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Forum Post: Sophos WLAN AP55 Firmware / Recover - HOWTO: Unbrick your Sophos AP!

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Hello, I have fixed my AP55 over the serial connection (called cosole port at the AP). Sophos doesn't provide a recovery tool to fix a broken AP55, you must send it back! That was not a solution for me, so I try to bring it back to life! I have droped my AP55 from the AP-List on the UTM, but then it doesn't come up again. It stays weak green, no blinking, nothing. Then I have found the following post: https://community.sophos.com/products/unified-threat-management/f/wireless-security/56598/accesspoint-howto-troubleshoot-on-console But the interesting thing ist the following: For troubleshooting issues, I needed to know some more Informations about why an AP 55 was not getting discovered by my Sophos UTM. Therefore I decided to connect my Notebook to the AP's Console Port to figure out what can be done via Console Port. Because those Informations could be helpful for anybody else, here you are. Connection can be established, using 115200 Baud. There is no login Password required. Just press enter. So, you buy a RJ-45 to serial-connector and plug the serial-connector in your PC. I have done that with a USB-to-Serial-Converter. A cheap adpater from amazon. But with Windows 10, the device doesn’t come up. I found the following driver: http://www.totalcardiagnostics.com/support/Knowledgebase/Article/View/92/20/prolific-usb-to-serial-fix-official-solution-to-code-10-error http://www.totalcardiagnostics.com/files/PL2303_64bit_Installer.exe An then, tada. You are able to connect to the AP through the adapter. I have connected me to the AP with putty, You must switch to serial connection and add the Baudrate: 115200. The right COM-Port can you see in the Windows Device Manager. In the empty window you must press enter. When you pull out the power from the AP, you can see U-Boot comes up an try to load the OpenWRT-Firmware, that SOPHOS deploys for the APs. But in my case, the following problem occured: U-Boot 1.1.4-gcb612594 (Dec 23 2016 - 12:50:03) ELX version: 1.0.0 7679WSC - Scorpion 1.0DRAM: sri Scorpion 1.0 ath_ddr_initial_config(178): (32bit) ddr2 init tap = 0x00000003 Tap (low, high) = (0x5, 0x1b) Tap values = (0x10, 0x10, 0x10, 0x10) 128 MB Flash Manuf Id 0xc2, DeviceId0 0x20, DeviceId1 0x18 Flash [MX25L12845E] sectors: 256 Flash: 16 MB In: serial Out: serial Err: serial Net: ath_gmac_enet_initialize... athrs_sgmii_res_cal: cal value = 0xe Fetching MAC Address from 0x87fed9ec ath_gmac_enet_initialize: reset mask:c02200 Scorpion ---->8035 PHY* AR8035 PHY reg init : cfg1 0x80000000 cfg2 0x7114 eth0: 00:aa:bb:cc:dd:00 AR8035 found! [0:4]Phy ID 4d:d072 Port 0, Neg Success eth0 up eth0 Setting 0x18116290 to 0x458ba14f Hit any key to stop autoboot: 0 ## Booting image at 9f070000 ... Image Name: MIPS OpenWrt Linux-3.18.11 Created: 2016-12-23 12:57:39 UTC Image Type: MIPS Linux Kernel Image (gzip compressed) Data Size: 7132027 Bytes = 6.8 MB Load Address: 80060000 Entry Point: 80060000 Verifying Checksum at 0x9f070040 ...Bad Data CRC Speed is 1000T The firmware is corrupt, that is the problem. It takes me one day to find the right solution, but I don’t want to show you the whole shit i tried. So, only the interesting things. First we must make a little network from the PC to the Sophos AP. On the PC or an other device you must provide a TFTP-Server and a DHCP-Server. I use the following tools: http://www.dhcpserver.de/cms/ https://sourceforge.net/projects/tftp-server/ The problem is the AP knows rests of the network configuartion. When you download the firmware to the AP, It only takes it from the IP, that it shows up. Back in the putty-serial-session, you must stop U-Boot to load the corrupt image. At this step at the boot, press any key: Setting 0x18116290 to 0x458ba14f Hit any key to stop autoboot: 0 Then you are in the U-Boot-Bootloader, where the magic happends. Type help to see the possible commands: ath> help ? - alias for 'help' autoscr - run script from memory base - print or set address offset bdinfo - print Board Info structure boot - boot default, i.e., run 'bootcmd' bootd - boot default, i.e., run 'bootcmd' bootelf - Boot from an ELF image in memory bootm - boot application image from memory bootp - boot image via network using BootP/TFTP protocol bootvx - Boot vxWorks from an ELF image cmp - memory compare coninfo - print console devices and information cp - memory copy crc32 - checksum calculation dhcp - invoke DHCP client to obtain IP/boot params echo - echo args to console erase - erase FLASH memory ethreg - S26 PHY Reg rd/wr utility exit - exit script flinfo - print FLASH memory information go - start application at address 'addr' help - print online help iminfo - print header information for application image itest - return true/false on integer compare loop - infinite loop on address range md - memory display compute MD5 message digestmii - MII utility commands mm - memory modify (auto-incrementing) mtest - simple RAM test mw - memory write (fill) nfs - boot image via network using NFS protocol nm - memory modify (constant address) pci - list and access PCI Configuration Space ping - send ICMP ECHO_REQUEST to network host pll cpu-pll dither ddr-pll dither - Set to change CPU & DDR speed pll erase pll get printenv- print environment variables progmac - Set ethernet MAC addresses protect - enable or disable FLASH write protection rarpboot- boot image via network using RARP/TFTP protocol reset - Perform RESET of the CPU run - run commands in an environment variable saveenv - save environment variables to persistent storage sendmagic - (usage) send/broadcast MAGIC PACKET to network host - timeout for response - number of times magic to be sent to network host - baseaddr of sector containing devid - offset to base addr - offset to base addr sendsts - send status of firmware recovery process - 0 - send apstate, non-zero - send specified statuscode setenv - set environment variables sleep - delay execution for some time test - minimal test like /bin/sh tftpboot- boot image via network using TFTP protocol version - print monitor version We want to know the IP, from where the AP expect the firmware, so type: Tftpboot ath> tftpboot Speed is 1000T dup 1 speed 1000 Using eth0 device TFTP from server 192.168.99.8; our IP address is 192.168.99.9 Filename 'uImage_AP100'. Load address: 0x81000000 Loading: T T T T T T T T T T T T T T My AP wants to download it from 192.168.99.8 (the firmware must named exactly like the „Filename“ above). Now you must setup the DHCP-Server and the TFTP-Server on your PC to the IP-Range that the AP wants and connect the AP to the NIC where you put the DHCP-Server on. Give the TFTP-Server the address that the AP wants to have (in my case 192.168.99.8). You can download all the firmware files for the APs from your UTM. Connect via WinSCP to the UTM (you must enable shell access in the WebAdmin), connect with the loginuser. Go to /etc/wireless/firmware and download AP55.uimage Copy your firmware in your TFTP-Server-Root-Directory on your PC and name it like the AP it wants to have. In my case: uImage_AP100 (without filetype!) Then type the following in the putty-serial-connection: ath> tftpboot Speed is 1000T dup 1 speed 1000 Using eth0 device TFTP from server 192.168.99.8; our IP address is 192.168.99.9 Filename 'uImage_AP100'. Load address: 0x81000000 Loading: ################################################################# ################################################################# ################################################################# ############################ done Bytes transferred = 7132091 (6cd3bb hex) Now you have the Image on the AP at the address: 0x81000000 Now erase the flash memory. You must calculate the right memory spaces in hex. We have made it for the AP55, for other APs it can be different. You can flash other APs with this procedure, but with other memory spaces and other firmwares. ;-) I show you how we calculate from where to where we must erase the flash memory. Type: ath> bdinfo boot_params = 0x87F7BFB0 memstart = 0x80000000 memsize = 0x08000000 flashstart = 0x9F000000 flashsize = 0x01000000 flashoffset = 0x00029CD4 ethaddr = 00:00:AA:BB:CC:DD ip_addr = 192.168.99.9 baudrate = 115200 bps You can see the flashsize, this is important. When you boot the AP, and it ends up with bad-checksum error, you can see the memory address where the AP wants to find the boot-image, look here: ath> boot ## Booting image at 9f070000 ... Image Name: MIPS OpenWrt Linux-3.18.11 Created: 2016-12-23 12:57:39 UTC So you must add 0x9f070000 plus 0x01000000 with a hex-calculator. With the Windows Calc you can do that, the result is: A0070000 Type the following: ath> era 0x9f070000 0xA0070000 Erasing flash... First 0x7 last 0xff sector size 0x10000 255 Erased 249 sectors So, now you are ready to flash the firmware image to flash memory, that we put with TFTP at the address: 0x81000000 0x6cd3bb is the size of the image. That info we get from TFTP-copy-process at the end, watch above. 0x9f070000 is the address where U-Boot want to find the image, you can see it above at the moment of the boot. More infos for U-Boot: www.denx.de/.../UBootCmdGroupFlash ath> cp.b 0x81000000 0x9f070000 0x6cd3bb Copy to Flash... Copy 7132091 [0x6cd3bb] byte to Flash... write addr: 9f070000 Done Now you are ready to go. Type boot and have fun, now the following must be appear: ath> boot ## Booting image at 9f070000 ... Image Name: MIPS OpenWrt Linux-3.18.11 Created: 2016-12-23 12:57:39 UTC Image Type: MIPS Linux Kernel Image (gzip compressed) Data Size: 7132027 Bytes = 6.8 MB Load Address: 80060000 Entry Point: 80060000 Verifying Checksum at 0x9f070040 ...OK Uncompressing Kernel Image ... OK Starting kernel ... Later you can find it at Sophos UTM as a new AP and manage it. I hope, I can help a manny people with this HOW-TO. Sorry for my english and grammar failures. I type this fast and with a german Microsoft WORD.. Enjoy your new AP! :)

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