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Merge pull request #18161 from owen-mc/java/weak-crypto-algo-more-informative
Java: Make `java/weak-cryptographic-algorithm` give a reason why the algo is insecure
2 parents 599411b + 0728b3b commit 8833019

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9 files changed

+67
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‎java/ql/lib/semmle/code/java/security/Encryption.qll

Lines changed: 32 additions & 23 deletions
Original file line numberDiff line numberDiff line change
@@ -198,19 +198,32 @@ private string algorithmRegex(string algorithmString) {
198198
}
199199

200200
/**
201-
* Gets the name of an algorithm that is known to be insecure.
201+
* Holds if `name` is the name of an algorithm that is known to be insecure and
202+
* `reason` explains why it is insecure.
202203
*/
203-
string getAnInsecureAlgorithmName() {
204-
result =
205-
[
206-
"DES", "RC2", "RC4", "RC5",
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// ARCFOUR is a variant of RC4
208-
"ARCFOUR",
209-
// Encryption mode ECB like AES/ECB/NoPadding is vulnerable to replay and other attacks
210-
"ECB",
211-
// CBC mode of operation with PKCS#5 or PKCS#7 padding is vulnerable to padding oracle attacks
212-
"AES/CBC/PKCS[57]Padding"
213-
]
204+
predicate insecureAlgorithm(string name, string reason) {
205+
name = "DES" and
206+
reason =
207+
"It has a short key length of 56 bits, making it vulnerable to brute-force attacks. Consider using AES instead."
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or
209+
name = "RC2" and
210+
reason = "It is vulnerable to related-key attacks. Consider using AES instead."
211+
or
212+
// ARCFOUR is a variant of RC4
213+
name = ["RC4", "ARCFOUR"] and
214+
reason =
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"It has multiple vulnerabilities, including biases in its output and susceptibility to several attacks. Consider using AES instead."
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or
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name = "RC5" and
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reason = "It is vulnerable to differential and related-key attacks. Consider using AES instead."
219+
or
220+
name = "ECB" and
221+
reason =
222+
"ECB mode, as in AES/ECB/NoPadding for example, is vulnerable to replay and other attacks. Consider using GCM instead."
223+
or
224+
name = "AES/CBC/PKCS[57]Padding" and
225+
reason =
226+
"CBC mode with PKCS#5 or PKCS#7 padding is vulnerable to padding oracle attacks. Consider using GCM instead."
214227
}
215228

216229
/**
@@ -222,22 +235,18 @@ string getAnInsecureHashAlgorithmName() {
222235
result = "MD5"
223236
}
224237

225-
private string rankedInsecureAlgorithm(int i) {
226-
result = rank[i](string s | s = getAnInsecureAlgorithmName())
227-
}
228-
229-
private string insecureAlgorithmString(int i) {
230-
i = 1 and result = rankedInsecureAlgorithm(i)
231-
or
232-
result = rankedInsecureAlgorithm(i) + "|" + insecureAlgorithmString(i - 1)
233-
}
234-
235238
/**
236239
* Gets the regular expression used for matching strings that look like they
237240
* contain an algorithm that is known to be insecure.
238241
*/
239242
string getInsecureAlgorithmRegex() {
240-
result = algorithmRegex(insecureAlgorithmString(max(int i | exists(rankedInsecureAlgorithm(i)))))
243+
result = algorithmRegex(concat(string name | insecureAlgorithm(name, _) | name, "|"))
244+
}
245+
246+
/** Gets the reason why `input` is an insecure algorithm, if any. */
247+
bindingset[input]
248+
string getInsecureAlgorithmReason(string input) {
249+
exists(string name | insecureAlgorithm(name, result) | input.regexpMatch(algorithmRegex(name)))
241250
}
242251

243252
/**

‎java/ql/src/Security/CWE/CWE-327/BrokenCryptoAlgorithm.ql

Lines changed: 3 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -18,10 +18,11 @@ import InsecureCryptoFlow::PathGraph
1818

1919
from
2020
InsecureCryptoFlow::PathNode source, InsecureCryptoFlow::PathNode sink, CryptoAlgoSpec spec,
21-
BrokenAlgoLiteral algo
21+
BrokenAlgoLiteral algo, string reason
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where
2323
sink.getNode().asExpr() = spec.getAlgoSpec() and
2424
source.getNode().asExpr() = algo and
25+
reason = getInsecureAlgorithmReason(algo.getValue()) and
2526
InsecureCryptoFlow::flowPath(source, sink)
26-
select spec, source, sink, "Cryptographic algorithm $@ is weak and should not be used.", algo,
27+
select spec, source, sink, "Cryptographic algorithm $@ is insecure. " + reason, algo,
2728
algo.getValue()

‎java/ql/src/change-notes/2024-11-29-java-weak-crypto-algorithm-explanation.md

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,4 @@
1+
---
2+
category: fix
3+
---
4+
* The query "Use of a broken or risky cryptographic algorithm" (`java/weak-cryptographic-algorithm`) now gives the reason why the cryptographic algorithm is considered weak.

‎java/ql/test/library-tests/Encryption/Test.java

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -11,6 +11,10 @@ class Test {
1111
"des_function",
1212
"function_using_des",
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"EncryptWithDES",
14+
"RC2",
15+
"RC4",
16+
"ARCFOUR",
17+
"RC5",
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"AES/ECB/NoPadding",
1519
"AES/CBC/PKCS5Padding");
1620

‎java/ql/test/library-tests/Encryption/cryptoalgospec.expected

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,2 +1,2 @@
1-
| Test.java:37:4:37:17 | super(...) | Test.java:37:10:37:15 | "some" |
2-
| Test.java:41:3:41:38 | getInstance(...) | Test.java:41:29:41:37 | "another" |
1+
| Test.java:41:4:41:17 | super(...) | Test.java:41:10:41:15 | "some" |
2+
| Test.java:45:3:45:38 | getInstance(...) | Test.java:45:29:45:37 | "another" |

‎java/ql/test/library-tests/Encryption/insecure.expected

Lines changed: 11 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -1,7 +1,11 @@
1-
| Test.java:9:4:9:8 | "DES" |
2-
| Test.java:10:4:10:8 | "des" |
3-
| Test.java:11:4:11:17 | "des_function" |
4-
| Test.java:12:4:12:23 | "function_using_des" |
5-
| Test.java:13:4:13:19 | "EncryptWithDES" |
6-
| Test.java:14:4:14:22 | "AES/ECB/NoPadding" |
7-
| Test.java:15:4:15:25 | "AES/CBC/PKCS5Padding" |
1+
| Test.java:9:4:9:8 | "DES" | It has a short key length of 56 bits, making it vulnerable to brute-force attacks. Consider using AES instead. |
2+
| Test.java:10:4:10:8 | "des" | It has a short key length of 56 bits, making it vulnerable to brute-force attacks. Consider using AES instead. |
3+
| Test.java:11:4:11:17 | "des_function" | It has a short key length of 56 bits, making it vulnerable to brute-force attacks. Consider using AES instead. |
4+
| Test.java:12:4:12:23 | "function_using_des" | It has a short key length of 56 bits, making it vulnerable to brute-force attacks. Consider using AES instead. |
5+
| Test.java:13:4:13:19 | "EncryptWithDES" | It has a short key length of 56 bits, making it vulnerable to brute-force attacks. Consider using AES instead. |
6+
| Test.java:14:4:14:8 | "RC2" | It is vulnerable to related-key attacks. Consider using AES instead. |
7+
| Test.java:15:4:15:8 | "RC4" | It has multiple vulnerabilities, including biases in its output and susceptibility to several attacks. Consider using AES instead. |
8+
| Test.java:16:4:16:12 | "ARCFOUR" | It has multiple vulnerabilities, including biases in its output and susceptibility to several attacks. Consider using AES instead. |
9+
| Test.java:17:4:17:8 | "RC5" | It is vulnerable to differential and related-key attacks. Consider using AES instead. |
10+
| Test.java:18:4:18:22 | "AES/ECB/NoPadding" | ECB mode, as in AES/ECB/NoPadding for example, is vulnerable to replay and other attacks. Consider using GCM instead. |
11+
| Test.java:19:4:19:25 | "AES/CBC/PKCS5Padding" | CBC mode with PKCS#5 or PKCS#7 padding is vulnerable to padding oracle attacks. Consider using GCM instead. |

‎java/ql/test/library-tests/Encryption/insecure.ql

Lines changed: 7 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,10 @@
11
import default
22
import semmle.code.java.security.Encryption
33

4-
from StringLiteral s
5-
where s.getValue().regexpMatch(getInsecureAlgorithmRegex())
6-
select s
4+
from StringLiteral s, string reason
5+
where
6+
s.getValue().regexpMatch(getInsecureAlgorithmRegex()) and
7+
if exists(getInsecureAlgorithmReason(s.getValue()))
8+
then reason = getInsecureAlgorithmReason(s.getValue())
9+
else reason = "<no reason>"
10+
select s, reason

‎java/ql/test/library-tests/Encryption/secure.expected

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,2 +1,2 @@
1-
| Test.java:18:4:18:8 | "AES" |
2-
| Test.java:19:4:19:17 | "AES_function" |
1+
| Test.java:22:4:22:8 | "AES" |
2+
| Test.java:23:4:23:17 | "AES_function" |

‎java/ql/test/query-tests/security/CWE-327/semmle/tests/BrokenCryptoAlgorithm.expected

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,6 @@
11
#select
2-
| Test.java:19:20:19:50 | getInstance(...) | Test.java:19:45:19:49 | "DES" | Test.java:19:45:19:49 | "DES" | Cryptographic algorithm $@ is weak and should not be used. | Test.java:19:45:19:49 | "DES" | DES |
3-
| Test.java:42:14:42:38 | getInstance(...) | Test.java:42:33:42:37 | "RC2" | Test.java:42:33:42:37 | "RC2" | Cryptographic algorithm $@ is weak and should not be used. | Test.java:42:33:42:37 | "RC2" | RC2 |
2+
| Test.java:19:20:19:50 | getInstance(...) | Test.java:19:45:19:49 | "DES" | Test.java:19:45:19:49 | "DES" | Cryptographic algorithm $@ is insecure. It has a short key length of 56 bits, making it vulnerable to brute-force attacks. Consider using AES instead. | Test.java:19:45:19:49 | "DES" | DES |
3+
| Test.java:42:14:42:38 | getInstance(...) | Test.java:42:33:42:37 | "RC2" | Test.java:42:33:42:37 | "RC2" | Cryptographic algorithm $@ is insecure. It is vulnerable to related-key attacks. Consider using AES instead. | Test.java:42:33:42:37 | "RC2" | RC2 |
44
edges
55
nodes
66
| Test.java:19:45:19:49 | "DES" | semmle.label | "DES" |

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