зеркало из https://github.com/github/codeql.git
Factor out string prefix logic
This commit is contained in:
Chris Smowton
Родитель
b975e12f41
Коммит
b71920209e
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@ -0,0 +1,151 @@
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/**
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* Provides classes and predicates for identifying expressions that may be appended to an interesting prefix.
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*
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* To use this library, extend the abstract class `InterestingPrefix` to have the library identify expressions that
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* may be appended to it, then check `InterestingPrefix.getAnAppendedExpression(Expr)` to get your results.
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*
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* For example, `private class FooPrefix extends InterestingPrefix { FooPrefix() { this = "foo:" } };`
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* `predicate mayFollowFoo(Expr e) { e = any(FooPrefix fp).getAnAppendedExpression() }`
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*/
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import java
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import semmle.code.java.dataflow.TaintTracking
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private import semmle.code.java.StringFormat
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abstract class InterestingPrefix extends CompileTimeConstantExpr {
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/**
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* Gets the offset in this constant string where the interesting substring begins.
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*/
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abstract int getOffset();
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Expr getAnAppendedExpression() { mayFollowInterestingPrefix(this, result) }
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}
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private Expr getAnInterestingPrefix(InterestingPrefix root) {
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result = root
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or
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result.(AddExpr).getAnOperand() = getAnInterestingPrefix(root)
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}
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private class StringBuilderAppend extends MethodAccess {
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StringBuilderAppend() {
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this.getMethod().getDeclaringType() instanceof StringBuildingType and
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this.getMethod().hasName("append")
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}
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}
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private class StringBuilderConstructorOrAppend extends Call {
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StringBuilderConstructorOrAppend() {
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this instanceof StringBuilderAppend or
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this.(ClassInstanceExpr).getConstructedType() instanceof StringBuildingType
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}
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}
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private Expr getQualifier(Expr e) { result = e.(MethodAccess).getQualifier() }
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/**
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* An extension of `StringBuilderVar` that also accounts for strings appended in StringBuilder/Buffer's constructor
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* and in `append` calls chained onto the constructor call.
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*
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* The original `StringBuilderVar` doesn't care about these because it is designed to model taint, and
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* in taint rules terms these are not needed, as the connection between construction, appends and the
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* eventual `toString` is more obvious.
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*/
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private class StringBuilderVarExt extends StringBuilderVar {
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/**
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* Returns a first assignment after this StringBuilderVar is first assigned.
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*
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* For example, for `StringBuilder sbv = new StringBuilder("1").append("2"); sbv.append("3").append("4");`
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* this returns the append of `"3"`.
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*/
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private StringBuilderAppend getAFirstAppendAfterAssignment() {
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result = this.getAnAppend() and not result = this.getNextAppend(_)
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}
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/**
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* Gets the next `append` after `prev`, where `prev` is, perhaps after some more `append` or other
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* chained calls, assigned to this `StringBuilderVar`.
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*/
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private StringBuilderAppend getNextAssignmentChainedAppend(StringBuilderConstructorOrAppend prev) {
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getQualifier*(result) = this.getAnAssignedValue() and
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result.getQualifier() = prev
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}
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/**
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* Get a constructor call or `append` call that contributes a string to this string builder.
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*/
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StringBuilderConstructorOrAppend getAConstructorOrAppend() {
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exists(this.getNextAssignmentChainedAppend(result)) or
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result = this.getAnAssignedValue() or
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result = this.getAnAppend()
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}
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/**
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* Like `StringBuilderVar.getNextAppend`, except including appends and constructors directly
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* assigned to this `StringBuilderVar`.
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*/
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private StringBuilderAppend getNextAppendIncludingAssignmentChains(
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StringBuilderConstructorOrAppend prev
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) {
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result = getNextAssignmentChainedAppend(prev)
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or
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prev = this.getAnAssignedValue() and
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result = this.getAFirstAppendAfterAssignment()
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or
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result = this.getNextAppend(prev)
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}
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/**
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* Implements `StringBuilderVarExt.getNextAppendIncludingAssignmentChains+(prev)`.
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*/
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pragma[nomagic]
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StringBuilderAppend getSubsequentAppendIncludingAssignmentChains(
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StringBuilderConstructorOrAppend prev
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) {
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result = this.getNextAppendIncludingAssignmentChains(prev) or
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result =
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this.getSubsequentAppendIncludingAssignmentChains(this.getNextAppendIncludingAssignmentChains(prev))
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}
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}
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/**
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* Holds if `follows` may be concatenated after `prefix`.
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*/
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private predicate mayFollowInterestingPrefix(InterestingPrefix prefix, Expr follows) {
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// Expressions that come after an interesting prefix in a tree of string additions:
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follows =
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any(AddExpr add | add.getLeftOperand() = getAnInterestingPrefix(prefix)).getRightOperand()
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or
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// Sanitize expressions that come after an interesting prefix in a sequence of StringBuilder operations:
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exists(
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StringBuilderConstructorOrAppend appendSanitizingConstant, StringBuilderAppend subsequentAppend,
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StringBuilderVarExt v
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appendSanitizingConstant = v.getAConstructorOrAppend() and
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appendSanitizingConstant.getArgument(0) = getAnInterestingPrefix(prefix) and
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v.getSubsequentAppendIncludingAssignmentChains(appendSanitizingConstant) = subsequentAppend and
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follows = subsequentAppend.getArgument(0)
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)
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or
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// Sanitize expressions that come after an interesting prefix in the args to a format call:
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exists(
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FormattingCall formatCall, FormatString formatString, int prefixOffset, int laterOffset,
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int sanitizedArg
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formatString = unique(FormatString fs | fs = formatCall.getAFormatString()) and
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(
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// An interesting prefix argument comes before this:
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exists(int argIdx |
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formatCall.getArgumentToBeFormatted(argIdx) = prefix and
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prefixOffset = formatString.getAnArgUsageOffset(argIdx)
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)
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or
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// The format string itself contains an interesting prefix that precedes subsequent arguments:
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formatString = prefix.getStringValue() and
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prefixOffset = prefix.getOffset()
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) and
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laterOffset > prefixOffset and
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laterOffset = formatString.getAnArgUsageOffset(sanitizedArg) and
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follows = formatCall.getArgumentToBeFormatted(sanitizedArg)
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)
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}
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@ -7,8 +7,7 @@ import semmle.code.java.frameworks.spring.Spring
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import semmle.code.java.frameworks.JaxWS
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import semmle.code.java.frameworks.javase.Http
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import semmle.code.java.dataflow.DataFlow
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import semmle.code.java.dataflow.TaintTracking
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private import semmle.code.java.StringFormat
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import semmle.code.java.dataflow.StringPrefixes
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private import semmle.code.java.dataflow.ExternalFlow
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/**
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@ -52,10 +51,10 @@ private class PrimitiveSanitizer extends RequestForgerySanitizer {
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}
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}
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private class HostnameSanitizingConstantPrefix extends CompileTimeConstantExpr {
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private class HostnameSanitizingPrefix extends InterestingPrefix {
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int offset;
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HostnameSanitizingConstantPrefix() {
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HostnameSanitizingPrefix() {
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// Matches strings that look like when prepended to untrusted input, they will restrict
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// the host or entity addressed: for example, anything containing `?` or `#`, or a slash that
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// doesn't appear to be a protocol specifier (e.g. `http://` is not sanitizing), or specifically
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@ -66,143 +65,7 @@ private class HostnameSanitizingConstantPrefix extends CompileTimeConstantExpr {
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)
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}
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/**
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* Gets the offset in this constant string where a sanitizing substring begins.
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*/
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int getOffset() { result = offset }
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}
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private Expr getAHostnameSanitizingPrefix() {
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result instanceof HostnameSanitizingConstantPrefix
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or
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result.(AddExpr).getAnOperand() = getAHostnameSanitizingPrefix()
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}
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private class StringBuilderAppend extends MethodAccess {
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StringBuilderAppend() {
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this.getMethod().getDeclaringType() instanceof StringBuildingType and
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this.getMethod().hasName("append")
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}
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}
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private class StringBuilderConstructorOrAppend extends Call {
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StringBuilderConstructorOrAppend() {
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this instanceof StringBuilderAppend or
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this.(ClassInstanceExpr).getConstructedType() instanceof StringBuildingType
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}
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}
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private Expr getQualifier(Expr e) { result = e.(MethodAccess).getQualifier() }
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/**
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* An extension of `StringBuilderVar` that also accounts for strings appended in StringBuilder/Buffer's constructor
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* and in `append` calls chained onto the constructor call.
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*
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* The original `StringBuilderVar` doesn't care about these because it is designed to model taint, and
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* in taint rules terms these are not needed, as the connection between construction, appends and the
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* eventual `toString` is more obvious.
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*/
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private class StringBuilderVarExt extends StringBuilderVar {
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/**
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* Returns a first assignment after this StringBuilderVar is first assigned.
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*
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* For example, for `StringBuilder sbv = new StringBuilder("1").append("2"); sbv.append("3").append("4");`
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* this returns the append of `"3"`.
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*/
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private StringBuilderAppend getAFirstAppendAfterAssignment() {
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result = this.getAnAppend() and not result = this.getNextAppend(_)
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}
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/**
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* Gets the next `append` after `prev`, where `prev` is, perhaps after some more `append` or other
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* chained calls, assigned to this `StringBuilderVar`.
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*/
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private StringBuilderAppend getNextAssignmentChainedAppend(StringBuilderConstructorOrAppend prev) {
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getQualifier*(result) = this.getAnAssignedValue() and
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result.getQualifier() = prev
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}
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/**
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* Get a constructor call or `append` call that contributes a string to this string builder.
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*/
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StringBuilderConstructorOrAppend getAConstructorOrAppend() {
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exists(this.getNextAssignmentChainedAppend(result)) or
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result = this.getAnAssignedValue() or
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result = this.getAnAppend()
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}
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/**
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* Like `StringBuilderVar.getNextAppend`, except including appends and constructors directly
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* assigned to this `StringBuilderVar`.
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*/
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private StringBuilderAppend getNextAppendIncludingAssignmentChains(
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StringBuilderConstructorOrAppend prev
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) {
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result = this.getNextAssignmentChainedAppend(prev)
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or
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prev = this.getAnAssignedValue() and
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result = this.getAFirstAppendAfterAssignment()
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or
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result = this.getNextAppend(prev)
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}
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/**
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* Implements `StringBuilderVarExt.getNextAppendIncludingAssignmentChains+(prev)`.
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*/
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pragma[nomagic]
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StringBuilderAppend getSubsequentAppendIncludingAssignmentChains(
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StringBuilderConstructorOrAppend prev
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) {
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result = this.getNextAppendIncludingAssignmentChains(prev) or
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result =
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this.getSubsequentAppendIncludingAssignmentChains(this.getNextAppendIncludingAssignmentChains(prev))
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}
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}
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/**
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* An expression that is sanitized because it is concatenated onto a string that looks like
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* a hostname or a URL separator, preventing the appended string from arbitrarily controlling
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* the addressed server.
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*/
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private class HostnameSanitizedExpr extends Expr {
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HostnameSanitizedExpr() {
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// Sanitize expressions that come after a sanitizing prefix in a tree of string additions:
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this =
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any(AddExpr add | add.getLeftOperand() = getAHostnameSanitizingPrefix()).getRightOperand()
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or
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// Sanitize expressions that come after a sanitizing prefix in a sequence of StringBuilder operations:
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exists(
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StringBuilderConstructorOrAppend appendSanitizingConstant,
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StringBuilderAppend subsequentAppend, StringBuilderVarExt v
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appendSanitizingConstant = v.getAConstructorOrAppend() and
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appendSanitizingConstant.getArgument(0) = getAHostnameSanitizingPrefix() and
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v.getSubsequentAppendIncludingAssignmentChains(appendSanitizingConstant) = subsequentAppend and
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this = subsequentAppend.getArgument(0)
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)
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or
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// Sanitize expressions that come after a sanitizing prefix in the args to a format call:
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exists(
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FormattingCall formatCall, FormatString formatString, HostnameSanitizingConstantPrefix prefix,
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int sanitizedFromOffset, int laterOffset, int sanitizedArg
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formatString = unique(FormatString fs | fs = formatCall.getAFormatString()) and
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(
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// A sanitizing argument comes before this:
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exists(int argIdx |
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formatCall.getArgumentToBeFormatted(argIdx) = prefix and
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sanitizedFromOffset = formatString.getAnArgUsageOffset(argIdx)
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)
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or
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// The format string itself sanitizes subsequent arguments:
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formatString = prefix.getStringValue() and
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sanitizedFromOffset = prefix.getOffset()
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) and
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laterOffset > sanitizedFromOffset and
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laterOffset = formatString.getAnArgUsageOffset(sanitizedArg) and
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this = formatCall.getArgumentToBeFormatted(sanitizedArg)
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)
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}
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override int getOffset() { result = offset }
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}
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/**
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@ -210,5 +73,5 @@ private class HostnameSanitizedExpr extends Expr {
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* host of a URL.
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*/
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private class HostnameSantizer extends RequestForgerySanitizer {
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HostnameSantizer() { this.asExpr() instanceof HostnameSanitizedExpr }
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HostnameSantizer() { this.asExpr() = any(HostnameSanitizingPrefix hsp).getAnAppendedExpression() }
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}
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