Environ() returns multiple empty strings

[ariel-miculas]

Environ() returns a list of strings, but a lot of returned entries are the empty string instead of a valid environment variable in the form A=B.

[discordianfish]

This is really not enough detail to be actionable. The function is straight forward:

procfs/proc_environ.go

Line 23 in 54b2b56

func (p Proc) Environ() ([]string, error) {

- I doubt the issue is in the code but more likely in your env

[ariel-miculas]

Thanks for taking the time to respond.
I think the issue happens for processes which have a lot of NUL bytes in /proc/PID/environ. For example, I have the following Chrome process:

❯ sudo hexdump -C /proc/38905/environ
00000000  6d 61 67 65 73 20 2d 2d  63 68 61 6e 67 65 2d 73  |mages --change-s|
00000010  74 61 63 6b 2d 67 75 61  72 64 2d 6f 6e 2d 66 6f  |tack-guard-on-fo|
00000020  72 6b 3d 65 6e 61 62 6c  65 20 2d 2d 6c 61 6e 67  |rk=enable --lang|
00000030  3d 65 6e 2d 55 53 20 2d  2d 6e 75 6d 2d 72 61 73  |=en-US --num-ras|
00000040  74 65 72 2d 74 68 72 65  61 64 73 3d 34 20 2d 2d  |ter-threads=4 --|
00000050  65 6e 61 62 6c 65 2d 6d  61 69 6e 2d 66 72 61 6d  |enable-main-fram|
00000060  65 2d 62 65 66 6f 72 65  2d 61 63 74 69 76 61 74  |e-before-activat|
00000070  69 6f 6e 20 2d 2d 72 65  6e 64 65 72 65 72 2d 63  |ion --renderer-c|
00000080  6c 69 65 6e 74 2d 69 64  3d 31 31 32 20 2d 2d 74  |lient-id=112 --t|
00000090  69 6d 65 2d 74 69 63 6b  73 2d 61 74 2d 75 6e 69  |ime-ticks-at-uni|
000000a0  78 2d 65 70 6f 63 68 3d  2d 31 37 33 30 32 38 31  |x-epoch=-1730281|
000000b0  33 39 39 37 34 31 31 38  36 20 2d 2d 6c 61 75 6e  |399741186 --laun|
000000c0  63 68 2d 74 69 6d 65 2d  74 69 63 6b 73 3d 32 32  |ch-time-ticks=22|
000000d0  30 36 37 32 36 30 32 20  2d 2d 73 68 61 72 65 64  |0672602 --shared|
000000e0  2d 66 69 6c 65 73 3d 76  38 5f 63 6f 6e 74 65 78  |-files=v8_contex|
000000f0  74 5f 73 6e 61 70 73 68  6f 74 5f 64 61 74 61 3a  |t_snapshot_data:|
00000100  31 30 30 20 2d 2d 66 69  65 6c 64 2d 74 72 69 61  |100 --field-tria|
00000110  6c 2d 68 61 6e 64 6c 65  3d 33 2c 69 2c 36 36 35  |l-handle=3,i,665|
00000120  32 34 35 38 35 30 35 36  38 34 30 37 32 30 34 33  |2458505684072043|
00000130  2c 35 35 37 35 39 37 36  35 34 35 39 31 32 36 37  |,557597654591267|
00000140  33 30 36 32 2c 32 36 32  31 34 34 20 2d 2d 76 61  |3062,262144 --va|
00000150  72 69 61 74 69 6f 6e 73  2d 73 65 65 64 2d 76 65  |riations-seed-ve|
00000160  72 73 69 6f 6e 3d 32 30  32 34 31 30 32 39 2d 30  |rsion=20241029-0|
00000170  35 30 30 35 39 2e 31 39  38 30 30 30 00 00 00 00  |50059.198000....|
00000180  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
00000880  00 00 00 00 00 00 00 00  00 00 00 00              |............|
0000088c

As you can see, it contains a lot of NUL bytes at the end of the file.
This means that the Environ() function will return a lot of empty strings, as shown in this example: https://go.dev/play/p/tAxwKy6rGsZ

Are you open to a Pull Request that makes Environ skip the empty strings and only return non-empty strings?

[discordianfish]

Hrm wondering why chrome would do this? Not sure how to handle this. If env is defined to be NUL seperated strings, then technically returning an empty list is correct.

[ariel-miculas]

You are right, quoting from https://manpages.ubuntu.com/manpages/trusty/en/man5/proc.5.html

This file contains the environment for the process. The entries are separated by
null bytes ('\0'), and there may be a null byte at the end. Thus, to print out the
environment of process 1, you would do:
$ strings /proc/1/environ

I found stackoverflow post that says processes can overwrite their environment strings, for example by writing zeroes to hide them.

From a practical standpoint, I don't think returning a bunch of empty strings is useful in any way.

[discordianfish]

In this case I think procfs is handling this properly. The caller can easily skip empty strings and there might be some cases where you actually want to know if there are empty/overwritten env vars.