NMT:firmware
Network Media Tank Firmware
I downloaded a random version of the firmware, which looks like:
-rw-rw-r-- 1 lundman lundman 32380583 Nov 8 00:58 01-13-071101-13-POP-402.zip
32Megs compressed. Inside that we have:
-rw-rw-r-- 1 lundman lundman 17970150 Nov 2 11:11 01-13-071101-13-POP-402-000.bin -rw-rw-r-- 1 lundman lundman 723 Nov 7 23:32 README.txt -rw-rw-r-- 1 lundman lundman 14536029 Nov 7 15:44 syb8634.nmt -rw-rw-r-- 1 lundman lundman 108 Nov 2 22:27 usbupdate.html
Looking at the large 01-13-071101-13-POP-402-000.bin file first, we notice that it seems to have 76 byte header of some sort, followed by a romfs called SPLASH_BOOT.
00000000 4c 00 00 00 22 5b 91 94 6c 2f 9f 6e 37 20 a1 2e |L..."[..l/.n7 ..| 00000010 8f 31 3c cd 61 59 d4 c4 53 aa 66 5b e6 00 ae 58 |.1<.aY..S.f[...X| 00000020 ee 3a 1a 92 0c e6 02 b3 22 8b 29 7c 50 9f 8e d0 |.:......".)|P...| 00000030 87 8a 91 09 32 a9 df df 68 0a 86 43 3d 7c 59 93 |....2...h..C=|Y.| 00000040 ce 85 27 59 56 bd 36 bf 76 8d 6d db 2d 72 6f 6d |..'YV.6.v.m.-rom| 00000050 31 66 73 2d 00 53 18 f0 40 a7 b4 ad 53 50 4c 41 |1fs-.S..@...SPLA| 00000060 53 48 5f 42 4f 4f 54 00 00 00 00 00 00 00 00 49 |SH_BOOT........I|
If we cut out the first 76 bytes and mount it, we get:
-rw-r--r-- 1 root root 881252 Jan 1 1970 10xrpc_xload_audio_ucode_SMP8634_2.7.176sybs1.7972x_GCC4_facsprod.bin -rw-r--r-- 1 root root 326500 Jan 1 1970 11xrpc_xload_video_ucode_SMP8634_2.7.176sybs1.7972x_GCC4_facsprod.bin -rw-r--r-- 1 root root 30724 Jan 1 1970 12xrpc_xload_demux_ucode_SMP8634_2.7.176sybs1.7972x_GCC4_facsprod.bin -rwxr-xr-x 1 root root 773 Jan 1 1970 30vsyncparam_SMP8634_2.7.176sybs1.7972x_GCC4_facsprod.zbf -rwxr-xr-x 1 root root 34262 Jan 1 1970 31bitmap_SMP8634_2.7.176sybs1.7972x_GCC4_facsprod.zbf -rw-r--r-- 1 root root 6404 Jan 1 1970 32xrpc_xload_dviinit_prod.bin -rw-r--r-- 1 root root 189524 Jan 1 1970 33xrpc_xload_irq_handler_SMP8634_2.7.176sybs1.7972x_GCC4_facsprod.bin -rw-r--r-- 1 root root 3975492 Jan 1 1970 50xrpc_xload_vmlinux_ES4_prod.bin -rwxr-xr-x 1 root root 64 Jan 1 1970 dvi.bin
Definitely hardware boot. Loads the various microcodes for the Sigma 8635 chip, which personally I am not interested in. Lastly we appear to have the kernel itself at about 4Megs. However, all up, the whole thing is only 5MB in size. So there is more in the first file after the romfs. One of the values in the header is probably an offset. The size of the romfs is roughly 5.2MB, or 00531c00 in hex. Romfs header has 005318f0, plus 76 bytes at a guess.
But romfs are padded up to nearest 1024. So the size will be 00531c00, plus 76 bytes. This becomes 00531c4c.
005318e0 00 00 00 00 00 00 00 40 39 20 28 88 64 76 69 2e |.......@9 (.dvi.|
005318f0 62 69 6e 00 00 00 00 00 00 00 00 00 00 00 00 00 |bin.............|
00531900 01 00 00 00 00 00 64 00 72 00 00 00 02 00 00 00 |......d.r.......|
00531910 08 00 00 00 37 00 00 00 0c 00 00 00 89 00 00 00 |....7...........|
00531920 0f 00 00 00 04 00 00 00 33 00 00 00 30 00 00 00 |........3...0...|
00531930 3e 00 00 00 00 00 00 00 03 fe 9b ff 00 00 00 00 |>...............|
00531940 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 |................|
00531c50 05 00 00 00 c0 7c 00 00 00 00 00 00 00 00 00 00 |.....|..........|
00531c60 00 00 00 00 00 00 00 00 f4 80 00 00 04 00 ff 07 |................|
00531c70 d5 94 c5 33 40 8d 18 9e 17 41 5c e2 ad 49 9e 19 |...3@....A\..I..|
00531c80 11 6b a1 d5 21 76 76 4e 10 60 40 9e 7a 1d 01 52 |.k..!vvN.`@.z..R|
00531c90 89 5f c7 3a 98 bc 7f ef b5 fe fd fa 7b 36 0b 32 |._.:........{6.2|
00531ca0 7f 29 ba 91 91 85 2c 77 fe 4a 14 c8 cf 91 0c 34 |.)....,w.J.....4|
00531cb0 5b 55 44 45 32 85 c7 9f ed d0 26 d7 93 3d c7 b1 |[UDE2.....&..=..|
00531cc0 1a 7c 59 6b de db 10 c5 48 da 73 c7 6c a2 f1 0e |.|Yk....H.s.l...|
I have no idea what this is. Probably compressed as it has no strings in it, nor repeated patterns. If I attempt to compress it, the filesize changes by less than 1%, so it is most likely compressed.
Appears not to be jffs2. Does not have the expected magic, not does jffs2dump like it at all.
Similarly, if you read the kernel image itself (to find out what filesystems it supports) I find it has the same header:
00000000 00 00 00 00 05 00 00 00 20 a6 3c 00 00 00 00 13 |........ .<.....| 00000010 02 00 00 00 03 00 00 00 04 00 00 00 44 a9 3c 00 |............D.<.| 00000020 0c 00 01 ff 97 80 fc f4 6b 69 38 93 ef 8a 6e cf |........ki8...n.| 00000320 3c 0f e2 a6 46 4e 49 42 11 00 00 10 00 00 02 90 |<...FNIB........| 00000330 00 00 02 90 ac f6 e5 ba 00 00 03 02 f1 a5 3c 00 |..............<.| 00000340 00 00 00 00 1f 8b 08 08 26 a6 2a 47 02 03 76 6d |........&.*G..vm| 00000350 6c 69 6e 75 78 2e 62 69 6e 00 ec 5b 0f 6c 1c 55 |linux.bin..[.l.U| 00000360 7a ff 76 76 76 bd 0e 1b 3c 76 36 61 43 02 d9 b1 |z.vvv...<v6aC...|
Indeed all files inside the romfs has this header. Could just mean they are signed.
The syb8634.nmt is completely different. It has repeating patterns of 80 bf 00 fe 02 f8 0b e0 2f (weakness?) but not much else to go on.