1 b9220ca4 2021-01-11 op # gmid
 2 3e4749f7 2020-10-02 op 
 3 b9220ca4 2021-01-11 op > dead simple, zero configuration Gemini server
 4 3e4749f7 2020-10-02 op 
 5 881a9dd9 2021-01-16 op gmid is a simple and minimal Gemini server.  It can run without
 6 881a9dd9 2021-01-16 op configuration, so it's well suited for local development, but at the
 7 881a9dd9 2021-01-16 op same time has a configuration file flexible enough to meet the
 8 881a9dd9 2021-01-16 op requirements of most capsules.
 9 3e4749f7 2020-10-02 op 
10 881a9dd9 2021-01-16 op gmid was initially written to serve static files, but can also
11 881a9dd9 2021-01-16 op optionally execute CGI scripts.  It was also written with security in
12 ea58dab1 2021-01-17 op mind: on Linux, FreeBSD and OpenBSD is sandboxed via `seccomp(2)`,
13 ea58dab1 2021-01-17 op `capsicum(4)`and `pledge(2)`+`unveil(2)` respectively.
14 3e4749f7 2020-10-02 op 
15 3e4749f7 2020-10-02 op 
16 b9220ca4 2021-01-11 op ## Features
17 3e4749f7 2020-10-02 op 
18 4d2ec6d7 2021-01-13 op  - IRI support (RFC3987)
19 b9220ca4 2021-01-11 op  - dual stack: can serve over both IPv4 and IPv6
20 b9220ca4 2021-01-11 op  - CGI scripts
21 b9220ca4 2021-01-11 op  - (very) low memory footprint
22 b9220ca4 2021-01-11 op  - small codebase, easily hackable
23 b9220ca4 2021-01-11 op  - virtual hosts
24 ea58dab1 2021-01-17 op  - sandboxed by default on OpenBSD, Linux and FreeBSD
25 3e4749f7 2020-10-02 op 
26 fab952e1 2020-10-03 op 
27 b9220ca4 2021-01-11 op ## Drawbacks
28 3e4749f7 2020-10-02 op 
29 b9220ca4 2021-01-11 op  - not suited for very busy hosts.  If you receive an high number of
30 b9220ca4 2021-01-11 op    connection per-second you'd probably want to run multiple gmid
31 b9220ca4 2021-01-11 op    instances behind relayd/haproxy or a different server.
32 85dff1f9 2021-01-11 op 
33 b9220ca4 2021-01-11 op ## Building
34 3e4749f7 2020-10-02 op 
35 5f564d23 2021-01-17 op gmid depends on a POSIX libc and libtls (provided either by LibreSSL
36 5f564d23 2021-01-17 op or libretls).  At build time, flex and yacc (or GNU bison) are also
37 5f564d23 2021-01-17 op needed.
38 3e4749f7 2020-10-02 op 
39 771d8f28 2021-01-17 op The build is as simple as
40 3e4749f7 2020-10-02 op 
41 b9220ca4 2021-01-11 op     make
42 3e4749f7 2020-10-02 op 
43 771d8f28 2021-01-17 op To install execute:
44 881a9dd9 2021-01-16 op 
45 771d8f28 2021-01-17 op     make install
46 771d8f28 2021-01-17 op 
47 17b09e3c 2021-01-18 op If you have trouble installing LibreSSL or libretls, as they aren't
48 17b09e3c 2021-01-18 op available as package on various Linux distribution, you can use Docker
49 17b09e3c 2021-01-18 op to build a `gmid` image with:
50 771d8f28 2021-01-17 op 
51 17b09e3c 2021-01-18 op     docker build -t gmid .
52 17b09e3c 2021-01-18 op 
53 17b09e3c 2021-01-18 op and then run it with something along the lines of
54 17b09e3c 2021-01-18 op 
55 17b09e3c 2021-01-18 op     docker run --rm -it -p 1965:1965 \
56 17b09e3c 2021-01-18 op         -v /path/to/cert.pem:...:ro \
57 17b09e3c 2021-01-18 op         -v /path/to/key.pem:...:ro \
58 17b09e3c 2021-01-18 op         -v /path/to/docs:/var/gemini \
59 17b09e3c 2021-01-18 op         gmid -f -d /var/gemini -K ... -C ...
60 17b09e3c 2021-01-18 op 
61 17b09e3c 2021-01-18 op ellipses used for brevity.
62 17b09e3c 2021-01-18 op 
63 17b09e3c 2021-01-18 op 
64 881a9dd9 2021-01-16 op ## Architecture/Security considerations
65 881a9dd9 2021-01-16 op 
66 881a9dd9 2021-01-16 op gmid is composed by two processes: a listener and an executor.  The
67 881a9dd9 2021-01-16 op listener process is the only one that needs internet access and is
68 881a9dd9 2021-01-16 op sandboxed.  When a CGI script needs to be executed, the executor
69 881a9dd9 2021-01-16 op (outside of the sandbox) sets up a pipe and gives one end to the
70 881a9dd9 2021-01-16 op listener, while the other is bound to the CGI script standard output.
71 881a9dd9 2021-01-16 op This way, is still possible to execute CGI scripts without restriction
72 15209ad9 2021-01-21 op even in the presence of a sandbox.
73 881a9dd9 2021-01-16 op 
74 881a9dd9 2021-01-16 op On OpenBSD, the listener process runs with the `stdio recvfd rpath
75 881a9dd9 2021-01-16 op inet` pledges and has `unveil(2)`ed only the directories that it
76 ea58dab1 2021-01-17 op serves; the executor has `stdio sendfd proc exec` as pledges.
77 881a9dd9 2021-01-16 op 
78 ea58dab1 2021-01-17 op On FreeBSD, the executor process is sandboxed with `capsicum(4)`.
79 d939d0f0 2021-01-17 op 
80 76fd55f4 2021-01-17 op On Linux, a `seccomp(2)` filter is installed to allow only certain
81 76fd55f4 2021-01-17 op syscalls, see [sandbox.c](sandbox.c) for more information on the BPF
82 ea58dab1 2021-01-17 op program.
83 ea58dab1 2021-01-17 op 
84 ea58dab1 2021-01-17 op In any case, you are invited to run gmid inside some sort of
85 ea58dab1 2021-01-17 op container/jail.