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C++: Rewrite so that we look for additional evidence.

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This commit is contained in:
Geoffrey White
2021-05-13 10:04:57 +01:00
parent 123889a671
commit e4d2c7cfc4
4 changed files with 79 additions and 50 deletions
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94
cpp/ql/src/Security/CWE/CWE-327/BrokenCryptoAlgorithm.ql
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@@ -13,52 +13,72 @@
import cpp
import semmle.code.cpp.security.Encryption
abstract class InsecureCryptoSpec extends Locatable {
abstract string description();
}
Function getAnInsecureFunction() {
isInsecureEncryption(result.getName()) and
/**
* A function which may relate to an insecure encryption algorithm.
*/
Function getAnInsecureEncryptionFunction() {
(
isInsecureEncryption(result.getName()) or
isInsecureEncryption(result.getAParameter().getName())
) and
exists(result.getACallToThisFunction())
}
class InsecureFunctionCall extends InsecureCryptoSpec, FunctionCall {
InsecureFunctionCall() {
// the function name suggests it relates to an insecure crypto algorithm.
this.getTarget() = getAnInsecureFunction()
}
override string description() { result = "function call" }
override string toString() { result = FunctionCall.super.toString() }
override Location getLocation() { result = FunctionCall.super.getLocation() }
/**
* A function with additional evidence it is related to encryption.
*/
Function getAdditionalEvidenceFunction() {
(
isEncryptionAdditionalEvidence(result.getName()) or
isEncryptionAdditionalEvidence(result.getAParameter().getName())
) and
exists(result.getACallToThisFunction())
}
Macro getAnInsecureMacro() {
/**
* A macro which may relate to an insecure encryption algorithm.
*/
Macro getAnInsecureEncryptionMacro() {
isInsecureEncryption(result.getName()) and
exists(result.getAnInvocation())
}
class InsecureMacroSpec extends InsecureCryptoSpec, MacroInvocation {
InsecureMacroSpec() {
// the macro name suggests it relates to an insecure crypto algorithm.
this.getMacro() = getAnInsecureMacro() and
// the macro invocation generates something.
exists(this.getAGeneratedElement().(ControlFlowNode)) and
// exclude expressions controlling ifs/switches (as they may not be used).
not any(IfStmt c).getCondition().getAChild*() = this.getAGeneratedElement() and
not any(SwitchCase c).getExpr().getAChild*() = this.getAGeneratedElement() and
// exclude expressions in array initializers (as they may not be used).
not any(AggregateLiteral i).getAChild*() = this.getAGeneratedElement()
}
override string description() { result = "macro invocation" }
override string toString() { result = MacroInvocation.super.toString() }
override Location getLocation() { result = MacroInvocation.super.getLocation() }
/**
* A macro with additional evidence it is related to encryption.
*/
Macro getAdditionalEvidenceMacro() {
isEncryptionAdditionalEvidence(result.getName()) and
exists(result.getAnInvocation())
}
from InsecureCryptoSpec c
/**
* A function call we have a high confidence is related to use of an insecure
* encryption algorithm.
*/
class InsecureFunctionCall extends FunctionCall {
InsecureFunctionCall() {
// find use of an insecure algorithm name
(
getTarget() = getAnInsecureEncryptionFunction()
or
exists(MacroInvocation mi |
mi.getAGeneratedElement() = this.getAChild*() and
mi.getMacro() = getAnInsecureEncryptionMacro()
)
) and
// find additional evidence that this function is related to encryption.
(
getTarget() = getAdditionalEvidenceFunction()
or
exists(MacroInvocation mi |
mi.getAGeneratedElement() = this.getAChild*() and
mi.getMacro() = getAdditionalEvidenceMacro()
)
)
}
string description() { result = "function call" }
}
from InsecureFunctionCall c
select c, "This " + c.description() + " specifies a broken or weak cryptographic algorithm."

11
cpp/ql/src/semmle/code/cpp/security/Encryption.qll
View File

@@ -60,6 +60,17 @@ predicate isInsecureEncryption(string name) {
not name.toUpperCase().regexpMatch(".*TRIPLE.*")
}
/**
* Holds if there is additional evidence that `name` looks like it might be
* related to operations with an encyption algorithm, besides the name of a
* specific algorithm. This can be used in conjuction with
* `isInsecureEncryption` to produce a stronger heuristic.
*/
bindingset[name]
predicate isEncryptionAdditionalEvidence(string name) {
name.toUpperCase().regexpMatch(".*(CRYPT|CODE|CODING|CBC|KEY).*")
}
/**
* Gets a regular expression for matching strings that look like they
* contain an algorithm that is known to be secure.

20
cpp/ql/test/query-tests/Security/CWE/CWE-327/BrokenCryptoAlgorithm.expected
View File

@@ -1,16 +1,14 @@
| test2.cpp:49:4:49:24 | call to my_des_implementation | This function call specifies a broken or weak cryptographic algorithm. |
| test2.cpp:62:33:62:40 | ALGO_DES | This macro invocation specifies a broken or weak cryptographic algorithm. |
| test2.cpp:62:2:62:12 | call to encrypt_bad | This function call specifies a broken or weak cryptographic algorithm. |
| test2.cpp:124:4:124:24 | call to my_des_implementation | This function call specifies a broken or weak cryptographic algorithm. |
| test2.cpp:172:28:172:35 | ALGO_DES | This macro invocation specifies a broken or weak cryptographic algorithm. |
| test2.cpp:182:38:182:45 | ALGO_DES | This macro invocation specifies a broken or weak cryptographic algorithm. |
| test.cpp:38:2:38:31 | ENCRYPT_WITH_DES(data,amount) | This macro invocation specifies a broken or weak cryptographic algorithm. |
| test.cpp:39:2:39:31 | ENCRYPT_WITH_RC2(data,amount) | This macro invocation specifies a broken or weak cryptographic algorithm. |
| test.cpp:51:2:51:32 | DES_DO_ENCRYPTION(data,amount) | This macro invocation specifies a broken or weak cryptographic algorithm. |
| test.cpp:52:2:52:31 | RUN_DES_ENCODING(data,amount) | This macro invocation specifies a broken or weak cryptographic algorithm. |
| test.cpp:53:2:53:25 | DES_ENCODE(data,amount) | This macro invocation specifies a broken or weak cryptographic algorithm. |
| test.cpp:54:2:54:26 | DES_SET_KEY(data,amount) | This macro invocation specifies a broken or weak cryptographic algorithm. |
| test.cpp:56:2:56:9 | DES(str) | This macro invocation specifies a broken or weak cryptographic algorithm. |
| test.cpp:59:12:59:25 | SORT_ORDER_DES | This macro invocation specifies a broken or weak cryptographic algorithm. |
| test2.cpp:172:2:172:26 | call to set_encryption_algorithm1 | This function call specifies a broken or weak cryptographic algorithm. |
| test2.cpp:182:2:182:17 | call to encryption_with1 | This function call specifies a broken or weak cryptographic algorithm. |
| test.cpp:38:2:38:31 | call to my_implementation1 | This function call specifies a broken or weak cryptographic algorithm. |
| test.cpp:39:2:39:31 | call to my_implementation2 | This function call specifies a broken or weak cryptographic algorithm. |
| test.cpp:51:2:51:32 | call to my_implementation1 | This function call specifies a broken or weak cryptographic algorithm. |
| test.cpp:52:2:52:31 | call to my_implementation1 | This function call specifies a broken or weak cryptographic algorithm. |
| test.cpp:53:2:53:25 | call to my_implementation1 | This function call specifies a broken or weak cryptographic algorithm. |
| test.cpp:54:2:54:26 | call to my_implementation1 | This function call specifies a broken or weak cryptographic algorithm. |
| test.cpp:88:2:88:11 | call to encryptDES | This function call specifies a broken or weak cryptographic algorithm. |
| test.cpp:89:2:89:11 | call to encryptRC2 | This function call specifies a broken or weak cryptographic algorithm. |
| test.cpp:101:2:101:15 | call to do_des_encrypt | This function call specifies a broken or weak cryptographic algorithm. |

4
cpp/ql/test/query-tests/Security/CWE/CWE-327/test.cpp
View File

@@ -53,10 +53,10 @@ void test_macros(void *data, size_t amount, const char *str)
DES_ENCODE(data, amount); // BAD
DES_SET_KEY(data, amount); // BAD
DES(str); // GOOD (probably nothing to do with encryption) [FALSE POSITIVE]
DES(str); // GOOD (probably nothing to do with encryption)
DESMOND(str); // GOOD (probably nothing to do with encryption)
ANODES(str); // GOOD (probably nothing to do with encryption)
int ord = SORT_ORDER_DES; // GOOD (probably nothing to do with encryption) [FALSE POSITIVE]
int ord = SORT_ORDER_DES; // GOOD (probably nothing to do with encryption)
}
// --- simple encryption function calls ---