Signature dictionary parsing

PdfForQtLib/sources/pdfsignaturehandler.h

@@ -0,0 +1,153 @@
+//    Copyright (C) 2020 Jakub Melka
+//
+//    This file is part of PdfForQt.
+//
+//    PdfForQt is free software: you can redistribute it and/or modify
+//    it under the terms of the GNU Lesser General Public License as published by
+//    the Free Software Foundation, either version 3 of the License, or
+//    (at your option) any later version.
+//
+//    PdfForQt is distributed in the hope that it will be useful,
+//    but WITHOUT ANY WARRANTY; without even the implied warranty of
+//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//    GNU Lesser General Public License for more details.
+//
+//    You should have received a copy of the GNU Lesser General Public License
+//    along with PDFForQt.  If not, see <https://www.gnu.org/licenses/>.
+
+#ifndef PDFSIGNATUREHANDLER_H
+#define PDFSIGNATUREHANDLER_H
+
+#include "pdfglobal.h"
+#include "pdfobject.h"
+
+#include <optional>
+
+namespace pdf
+{
+class PDFObjectStorage;
+
+/// Signature reference dictionary.
+class PDFSignatureReference
+{
+public:
+
+    enum class TransformMethod
+    {
+        Invalid,
+        DocMDP,
+        UR,
+        FieldMDP
+    };
+
+    TransformMethod getTransformMethod() const { return m_transformMethod; }
+    const PDFObject& getTransformParams() const { return m_transformParams; }
+    const PDFObject& getData() const { return m_data; }
+    const QByteArray& getDigestMethod() const { return m_digestMethod; }
+
+    /// Tries to parse the signature reference. No exception is thrown, in case of error,
+    /// invalid signature reference object is returned.
+    /// \param storage Object storage
+    /// \param object Object containing the signature
+    static PDFSignatureReference parse(const PDFObjectStorage* storage, PDFObject object);
+
+private:
+    TransformMethod m_transformMethod = TransformMethod::Invalid;
+    PDFObject m_transformParams;
+    PDFObject m_data;
+    QByteArray m_digestMethod;
+};
+
+/// Signature dictionary. Contains digital signature. This signature can be validated by signature validator.
+/// This object contains certificates, digital signatures, and other information about signature.
+class PDFSignature
+{
+public:
+
+    enum class Type
+    {
+        Invalid,
+        Sig,
+        DocTimeStamp
+    };
+
+    struct ByteRange
+    {
+        PDFInteger offset = 0;
+        PDFInteger size = 0;
+    };
+
+    using ByteRanges = std::vector<ByteRange>;
+
+    struct Changes
+    {
+        PDFInteger pagesAltered = 0;
+        PDFInteger fieldsAltered = 0;
+        PDFInteger fieldsFilled = 0;
+    };
+
+    enum class AuthentificationType
+    {
+        Invalid,
+        PIN,
+        Password,
+        Fingerprint
+    };
+
+    /// Tries to parse the signature. No exception is thrown, in case of error,
+    /// invalid signature object is returned.
+    /// \param storage Object storage
+    /// \param object Object containing the signature
+    static PDFSignature parse(const PDFObjectStorage* storage, PDFObject object);
+
+    Type getType() const { return m_type; }
+    const QByteArray& getFilter() const { return m_filter; }
+    const QByteArray& getSubfilter() const { return m_subfilter; }
+    const QByteArray& getContents() const { return m_contents; }
+    const std::vector<QByteArray>* getCertificates() const { return m_certificates.has_value() ? &m_certificates.value() : nullptr; }
+    const ByteRanges& getByteRanges() const { return m_byteRanges; }
+    const std::vector<PDFSignatureReference>& getReferences() const { return m_references; }
+    const Changes* getChanges() const { return m_changes.has_value() ? &m_changes.value() : nullptr; }
+
+    const QString& getName() const { return m_name; }
+    const QDateTime& getSigningDateTime() const { return m_signingDateTime; }
+    const QString& getLocation() const { return m_location; }
+    const QString& getReason() const { return m_reason; }
+    const QString& getContactInfo() const { return m_contactInfo; }
+    PDFInteger getR() const { return m_R; }
+    PDFInteger getV() const { return m_V; }
+    const PDFObject& getPropBuild() const { return m_propBuild; }
+    PDFInteger getPropTime() const { return m_propTime; }
+    AuthentificationType getAuthentificationType() const { return m_propType; }
+
+private:
+    Type m_type = Type::Invalid;
+    QByteArray m_filter;    ///< Preferred signature handler name
+    QByteArray m_subfilter; ///< Describes encoding of signature
+    QByteArray m_contents;
+    std::optional<std::vector<QByteArray>> m_certificates; ///< Certificate chain (only for adbe.x509.rsa_sha1)
+    ByteRanges m_byteRanges;
+    std::vector<PDFSignatureReference> m_references;
+    std::optional<Changes> m_changes;
+
+    QString m_name; ///< Name of signer. Should rather be extracted from signature.
+    QDateTime m_signingDateTime; ///< Signing date and time. Should be extracted from signature, if possible.
+    QString m_location; ///< CPU hostname or physical location of signing
+    QString m_reason; ///< Reason for signing
+    QString m_contactInfo; ///< Contact info for verifying the signature
+    PDFInteger m_R; ///< Version of signature handler. Obsolete.
+    PDFInteger m_V; ///< Version of signature dictionary format. 1 if References should be used.
+    PDFObject m_propBuild;
+    PDFInteger m_propTime = 0;
+    AuthentificationType m_propType = AuthentificationType::Invalid;
+};
+
+class PDFSignatureHandler
+{
+public:
+    PDFSignatureHandler();
+};
+
+} // namespace pdf
+
+#endif // PDFSIGNATUREHANDLER_H