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procd: make mDNS TXT record parsing more solid

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mDNS broadcast can't accept empty TXT record and would fail
registration.

Current procd_add_mdns_service checks only if the first passed arg is
empty but don't make any verification on the other args permittins
insertion of empty values in TXT record.

Example:

	procd_add_mdns "blah" \
				"tcp" "50" \
				"1" \
				"" \
				"3"

Produce:

{ "blah_50": { "service": "_blah._tcp.local", "port": 50, "txt": [ "1", "", "3" ] } }

The middle empty TXT record should never be included as it's empty.

This can happen with scripts that make fragile parsing and include
variables even if they are empty.

Prevent this and make the TXT record more solid by checking every
provided TXT record and include only the non-empty ones.

The fixed JSON is the following:

{ "blah_50": { "service": "_blah._tcp.local", "port": 50, "txt": [ "1", "3" ] } }

Fixes: b0d9dcf84d ("procd: update to latest git HEAD")
Reported-by: Paul Donald <newtwen@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/15331
Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
(cherry picked from commit 4b04304713)
This commit is contained in:
Christian Marangi 2024-04-29 21:17:31 +02:00
parent 5f07510cdc
commit ebb3faf31f
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1 changed files with 9 additions and 6 deletions
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15
package/system/procd/files/procd.sh
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@ -570,18 +570,21 @@ _procd_set_config_changed() {
}
procd_add_mdns_service() {
local service proto port
local service proto port txt_count=0
service=$1; shift
proto=$1; shift
port=$1; shift
json_add_object "${service}_$port"
json_add_string "service" "_$service._$proto.local"
json_add_int port "$port"
[ -n "$1" ] && {
json_add_array txt
for txt in "$@"; do json_add_string "" "$txt"; done
json_select ..
}
for txt in "$@"; do
[ -z "$txt" ] && continue
txt_count=$((txt_count+1))
[ $txt_count -eq 1 ] && json_add_array txt
json_add_string "" "$txt"
done
[ $txt_count -gt 0 ] && json_select ..
json_select ..
}