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fix(certs): Only filter algorithms on 2 chains #22

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fix(certs): Only filter algorithms on 2 chains #22

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38 changes: 29 additions & 9 deletions app/src/main/java/io/github/vvb2060/keyattestation/repository/AttestationRepository.java
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Original file line number Diff line number Diff line change
Expand Up @@ -269,15 +269,26 @@ public Resource<BaseData> loadCerts(ParcelFileDescriptor pfd, boolean preferRsa)

// 2a. Filter to RSA certs only
if (parsedBinary && preferRsa && !currentCerts.isEmpty()) {
List<X509Certificate> rsaCerts = new ArrayList<>();
int leafCount = 0;
for (X509Certificate cert : currentCerts) {
if (cert.getPublicKey().getAlgorithm().equalsIgnoreCase("RSA")) {
rsaCerts.add(cert);
}
if (cert.getBasicConstraints() == -1) leafCount++;
}
if (!rsaCerts.isEmpty()) {
currentCerts.clear();
currentCerts.addAll(rsaCerts);
// A single end-entity cert == single chain, which may legitimately mix
// algorithms (EC leaf under the RSA root)
// Leave it intact and let the key type check below report any mismatch
if (leafCount > 1) {
List<X509Certificate> rsaCerts = new ArrayList<>();
boolean hasLeaf = false;
for (X509Certificate cert : currentCerts) {
if (cert.getPublicKey().getAlgorithm().equalsIgnoreCase("RSA")) {
rsaCerts.add(cert);
if (cert.getBasicConstraints() == -1) hasLeaf = true;
}
}
if (hasLeaf) {
currentCerts.clear();
currentCerts.addAll(rsaCerts);
}
}
}

Expand Down Expand Up @@ -355,17 +366,26 @@ public Resource<BaseData> loadCerts(ParcelFileDescriptor pfd, boolean preferRsa)
// Same algorithm filter as the binary path (2a)
// the parser doesn't distinguish key blocks, so a mixed-algorithm keybox would
// otherwise concatenate two unrelated chains into one list
if (!currentCerts.isEmpty()) {
int leafCount = 0;
for (X509Certificate cert : currentCerts) {
if (cert.getBasicConstraints() == -1) leafCount++;
}
// A single end-entity cert == single chain, which may legitimately mix
// algorithms (EC leaf under the RSA root)
// Leave it intact and let the key type check below report any mismatch
if (leafCount > 1) {
List<X509Certificate> matching = new ArrayList<>();
boolean hasLeaf = false;
for (X509Certificate cert : currentCerts) {
var algo = cert.getPublicKey().getAlgorithm();
if (algo.equalsIgnoreCase(preferRsa ? "RSA" : "EC") ||
(!preferRsa && algo.equalsIgnoreCase("ECDSA"))
) {
matching.add(cert);
if (cert.getBasicConstraints() == -1) hasLeaf = true;
}
}
if (!matching.isEmpty()) {
if (hasLeaf) {
currentCerts.clear();
currentCerts.addAll(matching);
}
Expand Down
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