permissions: calculation

[ihipop]

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  YES
• State your OS and OS version
  Linux

pdfcpu/pkg/pdfcpu/configuration.go

Lines 170 to 171 in 11d755a

	// Supplied user access permissions, see Table 22.
	Permissions int16

I can only find 3 permission listed here

pdfcpu/pkg/pdfcpu/configuration.go

Lines 46 to 52 in 11d755a

	PermissionsAll int16 = -1 // 0xFFFF
	// PermissionsPrint disables all user access permissions bits except for printing.
	PermissionsPrint int16 = -1849 // 0xF8C7
	// PermissionsNone disables all user access permissions bits.
	PermissionsNone int16 = -3901 // 0xF0C3

But there is more permission bit listed here

https://pdfcpu.io/encrypt/perm_list.html#examples

How can I calc them myself ?

[hhrutter]

Hello!

Thanks for the tip! This is what you need:

[ihipop]

according to this table

44 permits print and copy

according to this table

Bit\POS	12	11	10	9	8	7	6	5	4	3	2	1	0
44	0	0	0	0	0	0	0	1	0	1	1	0	0
0	0	0	0	0	0	0	0	0	0	0	0	0	0

so I should define ~44 as -45 to make the pdf copy and printable ?right?

I tried, but it not works like this , -45 means copy / extract / fill exists form

and,
I think it's very counterintuitive, why don't we design the API like this?

const (
	PermissionPrint                                  = 1 << 3
	PermissionModifyDocContent                       = 1 << 4
	PermissionCopyDocText                            = 1 << 5
	PermissionModifyTextAnnotationsOrInteractiveForm = 1 << 6
	PermissionFillExistsForm                         = 1 << 9
        //..........
)

and set permission like this PermissionPrint | PermissionCopyDocText ?

[hhrutter]

The example from the spec turns on bits 3 and 5: 1111 1111 1101 0100 = -44

When you count the bit positions you start with 1 (not with 0).

The example assumes security handler rev 2 so bits 9-12 are disregarded.
Bits 1 and 2 are not interpreted so you should be getting the same permissions with: 1111 1111 1101 0111 = -41
My guess is the same applies to bits 7 and 8.

In order to calculate specific permissions you just turn on the corresponding bits which will get you a two's complement binary integer for which you define the corresponding negative integer value in your code.

It's all explained in the screenshot above.

[hhrutter]

Please see the optimized permissions command of https://github.com/pdfcpu/pdfcpu/releases/tag/v0.6.0