diff options
Diffstat (limited to 'pdf')
| -rw-r--r-- | pdf/pdf.go | 40 |
1 files changed, 31 insertions, 9 deletions
@@ -670,7 +670,7 @@ func (u *Updater) loadXref(lex *Lexer, loadedEntries map[uint]struct{}) error { // ----------------------------------------------------------------------------- -var haystackRE = regexp.MustCompile(`(?s:.*)\sstartxref\s+(\d+)\s+%%EOF`) +var trailerRE = regexp.MustCompile(`(?s:.*)\sstartxref\s+(\d+)\s+%%EOF`) // NewUpdater initializes an Updater, building the cross-reference table and // preparing a new trailer dictionary. @@ -685,7 +685,7 @@ func NewUpdater(document []byte) (*Updater, error) { haystack = haystack[len(haystack)-1024:] } - m := haystackRE.FindSubmatch(haystack) + m := trailerRE.FindSubmatch(haystack) if m == nil { return nil, errors.New("cannot find startxref") } @@ -739,6 +739,31 @@ func NewUpdater(document []byte) (*Updater, error) { return u, nil } +var versionRE = regexp.MustCompile( + `(?:^|[\r\n])%(?:!PS-Adobe-\d\.\d )?PDF-(\d)\.(\d)[\r\n]`) + +// Version extracts the claimed PDF version as a positive decimal number, +// e.g. 17 for PDF 1.7. Returns zero on failure. +func (u *Updater) Version(root *Object) int { + if version, ok := root.Dict["Version"]; ok && version.Kind == Name { + if v := version.String; len(v) == 3 && v[1] == '.' && + v[0] >= '0' && v[0] <= '9' && v[2] >= '0' && v[2] <= '9' { + return int(v[0]-'0')*10 + int(v[2]-'0') + } + } + + // We only need to look for the comment roughly within + // the first kibibyte of the document. + haystack := u.Document + if len(haystack) > 1024 { + haystack = haystack[:1024] + } + if m := versionRE.FindSubmatch(haystack); m != nil { + return int(m[1][0]-'0')*10 + int(m[2][0]-'0') + } + return 0 +} + // Get retrieves an object by its number and generation--may return // Nil or End with an error. // @@ -1094,9 +1119,6 @@ func FillInSignature(document []byte, signOff, signLen int, // employ cross-reference 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. func Sign(document []byte, key crypto.PrivateKey, certs []*x509.Certificate) ([]byte, error) { pdf, err := NewUpdater(document) @@ -1195,10 +1217,10 @@ func Sign(document []byte, }) // 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 that 1.5, it's not a bad idea to use - // cairo_pdf_surface_restrict_to_version(). - root.Dict["Version"] = NewName("1.6") + if pdf.Version(&root) < 16 { + root.Dict["Version"] = NewName("1.6") + } + pdf.Update(rootRef.N, func(buf BytesWriter) { buf.WriteString(root.Serialize()) }) |