These images will get you back to stock, but according to https://github.com/sowbug/archer-c9-back-to-stock/issues/4 you won't be able to upgrade to anything else after that, including via tftp. Don't use these images unless you're OK being on this single stock version forever! (Note that you can reinstall dd-wrt or other non-stock firmware, but for some reason these images are too picky about stock images.)
Disclaimer: I have only an Archer C9 v3, not a v1 or v2, so I haven't tested the v1/v2 images included in this repository.
Do the same thing I did below for whichever version of the router you have. Then go to the DD-WRT admin tab and flash c9-webflash.bin using the web UI. It'll take a few minutes, and in the end you'll have a stock Archer C9, without having to open the case.
$ binwalk archer_c9v1_us-up-ver3-17-1-P1\[20180125-rel56387\].bin
DECIMAL HEXADECIMAL DESCRIPTION
--------------------------------------------------------------------------------
155672 0x26018 LZMA compressed data, properties: 0x5D, dictionary size: 65536 bytes, uncompressed size: 299376 bytes
234363 0x3937B TRX firmware header, little endian, image size: 1728512 bytes, CRC32: 0xF4A39915, flags: 0x0, version: 1, header size: 28 bytes, loader offset: 0x1C, linux kernel offset: 0x0, rootfs offset: 0x0
234391 0x39397 LZMA compressed data, properties: 0x5D, dictionary size: 65536 bytes, uncompressed size: 4240704 bytes
1962876 0x1DF37C Squashfs filesystem, little endian, version 4.0, compression:xz, size: 9178593 bytes, 771 inodes, blocksize: 131072 bytes, created: 2018-01-25 07:39:46
$ dd if=archer_c9v1_us-up-ver3-17-1-P1\[20180125-rel56387\].bin of=c9v1-loader.bin skip=234391 iflag=skip_bytes bs=1728485 count=1
1+0 records in
1+0 records out
1728485 bytes (1.7 MB, 1.6 MiB) copied, 0.00392719 s, 440 MB/s
$ dd if=archer_c9v1_us-up-ver3-17-1-P1\[20180125-rel56387\].bin of=c9v1-squashfs.bin skip=1962876 iflag=skip_bytes
17928+1 records in
17928+1 records out
9179453 bytes (9.2 MB, 8.8 MiB) copied, 0.0359788 s, 255 MB/s
$ ~/src/source-master/tools/firmware-utils/src/a.out -f c9v1-loader.bin -f c9v1-squashfs.bin > c9v1-webflash.bin
mjn3's trx replacement - v0.81.1
$ binwalk c9v1-webflash.bin
DECIMAL HEXADECIMAL DESCRIPTION
--------------------------------------------------------------------------------
0 0x0 TRX firmware header, little endian, image size: 10911744 bytes, CRC32: 0x64CC457C, flags: 0x0, version: 1, header size: 28 bytes, loader offset: 0x1C, linux kernel offset: 0x1A6004, rootfs offset: 0x0
28 0x1C LZMA compressed data, properties: 0x5D, dictionary size: 65536 bytes, uncompressed size: 4240704 bytes
1728516 0x1A6004 Squashfs filesystem, little endian, version 4.0, compression:xz, size: 9178593 bytes, 771 inodes, blocksize: 131072 bytes, created: 2018-01-25 07:39:46
$ shasum archer_c9v1_us-up-ver3-17-1-P1\[20180125-rel56387\].bin c9v1-loader.bin c9v1-squashfs.bin c9v1-webflash.bin
254ec5916cdd613c55cd6c26d2e64abc344495a8 archer_c9v1_us-up-ver3-17-1-P1[20180125-rel56387].bin
8044020e597ff5680c04fceceda66ac20181431c c9v1-loader.bin
fb9f591bef55bc7a88ca93b8ef339db6a54fdd3c c9v1-squashfs.bin
22e2d7d3a1b45da0348820f03a47f99a63aae08f c9v1-webflash.binsource https://static.tp-link.com/res/down/soft/Archer_C9_V2_160315.zip
$ binwalk c9v2_un-up-ver4-0-0-P24\[20160315-rel34536\].bin
DECIMAL HEXADECIMAL DESCRIPTION
--------------------------------------------------------------------------------
155672 0x26018 LZMA compressed data, properties: 0x5D, dictionary size: 65536 bytes, uncompressed size: 299260 bytes
234269 0x3931D TRX firmware header, little endian, image size: 1916928 bytes, CRC32: 0xFD45640D, flags: 0x0, version: 1, header size: 28 bytes, loader offset: 0x1C, linux kernel offset: 0x0, rootfs offset: 0x0
234297 0x39339 LZMA compressed data, properties: 0x5D, dictionary size: 65536 bytes, uncompressed size: 4570816 bytes
2151198 0x20D31E Squashfs filesystem, little endian, version 4.0, compression:xz, size: 12505569 bytes, 2511 inodes, blocksize: 131072 bytes, created: 2016-03-15 01:17:48
14660496 0xDFB390 XML document, version: "1.0"
14668042 0xDFD10A XML document, version: "1.0"
14669474 0xDFD6A2 Unix path: /var/run/appflow/tccpipe</listen_path>
14673514 0xDFE66A Unix path: /usr/share/miniupnpd/firewall.include</path>
14677564 0xDFF63C Unix path: /cover.jpg/AlbumArtSmall.jpg/albumartsmall.jpg/AlbumArt.jpg/albumart.jpg/Album.jpg/album.jpg/Folder.jpg/folder.jpg/Thumb.jpg/thu
14682556 0xE009BC Unix path: /usr/local/bin/jiggle_firewall</exec>
14683402 0xE00D0A Unix path: /usr/local/bin/apply_appflow</exec>
$ dd if=c9v2_un-up-ver4-0-0-P24\[20160315-rel34536\].bin of=c9v2-loader.bin skip=234297 iflag=skip_bytes bs=1916901 count=1
1+0 records in
1+0 records out
1916901 bytes (1.9 MB, 1.8 MiB) copied, 0.0051192 s, 374 MB/s
$ dd if=c9v2_un-up-ver4-0-0-P24\[20160315-rel34536\].bin of=c9v2-squashfs.bin skip=2151198 iflag=skip_bytes bs=12509298 count=1
1+0 records in
1+0 records out
12509298 bytes (13 MB, 12 MiB) copied, 0.0189874 s, 659 MB/s
$ ../lede-project-source/tools/firmware-utils/src/a.out -f c9v2-loader.bin -f c9v2-squashfs.bin > c9v2-webflash.bin
mjn3's trx replacement - v0.81.1
$ binwalk c9v2-webflash.bin
DECIMAL HEXADECIMAL DESCRIPTION
--------------------------------------------------------------------------------
0 0x0 TRX firmware header, little endian, image size: 14430208 bytes, CRC32: 0xBAF67D77, flags: 0x0, version: 1, header size: 28 bytes, loader offset: 0x1C, linux kernel offset: 0x1D4004, rootfs offset: 0x0
28 0x1C LZMA compressed data, properties: 0x5D, dictionary size: 65536 bytes, uncompressed size: 4570816 bytes
1916932 0x1D4004 Squashfs filesystem, little endian, version 4.0, compression:xz, size: 12505569 bytes, 2511 inodes, blocksize: 131072 bytes, created: 2016-03-15 01:17:48
$ shasum c9v2_un-up-ver4-0-0-P24\[20160315-rel34536\].bin c9v2-loader.bin c9v2-squashfs.bin c9v2-webflash.bin
b588c06fb1035bff22340d7475cf0ef7a1132b8a c9v2_un-up-ver4-0-0-P24[20160315-rel34536].bin
c880be5648a71579880b0a633b7c6a50488333e4 c9v2-loader.bin
40dec777ae504f46d85ff78bdaf863011d9fad37 c9v2-squashfs.bin
a168a3808d52a920d734cc2d8e73f54a6f8e998e c9v2-webflash.binSource for 170511 version: https://static.tp-link.com/Archer%20C9(UN)_V2_170511.zip
$ binwalk Archer\ C9\(UN\)_V2_170511.bin
DECIMAL HEXADECIMAL DESCRIPTION
--------------------------------------------------------------------------------
155672 0x26018 LZMA compressed data, properties: 0x5D, dictionary size: 65536 bytes, uncompressed size: 299316 bytes
234301 0x3933D TRX firmware header, little endian, image size: 1916928 bytes, CRC32: 0x5AC9D15A, flags: 0x0, version: 1, header size: 28 bytes, loader offset: 0x1C, linux kernel offset: 0x0, rootfs offset: 0x0
234329 0x39359 LZMA compressed data, properties: 0x5D, dictionary size: 65536 bytes, uncompressed size: 4570816 bytes
2151230 0x20D33E Squashfs filesystem, little endian, version 4.0, compression:xz, size: 13073427 bytes, 2671 inodes, blocksize: 131072 bytes, created: 2017-05-11 02:17:25
15225776 0xE853B0 XML document, version: "1.0"
15233457 0xE871B1 XML document, version: "1.0"
15234889 0xE87749 Unix path: /var/run/appflow/tccpipe</listen_path>
15238929 0xE88711 Unix path: /usr/share/miniupnpd/firewall.include</path>
15242979 0xE896E3 Unix path: /cover.jpg/AlbumArtSmall.jpg/albumartsmall.jpg/AlbumArt.jpg/albumart.jpg/Album.jpg/album.jpg/Folder.jpg/folder.jpg/Thumb.jpg/thu
15247985 0xE8AA71 Unix path: /usr/local/bin/jiggle_firewall</exec>
15248831 0xE8ADBF Unix path: /usr/local/bin/apply_appflow</exec>
$ dd if=Archer\ C9\(UN\)_V2_170511.bin of=c9-loader.bin skip=234329 iflag=skip_bytes bs=1916901 count=1
1+0 records in
1+0 records out
1916901 bytes (1.9 MB, 1.8 MiB) copied, 0.00412536 s, 465 MB/s
$ dd if=Archer\ C9\(UN\)_V2_170511.bin of=c9-squashfs.bin skip=2151230 iflag=skip_bytes bs=13074546 count=1
1+0 records in
1+0 records out
13074546 bytes (13 MB, 12 MiB) copied, 0.0151488 s, 863 MB/s
$ ~/src/lede-project/tools/firmware-utils/src/a.out -f c9-loader.bin -f c9-squashfs.bin > c9v3-170511-webflash.bin
mjn3's trx replacement - v0.81.1
miket@siren-grit:~/src/archer-c9-back-to-stock$ shasum *.bin
669838435b4552c3ee60cf8a6758ff04b3236ae8 Archer C9(UN)_V2_170511.bin
3649170d575bf6663830c66f50ffcf4a58a11668 c9-loader.bin
f27a9d633c4a112ab5ea15ff24cbff010b9033f4 c9-squashfs.bin
7c3528754c2ba68bef8b0600321f6136cf9356ff c9v3-170511-webflash.binGo get the stock firmware from the TP-Link site. Then unzip it and cd into the resulting directory.
$ ls -l
total 14956
-rw-r--r-- 1 sowbug sowbug 14820016 Dec 15 2017 c9v4_eu-us-ca_up_1-3-1-20171215rel35219.bin
-rw-r--r-- 1 sowbug sowbug 112046 Sep 14 2015 'GPL License Terms.pdf'
-rw-r--r-- 1 sowbug sowbug 373590 Oct 14 2016 'How to upgrade TP-LINK Wireless AC Router.pdf'
$ binwalk c9v4_eu-us-ca_up_1-3-1-20171215rel35219.bin
DECIMAL HEXADECIMAL DESCRIPTION
--------------------------------------------------------------------------------
155672 0x26018 LZMA compressed data, properties: 0x5D, dictionary size: 65536 bytes, uncompressed size: 327460 bytes
241100 0x3ADCC TRX firmware header, little endian, image size: 1916928 bytes, CRC32: 0xF7F42AEE, flags: 0x0, version: 1, header size: 28 bytes, loader offset: 0x1C, linux kernel offset: 0x0, rootfs offset: 0x0
241128 0x3ADE8 LZMA compressed data, properties: 0x5D, dictionary size: 65536 bytes, uncompressed size: 4562560 bytes
2158029 0x20EDCD Squashfs filesystem, little endian, version 4.0, compression:xz, size: 12413672 bytes, 2645 inodes, blocksize: 262144 bytes, created: 2017-12-15 01:46:56
14573322 0xDE5F0A XML document, version: "1.0"
14581037 0xDE7D2D XML document, version: "1.0"
14582469 0xDE82C5 Unix path: /var/run/appflow/tccpipe</listen_path>
14586651 0xDE931B Unix path: /usr/share/miniupnpd/firewall.include</path>
14590726 0xDEA306 Unix path: /cover.jpg/AlbumArtSmall.jpg/albumartsmall.jpg/AlbumArt.jpg/albumart.jpg/Album.jpg/album.jpg/Folder.jpg/folder.jpg/Thumb.jpg/thu
14595966 0xDEB77E Unix path: /usr/local/bin/jiggle_firewall</exec>
14596812 0xDEBACC Unix path: /usr/local/bin/apply_appflow</exec>
# The 1916901 figure is 2158029 - 241128
$ dd if=c9v4_eu-us-ca_up_1-3-1-20171215rel35219.bin of=c9-loader.bin skip=241128 iflag=skip_bytes bs=1916901 count=1
1+0 records in
1+0 records out
1916901 bytes (1.9 MB, 1.8 MiB) copied, 0.00746417 s, 257 MB/s
# 12415293 is 14573322 - 2158029
$ dd if=c9v4_eu-us-ca_up_1-3-1-20171215rel35219.bin of=c9-squashfs.bin skip=2158029 iflag=skip_bytes bs=12415293 count=1
1+0 records in
1+0 records out
12415293 bytes (12 MB, 12 MiB) copied, 0.0318187 s, 390 MB/s
# This repo came from https://github.com/lede-project/source/, and then I hacked on it until
# I could `gcc trx.c`. I had to change to `#define TRX_MAX_LEN 0xF20000` to get it to handle the larger file sizes.
$ ~/src/source-master/tools/firmware-utils/src/a.out -f c9-loader.bin -f c9-squashfs.bin > c9v3-webflash.bin
mjn3's trx replacement - v0.81.1
# You can check and see whether your files turn out the same as mine.
$ shasum *.bin
ce5b20da5dc60a10935ad3f743f8d12bc9664aa2 c9-loader.bin
da1a28a6ab4b233dda104e7f7bcb00d55bee65e0 c9-squashfs.bin
71b876578be3d42446778633602689b4f1ed5afd c9v4_eu-us-ca_up_1-3-1-20171215rel35219.bin
d362c4288a4b870d305d41180488f0bc88091192 c9v3-webflash.binDownload the original firmware from here
root@2c9f6d555060:/mnt# binwalk ./c9v3_jp_cloud-up-1.2.0_Build_20170111_rel.69305_2017-01-12_10.46.13.bin
DECIMAL HEXADECIMAL DESCRIPTION
--------------------------------------------------------------------------------
155672 0x26018 LZMA compressed data, properties: 0x5D, dictionary size: 65536 bytes, uncompressed size: 327460 bytes
241099 0x3ADCB TRX firmware header, little endian, image size: 1916928 bytes, CRC32: 0x17CE53DF, flags: 0x0, version: 1, header size: 28 bytes, loader offset: 0x1C, linux kernel offset: 0x0, rootfs offset: 0x0
241127 0x3ADE7 LZMA compressed data, properties: 0x5D, dictionary size: 65536 bytes, uncompressed size: 4570816 bytes
2158028 0x20EDCC Squashfs filesystem, little endian, version 4.0, compression:xz, size: 12378910 bytes, 2634 inodes, blocksize: 262144 bytes, created: 2017-01-11 11:15:03
14540491 0xDDDECB XML document, version: "1.0"
14548206 0xDDFCEE XML document, version: "1.0"
14549637 0xDE0285 Unix path: /var/run/appflow/tccpipe</listen_path>
14553677 0xDE124D Unix path: /usr/share/miniupnpd/firewall.include</path>
14553831 0xDE12E7 Unix path: /etc/firewall.d/qca-nss-connmgr</path>
14556954 0xDE1F1A Unix path: /lib/uci/upload/</uploads>
14557582 0xDE218E Unix path: /var/run/minidlna</db_dir>
14562752 0xDE35C0 Unix path: /usr/local/bin/jiggle_firewall</exec>
14563598 0xDE390E Unix path: /usr/local/bin/apply_appflow</exec>
root@2c9f6d555060:/mnt# dd if=./c9v3_jp_cloud-up-1.2.0_Build_20170111_rel.69305_2017-01-12_10.46.13.bin of=c9-loader.bin skip=241127 iflag=skip_bytes bs=$(echo 2158028-241127|bc) count=1
1+0 records in
1+0 records out
1916901 bytes (1.9 MB, 1.8 MiB) copied, 0.0262399 s, 73.1 MB/s
root@2c9f6d555060:/mnt# dd if=./c9v3_jp_cloud-up-1.2.0_Build_20170111_rel.69305_2017-01-12_10.46.13.bin of=c9-squashfs.bin skip=2158028 iflag=skip_bytes bs=$(echo 14540491-2158028|bc) count=1
1+0 records in
1+0 records out
12382463 bytes (12 MB, 12 MiB) copied, 0.195586 s, 63.3 MB/s
root@2c9f6d555060:/mnt# ./source/tools/firmware-utils/src/a.out -f c9-loader.bin -f c9-squashfs.bin > c9v3-webflash-jp.bin
mjn3's trx replacement - v0.81.1(I don't know why v4 and v5 are different, but binwalk reported only a JFFS2 filesystem, which I don't recognize. I don't know how to handle that.)