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Third-party and open-source code in the VT1200 ROM

A map of the non-DEC code in vt1200_v22.bin (md5 b46a3e442ccb86134d2356bd70d22fd2), and how each identification was made.

Two kinds of evidence are used, and they are not equivalent:

  • Source IDs — $Header: (RCS) and @(#) (SCCS) strings compiled into the image. These name the original source file and, for RCS, the revision and date. Strong, but they are file names, not a licence statement.
  • Code match — disassembly compared with a known source tree (e.g. the X11R4 sources under reference/x11/r4).

Copyright strings are quoted where they exist. The absence of a copyright string is not evidence of absence: most of this code carries its notice in source comments, which do not survive compilation.

Summary

component evidence notes
MIT X11 R4 mfb*, pcf*, snf*, bdf*, Xlib strings; exact match to reference/x11/r4/.../pcfrbitmaps.c X server + Xlib + font parsers
BSD 4.3-era TCP/IP $Header/@(#) IDs for the full socket/TCP/IP/mbuf file set ported at DEC by craig, 1989-10-05/06
BSD BIND resolver res_comp.c, res_init.c, res_mkquery.c, res_send.c, gethostent.c classic 4.8/4.9-era resolver
BSD telnet + TN3270 telnet.c, commands.c, network.c, ring.c, sys_bsd.c, terminal.c, utilities.c, tn3270.c same 1989 import
BSD inetd inetd.c
BSD lpd lineage lpd_lance_devdriver.c LANCE driver for the printer daemon
BSD libc pieces strcasecmp.c, ctype.c, errlst.c, inet_addr.c, inet_ntoa.c mixed with the TI runtime (below)
TI C runtime V2.00 ROM strlen/strcpy/strcmp match RTS.SRC instruction for instruction proprietary, shipped with the SDK
Bitstream / Bigelow & Holmes / DEC Japan fonts copyright strings, font names third-party, not open source

1. MIT X11 R4

The largest non-BSD body. The server is the MIT sample server, with both framebuffer implementations:

  • mfbValidateGC, mfbFaultGlyph, mfbFreeGlyphCacheSpace, mfbDestroyDMD — monochrome framebuffer (mfb).
  • cfb strings are present as well (colour framebuffer), though the VT1200 is monochrome.
  • Font formats: pcfReadBitmaps, pcfReadProperties, pcfReadMetrics, pcfReadEncoding, pcfReadAccelerators, Invalid SNF font file format, unknown bdf encoding format.
  • Xlib: BadLength - request length incorrect; internal Xlib error, Xlib: sequence lost, XlibMessage, /usr/lib/X11/XErrorDB.

The PCF error strings match reference/x11/r4/contrib/server/pcf/fonts/lib/pcf/pcfrbitmaps.c byte for byte (including allocation failure in pcfReadBitmaps (offsets,%d), which R5's monolithic pcfread.c does not contain). That is the basis for calling it R4 rather than "X11 generally".

There is no X11 copyright string in the image; the identification is code-level.

2. BSD TCP/IP stack

The file IDs are the classic BSD 4.3/Net-1 set. RCS headers show a bulk import by craig on 1989-10-05/06, with later files (e.g. route.c) on 1990-03-15.

layer source files
sockets / mbufs uipc_domain.c, uipc_mbuf.c, uipc_proto.c, uipc_socket.c, uipc_socket2.c, uipc_usrreq.c, sys_socket.c, mbuf_calls.c, uio.c, syscalls.c, af.c
TCP tcp_input.c, tcp_output.c, tcp_subr.c, tcp_timer.c, tcp_usrreq.c, tcp_debug.c
UDP / IP / ICMP / raw udp_usrreq.c, ip_input.c, ip_output.c, ip_icmp.c, raw_ip.c, raw_cb.c, raw_usrreq.c
interfaces / routing if.c, if_ether.c, if_loop.c, if_sl.c, route.c, in.c, in_pcb.c, in_cksum.c, in_proto.c, inet_addr.c, inet_ntoa.c

if_sl.c (SLIP) is the clearest sign that this is the stock BSD file set rather than a lookalike.

DEC's own additions in the same area are distinguishable by name and by the absence of SCCS/RCS IDs: lance_inet_interface.c, dwt_file.c, dwt_tftp.c, sys_dwt.c, server.c, init.c, test.c, xclients_smlat_dispatch.c, inode.c.

Licence caveat: no "Regents of the University of California" string appears in the image. The BSD notice was in source comments. The RCS/SCCS IDs and the file set establish lineage; they do not establish the licence text that accompanied it.

3. BSD resolver, telnet and inetd

  • BIND resolver: res_comp.c, res_init.c, res_mkquery.c, res_send.c, plus gethostent.c. This is the 4.8/4.9-era resolver, the source of the "Primary name server IP address %s is invalid." path.
  • telnet: telnet.c, commands.c, main.c, network.c, ring.c, sys_bsd.c, terminal.c, utilities.c, tn3270.c. This is the whole BSD telnet client source set, including TN3270.
  • inetd: inetd.c.
  • lpd lineage: lpd_lance_devdriver.c — the LANCE device driver for the printer daemon; the lpd_ prefix points at BSD lpd.

4. TI C runtime — not open source, but identifiable

The ROM's string and memory functions are the TI RTS V2.00, not BSD:

  • ROM strlen at 0x07F68B1A implements exactly rstr = string - 1; n = 0; while (*++rstr) n++;
  • ROM strcpy at 0x07F68AE4 matches the RTS loop and return value.
  • ROM strcmp at 0x07F68AA0 matches the RTS comparison.
  • ROM memcpy at 0x07F68880 is PIXBLT_L_L, consistent with the RTS memcpy → movmem.

The SDK ships RTS.LIB, RTS.SRC (full source), FLIB.LIB and the headers on the 1987 C-tools floppy (1987-11-06 TMS34010 Simulator-C Tools-ASM Tools.img, dir C2).

The allocator is not the RTS one. RTS.SRC's memory.c uses a 1000-byte static sys_memory; the ROM's malloc (0x07EE0246) is a multi-arena allocator over the 4 MiB RAM (0x1E8930 arenas, global pool 0x1E8AC0). So the firmware mixes the TI runtime (strings, ctype, qsort, printf) with a different memory manager.

5. Fonts (third-party, not open source)

Copyright strings in the font data:

  • Copyright (c) 1988 Bigelow & Holmes Inc. — Pellucida.
  • Copyright (c) 1988 Bitstream, Inc., Portions Copyright 1988 Digital Equipment Corp. — Bitstream Terminal.
  • Copyright (c) 1988 Digital Equipment Corporation Japan. — JISX0208 Kanji.
  • Copyright (c) 1988/1990 Digital Equipment Corp. — DEC Terminal, DECtech.

6. Checked and not found

No regex/regcomp, no curses or termcap, no getopt, no crypt strings, no MD5, no zlib, no NFS, no SNMP, no Kerberos, no PEX/XIE server extensions. The ICE and XIE substring counts are noise ("device", "service", …), not the X11 protocols.

7. Open question: the dwt_prf transform

The rdebug challenge is structurally DES: eight 64-entry S-box tables at 0x1C0200, 6-bit indices, 16 Feistel rounds, a fixed key schedule. There are no DES or crypt strings, so the implementation is not attributable from the binary alone. If it is standard DES with a fixed key, the challenge is much weaker than the "font render + Feistel" description first suggested.

Reproduce

cd /home/arti/code/k-space/vt1200

# every compiled source id, unique
rg -o '@\(#\)[A-Za-z0-9_.-]+|\$Header: [A-Za-z0-9_.-]+' \
   reference/rom-strings.txt | sed 's/@(#)//; s/\$Header: //' | sort -u

# X11 fingerprints
rg -n 'mfb|pcf|snf|bdf|Xlib|XErrorDB' reference/rom-strings.txt

# font copyrights
rg -n 'Copyright \(c\) 1988 (Bigelow|Bitstream)|Digital Equipment Corporation Japan' \
   reference/rom-strings.txt
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