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Git-aware CGI to provide dumb HTTP transport

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The git-http-backend CGI can be configured into any Apache server
using ScriptAlias, such as with the following configuration:

  LoadModule cgi_module /usr/libexec/apache2/mod_cgi.so
  LoadModule alias_module /usr/libexec/apache2/mod_alias.so
  ScriptAlias /git/ /usr/libexec/git-core/git-http-backend/

Repositories are accessed via the translated PATH_INFO.

The CGI is backwards compatible with the dumb client, allowing all
older HTTP clients to continue to download repositories which are
managed by the CGI.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Shawn O. Pearce 2009-10-30 17:47:32 -07:00 committed by Junio C Hamano
parent d8f67d205e
commit 2f4038ab33
4 changed files with 396 additions and 0 deletions
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1
.gitignore vendored
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@ -55,6 +55,7 @@ git-get-tar-commit-id
git-grep
git-hash-object
git-help
git-http-backend
git-http-fetch
git-http-push
git-imap-send

105
Documentation/git-http-backend.txt Normal file
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@ -0,0 +1,105 @@
git-http-backend(1)
===================
NAME
----
git-http-backend - Server side implementation of Git over HTTP
SYNOPSIS
--------
[verse]
'git-http-backend'
DESCRIPTION
-----------
A simple CGI program to serve the contents of a Git repository to Git
clients accessing the repository over http:// and https:// protocols.
By default, only the `upload-pack` service is enabled, which serves
'git-fetch-pack' and 'git-ls-remote' clients, which are invoked from
'git-fetch', 'git-pull', and 'git-clone'.
This is ideally suited for read-only updates, i.e., pulling from
git repositories.
URL TRANSLATION
---------------
'git-http-backend' relies on the invoking web server to perform
URL to path translation, and store the repository path into the
PATH_TRANSLATED environment variable. Most web servers will do
this translation automatically, resolving the suffix after the
CGI name relative to the server's document root.
EXAMPLES
--------
Apache 2.x::
To serve all Git repositories contained within the '/git/'
subdirectory of the DocumentRoot, ensure mod_cgi and
mod_alias are enabled, and create a ScriptAlias to the CGI:
+
----------------------------------------------------------------
ScriptAlias /git/ /usr/libexec/git-core/git-http-backend/git/
<Directory /usr/libexec/git-core>
Options None
</Directory>
<Files /usr/libexec/git-core/git-http-backend>
Options ExecCGI
</Files>
----------------------------------------------------------------
+
To require authentication for reads, use a Directory
directive around the repository, or one of its parent directories:
+
----------------------------------------------------------------
<Directory /var/www/git/private>
AuthType Basic
AuthName "Private Git Access"
Require group committers
...
</Directory>
----------------------------------------------------------------
Accelerated static Apache 2.x::
Similar to the above, but Apache can be used to return static
files that are stored on disk. On many systems this may
be more efficient as Apache can ask the kernel to copy the
file contents from the file system directly to the network:
+
----------------------------------------------------------------
DocumentRoot /var/www
ScriptAlias /git/ /usr/libexec/git-core/git-http-backend/git/
Alias /git_static/ /var/www/git/
RewriteEngine on
RewriteRule ^/git/(.*/objects/[0-9a-f]{2}/[0-9a-f]{38})$ /git_static/$1 [PT]
RewriteRule ^/git/(.*/objects/pack/pack-[0-9a-f]{40}.pack)$ /git_static/$1 [PT]
RewriteRule ^/git/(.*/objects/pack/pack-[0-9a-f]{40}.idx)$ /git_static/$1 [PT]
----------------------------------------------------------------
ENVIRONMENT
-----------
'git-http-backend' relies upon the CGI environment variables set
by the invoking web server, including:
* PATH_TRANSLATED
* REMOTE_USER
* REMOTE_ADDR
* CONTENT_TYPE
* QUERY_STRING
* REQUEST_METHOD
Author
------
Written by Shawn O. Pearce <spearce@spearce.org>.
Documentation
--------------
Documentation by Shawn O. Pearce <spearce@spearce.org>.
GIT
---
Part of the linkgit:git[1] suite

1
Makefile
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@ -365,6 +365,7 @@ PROGRAMS += git-show-index$X
PROGRAMS += git-unpack-file$X
PROGRAMS += git-upload-pack$X
PROGRAMS += git-var$X
PROGRAMS += git-http-backend$X
# List built-in command $C whose implementation cmd_$C() is not in
# builtin-$C.o but is linked in as part of some other command.

289
http-backend.c Normal file
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@ -0,0 +1,289 @@
#include "cache.h"
#include "refs.h"
#include "pkt-line.h"
#include "object.h"
#include "tag.h"
#include "exec_cmd.h"
static const char content_type[] = "Content-Type";
static const char content_length[] = "Content-Length";
static const char last_modified[] = "Last-Modified";
static void format_write(int fd, const char *fmt, ...)
{
static char buffer[1024];
va_list args;
unsigned n;
va_start(args, fmt);
n = vsnprintf(buffer, sizeof(buffer), fmt, args);
va_end(args);
if (n >= sizeof(buffer))
die("protocol error: impossibly long line");
safe_write(fd, buffer, n);
}
static void http_status(unsigned code, const char *msg)
{
format_write(1, "Status: %u %s\r\n", code, msg);
}
static void hdr_str(const char *name, const char *value)
{
format_write(1, "%s: %s\r\n", name, value);
}
static void hdr_int(const char *name, size_t value)
{
format_write(1, "%s: %" PRIuMAX "\r\n", name, value);
}
static void hdr_date(const char *name, unsigned long when)
{
const char *value = show_date(when, 0, DATE_RFC2822);
hdr_str(name, value);
}
static void hdr_nocache(void)
{
hdr_str("Expires", "Fri, 01 Jan 1980 00:00:00 GMT");
hdr_str("Pragma", "no-cache");
hdr_str("Cache-Control", "no-cache, max-age=0, must-revalidate");
}
static void hdr_cache_forever(void)
{
unsigned long now = time(NULL);
hdr_date("Date", now);
hdr_date("Expires", now + 31536000);
hdr_str("Cache-Control", "public, max-age=31536000");
}
static void end_headers(void)
{
safe_write(1, "\r\n", 2);
}
static NORETURN void not_found(const char *err, ...)
{
va_list params;
http_status(404, "Not Found");
hdr_nocache();
end_headers();
va_start(params, err);
if (err && *err)
vfprintf(stderr, err, params);
va_end(params);
exit(0);
}
static void send_strbuf(const char *type, struct strbuf *buf)
{
hdr_int(content_length, buf->len);
hdr_str(content_type, type);
end_headers();
safe_write(1, buf->buf, buf->len);
}
static void send_file(const char *the_type, const char *name)
{
const char *p = git_path("%s", name);
size_t buf_alloc = 8192;
char *buf = xmalloc(buf_alloc);
int fd;
struct stat sb;
size_t size;
fd = open(p, O_RDONLY);
if (fd < 0)
not_found("Cannot open '%s': %s", p, strerror(errno));
if (fstat(fd, &sb) < 0)
die_errno("Cannot stat '%s'", p);
size = xsize_t(sb.st_size);
hdr_int(content_length, size);
hdr_str(content_type, the_type);
hdr_date(last_modified, sb.st_mtime);
end_headers();
while (size) {
ssize_t n = xread(fd, buf, buf_alloc);
if (n < 0)
die_errno("Cannot read '%s'", p);
if (!n)
break;
safe_write(1, buf, n);
}
close(fd);
free(buf);
}
static void get_text_file(char *name)
{
hdr_nocache();
send_file("text/plain", name);
}
static void get_loose_object(char *name)
{
hdr_cache_forever();
send_file("application/x-git-loose-object", name);
}
static void get_pack_file(char *name)
{
hdr_cache_forever();
send_file("application/x-git-packed-objects", name);
}
static void get_idx_file(char *name)
{
hdr_cache_forever();
send_file("application/x-git-packed-objects-toc", name);
}
static int show_text_ref(const char *name, const unsigned char *sha1,
int flag, void *cb_data)
{
struct strbuf *buf = cb_data;
struct object *o = parse_object(sha1);
if (!o)
return 0;
strbuf_addf(buf, "%s\t%s\n", sha1_to_hex(sha1), name);
if (o->type == OBJ_TAG) {
o = deref_tag(o, name, 0);
if (!o)
return 0;
strbuf_addf(buf, "%s\t%s^{}\n", sha1_to_hex(o->sha1), name);
}
return 0;
}
static void get_info_refs(char *arg)
{
struct strbuf buf = STRBUF_INIT;
for_each_ref(show_text_ref, &buf);
hdr_nocache();
send_strbuf("text/plain", &buf);
strbuf_release(&buf);
}
static void get_info_packs(char *arg)
{
size_t objdirlen = strlen(get_object_directory());
struct strbuf buf = STRBUF_INIT;
struct packed_git *p;
size_t cnt = 0;
prepare_packed_git();
for (p = packed_git; p; p = p->next) {
if (p->pack_local)
cnt++;
}
strbuf_grow(&buf, cnt * 53 + 2);
for (p = packed_git; p; p = p->next) {
if (p->pack_local)
strbuf_addf(&buf, "P %s\n", p->pack_name + objdirlen + 6);
}
strbuf_addch(&buf, '\n');
hdr_nocache();
send_strbuf("text/plain; charset=utf-8", &buf);
strbuf_release(&buf);
}
static NORETURN void die_webcgi(const char *err, va_list params)
{
char buffer[1000];
http_status(500, "Internal Server Error");
hdr_nocache();
end_headers();
vsnprintf(buffer, sizeof(buffer), err, params);
fprintf(stderr, "fatal: %s\n", buffer);
exit(0);
}
static struct service_cmd {
const char *method;
const char *pattern;
void (*imp)(char *);
} services[] = {
{"GET", "/HEAD$", get_text_file},
{"GET", "/info/refs$", get_info_refs},
{"GET", "/objects/info/alternates$", get_text_file},
{"GET", "/objects/info/http-alternates$", get_text_file},
{"GET", "/objects/info/packs$", get_info_packs},
{"GET", "/objects/[0-9a-f]{2}/[0-9a-f]{38}$", get_loose_object},
{"GET", "/objects/pack/pack-[0-9a-f]{40}\\.pack$", get_pack_file},
{"GET", "/objects/pack/pack-[0-9a-f]{40}\\.idx$", get_idx_file}
};
int main(int argc, char **argv)
{
char *method = getenv("REQUEST_METHOD");
char *dir = getenv("PATH_TRANSLATED");
struct service_cmd *cmd = NULL;
char *cmd_arg = NULL;
int i;
git_extract_argv0_path(argv[0]);
set_die_routine(die_webcgi);
if (!method)
die("No REQUEST_METHOD from server");
if (!strcmp(method, "HEAD"))
method = "GET";
if (!dir)
die("No PATH_TRANSLATED from server");
for (i = 0; i < ARRAY_SIZE(services); i++) {
struct service_cmd *c = &services[i];
regex_t re;
regmatch_t out[1];
if (regcomp(&re, c->pattern, REG_EXTENDED))
die("Bogus regex in service table: %s", c->pattern);
if (!regexec(&re, dir, 1, out, 0)) {
size_t n = out[0].rm_eo - out[0].rm_so;
if (strcmp(method, c->method)) {
const char *proto = getenv("SERVER_PROTOCOL");
if (proto && !strcmp(proto, "HTTP/1.1"))
http_status(405, "Method Not Allowed");
else
http_status(400, "Bad Request");
hdr_nocache();
end_headers();
return 0;
}
cmd = c;
cmd_arg = xmalloc(n);
strncpy(cmd_arg, dir + out[0].rm_so + 1, n);
cmd_arg[n] = '\0';
dir[out[0].rm_so] = 0;
break;
}
regfree(&re);
}
if (!cmd)
not_found("Request not supported: '%s'", dir);
setup_path();
if (!enter_repo(dir, 0))
not_found("Not a git repository: '%s'", dir);
cmd->imp(cmd_arg);
return 0;
}