jail(8): implement NUL-terminated output

[kraken-jim]

Specifiying an empty string as the argument to "-e" will cause this version of jail(8) to output NUL-terminated lines, to make string quoting unambiguous. The NUL-terminated lines are the exact verbatim values of the variables defined in jail.conf(5). man page jail(8) is also updated to reflect the change in behavior.

[github-actions]

Thank you for taking the time to contribute to FreeBSD!
There is an issue that needs to be fixed:

• Missing Signed-off-by lines^{f17cc62, 3f761bd, 513020e}

Please review CONTRIBUTING.md, then update and push your branch again.

[kraken-jim]

Sample output scenarios:

# cat /etc/jail.conf.d/test.conf 
test {
    host.hostname = "test.example.edu";
    ip4.addr  = "vlan3|192.168.1.50/32";
    ip4.addr += "private|192.168.1.95-99/32";

    allow.raw_sockets   = 1;

    mount  = "/filesystem-a   $path/mnt/a nullfs  ro  0   0";
    mount += "/filesystem-b   $path/mnt/b nullfs  ro  0   0";
    mount += "/filesystem-c   $path/mnt/c nullfs  ro  0   0";
    mount += "/filesystem-d   $path/mnt/d nullfs  ro  0   0";
    mount += "/filesystem-e   $path/mnt/e nullfs  ro  0   0";
}

Existing behavior:

# jail.old -e $'\n'; jail.old -e $'\n' | sha256sum
name=test
exec.start="/bin/sh /etc/rc"
exec.stop="/bin/sh /etc/rc.shutdown"
exec.consolelog=/var/log/jail_test.log
host.hostname=test.example.edu
path=/jail/test
interface=private
linux.osname=FreeBSD
mount.devfs
ip4.addr=vlan3|192.168.1.50/32,private|192.168.1.95-99/32
allow.raw_sockets=1
mount="/filesystem-a    /jail/test/mnt/a    nullfs  ro  0   0","/filesystem-b   /jail/test/mnt/b    nullfs  ro  0   0","/filesystem-c    /jail/test/mnt/c    nullfs  ro  0   0","/filesystem-d   /jail/test/mnt/d    nullfs  ro  0   0","/filesystem-e   /jail/test/mnt/e nullfs  ro  0   0"
1078af124c2a887aed44377860543a96e656f6213e492430d646727c3beb8670  -

New behavior (unchanged):

# jail -e $'\n'; jail -e $'\n' | sha256sum
name=test
exec.start="/bin/sh /etc/rc"
exec.stop="/bin/sh /etc/rc.shutdown"
exec.consolelog=/var/log/jail_test.log
host.hostname=test.example.edu
path=/jail/test
interface=private
linux.osname=FreeBSD
mount.devfs
ip4.addr=vlan3|192.168.1.50/32,private|192.168.1.95-99/32
allow.raw_sockets=1
mount="/filesystem-a    /jail/test/mnt/a    nullfs  ro  0   0","/filesystem-b   /jail/test/mnt/b    nullfs  ro  0   0","/filesystem-c    /jail/test/mnt/c    nullfs  ro  0   0","/filesystem-d   /jail/test/mnt/d    nullfs  ro  0   0","/filesystem-e   /jail/test/mnt/e nullfs  ro  0   0"
1078af124c2a887aed44377860543a96e656f6213e492430d646727c3beb8670  -

New behavior (NUL-delimited):

# jail -e '' | xargs -0 -Ixx echo xx
name=test
exec.start=/bin/sh /etc/rc
exec.stop=/bin/sh /etc/rc.shutdown
exec.consolelog=/var/log/jail_test.log
host.hostname=test.example.edu
path=/jail/test
interface=private
linux.osname=FreeBSD
mount.devfs
ip4.addr=vlan3|192.168.1.50/32
private|192.168.1.95-99/32
allow.raw_sockets=1
mount=/filesystem-a /jail/test/mnt/a    nullfs  ro  0   0
/filesystem-b   /jail/test/mnt/b    nullfs  ro  0   0
/filesystem-c   /jail/test/mnt/c    nullfs  ro  0   0
/filesystem-d   /jail/test/mnt/d    nullfs  ro  0   0
/filesystem-e   /jail/test/mnt/e    nullfs  ro  0   0

# jail -e '' | hexdump -Cv
00000000  6e 61 6d 65 3d 74 65 73  74 00 65 78 65 63 2e 73  |name=test.exec.s|
00000010  74 61 72 74 3d 2f 62 69  6e 2f 73 68 20 2f 65 74  |tart=/bin/sh /et|
00000020  63 2f 72 63 00 65 78 65  63 2e 73 74 6f 70 3d 2f  |c/rc.exec.stop=/|
00000030  62 69 6e 2f 73 68 20 2f  65 74 63 2f 72 63 2e 73  |bin/sh /etc/rc.s|
00000040  68 75 74 64 6f 77 6e 00  65 78 65 63 2e 63 6f 6e  |hutdown.exec.con|
00000050  73 6f 6c 65 6c 6f 67 3d  2f 76 61 72 2f 6c 6f 67  |solelog=/var/log|
00000060  2f 6a 61 69 6c 5f 74 65  73 74 2e 6c 6f 67 00 68  |/jail_test.log.h|
00000070  6f 73 74 2e 68 6f 73 74  6e 61 6d 65 3d 74 65 73  |ost.hostname=tes|
00000080  74 2e 65 78 61 6d 70 6c  65 2e 65 64 75 00 70 61  |t.example.edu.pa|
00000090  74 68 3d 2f 6a 61 69 6c  2f 74 65 73 74 00 69 6e  |th=/jail/test.in|
000000a0  74 65 72 66 61 63 65 3d  70 72 69 76 61 74 65 00  |terface=private.|
000000b0  6c 69 6e 75 78 2e 6f 73  6e 61 6d 65 3d 46 72 65  |linux.osname=Fre|
000000c0  65 42 53 44 00 6d 6f 75  6e 74 2e 64 65 76 66 73  |eBSD.mount.devfs|
000000d0  00 69 70 34 2e 61 64 64  72 3d 76 6c 61 6e 33 7c  |.ip4.addr=vlan3||
000000e0  31 39 32 2e 31 36 38 2e  31 2e 35 30 2f 33 32 0a  |192.168.1.50/32.|
000000f0  70 72 69 76 61 74 65 7c  31 39 32 2e 31 36 38 2e  |private|192.168.|
00000100  31 2e 39 35 2d 39 39 2f  33 32 00 61 6c 6c 6f 77  |1.95-99/32.allow|
00000110  2e 72 61 77 5f 73 6f 63  6b 65 74 73 3d 31 00 6d  |.raw_sockets=1.m|
00000120  6f 75 6e 74 3d 2f 66 69  6c 65 73 79 73 74 65 6d  |ount=/filesystem|
00000130  2d 61 09 2f 6a 61 69 6c  2f 74 65 73 74 2f 6d 6e  |-a./jail/test/mn|
00000140  74 2f 61 09 6e 75 6c 6c  66 73 09 72 6f 09 30 09  |t/a.nullfs.ro.0.|
00000150  30 0a 2f 66 69 6c 65 73  79 73 74 65 6d 2d 62 09  |0./filesystem-b.|
00000160  2f 6a 61 69 6c 2f 74 65  73 74 2f 6d 6e 74 2f 62  |/jail/test/mnt/b|
00000170  09 6e 75 6c 6c 66 73 09  72 6f 09 30 09 30 0a 2f  |.nullfs.ro.0.0./|
00000180  66 69 6c 65 73 79 73 74  65 6d 2d 63 09 2f 6a 61  |filesystem-c./ja|
00000190  69 6c 2f 74 65 73 74 2f  6d 6e 74 2f 63 09 6e 75  |il/test/mnt/c.nu|
000001a0  6c 6c 66 73 09 72 6f 09  30 09 30 0a 2f 66 69 6c  |llfs.ro.0.0./fil|
000001b0  65 73 79 73 74 65 6d 2d  64 09 2f 6a 61 69 6c 2f  |esystem-d./jail/|
000001c0  74 65 73 74 2f 6d 6e 74  2f 64 09 6e 75 6c 6c 66  |test/mnt/d.nullf|
000001d0  73 09 72 6f 09 30 09 30  0a 2f 66 69 6c 65 73 79  |s.ro.0.0./filesy|
000001e0  73 74 65 6d 2d 65 09 2f  6a 61 69 6c 2f 74 65 73  |stem-e./jail/tes|
000001f0  74 2f 6d 6e 74 2f 65 09  6e 75 6c 6c 66 73 09 72  |t/mnt/e.nullfs.r|
00000200  6f 09 30 09 30 00 00                              |o.0.0..|
00000207