diff options
Diffstat (limited to 'pdf-simple-sign.cpp')
| -rw-r--r-- | pdf-simple-sign.cpp | 32 |
1 files changed, 26 insertions, 6 deletions
diff --git a/pdf-simple-sign.cpp b/pdf-simple-sign.cpp index b724f69..6d01211 100644 --- a/pdf-simple-sign.cpp +++ b/pdf-simple-sign.cpp @@ -342,6 +342,9 @@ public: /// Build the cross-reference table and prepare a new trailer dictionary std::string initialize(); + /// Try to extract the claimed PDF version as a positive decimal number, e.g. 17 for PDF 1.7. + /// Returns zero on failure. + int version(const pdf_object& root) const; /// Retrieve an object by its number and generation -- may return NIL or END with an error pdf_object get(uint n, uint generation) const; /// Allocate a new object number @@ -512,7 +515,7 @@ std::string pdf_updater::load_xref(pdf_lexer& lex, std::set<uint>& loaded_entrie std::string pdf_updater::initialize() { // We only need to look for startxref roughly within the last kibibyte of the document - static std::regex haystack_re("[\\s\\S]*\\sstartxref\\s+(\\d+)\\s+%%EOF"); + static std::regex haystack_re(R"([\s\S]*\sstartxref\s+(\d+)\s+%%EOF)"); std::string haystack = document.substr(document.length() < 1024 ? 0 : document.length() - 1024); std::smatch m; @@ -560,6 +563,25 @@ std::string pdf_updater::initialize() { return ""; } +int pdf_updater::version(const pdf_object& root) const { + auto version = root.dict.find("Version"); + if (version != root.dict.end() && version->second.type == pdf_object::NAME) { + const auto& v = version->second.string; + if (isdigit(v[0]) && v[1] == '.' && isdigit(v[2]) && !v[3]) + return (v[0] - '0') * 10 + (v[2] - '0'); + } + + // We only need to look for the comment roughly within the first kibibyte of the document + static std::regex version_re(R"((?:^|[\r\n])%(?:!PS-Adobe-\d\.\d )?PDF-(\d)\.(\d)[\r\n])"); + std::string haystack = document.substr(0, 1024); + + std::smatch m; + if (std::regex_search(haystack, m, version_re, std::regex_constants::match_default)) + return std::stoul(m.str(1)) * 10 + std::stoul(m.str(2)); + + return 0; +} + pdf_object pdf_updater::get(uint n, uint generation) const { if (n >= xref_size) return {pdf_object::NIL}; @@ -806,8 +828,6 @@ error: /// streams from PDF 1.5, or at least constitutes a hybrid-reference file. The results with /// PDF 2.0 (2017) are currently unknown as the standard costs money. /// -/// Carelessly assumes that the version of the original document is at most PDF 1.6. -/// /// https://www.adobe.com/devnet-docs/acrobatetk/tools/DigSig/Acrobat_DigitalSignatures_in_PDF.pdf /// https://www.adobe.com/content/dam/acom/en/devnet/acrobat/pdfs/pdf_reference_1-7.pdf /// https://www.adobe.com/content/dam/acom/en/devnet/acrobat/pdfs/PPKAppearances.pdf @@ -892,9 +912,9 @@ static std::string pdf_sign(std::string& document) { }}; // Upgrade the document version for SHA-256 etc. - // XXX assuming that it's not newer than 1.6 already -- while Cairo can't currently use a newer - // version than 1.5, it's not a bad idea to use cairo_pdf_surface_restrict_to_version() - root.dict["Version"] = {pdf_object::NAME, "1.6"}; + if (pdf.version(root) < 16) + root.dict["Version"] = {pdf_object::NAME, "1.6"}; + pdf.update(root_ref->second.n, [&]{ pdf.document += pdf_serialize(root); }); pdf.flush_updates(); |