pdf - signature is invalid in revision 2 - caused by attachmens -

i've write code attaches files pdf document. i've seen code in pdfbox page.

pdembeddedfilesnametreenode eftree = new pdembeddedfilesnametreenode();  pdcomplexfilespecification fs = new pdcomplexfilespecification(); fs.setfile( "test.txt" ); inputstream = ...; pdembeddedfile ef = new pdembeddedfile(doc, ); ef.setsubtype( "test/plain" ); ef.setsize( data.length ); ef.setcreationdate( new gregoriancalendar() ); fs.setembeddedfile( ef ); map efmap = new hashmap(); efmap.put( "my first attachment", fs ); eftree.setnames( efmap ); pddocumentnamedictionary names = new pddocumentnamedictionary( doc.getdocumentcatalog() ); names.setembeddedfiles( eftree ); doc.getdocumentcatalog().setnames( names ); doc.save("attachedpdf");  

that, works.

then, i've attached files, , sign document. result -everything works!

then, signed document (which have attachments), , sign document with attachment (i create revision 2. in other words, attach files signed document , sign again). result was that, there no old file. new file have overwrite old files (signature become invalid , because of changing hash- that's correct);

so, i've done oldfiles pdembeddedfilesnametreenode , add new file map.

pdembeddedfilesnametreenode oldfiles=names.getembeddedfiles();         if(oldfiles!=null){             map oldfilesmap = oldfiles.getnames();             iterator iterator = oldfilesmap.entryset().iterator();             while (iterator.hasnext()) {                 map.entry mapentry = (map.entry) iterator.next();                 system.out.println("the key is: " + mapentry.getkey()+ ",value :" + mapentry.getvalue());                 efmap.put(mapentry.getkey(),  mapentry.getvalue());             }          } eftree.setnames(efmap); 

that works. signature again invalid when create second revision. think, main problem that, when add new files same file namedictionary, hash of document changes.

so, think, should create new namedictionary in next revision , may i wrong (i must not use existed namedictionary). dont understand. can know? think?

by way, think incorrect me, next revision

pddocumentnamedictionary names = new pddocumentnamedictionary(doc.getdocumentcatalog()); 

that's my sample documents

then, signed document (which have attachments), , sign document with attachment (i create revision 2. in other words, attach files signed document , sign again).

whatever other problems have trying this, undertaking doomed. if incremental update, not allowed operation on signed document.

the operations allowed on signed documents either restricted specification (in case of certification signatures) or extrapolation certification rules (in case of approval signatures only).

in case of certification signatures (docmdp signatures), p value in docmdp transform parameters dictionary selects set of operations allowed on document:

(optional) access permissions granted document. valid values shall be:

1 no changes document shall permitted; change document shall invalidate signature.

2 permitted changes shall filling in forms, instantiating page templates, , signing; other changes shall invalidate signature.

3 permitted changes shall same 2, annotation creation, deletion, , modification; other changes shall invalidate signature.

default value: 2.

(section 12.8.2.2.2 in iso 32000-1)

as see, attaching files not among them.

unfortunately specification not changes shall permitted if there no certification signature (docmdp signature); therefore, 1 might tempted assume allowed.

actually, though, current pdf viewers, dominant adobe reader, assume differently , extrapolate set of permitted changes. in case adobe reader these (cf. this answer details) same docmdp p = 3 plus adding signature fields. (it assumed author did not consider signing use case and, therefore, forgot adding empty signature fields; otherwise, though, set of allowed changes considered apropos.)

thus, no attaching of files either.

if want handle multiple attachments , multiple signatures, may consider supplement signed pdf creating new pdf, adding original pdf , new files attachments (and setting enw pdf display original pdf default), , sign whole construct.

ps: concerning actual attempt: when trying manipulate signed document doc-signed.pdf, seem have started reading , writing using pdfbox; assume because doc-signed.pdf not starting piece of doc-signed-signed.pdf latter document indeed contains new attachment , second signature in incremental update.

this caused original file internally reorganized , original signature broken in process. should instead start creating identical copy of file , add second signature incremental update.