lpg: improve Picture sizing, clean up

Restraining a Picture in one dimension with a Frame should make it
report the right overall dimensions (keeping its aspect ratio).

Also applying the F.9 C++ Core Guideline.

.clang-format

@@ -0,0 +1,8 @@
+BasedOnStyle: Chromium
+ColumnLimit: 100
+IndentCaseLabels: false
+AccessModifierOffset: -2
+ContinuationIndentWidth: 2
+SpaceAfterTemplateKeyword: false
+SpaceAfterCStyleCast: true
+SpacesBeforeTrailingComments: 2

.gitignore

@@ -0,0 +1,8 @@
+/builddir
+/pdf-simple-sign.cflags
+/pdf-simple-sign.config
+/pdf-simple-sign.creator
+/pdf-simple-sign.creator.user
+/pdf-simple-sign.cxxflags
+/pdf-simple-sign.files
+/pdf-simple-sign.includes

LICENSE

@@ -1,4 +1,4 @@
-Copyright (c) 2017, Přemysl Janouch <p@janouch.name>
+Copyright (c) 2017 - 2025, Přemysl Eric Janouch <p@janouch.name>
 
 Permission to use, copy, modify, and/or distribute this software for any
 purpose with or without fee is hereby granted.

NEWS

@@ -1,3 +1,28 @@
+1.1.1 (2020-09-06)
+
+ * Fix a dysfunctional example in the manual
+
+ * Go: write the xref table in a deterministic order
+
+ * Add a trivial test suite, based on pdfsig from poppler-utils
+
+
+1.1 (2020-09-05)
+
+ * Make it possible to change the signature reservation with an option
+
+ * Return errors rather than mangle documents in some cases,
+   notably with pre-existing PDF forms
+
+ * Avoid downgrading the document's PDF version to 1.6
+
+ * A few fixes for PDF parsing and serialisation
+
+ * Add an instructive man page
+
+ * Add a native Go port of the utility, also usable as a library
+
+
 1.0 (2018-08-03)
 
  * Initial release

README.adoc

@@ -1,27 +1,30 @@
 pdf-simple-sign
 ===============
-:compact-option:
 
-'pdf-simple-sign' is a simple open source PDF signer intended for documents
-generated by Cairo.  As such, it currently comes with some restrictions:
-
- * the document may not have any forms or signatures already, as they will be
-   overwitten
- * the document may not employ cross-reference streams, or must constitute
-   a hybrid-reference file at least
- * the document may not be newer than PDF 1.6 already, or it will get downgraded
-   to that version
- * the signature may take at most 4 kilobytes as a compile-time limit,
-   which should be enough space even for one intermediate certificate
-
-The signature is attached to the first page and has no appearance.
+'pdf-simple-sign' is a simple PDF signer intended for documents produced by
+the Cairo library (≤ 1.17.4 or using PDF 1.4), GNU troff, ImageMagick,
+or similar.
 
 I don't aim to extend the functionality any further.  The project is fairly
 self-contained and it should be easy to grasp and change to suit to your needs.
 
+Packages
+--------
+Regular releases are sporadic.  git master should be stable enough.
+You can get a package with the latest development version using Arch Linux's
+https://aur.archlinux.org/packages/pdf-simple-sign-git[AUR],
+or as a https://git.janouch.name/p/nixexprs[Nix derivation].
+
+Documentation
+-------------
+See the link:pdf-simple-sign.adoc[man page] for information about usage.
+The rest of this README will concern itself with externalities.
+
+image:https://pkg.go.dev/badge/janouch.name/pdf-simple-sign@master/pdf["PkgGoDev", link="https://pkg.go.dev/janouch.name/pdf-simple-sign@master/pdf"]
+
 Building
 --------
-Build dependencies: Meson, a C++11 compiler, pkg-config +
+Build dependencies: Meson, Asciidoctor, a C++11 compiler, pkg-config +
 Runtime dependencies: libcrypto (OpenSSL 1.1 API)
 
  $ git clone https://git.janouch.name/p/pdf-simple-sign.git
@@ -30,10 +33,39 @@ Runtime dependencies: libcrypto (OpenSSL 1.1 API)
  $ cd builddir
  $ ninja
 
-Usage
------
+Go
+~~
+In addition to the C++ version, also included is a native Go port,
+which has enhanced PDF 1.5 support:
 
- $ ./pdf-simple-sign document.pdf document.signed.pdf KeyAndCerts.p12 password
+----
+$ go install janouch.name/pdf-simple-sign/cmd/pdf-simple-sign@master
+----
+
+and a crude external VFS for Midnight Commander, that may be used to extract
+all streams from a given PDF file:
+
+----
+$ GOBIN=$HOME/.local/share/mc/extfs.d \
+  go install janouch.name/pdf-simple-sign/cmd/extfs-pdf@master
+----
+
+To enable the VFS, edit your _~/.config/mc/mc.ext.ini_ to contain:
+
+----
+[pdf]
+Type=^PDF
+Open=%cd %p/extfs-pdf://
+----
+
+Lua PDF generator
+~~~~~~~~~~~~~~~~~
+Build dependencies: Meson, a C++17 compiler, pkg-config +
+Runtime dependencies: C++ Lua >= 5.3 (custom Meson wrap fallback),
+ cairo >= 1.15.4, pangocairo, libqrencode
+
+This is a parasitic subproject located in the _lpg_ subdirectory.
+It will generate its own documentation.
 
 Contributing and Support
 ------------------------

cmd/extfs-pdf/main.go

@@ -0,0 +1,141 @@
+//
+// Copyright (c) 2021 - 2024, Přemysl Eric Janouch <p@janouch.name>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+//
+
+// extfs-pdf is an external VFS plugin for Midnight Commander.
+// More serious image extractors should rewrite this to use pdfimages(1).
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"time"
+
+	"janouch.name/pdf-simple-sign/pdf"
+)
+
+func die(status int, format string, args ...interface{}) {
+	os.Stderr.WriteString(fmt.Sprintf(format+"\n", args...))
+	os.Exit(status)
+}
+
+func usage() {
+	die(1, "Usage: %s [-h] COMMAND DOCUMENT [ARG...]", os.Args[0])
+}
+
+func streamSuffix(o *pdf.Object) string {
+	if filter, _ := o.Dict["Filter"]; filter.Kind == pdf.Name {
+		switch filter.String {
+		case "JBIG2Decode":
+			// This is the file extension used by pdfimages(1).
+			// This is not a complete JBIG2 standalone file.
+			return "jb2e"
+		case "JPXDecode":
+			return "jp2"
+		case "DCTDecode":
+			return "jpg"
+		case "FlateDecode":
+			return "zz"
+		default:
+			return filter.String
+		}
+	}
+	return "stream"
+}
+
+func list(mtime time.Time, updater *pdf.Updater) {
+	stamp := mtime.Local().Format("01-02-2006 15:04:05")
+	for _, o := range updater.ListIndirect() {
+		object, err := updater.Get(o.N, o.Generation)
+		size := 0
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "%s\n", err)
+		} else {
+			// Accidental transformation, retrieving original data is more work.
+			size = len(object.Serialize())
+		}
+		fmt.Printf("-r--r--r-- 1 0 0 %d %s n%dg%d\n",
+			size, stamp, o.N, o.Generation)
+		if object.Kind == pdf.Stream {
+			fmt.Printf("-r--r--r-- 1 0 0 %d %s n%dg%d.%s\n", len(object.Stream),
+				stamp, o.N, o.Generation, streamSuffix(&object))
+		}
+	}
+}
+
+func copyout(updater *pdf.Updater, storedFilename, extractTo string) {
+	var (
+		n, generation uint
+		suffix        string
+	)
+	m, err := fmt.Sscanf(storedFilename, "n%dg%d%s", &n, &generation, &suffix)
+	if m < 2 {
+		die(3, "%s: %s", storedFilename, err)
+	}
+
+	object, err := updater.Get(n, generation)
+	if err != nil {
+		die(3, "%s: %s", storedFilename, err)
+	}
+
+	content := []byte(object.Serialize())
+	if suffix != "" {
+		content = object.Stream
+	}
+	if err = os.WriteFile(extractTo, content, 0666); err != nil {
+		die(3, "%s", err)
+	}
+}
+
+func main() {
+	flag.Usage = usage
+	flag.Parse()
+	if flag.NArg() < 2 {
+		usage()
+	}
+
+	command, documentPath := flag.Arg(0), flag.Arg(1)
+	doc, err := os.ReadFile(documentPath)
+	if err != nil {
+		die(1, "%s", err)
+	}
+
+	mtime := time.UnixMilli(0)
+	if info, err := os.Stat(documentPath); err == nil {
+		mtime = info.ModTime()
+	}
+
+	updater, err := pdf.NewUpdater(doc)
+	if err != nil {
+		die(2, "%s", err)
+	}
+
+	switch command {
+	default:
+		die(1, "unsupported command: %s", command)
+	case "list":
+		if flag.NArg() != 2 {
+			usage()
+		} else {
+			list(mtime, updater)
+		}
+	case "copyout":
+		if flag.NArg() != 4 {
+			usage()
+		} else {
+			copyout(updater, flag.Arg(2), flag.Arg(3))
+		}
+	}
+}

cmd/pdf-simple-sign/main.go

@@ -0,0 +1,76 @@
+//
+// Copyright (c) 2018 - 2020, Přemysl Eric Janouch <p@janouch.name>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted.
+//
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
+// SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION
+// OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN
+// CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+//
+
+// pdf-simple-sign is a simple PDF signer.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io/ioutil"
+	"os"
+
+	"janouch.name/pdf-simple-sign/pdf"
+)
+
+// #include <unistd.h>
+import "C"
+
+func isatty(fd uintptr) bool { return C.isatty(C.int(fd)) != 0 }
+
+func die(status int, format string, args ...interface{}) {
+	msg := fmt.Sprintf(format+"\n", args...)
+	if isatty(os.Stderr.Fd()) {
+		msg = "\x1b[0;31m" + msg + "\x1b[m"
+	}
+	os.Stderr.WriteString(msg)
+	os.Exit(status)
+}
+
+func usage() {
+	die(1, "Usage: %s [-h] [-r RESERVATION] INPUT-FILENAME OUTPUT-FILENAME "+
+		"PKCS12-PATH PKCS12-PASS", os.Args[0])
+}
+
+var reservation = flag.Int(
+	"r", 4096, "signature reservation as a number of bytes")
+
+func main() {
+	flag.Usage = usage
+	flag.Parse()
+	if flag.NArg() != 4 {
+		usage()
+	}
+
+	inputPath, outputPath := flag.Arg(0), flag.Arg(1)
+	doc, err := ioutil.ReadFile(inputPath)
+	if err != nil {
+		die(1, "%s", err)
+	}
+	p12, err := ioutil.ReadFile(flag.Arg(2))
+	if err != nil {
+		die(2, "%s", err)
+	}
+	key, certs, err := pdf.PKCS12Parse(p12, flag.Arg(3))
+	if err != nil {
+		die(3, "%s", err)
+	}
+	if doc, err = pdf.Sign(doc, key, certs, *reservation); err != nil {
+		die(4, "error: %s", err)
+	}
+	if err = ioutil.WriteFile(outputPath, doc, 0666); err != nil {
+		die(5, "%s", err)
+	}
+}

go.mod

@@ -0,0 +1,8 @@
+module janouch.name/pdf-simple-sign
+
+go 1.17
+
+require (
+	go.mozilla.org/pkcs7 v0.0.0-20210826202110-33d05740a352
+	golang.org/x/crypto v0.10.0
+)

go.sum

@@ -0,0 +1,13 @@
+go.mozilla.org/pkcs7 v0.0.0-20200128120323-432b2356ecb1 h1:A/5uWzF44DlIgdm/PQFwfMkW0JX+cIcQi/SwLAmZP5M=
+go.mozilla.org/pkcs7 v0.0.0-20200128120323-432b2356ecb1/go.mod h1:SNgMg+EgDFwmvSmLRTNKC5fegJjB7v23qTQ0XLGUNHk=
+go.mozilla.org/pkcs7 v0.0.0-20210826202110-33d05740a352 h1:CCriYyAfq1Br1aIYettdHZTy8mBTIPo7We18TuO/bak=
+go.mozilla.org/pkcs7 v0.0.0-20210826202110-33d05740a352/go.mod h1:SNgMg+EgDFwmvSmLRTNKC5fegJjB7v23qTQ0XLGUNHk=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20200728195943-123391ffb6de h1:ikNHVSjEfnvz6sxdSPCaPt572qowuyMDMJLLm3Db3ig=
+golang.org/x/crypto v0.0.0-20200728195943-123391ffb6de/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
+golang.org/x/crypto v0.10.0 h1:LKqV2xt9+kDzSTfOhx4FrkEBcMrAgHSYgzywV9zcGmM=
+golang.org/x/crypto v0.10.0/go.mod h1:o4eNf7Ede1fv+hwOwZsTHl9EsPFO6q6ZvYR8vYfY45I=
+golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=

lpg/.clang-format

@@ -0,0 +1,9 @@
+BasedOnStyle: LLVM
+ColumnLimit: 80
+IndentWidth: 4
+TabWidth: 4
+UseTab: ForContinuationAndIndentation
+SpaceAfterCStyleCast: true
+AlignAfterOpenBracket: DontAlign
+AlignOperands: DontAlign
+SpacesBeforeTrailingComments: 2

lpg/lpg.lua

@@ -0,0 +1,240 @@
+#!/usr/bin/env lpg
+local project_url = "https://git.janouch.name/p/pdf-simple-sign"
+
+function h1 (title)
+	return lpg.VBox {fontsize=18., fontweight=600,
+		title, lpg.HLine {2}, lpg.Filler {-1, 6}}
+end
+function h2 (title)
+	return lpg.VBox {fontsize=16., fontweight=600,
+		lpg.Filler {-1, 8}, title, lpg.HLine {1}, lpg.Filler {-1, 6}}
+end
+function h3 (title)
+	return lpg.VBox {fontsize=14., fontweight=600,
+		lpg.Filler {-1, 8}, title, lpg.HLine {.25}, lpg.Filler {-1, 6}}
+end
+function p (...)
+	return lpg.VBox {..., lpg.Filler {-1, 6}}
+end
+function code (...)
+	return lpg.VBox {
+		lpg.Filler {-1, 4},
+		lpg.HBox {
+			lpg.Filler {12},
+			lpg.VBox {"<tt>" .. table.concat {...} .. "</tt>"},
+			lpg.Filler {},
+		},
+		lpg.Filler {-1, 6},
+	}
+end
+function define (name, ...)
+	return lpg.VBox {
+		lpg.Filler {-1, 2},
+		lpg.Text {fontweight=600, name}, lpg.Filler {-1, 2},
+		lpg.HBox {lpg.Filler {12}, lpg.VBox {...}, lpg.Filler {}},
+		lpg.Filler {-1, 2},
+	}
+end
+function pad (widget)
+	return lpg.VBox {
+		lpg.Filler {-1, 2},
+		lpg.HBox {lpg.Filler {4}, widget, lpg.Filler {}, lpg.Filler {4}},
+		lpg.Filler {-1, 2},
+	}
+end
+
+local page1 = lpg.VBox {fontfamily="sans serif", fontsize=12.,
+	h1("lpg User Manual"),
+	p("<b>lpg</b> is a Lua-based PDF document generator, exposing a trivial " ..
+		"layouting engine on top of the Cairo graphics library, " ..
+		"with manual paging."),
+	p("The author has primarily been using this system to typeset invoices."),
+
+	h2("Synopsis"),
+	p("<b>lpg</b> <i>program.lua</i> [<i>args...</i>]"),
+
+	h2("API"),
+	p("The Lua program receives <b>lpg</b>'s and its own path joined " ..
+		"as <tt>arg[0]</tt>.  Any remaining sequential elements " ..
+		"of this table represent the passed <i>args</i>."),
+
+	h3("Utilities"),
+
+	define("lpg.cm (centimeters)",
+		p("Returns how many document points are needed " ..
+			"for the given physical length.")),
+
+	define("lpg.ntoa {number [, precision=…]\n" ..
+		"\t[, thousands_sep=…] [, decimal_point=…] [, grouping=…]}",
+		p("Formats a number using the C++ localization " ..
+			"and I/O libraries.  " ..
+			"For example, the following call results in “3 141,59”:"),
+		code("ntoa {3141.592, precision=2,\n" ..
+			"  thousands_sep=\" \", decimal_point=\",\", " ..
+			"grouping=\"\\003\"}")),
+
+	define("lpg.escape (values...)",
+		p("Interprets all values as strings, " ..
+			"and escapes them to be used as literal text—" ..
+			"all text within <b>lpg</b> is parsed as Pango markup, " ..
+			"which is a subset of XML.")),
+
+	h3("PDF documents"),
+
+	define("lpg.Document (filename, width, height [, margin])",
+		p("Returns a new <i>Document</i> object, whose pages are all " ..
+			"the same size in 72 DPI points, as specified by <b>width</b> " ..
+			"and <b>height</b>.  The <b>margin</b> is used by <b>show</b> " ..
+			"on all sides of pages."),
+		p("The file is finalized when the object is garbage collected.")),
+
+	define("<i>Document</i>.title, author, subject, keywords, " ..
+		"creator, create_date, mod_date",
+		p("Write-only PDF <i>Info</i> dictionary metadata strings.")),
+
+	define("<i>Document</i>:show ([widget...])",
+		p("Starts a new document page, and renders <i>Widget</i> trees over " ..
+		"the whole print area.")),
+
+	lpg.Filler {},
+}
+
+local page2 = lpg.VBox {fontfamily="sans serif", fontsize=12.,
+	h3("Widgets"),
+	p("The layouting system makes heavy use of composition, " ..
+		"and thus stays simple."),
+	p("For convenience, anywhere a <i>Widget</i> is expected but another " ..
+		"kind of value is received, <b>lpg.Text</b> widget will be invoked " ..
+		"on that value."),
+	p("Once a <i>Widget</i> is included in another <i>Widget</i>, " ..
+		"the original Lua object can no longer be used, " ..
+		"as its reference has been consumed."),
+	p("<i>Widgets</i> can be indexed by strings to get or set " ..
+		"their <i>attributes</i>.  All <i>Widget</i> constructor tables " ..
+		"also accept attributes, for convenience.  Attributes can be " ..
+		"either strings or numbers, mostly only act " ..
+		"on specific <i>Widget</i> kinds, and are hereditary.  " ..
+		"Prefix their names with an underscore to set them ‘privately’."),
+	p("<i>Widget</i> sizes can be set negative, which signals to their " ..
+		"container that they should take any remaining space, " ..
+		"after all their siblings’ requests have been satisfied.  " ..
+		"When multiple widgets make this request, that space is distributed " ..
+		"in proportion to these negative values."),
+
+	define("lpg.Filler {[width] [, height]}",
+		p("Returns a new blank widget with the given dimensions, " ..
+			"which default to -1, -1.")),
+	define("lpg.HLine {[thickness]}",
+		p("Returns a new widget that draws a simple horizontal line " ..
+			"of the given <b>thickness</b>.")),
+	define("lpg.VLine {[thickness]}",
+		p("Returns a new widget that draws a simple vertical line " ..
+			"of the given <b>thickness</b>.")),
+	define("lpg.Text {[value...]}",
+		p("Returns a new text widget that renders the concatenation of all " ..
+			"passed values filtered through Lua’s <b>tostring</b> " ..
+			"function.  Non-strings will additionally be escaped."),
+		define("<i>Text</i>.fontfamily, fontsize, fontweight, lineheight",
+			p("Various font properties, similar to their CSS counterparts."))),
+	define("lpg.Frame {widget}",
+		p("Returns a special container widget that can override " ..
+			"a few interesting properties."),
+		define("<i>Frame</i>.color",
+			p("Text and line colour, for example <tt>0xff0000</tt> for red.")),
+		define("<i>Frame</i>.w_override",
+			p("Forcefully changes the child <i>Widget</i>’s " ..
+				"requested width, such as to negative values.")),
+		define("<i>Frame</i>.h_override",
+			p("Forcefully changes the child <i>Widget</i>’s " ..
+				"requested height, such as to negative values."))),
+
+	lpg.Filler {},
+}
+
+local page3 = lpg.VBox {fontfamily="sans serif", fontsize=12.,
+	define("lpg.Link {target, widget}",
+		p("Returns a new hyperlink widget pointing to the <b>target</b>, " ..
+			"which is a URL.  The hyperlink applies " ..
+			"to the entire area of the child widget.  " ..
+			"It has no special appearance.")),
+	define("lpg.HBox {[widget...]}",
+		p("Returns a new container widget that places children " ..
+			"horizontally, from left to right."),
+		p("If any space remains after satisfying the children widgets’ " ..
+			"requisitions, it is distributed equally amongst all of them.  " ..
+			"Also see the note about negative sizes.")),
+	define("lpg.VBox {[widget...]}",
+		p("Returns a new container widget that places children " ..
+			"vertically, from top to bottom.")),
+	define("lpg.Picture {filename}",
+		p("Returns a new picture widget, showing the given <b>filename</b>, " ..
+			"which currently must be in the PNG format.  " ..
+			"Pictures are rescaled to fit, but keep their aspect ratio.")),
+	define("lpg.QR {contents, module}",
+		p("Returns a new QR code widget, encoding the <b>contents</b> " ..
+			"string using the given <b>module</b> size.  " ..
+			"The QR code version is chosen automatically.")),
+	
+	h2("Examples"),
+	p("See the source code of this user manual " ..
+		"for the general structure of scripts."),
+
+	h3("Size distribution and composition"),
+	lpg.VBox {
+		lpg.HLine {},
+		lpg.HBox {
+			lpg.VLine {}, lpg.Frame {_w_override=lpg.cm(3), pad "3cm"},
+			lpg.VLine {}, lpg.Frame {pad "Measured"},
+			lpg.VLine {}, lpg.Frame {_w_override=-1, pad "-1"},
+			lpg.VLine {}, lpg.Frame {_w_override=-2, pad "-2"},
+			lpg.VLine {},
+		},
+		lpg.HLine {},
+	},
+	lpg.Filler {-1, 6},
+	code([[
+<small><b>function</b> pad (widget)
+  <b>local function</b> f (...) <b>return</b> lpg.Filler {...} <b>end</b>
+  <b>return</b> lpg.VBox {f(-1, 2), lpg.HBox {f(4), w, f(), f(4)}, f(-1, 2)}
+<b>end</b>
+
+lpg.VBox {lpg.HLine {}, lpg.HBox {
+  lpg.VLine {}, lpg.Frame {_w_override=lpg.cm(3), pad "3cm"},
+  lpg.VLine {}, lpg.Frame {pad "Measured"},
+  lpg.VLine {}, lpg.Frame {_w_override=-1, pad "-1"},
+  lpg.VLine {}, lpg.Frame {_w_override=-2, pad "-2"},
+  lpg.VLine {},
+}, lpg.HLine {}}</small>]]),
+
+	h3("Clickable QR code link"),
+	lpg.HBox {
+		lpg.VBox {
+			p("Go here to report bugs, request features, " ..
+				"or submit pull requests:"),
+			code(([[
+url = "%s"
+lpg.Link {url, lpg.QR {url, 2.5}}]]):format(project_url)),
+		},
+		lpg.Filler {},
+		lpg.Link {project_url, lpg.QR {project_url, 2.5}},
+	},
+
+	lpg.Filler {},
+}
+
+if #arg < 1 then
+	io.stderr:write("Usage: " .. arg[0] .. " OUTPUT-PDF..." .. "\n")
+	os.exit(false)
+end
+local width, height, margin = lpg.cm(21), lpg.cm(29.7), lpg.cm(2.0)
+for i = 1, #arg do
+	local pdf = lpg.Document(arg[i], width, height, margin)
+	pdf.title = "lpg User Manual"
+	pdf.subject = "lpg User Manual"
+	pdf.author = "Přemysl Eric Janouch"
+	pdf.creator = ("lpg (%s)"):format(project_url)
+
+	pdf:show(page1)
+	pdf:show(page2)
+	pdf:show(page3)
+end

lpg/meson.build

@@ -0,0 +1,24 @@
+project('lpg', 'cpp', default_options : ['cpp_std=c++17'],
+	version : '1.1.1')
+
+conf = configuration_data()
+conf.set_quoted('PROJECT_NAME', meson.project_name())
+conf.set_quoted('PROJECT_VERSION', meson.project_version())
+configure_file(output : 'config.h', configuration : conf)
+
+luapp = dependency('lua++', allow_fallback : true)
+cairo = dependency('cairo')
+pangocairo = dependency('pangocairo')
+libqrencode = dependency('libqrencode')
+lpg_exe = executable('lpg', 'lpg.cpp',
+	install : true,
+	dependencies : [luapp, cairo, pangocairo, libqrencode])
+
+# XXX: https://github.com/mesonbuild/meson/issues/825
+docdir = get_option('datadir') / 'doc' / meson.project_name()
+lpg_pdf = custom_target('lpg.pdf',
+	output : 'lpg.pdf',
+	input : 'lpg.lua',
+	command : [lpg_exe, '@INPUT@', '@OUTPUT@'],
+	install_dir : docdir,
+	build_by_default : true)

lpg/subprojects/lua++.wrap

@@ -0,0 +1,10 @@
+[wrap-file]
+directory = lua-5.4.7
+source_url = https://github.com/lua/lua/archive/refs/tags/v5.4.7.tar.gz
+source_filename = lua-5.4.7.tar.gz
+source_hash = 5c39111b3fc4c1c9e56671008955a1730f54a15b95e1f1bd0752b868b929d8e3
+patch_directory = lua-5.4.7
+
+[provide]
+lua++-5.4 = lua_dep
+lua++ = lua_dep

lpg/subprojects/packagefiles/lua-5.4.7/LICENSE.build

@@ -0,0 +1,20 @@
+Copyright (c) 2025 Přemysl Eric Janouch <p@janouch.name>
+Copyright (c) 2021 The Meson development team
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

lpg/subprojects/packagefiles/lua-5.4.7/meson.build

@@ -0,0 +1,50 @@
+project(
+  'lua-5.4',
+  'cpp',
+  license : 'MIT',
+  meson_version : '>=0.49.2',
+  version : '5.4.7',
+  default_options : ['c_std=c99', 'warning_level=2'],
+)
+
+cxx = meson.get_compiler('cpp')
+
+# Skip bogus warning.
+add_project_arguments(cxx.get_supported_arguments(
+  '-Wno-string-plus-int', '-Wno-stringop-overflow'), language : 'cpp')
+
+# Platform-specific defines.
+is_posix = host_machine.system() in ['cygwin', 'darwin', 'dragonfly', 'freebsd',
+  'gnu', 'haiku', 'linux', 'netbsd', 'openbsd', 'sunos']
+if is_posix
+  add_project_arguments('-DLUA_USE_POSIX', language : 'cpp')
+endif
+
+# Library dependencies.
+lua_lib_deps = [cxx.find_library('m', required : false)]
+
+if meson.version().version_compare('>= 0.62')
+  dl_dep = dependency('dl', required : get_option('loadlib'))
+else
+  dl_dep = cxx.find_library('dl', required : get_option('loadlib'))
+endif
+
+if dl_dep.found()
+  lua_lib_deps += dl_dep
+  add_project_arguments('-DLUA_USE_DLOPEN', language : 'cpp')
+endif
+
+# Targets.
+add_project_arguments('-DMAKE_LIB', language : 'cpp')
+lua_lib = static_library(
+  'lua',
+  'onelua.cpp',
+  dependencies : lua_lib_deps,
+  implicit_include_directories : false,
+)
+
+inc = include_directories('.')
+lua_dep = declare_dependency(
+  link_with : lua_lib,
+  include_directories : inc,
+)

lpg/subprojects/packagefiles/lua-5.4.7/meson_options.txt

@@ -0,0 +1,4 @@
+option(
+  'loadlib', type : 'feature',
+  description : 'Allow Lua to "require" C extension modules'
+)

lpg/subprojects/packagefiles/lua-5.4.7/onelua.cpp

@@ -0,0 +1 @@
+#include "onelua.c"

meson.build

@@ -1,5 +1,23 @@
-project('pdf-simple-sign', 'cpp', default_options : ['cpp_std=c++11'])
+project('pdf-simple-sign', 'cpp', default_options : ['cpp_std=c++11'],
+	version : '1.1.1')
+
+conf = configuration_data()
+conf.set_quoted('PROJECT_NAME', meson.project_name())
+conf.set_quoted('PROJECT_VERSION', meson.project_version())
+configure_file(output : 'config.h', configuration : conf)
+
 cryptodep = dependency('libcrypto')
 executable('pdf-simple-sign', 'pdf-simple-sign.cpp',
 	install : true,
 	dependencies : cryptodep)
+
+asciidoctor = find_program('asciidoctor')
+foreach page : ['pdf-simple-sign']
+	custom_target('manpage for ' + page,
+		input : page + '.adoc', output: page + '.1',
+		command : [asciidoctor, '-b', 'manpage',
+			'-a', 'release-version=' + meson.project_version(),
+			'@INPUT@', '-o', '@OUTPUT@'],
+		install : true,
+		install_dir : join_paths(get_option('mandir'), 'man1'))
+endforeach

pdf-simple-sign.adoc

@@ -0,0 +1,80 @@
+pdf-simple-sign(1)
+==================
+:doctype: manpage
+:manmanual: pdf-simple-sign Manual
+:mansource: pdf-simple-sign {release-version}
+
+Name
+----
+pdf-simple-sign - a simple PDF signer
+
+Synopsis
+--------
+*pdf-simple-sign* [_OPTION_]... _INPUT.pdf_ _OUTPUT.pdf_ _KEY-PAIR.p12_ _PASSWORD_
+
+Description
+-----------
+*pdf-simple-sign* is a simple PDF signer intended for documents produced by
+the Cairo library, GNU troff, ImageMagick, or similar.  As such, it currently
+comes with some restrictions:
+
+ * the document may not have any forms or signatures already, as they would be
+   overwritten,
+ * the document may not employ cross-reference streams, or must constitute
+   a hybrid-reference file at least.
+
+The key and certificate pair is accepted in the PKCS#12 format.  The _PASSWORD_
+must be supplied on the command line, and may be empty if it is not needed.
+
+The signature is attached to the first page and has no appearance.
+
+If signature data don't fit within the default reservation of 4 kibibytes,
+you might need to adjust it using the *-r* option, or throw out any unnecessary
+intermediate certificates.
+
+Options
+-------
+*-r* _RESERVATION_, *--reservation*=_RESERVATION_::
+  Set aside _RESERVATION_ amount of bytes for the resulting signature.
+  Feel free to try a few values in a loop.  The program itself has no
+  conceptions about the data, so it can't make accurate predictions.
+
+*-h*, *--help*::
+  Display a help message and exit.
+
+*-V*, *--version*::
+  Output version information and exit.
+
+Examples
+--------
+Create a self-signed certificate, make a document containing the current date,
+sign it and verify the attached signature:
+
+ $ openssl req -newkey rsa:2048 -subj /CN=Test -nodes \
+   -keyout key.pem -x509 -addext keyUsage=digitalSignature \
+   -out cert.pem 2>/dev/null
+ $ openssl pkcs12 -inkey key.pem -in cert.pem \
+   -export -passout pass: -out key-pair.p12
+ $ date | groff -T pdf > test.pdf
+ $ pdf-simple-sign test.pdf test.signed.pdf key-pair.p12 ""
+ $ pdfsig test.signed.pdf
+ Digital Signature Info of: test.signed.pdf
+ Signature #1:
+   - Signer Certificate Common Name: Test
+   - Signer full Distinguished Name: CN=Test
+   - Signing Time: Sep 05 2020 19:41:22
+   - Signing Hash Algorithm: SHA-256
+   - Signature Type: adbe.pkcs7.detached
+   - Signed Ranges: [0 - 6522], [14716 - 15243]
+   - Total document signed
+   - Signature Validation: Signature is Valid.
+   - Certificate Validation: Certificate issuer isn't Trusted.
+
+Reporting bugs
+--------------
+Use https://git.janouch.name/p/pdf-simple-sign to report bugs, request features,
+or submit pull requests.
+
+See also
+--------
+*openssl*(1), *pdfsig*(1)

pdf-simple-sign.cpp

@@ -2,7 +2,7 @@
 //
 // pdf-simple-sign: simple PDF signer
 //
-// Copyright (c) 2017, Přemysl Janouch <p@janouch.name>
+// Copyright (c) 2017 - 2020, Přemysl Eric Janouch <p@janouch.name>
 //
 // Permission to use, copy, modify, and/or distribute this software for any
 // purpose with or without fee is hereby granted.
@@ -16,30 +16,33 @@
 // CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
 //
 
-#include <cstdio>
 #include <cmath>
+#include <cstdio>
 #undef NDEBUG
 #include <cassert>
 
-#include <vector>
 #include <map>
-#include <regex>
 #include <memory>
+#include <regex>
 #include <set>
+#include <vector>
 
 #if defined __GLIBCXX__ && __GLIBCXX__ < 20140422
 #error Need libstdc++ >= 4.9 for <regex>
 #endif
 
-#include <unistd.h>
 #include <getopt.h>
 #include <openssl/err.h>
-#include <openssl/x509v3.h>
 #include <openssl/pkcs12.h>
+#include <openssl/x509v3.h>
+#include <unistd.h>
+
+#include "config.h"
 
 // -------------------------------------------------------------------------------------------------
 
 using uint = unsigned int;
+using ushort = unsigned short;
 
 static std::string concatenate(const std::vector<std::string>& v, const std::string& delim) {
   std::string res;
@@ -52,7 +55,7 @@ static std::string concatenate(const std::vector<std::string>& v, const std::str
 
 template<typename... Args>
 std::string ssprintf(const std::string& format, Args... args) {
-  size_t size = std::snprintf(nullptr, 0, format.c_str(), args... ) + 1;
+  size_t size = std::snprintf(nullptr, 0, format.c_str(), args...) + 1;
   std::unique_ptr<char[]> buf(new char[size]);
   std::snprintf(buf.get(), size, format.c_str(), args...);
   return std::string(buf.get(), buf.get() + size - 1);
@@ -61,7 +64,7 @@ std::string ssprintf(const std::string& format, Args... args) {
 // -------------------------------------------------------------------------------------------------
 
 /// PDF token/object thingy.  Objects may be composed either from one or a sequence of tokens.
-/// The PDF Reference doesn't actually speak of tokens.
+/// The PDF Reference doesn't actually speak of tokens, though ISO 32000-1:2008 does.
 struct pdf_object {
   enum type {
     END, NL, COMMENT, NIL, BOOL, NUMERIC, KEYWORD, NAME, STRING,
@@ -136,12 +139,11 @@ struct pdf_lexer {
           if (eat_newline(ch))
             continue;
           std::string octal;
-          if (*p && strchr(oct_alphabet, *p)) octal += *p++;
-          if (*p && strchr(oct_alphabet, *p)) octal += *p++;
-          if (*p && strchr(oct_alphabet, *p)) octal += *p++;
-          if (!octal.empty()) {
-            value += char(std::stoi(octal, nullptr, 8));
-            continue;
+          if (ch && strchr(oct_alphabet, ch)) {
+            octal += ch;
+            if (*p && strchr(oct_alphabet, *p)) octal += *p++;
+            if (*p && strchr(oct_alphabet, *p)) octal += *p++;
+            ch = std::stoi(octal, nullptr, 8);
           }
         }
       }
@@ -162,6 +164,7 @@ struct pdf_lexer {
         buf.clear();
       }
     }
+    p++;
     if (!buf.empty()) value += char(std::stoi(buf + '0', nullptr, 16));
     return {pdf_object::STRING, value};
   }
@@ -257,16 +260,14 @@ struct pdf_lexer {
 static std::string pdf_serialize(const pdf_object& o) {
   switch (o.type) {
   case pdf_object::NL:      return "\n";
-  case pdf_object::NIL:     return "nil";
+  case pdf_object::NIL:     return "null";
   case pdf_object::BOOL:    return o.number ? "true" : "false";
-  case pdf_object::NUMERIC:
-  {
+  case pdf_object::NUMERIC: {
     if (o.is_integer()) return std::to_string((long long) o.number);
     return std::to_string(o.number);
   }
   case pdf_object::KEYWORD: return o.string;
-  case pdf_object::NAME:
-  {
+  case pdf_object::NAME: {
     std::string escaped = "/";
     for (char c : o.string) {
       if (c == '#' || strchr(pdf_lexer::delimiters, c) || strchr(pdf_lexer::whitespace, c))
@@ -276,8 +277,7 @@ static std::string pdf_serialize(const pdf_object& o) {
     }
     return escaped;
   }
-  case pdf_object::STRING:
-  {
+  case pdf_object::STRING: {
     std::string escaped;
     for (char c : o.string) {
       if (c == '\\' || c == '(' || c == ')')
@@ -290,17 +290,16 @@ static std::string pdf_serialize(const pdf_object& o) {
   case pdf_object::E_ARRAY: return "]";
   case pdf_object::B_DICT:  return "<<";
   case pdf_object::E_DICT:  return ">>";
-  case pdf_object::ARRAY:
-  {
+  case pdf_object::ARRAY: {
     std::vector<std::string> v;
     for (const auto& i : o.array)
       v.push_back(pdf_serialize(i));
     return "[ " + concatenate(v, " ") + " ]";
   }
-  case pdf_object::DICT:
-  {
+  case pdf_object::DICT: {
     std::string s;
     for (const auto i : o.dict)
+      // FIXME the key is also supposed to be escaped by pdf_serialize()
       s += " /" + i.first + " " + pdf_serialize(i.second);
     return "<<" + s + " >>";
   }
@@ -341,6 +340,9 @@ 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
@@ -353,14 +355,20 @@ public:
 
 // -------------------------------------------------------------------------------------------------
 
+/// If the object is an error, forward its message, otherwise return err.
+static std::string pdf_error(const pdf_object& o, const char* err) {
+  if (o.type != pdf_object::END || o.string.empty()) return err;
+  return o.string;
+}
+
 pdf_object pdf_updater::parse_obj(pdf_lexer& lex, std::vector<pdf_object>& stack) const {
   if (stack.size() < 2)
     return {pdf_object::END, "missing object ID pair"};
 
   auto g = stack.back(); stack.pop_back();
   auto n = stack.back(); stack.pop_back();
-  if (!g.is_integer() || g.number < 0 || g.number > UINT_MAX
-   || !n.is_integer() || n.number < 0 || n.number > UINT_MAX)
+  if (!g.is_integer() || g.number < 0 || g.number > UINT_MAX ||
+      !n.is_integer() || n.number < 0 || n.number > UINT_MAX)
     return {pdf_object::END, "invalid object ID pair"};
 
   pdf_object obj{pdf_object::OBJECT};
@@ -370,7 +378,7 @@ pdf_object pdf_updater::parse_obj(pdf_lexer& lex, std::vector<pdf_object>& stack
   while (1) {
     auto object = parse(lex, obj.array);
     if (object.type == pdf_object::END)
-      return {pdf_object::END, "object doesn't end"};
+      return {pdf_object::END, pdf_error(object, "object doesn't end")};
     if (object.type == pdf_object::KEYWORD && object.string == "endobj")
       break;
     obj.array.push_back(std::move(object));
@@ -384,8 +392,8 @@ pdf_object pdf_updater::parse_R(std::vector<pdf_object>& stack) const {
 
   auto g = stack.back(); stack.pop_back();
   auto n = stack.back(); stack.pop_back();
-  if (!g.is_integer() || g.number < 0 || g.number > UINT_MAX
-   || !n.is_integer() || n.number < 0 || n.number > UINT_MAX)
+  if (!g.is_integer() || g.number < 0 || g.number > UINT_MAX ||
+      !n.is_integer() || n.number < 0 || n.number > UINT_MAX)
     return {pdf_object::END, "invalid reference ID pair"};
 
   pdf_object ref{pdf_object::REFERENCE};
@@ -402,26 +410,24 @@ pdf_object pdf_updater::parse(pdf_lexer& lex, std::vector<pdf_object>& stack) co
   case pdf_object::COMMENT:
     // These are not important to parsing, not even for this procedure's needs
     return parse(lex, stack);
-  case pdf_object::B_ARRAY:
-  {
+  case pdf_object::B_ARRAY: {
     std::vector<pdf_object> array;
     while (1) {
       auto object = parse(lex, array);
       if (object.type == pdf_object::END)
-        return {pdf_object::END, "array doesn't end"};
+        return {pdf_object::END, pdf_error(object, "array doesn't end")};
       if (object.type == pdf_object::E_ARRAY)
         break;
       array.push_back(std::move(object));
     }
     return array;
   }
-  case pdf_object::B_DICT:
-  {
+  case pdf_object::B_DICT: {
     std::vector<pdf_object> array;
     while (1) {
       auto object = parse(lex, array);
       if (object.type == pdf_object::END)
-        return {pdf_object::END, "dictionary doesn't end"};
+        return {pdf_object::END, pdf_error(object, "dictionary doesn't end")};
       if (object.type == pdf_object::E_DICT)
         break;
       array.push_back(std::move(object));
@@ -459,13 +465,13 @@ std::string pdf_updater::load_xref(pdf_lexer& lex, std::set<uint>& loaded_entrie
   while (1) {
     auto object = parse(lex, throwaway_stack);
     if (object.type == pdf_object::END)
-      return "unexpected EOF while looking for the trailer";
+      return pdf_error(object, "unexpected EOF while looking for the trailer");
     if (object.type == pdf_object::KEYWORD && object.string == "trailer")
       break;
 
     auto second = parse(lex, throwaway_stack);
-    if (!object.is_integer() || object.number < 0 || object.number > UINT_MAX
-     || !second.is_integer() || second.number < 0 || second.number > UINT_MAX)
+    if (!object.is_integer() || object.number < 0 || object.number > UINT_MAX ||
+        !second.is_integer() || second.number < 0 || second.number > UINT_MAX)
       return "invalid xref section header";
 
     const size_t start = object.number;
@@ -474,9 +480,9 @@ std::string pdf_updater::load_xref(pdf_lexer& lex, std::set<uint>& loaded_entrie
       auto off = parse(lex, throwaway_stack);
       auto gen = parse(lex, throwaway_stack);
       auto key = parse(lex, throwaway_stack);
-      if (!off.is_integer() || off.number < 0 || off.number > document.length()
-       || !gen.is_integer() || gen.number < 0 || gen.number > 65535
-       || key.type != pdf_object::KEYWORD)
+      if (!off.is_integer() || off.number < 0 || off.number > document.length() ||
+          !gen.is_integer() || gen.number < 0 || gen.number > 65535 ||
+          key.type != pdf_object::KEYWORD)
         return "invalid xref entry";
 
       bool free = true;
@@ -505,7 +511,7 @@ 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;
@@ -529,7 +535,7 @@ std::string pdf_updater::initialize() {
 
     auto trailer = parse(lex, throwaway_stack);
     if (trailer.type != pdf_object::DICT)
-      return "invalid trailer dictionary";
+      return pdf_error(trailer, "invalid trailer dictionary");
     if (loaded_xrefs.empty())
       this->trailer = trailer.dict;
     loaded_xrefs.insert(xref_offset);
@@ -537,7 +543,8 @@ std::string pdf_updater::initialize() {
     const auto prev_offset = trailer.dict.find("Prev");
     if (prev_offset == trailer.dict.end())
       break;
-    if (!prev_offset->second.is_integer())
+    // FIXME do not read offsets and sizes as floating point numbers
+    if (!prev_offset->second.is_integer() || prev_offset->second.number < 0)
       return "invalid Prev offset";
     xref_offset = prev_offset->second.number;
   }
@@ -552,11 +559,30 @@ 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};
 
-  auto& ref = xref[n];
+  const auto& ref = xref[n];
   if (ref.free || ref.generation != generation || ref.offset >= document.length())
     return {pdf_object::NIL};
 
@@ -624,8 +650,8 @@ void pdf_updater::flush_updates() {
   }
 
   trailer["Size"] = {pdf_object::NUMERIC, double(xref_size)};
-  document += "trailer\n" + pdf_serialize(trailer)
-    + ssprintf("\nstartxref\n%zu\n%%%%EOF\n", startxref);
+  document +=
+    "trailer\n" + pdf_serialize(trailer) + ssprintf("\nstartxref\n%zu\n%%%%EOF\n", startxref);
 }
 
 // -------------------------------------------------------------------------------------------------
@@ -667,9 +693,9 @@ static pdf_object pdf_get_first_page(pdf_updater& pdf, uint node_n, uint node_ge
   // XXX technically speaking, this may be an indirect reference.  The correct way to solve this
   //   seems to be having "pdf_updater" include a wrapper around "obj.dict.find"
   auto kids = obj.dict.find("Kids");
-  if (kids == obj.dict.end() || kids->second.type != pdf_object::ARRAY
-   || kids->second.array.empty()
-   || kids->second.array.at(0).type != pdf_object::REFERENCE)
+  if (kids == obj.dict.end() || kids->second.type != pdf_object::ARRAY ||
+      kids->second.array.empty() ||
+      kids->second.array.at(0).type != pdf_object::REFERENCE)
     return {pdf_object::NIL};
 
   // XXX nothing prevents us from recursing in an evil circular graph
@@ -707,8 +733,8 @@ static std::string pdf_fill_in_signature(std::string& document, size_t sign_off,
   // OpenSSL error reasons will usually be of more value than any distinction I can come up with
   std::string err = "OpenSSL failure";
 
-  if (!(p12 = d2i_PKCS12_fp(pkcs12_fp, nullptr))
-   || !PKCS12_parse(p12, pkcs12_pass.c_str(), &private_key, &certificate, &chain)) {
+  if (!(p12 = d2i_PKCS12_fp(pkcs12_fp, nullptr)) ||
+      !PKCS12_parse(p12, pkcs12_pass.c_str(), &private_key, &certificate, &chain)) {
     err = pkcs12_path + ": parse failure";
     goto error;
   }
@@ -733,8 +759,8 @@ static std::string pdf_fill_in_signature(std::string& document, size_t sign_off,
 #endif
 
   // The default digest is SHA1, which is mildly insecure now -- hence using PKCS7_sign_add_signer
-  if (!(p7 = PKCS7_sign(nullptr, nullptr, nullptr, nullptr, sign_flags))
-   || !PKCS7_sign_add_signer(p7, certificate, private_key, EVP_sha256(), sign_flags))
+  if (!(p7 = PKCS7_sign(nullptr, nullptr, nullptr, nullptr, sign_flags)) ||
+      !PKCS7_sign_add_signer(p7, certificate, private_key, EVP_sha256(), sign_flags))
     goto error;
   // For RFC 3161, this is roughly how a timestamp token would be attached (see Appendix A):
   //   PKCS7_add_attribute(signer_info, NID_id_smime_aa_timeStampToken, V_ASN1_SEQUENCE, value)
@@ -744,10 +770,10 @@ static std::string pdf_fill_in_signature(std::string& document, size_t sign_off,
 
   // Adaptation of the innards of the undocumented PKCS7_final() -- I didn't feel like making
   // a copy of the whole document.  Hopefully this writes directly into a digest BIO.
-  if (!(p7bio = PKCS7_dataInit(p7, nullptr))
-   || (ssize_t) sign_off != BIO_write(p7bio, document.data(), sign_off)
-   || (ssize_t) tail_len != BIO_write(p7bio, document.data() + tail_off, tail_len)
-   || BIO_flush(p7bio) != 1 || !PKCS7_dataFinal(p7, p7bio))
+  if (!(p7bio = PKCS7_dataInit(p7, nullptr)) ||
+      (ssize_t) sign_off != BIO_write(p7bio, document.data(), sign_off) ||
+      (ssize_t) tail_len != BIO_write(p7bio, document.data() + tail_off, tail_len) ||
+      BIO_flush(p7bio) != 1 || !PKCS7_dataFinal(p7, p7bio))
     goto error;
 
 #if 0
@@ -798,12 +824,10 @@ 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
-static std::string pdf_sign(std::string& document) {
+static std::string pdf_sign(std::string& document, ushort reservation) {
   pdf_updater pdf(document);
   auto err = pdf.initialize();
   if (!err.empty())
@@ -819,7 +843,7 @@ static std::string pdf_sign(std::string& document) {
   // 8.7 Digital Signatures - /signature dictionary/
   auto sigdict_n = pdf.allocate();
   size_t byterange_off = 0, byterange_len = 0, sign_off = 0, sign_len = 0;
-  pdf.update(sigdict_n, [&]{
+  pdf.update(sigdict_n, [&] {
     // The timestamp is important for Adobe Acrobat Reader DC.  The ideal would be to use RFC 3161.
     pdf.document.append("<< /Type/Sig /Filter/Adobe.PPKLite /SubFilter/adbe.pkcs7.detached\n"
                         "   /M" + pdf_serialize(pdf_date(time(nullptr))) + " /ByteRange ");
@@ -827,7 +851,7 @@ static std::string pdf_sign(std::string& document) {
     pdf.document.append((byterange_len = 32 /* fine for a gigabyte */), ' ');
     pdf.document.append("\n   /Contents <");
     sign_off = pdf.document.size();
-    pdf.document.append((sign_len = 8192 /* certificate, digest, encrypted digest, ... */), '0');
+    pdf.document.append((sign_len = reservation * 2), '0');
     pdf.document.append("> >>");
 
     // We actually need to exclude the hexstring quotes from signing
@@ -852,7 +876,7 @@ static std::string pdf_sign(std::string& document) {
   }}});
 
   auto sigfield_n = pdf.allocate();
-  pdf.update(sigfield_n, [&]{ pdf.document += pdf_serialize(sigfield); });
+  pdf.update(sigfield_n, [&] { pdf.document += pdf_serialize(sigfield); });
 
   auto pages_ref = root.dict.find("Pages");
   if (pages_ref == root.dict.end() || pages_ref->second.type != pdf_object::REFERENCE)
@@ -861,15 +885,21 @@ static std::string pdf_sign(std::string& document) {
   if (page.type != pdf_object::DICT)
     return "invalid or unsupported page tree";
 
-  // XXX assuming this won't be an indirectly referenced array
   auto& annots = page.dict["Annots"];
-  if (annots.type != pdf_object::ARRAY)
+  if (annots.type != pdf_object::ARRAY) {
+    // TODO indirectly referenced arrays might not be that hard to support
+    if (annots.type != pdf_object::END)
+      return "unexpected Annots";
+
     annots = {pdf_object::ARRAY};
+  }
   annots.array.emplace_back(pdf_object::REFERENCE, sigfield_n, 0);
-  pdf.update(page.n, [&]{ pdf.document += pdf_serialize(page); });
+  pdf.update(page.n, [&] { pdf.document += pdf_serialize(page); });
 
   // 8.6.1 Interactive Form Dictionary
-  // XXX assuming there are no forms already, overwriting everything
+  if (root.dict.count("AcroForm"))
+    return "the document already contains forms, they would be overwritten";
+
   root.dict["AcroForm"] = {std::map<std::string, pdf_object>{
     {"Fields", {std::vector<pdf_object>{
       {pdf_object::REFERENCE, sigfield_n, 0}
@@ -878,10 +908,10 @@ 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 that 1.5, it's not a bad idea to use cairo_pdf_surface_restrict_to_version()
-  root.dict["Version"] = {pdf_object::NAME, "1.6"};
-  pdf.update(root_ref->second.n, [&]{ pdf.document += pdf_serialize(root); });
+  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();
 
   // Now that we know the length of everything, store byte ranges of what we're about to sign,
@@ -910,26 +940,39 @@ static void die(int status, const char* format, ...) {
 
 int main(int argc, char* argv[]) {
   auto invocation_name = argv[0];
-  auto usage = [=]{
-    die(1, "Usage: %s [-h] INPUT-FILENAME OUTPUT-FILENAME PKCS12-PATH PKCS12-PASS",
-            invocation_name);
+  auto usage = [=] {
+    die(1, "Usage: %s [-h] [-r RESERVATION] INPUT-FILENAME OUTPUT-FILENAME PKCS12-PATH PKCS12-PASS",
+        invocation_name);
   };
 
   static struct option opts[] = {
     {"help", no_argument, 0, 'h'},
+    {"version", no_argument, 0, 'V'},
+    {"reservation", required_argument, 0, 'r'},
     {nullptr, 0, 0, 0},
   };
 
+  // Reserved space in bytes for the certificate, digest, encrypted digest, ...
+  long reservation = 4096;
   while (1) {
     int option_index = 0;
-    auto c = getopt_long(argc, const_cast<char* const*>(argv),
-                         "h", opts, &option_index);
+    auto c = getopt_long(argc, const_cast<char* const*>(argv), "hVr:", opts, &option_index);
     if (c == -1)
       break;
 
+    char* end = nullptr;
     switch (c) {
-    case 'h': usage(); break;
-    default: usage();
+    case 'r':
+      errno = 0, reservation = strtol(optarg, &end, 10);
+      if (errno || *end || reservation <= 0 || reservation > USHRT_MAX)
+        die(1, "%s: must be a positive number", optarg);
+      break;
+    case 'V':
+      die(0, "%s", PROJECT_NAME " " PROJECT_VERSION);
+      break;
+    case 'h':
+    default:
+      usage();
     }
   }
 
@@ -956,7 +999,7 @@ int main(int argc, char* argv[]) {
     die(1, "%s: %s", input_path, strerror(errno));
   }
 
-  auto err = pdf_sign(pdf_document);
+  auto err = pdf_sign(pdf_document, ushort(reservation));
   if (!err.empty()) {
     die(2, "Error: %s", err.c_str());
   }

test.sh

@@ -0,0 +1,86 @@
+#!/bin/sh -e
+# Test basic functionality of both versions
+# Usage: ./test.sh builddir/pdf-simple-sign cmd/pdf-simple-sign/pdf-simple-sign
+
+log() { echo "`tput sitm`-- $1`tput sgr0`"; }
+die() { echo "`tput bold`-- $1`tput sgr0`"; exit 1; }
+
+# Get rid of old test files
+rm -rf tmp
+mkdir tmp
+
+# Create documents in various tools
+log "Creating source documents"
+inkscape --pipe --export-filename=tmp/cairo.pdf --export-pdf-version=1.4 \
+<<'EOF' 2>/dev/null || :
+<svg xmlns="http://www.w3.org/2000/svg"><text x="5" y="10">Hello</text></svg>
+EOF
+
+date > tmp/lowriter.txt
+if command -v gropdf >/dev/null
+then groff -T pdf < tmp/lowriter.txt > tmp/groff.pdf
+fi
+lowriter --convert-to pdf tmp/lowriter.txt --outdir tmp >/dev/null || :
+convert rose: tmp/imagemagick.pdf || :
+
+# Create a root CA certificate pair
+log "Creating certificates"
+openssl req -newkey rsa:2048 -subj "/CN=Test CA" -nodes \
+	-keyout tmp/ca.key.pem -x509 -out tmp/ca.cert.pem 2>/dev/null
+
+# Create a private NSS database and insert our test CA there
+rm -rf tmp/nssdir
+mkdir tmp/nssdir
+certutil -N --empty-password -d sql:tmp/nssdir
+certutil -d sql:tmp/nssdir -A -n root -t ,C, -a -i tmp/ca.cert.pem
+
+# Create a leaf certificate pair
+cat > tmp/cert.cfg <<'EOF'
+[smime]
+basicConstraints = CA:FALSE
+keyUsage = digitalSignature
+extendedKeyUsage = emailProtection
+nsCertType = email
+EOF
+
+openssl req -newkey rsa:2048 -subj "/CN=Test Leaf" -nodes \
+	-keyout tmp/key.pem -out tmp/cert.csr 2>/dev/null
+openssl x509 -req -in tmp/cert.csr -out tmp/cert.pem \
+	-CA tmp/ca.cert.pem -CAkey tmp/ca.key.pem -set_serial 1 \
+	-extensions smime -extfile tmp/cert.cfg 2>/dev/null
+openssl verify -CAfile tmp/ca.cert.pem tmp/cert.pem >/dev/null
+
+# The second line accomodates the Go signer,
+# which doesn't support SHA-256 within pkcs12 handling
+openssl pkcs12 -inkey tmp/key.pem -in tmp/cert.pem \
+	-certpbe PBE-SHA1-3DES -keypbe PBE-SHA1-3DES -macalg sha1 \
+	-export -passout pass: -out tmp/key-pair.p12
+
+for tool in "$@"; do
+	rm -f tmp/*.signed.pdf
+	for source in tmp/*.pdf; do
+		log "Testing $tool with $source"
+		result=${source%.pdf}.signed.pdf
+		$tool "$source" "$result" tmp/key-pair.p12 ""
+		pdfsig -nssdir sql:tmp/nssdir "$result" | grep Validation
+
+		# Only some of our generators use PDF versions higher than 1.5
+		log "Testing $tool for version detection"
+		grep -q "/Version /1[.]6" "$result" \
+			|| grep -q "^%PDF-1[.][67]" "$result" \
+			|| die "Version detection seems to misbehave (no upgrade)"
+	done
+
+	log "Testing $tool for expected failures"
+	$tool "$result" "$source.fail.pdf" tmp/key-pair.p12 "" \
+		&& die "Double signing shouldn't succeed"
+	$tool -r 1 "$source" "$source.fail.pdf" tmp/key-pair.p12 "" \
+		&& die "Too low reservations shouldn't succeed"
+
+	sed '1s/%PDF-1../%PDF-1.7/' "$source" > "$source.alt"
+	$tool "$source.alt" "$result.alt" tmp/key-pair.p12 ""
+	grep -q "/Version /1.6" "$result.alt" \
+		&& die "Version detection seems to misbehave (downgraded)"
+done
+
+log "OK"