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Add signatureVerified flag for each signature #994

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merged 4 commits into from
Aug 25, 2021
Merged

Add signatureVerified flag for each signature #994

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2824574
Add signatureVerified flag for each signature
HoundThe Jul 29, 2021
3a64680
Simplify condition
HoundThe Aug 5, 2021
ff62028
Remove checking for version == 1 when validating signatures
HoundThe Aug 5, 2021
ff51de8
Modify plain signature presentation
HoundThe Aug 10, 2021
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1 change: 1 addition & 0 deletions include/retdec/fileformat/types/certificate_table/certificate_table.h
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@ struct Signer
/* naming - "Signature" was already taken by unpackers */
struct DigitalSignature
{
bool isValid;
std::string fileDigest;
std::string signedDigest;
std::string digestAlgorithm;
Expand Down
34 changes: 15 additions & 19 deletions src/fileformat/file_format/pe/authenticode/pkcs7_signature.cpp
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Expand Up @@ -106,7 +106,7 @@ Pkcs7Signature::Pkcs7Signature(const std::vector<std::uint8_t>& input) noexcept
{
/*
SignedData ::= SEQUENCE {
version Version, (Must be 1)
version Version,
digestAlgorithms DigestAlgorithmIdentifiers,
contentInfo ContentInfo,
certificates
Expand Down Expand Up @@ -203,7 +203,6 @@ Pkcs7Signature::SignerInfo::SignerInfo(const PKCS7* pkcs7, const PKCS7_SIGNER_IN
si_info->enc_digest->data + si_info->enc_digest->length);

ASN1_INTEGER_get_uint64(&version, si_info->version);
/* Version has to be equal to 1 */

serial = serialToString(si_info->issuer_and_serial->serial);
issuer = X509NameToString(si_info->issuer_and_serial->issuer);
Expand Down Expand Up @@ -360,7 +359,6 @@ const X509* Pkcs7Signature::SignerInfo::getSignerCert() const
std::vector<std::string> Pkcs7Signature::verify(const std::string& fileDigest) const
{
/* Check if signature is correctly parsed and complies with the spec:
- [x] Version is equal to 1
- [x] contentDigestAlgorithms contain single algorithm
- [x] SignedData and SignerInfo digestAlgorithm match
- [x] contentInfo contains PE hash, hashing algorithm and SpcIndirectDataOid
Expand All @@ -384,10 +382,6 @@ std::vector<std::string> Pkcs7Signature::verify(const std::string& fileDigest) c
warnings.emplace_back("Invalid PKCS#7 type, expected SignedData");
}

if (version != 1) {
warnings.emplace_back("Signature version is: " + std::to_string(version) + ", expected 1");
}

if (contentDigestAlgorithms.size() != 1) {
warnings.emplace_back("Invalid number of DigestAlgorithmIdentifiers: " + std::to_string(contentDigestAlgorithms.size()) + " - expected 1");
}
Expand All @@ -413,16 +407,12 @@ std::vector<std::string> Pkcs7Signature::verify(const std::string& fileDigest) c
if (!signerInfo->getSignerCert()) {
warnings.emplace_back("Signing cert is missing");
}
if (signerInfo->version != 1) {
warnings.emplace_back("SignerInfo version is: " + std::to_string(signerInfo->version) + ", expected 1");
}
if (contentDigestAlgorithms.size() > 0 && signerInfo->digestAlgorithm != contentDigestAlgorithms[0]) {
warnings.emplace_back("SignedData digest algorithm and signerInfo digest algorithm don't match");
}
if (signerInfo->encryptDigest.empty()) {
warnings.emplace_back("Encrypted digest is empty");
}

// verify auth attrs existence
if (!signerInfo->spcInfo) {
warnings.emplace_back("Couldn't get SpcSpOpusInfo");
Expand Down Expand Up @@ -534,6 +524,7 @@ std::vector<DigitalSignature> Pkcs7Signature::getSignatures(const retdec::filefo
/* No signer would mean, we have pretty much nothing */
if (!signerInfo.has_value()) {
signatures.push_back(signature);
signature.isValid = false;
return signatures;
}

Expand All @@ -556,18 +547,23 @@ std::vector<DigitalSignature> Pkcs7Signature::getSignatures(const retdec::filefo

signature.signer = signer;

// If there are warnings, then the signature is invalid
// We don't use the countersignature warnings here as
// previous implementation did when verifying
signature.isValid = signature.warnings.empty();

for (auto&& counterSig : signInfo.counterSignatures) {
CertificateProcessor processor;
auto certChain = processor.getChain(counterSig.signerCert, certs);
auto fileformatCertChain = convertToFileformatCertChain(certChain);

Signer counterSigner;
counterSigner.chain = fileformatCertChain;
counterSigner.signingTime = counterSig.signTime,
counterSigner.signingTime = counterSig.signTime;
counterSigner.digest = bytesToHexString(counterSig.messageDigest.data(),
counterSig.messageDigest.size()),
counterSigner.digestAlgorithm = OBJ_nid2ln(counterSig.digestAlgorithm),
counterSigner.warnings = counterSig.verify(signerInfo->encryptDigest),
counterSig.messageDigest.size());
counterSigner.digestAlgorithm = OBJ_nid2ln(counterSig.digestAlgorithm);
counterSigner.warnings = counterSig.verify(signerInfo->encryptDigest);
counterSigner.counterSigners = std::vector<Signer>();

signature.signer.counterSigners.push_back(counterSigner);
Expand All @@ -580,11 +576,11 @@ std::vector<DigitalSignature> Pkcs7Signature::getSignatures(const retdec::filefo

Signer counterSigner;
counterSigner.chain = fileformatCertChain;
counterSigner.signingTime = counterSig.signTime,
counterSigner.signingTime = counterSig.signTime;
counterSigner.digest = bytesToHexString(counterSig.messageDigest.data(),
counterSig.messageDigest.size()),
counterSigner.digestAlgorithm = OBJ_nid2ln(counterSig.digestAlgorithm),
counterSigner.warnings = counterSig.verify(signerInfo->encryptDigest),
counterSig.messageDigest.size());
counterSigner.digestAlgorithm = OBJ_nid2ln(counterSig.digestAlgorithm);
counterSigner.warnings = counterSig.verify(signerInfo->encryptDigest);
counterSigner.counterSigners = std::vector<Signer>();

signature.signer.counterSigners.push_back(counterSigner);
Expand Down
2 changes: 1 addition & 1 deletion src/fileformat/file_format/pe/pe_format.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1806,7 +1806,7 @@ void PeFormat::loadCertificates()
auto certBytes = securityDir.getCertificate(0);

authenticode::Authenticode authenticode(certBytes);

certificateTable = new CertificateTable(authenticode.getSignatures(this));
}

Expand Down
2 changes: 2 additions & 0 deletions src/fileinfo/file_presentation/json_presentation.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -487,6 +487,8 @@ void WriteSigner(JsonPresentation::Writer& writer, const Signer& signer)
void WriteSignature(JsonPresentation::Writer& writer, const DigitalSignature& signature)
{
writer.StartObject();
writer.String("signatureVerified");
writer.Bool(signature.isValid);
writer.String("warnings");
writer.StartArray();
for (auto&& warn : signature.warnings) {
Expand Down
7 changes: 5 additions & 2 deletions src/fileinfo/file_presentation/plain_presentation.cpp
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Expand Up @@ -724,7 +724,7 @@ static void printCertificate(const Certificate& cert, int indent)
Log::info() << std::string(indent, ' ') << "Valid until: " << cert.getValidUntil() << "\n";
Log::info() << std::string(indent, ' ') << "Signature Algorithm: " << cert.getSignatureAlgorithm() << "\n";
Log::info() << std::string(indent, ' ') << "Public Key Algorithm: " << cert.getPublicKeyAlgorithm() << "\n";
Log::info() << std::string(indent, ' ') << "Public key: " << cert.getPublicKey() << ":\n";
Log::info() << std::string(indent, ' ') << "Public key: " << cert.getPublicKey() << "\n";
}

static void printCertificateChain(const std::vector<Certificate>& certs, int indent)
Expand Down Expand Up @@ -756,6 +756,7 @@ static void printSigner(const Signer& signer, int indent)

static void printSignature(const DigitalSignature& signature, int indent)
{
Log::info() << std::string(indent, ' ') << "Is Valid: " << signature.isValid << "\n";
Log::info() << std::string(indent, ' ') << "Digest Algorithm: " << signature.digestAlgorithm << "\n";
Log::info() << std::string(indent, ' ') << "Signed Digest: " << signature.signedDigest << "\n";
Log::info() << std::string(indent, ' ') << "File Digest: " << signature.fileDigest << "\n";
Expand All @@ -772,7 +773,9 @@ void PlainPresentation::presentSignatures() const
if (!table) {
return;
}
Log::info() << "Digital Signatures:\n";
Log::info() << "\n";
Log::info() << "Digital Signatures\n";
Log::info() << "------------------\n\n";
int indent = 4;
Log::info() << std::string(indent, ' ') << "Signature count: " << table->signatureCount() << "\n";

Expand Down