest = a) else (src = a and dest = b)
)
)
}
/**
* Handles data flow from global variables to its usages.
* The tainting for the global variable itself is done at insideFunctionValueMoveTo.
*/
private predicate globalVariableValueMoveTo(GlobalOrNamespaceVariable src, Expr dest) {
not unreachable(dest) and
(
exists(GlobalOrNamespaceVariable v |
src = v and
dest = v.getAnAccess() and
not insideValueSource(dest)
)
or
exists(GlobalOrNamespaceVariable v, FieldAccess a |
unionAccess(v, _, a) and
src = v and
dest = a and
not insideValueSource(dest)
)
)
}
private predicate unionAccess(Variable v, Field f, FieldAccess a) {
f.getDeclaringType() instanceof Union and
a.getTarget() = f and
a.getQualifier() = v.getAnAccess()
}
deprecated GlobalOrNamespaceVariable globalVarFromId(string id) {
if result instanceof NamespaceVariable
then id = result.getNamespace() + "::" + result.getName()
else id = result.getName()
}
/**
* A variable that has any kind of upper-bound check anywhere in the program. This is
* biased towards being inclusive because there are a lot of valid ways of doing an
* upper bounds checks if we don't consider where it occurs, for example:
* ```
* if (x < 10) { sink(x); }
*
* if (10 > y) { sink(y); }
*
* if (z > 10) { z = 10; }
* sink(z);
* ```
*/
private predicate hasUpperBoundsCheck(Variable var) {
exists(RelationalOperation oper, VariableAccess access |
oper.getAnOperand() = access and
access.getTarget() = var and
// Comparing to 0 is not an upper bound check
not oper.getAnOperand().getValue() = "0"
)
}
cached
deprecated private predicate taintedWithArgsAndGlobalVars(
Element src, Element dest, boolean destFromArg, string globalVar
) {
isUserInput(src, _) and
not unreachable(src) and
dest = src and
destFromArg = false and
globalVar = ""
or
exists(Element other, boolean otherFromArg, string otherGlobalVar |
taintedWithArgsAndGlobalVars(src, other, otherFromArg, otherGlobalVar)
|
not unreachable(dest) and
not hasUpperBoundsCheck(dest) and
(
// Direct flow from one expression to another.
betweenFunctionsValueMoveTo(other, dest, destFromArg) and
(destFromArg = true or otherFromArg = false) and
globalVar = otherGlobalVar
or
insideFunctionValueMoveTo(other, dest) and
destFromArg = otherFromArg and
globalVar = otherGlobalVar
or
exists(GlobalOrNamespaceVariable v |
v = other and
globalVariableValueMoveTo(v, dest) and
destFromArg = false and
v = globalVarFromId(globalVar)
)
)
)
}
/**
* A tainted expression is either directly user input, or is
* computed from user input in a way that users can probably
* control the exact output of the computation.
*
* This doesn't include data flow through global variables.
* If you need that you must call taintedIncludingGlobalVars.
*/
deprecated predicate tainted(Expr source, Element tainted) {
taintedWithArgsAndGlobalVars(source, tainted, _, "")
}
/**
* A tainted expression is either directly user input, or is
* computed from user input in a way that users can probably
* control the exact output of the computation.
*
* This version gives the same results as tainted but also includes
* data flow through global variables.
*
* The parameter `globalVar` is the name of the last global variable used to move the
* value from source to tainted.
*/
deprecated predicate taintedIncludingGlobalVars(Expr source, Element tainted, string globalVar) {
taintedWithArgsAndGlobalVars(source, tainted, _, globalVar)
}
/**
* A predictable expression is one where an external user can predict
* the value. For example, a literal in the source code is considered
* predictable.
*/
private predicate predictable(Expr expr) {
expr instanceof Literal
or
exists(BinaryOperation binop | binop = expr |
predictable(binop.getLeftOperand()) and predictable(binop.getRightOperand())
)
or
exists(UnaryOperation unop | unop = expr | predictable(unop.getOperand()))
}
private int maxArgIndex(Function f) {
result =
max(FunctionCall fc, int toMax |
fc.getTarget() = f and toMax = fc.getNumberOfArguments() - 1
|
toMax
)
}
/** Functions that copy the value of one argument to another */
private predicate copyValueBetweenArguments(Function f, int sourceArg, int destArg) {
f.hasGlobalOrStdName("memcpy") and sourceArg = 1 and destArg = 0
or
f.hasGlobalName("__builtin___memcpy_chk") and sourceArg = 1 and destArg = 0
or
f.hasGlobalOrStdName("memmove") and sourceArg = 1 and destArg = 0
or
f.hasGlobalOrStdName("strcat") and sourceArg = 1 and destArg = 0
or
f.hasGlobalName("_mbscat") and sourceArg = 1 and destArg = 0
or
f.hasGlobalOrStdName("wcscat") and sourceArg = 1 and destArg = 0
or
f.hasGlobalOrStdName("strncat") and sourceArg = 1 and destArg = 0
or
f.hasGlobalName("_mbsncat") and sourceArg = 1 and destArg = 0
or
f.hasGlobalName("wcsncat") and sourceArg = 1 and destArg = 0
or
f.hasGlobalOrStdName("strcpy") and sourceArg = 1 and destArg = 0
or
f.hasGlobalName("_mbscpy") and sourceArg = 1 and destArg = 0
or
f.hasGlobalOrStdName("wcscpy") and sourceArg = 1 and destArg = 0
or
f.hasGlobalOrStdName("strncpy") and sourceArg = 1 and destArg = 0
or
f.hasGlobalName("_mbsncpy") and sourceArg = 1 and destArg = 0
or
f.hasGlobalOrStdName("wcsncpy") and sourceArg = 1 and destArg = 0
or
f.hasGlobalName("inet_aton") and sourceArg = 0 and destArg = 1
or
f.hasGlobalName("inet_pton") and sourceArg = 1 and destArg = 2
or
f.hasGlobalOrStdName("strftime") and sourceArg in [2 .. maxArgIndex(f)] and destArg = 0
or
exists(FormattingFunction ff | ff = f |
sourceArg in [ff.getFormatParameterIndex() .. maxArgIndex(f)] and
destArg = ff.getOutputParameterIndex(false)
)
}
/** Functions where if one of the arguments is tainted, the result should be tainted */
private predicate returnArgument(Function f, int sourceArg) {
f.hasGlobalName("memcpy") and sourceArg = 0
or
f.hasGlobalName("__builtin___memcpy_chk") and sourceArg = 0
or
f.hasGlobalOrStdName("memmove") and sourceArg = 0
or
f.hasGlobalOrStdName("strcat") and sourceArg = 0
or
f.hasGlobalName("_mbscat") and sourceArg = 0
or
f.hasGlobalOrStdName("wcsncat") and sourceArg = 0
or
f.hasGlobalOrStdName("strncat") and sourceArg = 0
or
f.hasGlobalName("_mbsncat") and sourceArg = 0
or
f.hasGlobalOrStdName("wcsncat") and sourceArg = 0
or
f.hasGlobalOrStdName("strcpy") and sourceArg = 0
or
f.hasGlobalName("_mbscpy") and sourceArg = 0
or
f.hasGlobalOrStdName("wcscpy") and sourceArg = 0
or
f.hasGlobalOrStdName("strncpy") and sourceArg = 0
or
f.hasGlobalName("_mbsncpy") and sourceArg = 0
or
f.hasGlobalOrStdName("wcsncpy") and sourceArg = 0
or
f.hasGlobalName("inet_ntoa") and sourceArg = 0
or
f.hasGlobalName("inet_addr") and sourceArg = 0
or
f.hasGlobalName("inet_network") and sourceArg = 0
or
f.hasGlobalName("inet_ntoa") and sourceArg = 0
or
f.hasGlobalName("inet_makeaddr") and
(sourceArg = 0 or sourceArg = 1)
or
f.hasGlobalName("inet_lnaof") and sourceArg = 0
or
f.hasGlobalName("inet_netof") and sourceArg = 0
or
f.hasGlobalName("gethostbyname") and sourceArg = 0
or
f.hasGlobalName("gethostbyaddr") and sourceArg = 0
}
/**
* Resolve potential target function(s) for `call`.
*
* If `call` is a call through a function pointer (`ExprCall`) or
* targets a virtual method, simple data flow analysis is performed
* in order to identify target(s).
*/
deprecated Function resolveCall(Call call) {
result = call.getTarget()
or
result = call.(DataSensitiveCallExpr).resolve()
}
/** A data sensitive call expression. */
abstract deprecated library class DataSensitiveCallExpr extends Expr {
DataSensitiveCallExpr() { not unreachable(this) }
abstract Expr getSrc();
cached
abstract Function resolve();
/**
* Whether `src` can flow to this call expression.
*
* Searches backwards from `getSrc()` to `src`.
*/
predicate flowsFrom(Element src, boolean allowFromArg) {
src = this.getSrc() and allowFromArg = true
or
exists(Element other, boolean allowOtherFromArg | this.flowsFrom(other, allowOtherFromArg) |
exists(boolean otherFromArg | betweenFunctionsValueMoveToStatic(src, other, otherFromArg) |
otherFromArg = true and allowOtherFromArg = true and allowFromArg = true
or
otherFromArg = false and allowFromArg = false
)
or
insideFunctionValueMoveTo(src, other) and allowFromArg = allowOtherFromArg
or
globalVariableValueMoveTo(src, other) and allowFromArg = true
)
}
}
/** Call through a function pointer. */
deprecated library class DataSensitiveExprCall extends DataSensitiveCallExpr, ExprCall {
override Expr getSrc() { result = this.getExpr() }
override Function resolve() {
exists(FunctionAccess fa | this.flowsFrom(fa, true) | result = fa.getTarget())
}
}
/** Call to a virtual function. */
deprecated library class DataSensitiveOverriddenFunctionCall extends DataSensitiveCallExpr,
FunctionCall
{
DataSensitiveOverriddenFunctionCall() {
exists(this.getTarget().(VirtualFunction).getAnOverridingFunction())
}
override Expr getSrc() { result = this.getQualifier() }
override MemberFunction resolve() {
exists(NewExpr new |
this.flowsFrom(new, true) and
memberFunctionFromNewExpr(new, result) and
result.overrides*(this.getTarget().(VirtualFunction))
)
}
}
private predicate memberFunctionFromNewExpr(NewExpr new, MemberFunction f) {
f = new.getAllocatedType().(Class).getAMemberFunction()
}
/** Same as `betweenFunctionsValueMoveTo`, but calls are resolved to their static target. */
private predicate betweenFunctionsValueMoveToStatic(Element src, Element dest, boolean destFromArg) {
not unreachable(src) and
not unreachable(dest) and
(
exists(FunctionCall call, Function called, int i |
src = call.getArgument(i) and
called = call.getTarget() and
dest = called.getParameter(i) and
destFromArg = true
)
or
// Only move the return of the function to the function itself if the value didn't came from an
// argument, or else we would taint all the calls to one function if one argument is tainted
// somewhere
exists(Function f, ReturnStmt ret |
ret.getEnclosingFunction() = f and
src = ret.getExpr() and
destFromArg = false and
dest = f
)
or
exists(FunctionCall call, Function f |
call.getTarget() = f and
src = f and
dest = call and
destFromArg = false
)
or
// If a parameter of type reference is tainted inside a function, taint the argument too
exists(FunctionCall call, Function f, int pi, Parameter p |
call.getTarget() = f and
f.getParameter(pi) = p and
p.getType() instanceof ReferenceType and
src = p and
dest = call.getArgument(pi) and
destFromArg = false
)
)
}