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connect: tell server that the client understands v1

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Teach the connection logic to tell a serve that it understands protocol
v1.  This is done in 2 different ways for the builtin transports, both
of which ultimately set 'GIT_PROTOCOL' to 'version=1' on the server.

1. git://
   A normal request to git-daemon is structured as
   "command path/to/repo\0host=..\0" and due to a bug introduced in
   49ba83fb6 (Add virtualization support to git-daemon, 2006-09-19) we
   aren't able to place any extra arguments (separated by NULs) besides
   the host otherwise the parsing of those arguments would enter an
   infinite loop.  This bug was fixed in 73bb33a94 (daemon: Strictly
   parse the "extra arg" part of the command, 2009-06-04) but a check
   was put in place to disallow extra arguments so that new clients
   wouldn't trigger this bug in older servers.

   In order to get around this limitation git-daemon was taught to
   recognize additional request arguments hidden behind a second
   NUL byte.  Requests can then be structured like:
   "command path/to/repo\0host=..\0\0version=1\0key=value\0".
   git-daemon can then parse out the extra arguments and set
   'GIT_PROTOCOL' accordingly.

   By placing these extra arguments behind a second NUL byte we can
   skirt around both the infinite loop bug in 49ba83fb6 (Add
   virtualization support to git-daemon, 2006-09-19) as well as the
   explicit disallowing of extra arguments introduced in 73bb33a94
   (daemon: Strictly parse the "extra arg" part of the command,
   2009-06-04) because both of these versions of git-daemon check for a
   single NUL byte after the host argument before terminating the
   argument parsing.

2. ssh://, file://
   Set 'GIT_PROTOCOL' environment variable with the desired protocol
   version.  With the file:// transport, 'GIT_PROTOCOL' can be set
   explicitly in the locally running git-upload-pack or git-receive-pack
   processes.  With the ssh:// transport and OpenSSH compliant ssh
   programs, 'GIT_PROTOCOL' can be sent across ssh by using '-o
   SendEnv=GIT_PROTOCOL' and having the server whitelist this
   environment variable.

Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Brandon Williams
2017-10-16 10:55:28 -07:00
committed by Junio C Hamano
parent 2609043da0
commit 0c2f0d2703
2 changed files with 255 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

37
connect.c
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@ -871,6 +871,7 @@ struct child_process *git_connect(int fd[2], const char *url,
printf("Diag: path=%s\n", path ? path : "NULL");
conn = NULL;
} else if (protocol == PROTO_GIT) {
struct strbuf request = STRBUF_INIT;
/*
* Set up virtual host information based on where we will
* connect, unless the user has overridden us in
@ -898,13 +899,25 @@ struct child_process *git_connect(int fd[2], const char *url,
* Note: Do not add any other headers here! Doing so
* will cause older git-daemon servers to crash.
*/
packet_write_fmt(fd[1],
"%s %s%chost=%s%c",
prog, path, 0,
target_host, 0);
strbuf_addf(&request,
"%s %s%chost=%s%c",
prog, path, 0,
target_host, 0);
/* If using a new version put that stuff here after a second null byte */
if (get_protocol_version_config() > 0) {
strbuf_addch(&request, '\0');
strbuf_addf(&request, "version=%d%c",
get_protocol_version_config(), '\0');
}
packet_write(fd[1], request.buf, request.len);
free(target_host);
strbuf_release(&request);
} else {
struct strbuf cmd = STRBUF_INIT;
const char *const *var;
conn = xmalloc(sizeof(*conn));
child_process_init(conn);
@ -917,7 +930,9 @@ struct child_process *git_connect(int fd[2], const char *url,
sq_quote_buf(&cmd, path);
/* remove repo-local variables from the environment */
conn->env = local_repo_env;
for (var = local_repo_env; *var; var++)
argv_array_push(&conn->env_array, *var);
conn->use_shell = 1;
conn->in = conn->out = -1;
if (protocol == PROTO_SSH) {
@ -971,6 +986,14 @@ struct child_process *git_connect(int fd[2], const char *url,
}
argv_array_push(&conn->args, ssh);
if (get_protocol_version_config() > 0) {
argv_array_push(&conn->args, "-o");
argv_array_push(&conn->args, "SendEnv=" GIT_PROTOCOL_ENVIRONMENT);
argv_array_pushf(&conn->env_array, GIT_PROTOCOL_ENVIRONMENT "=version=%d",
get_protocol_version_config());
}
if (flags & CONNECT_IPV4)
argv_array_push(&conn->args, "-4");
else if (flags & CONNECT_IPV6)
@ -985,6 +1008,10 @@ struct child_process *git_connect(int fd[2], const char *url,
argv_array_push(&conn->args, ssh_host);
} else {
transport_check_allowed("file");
if (get_protocol_version_config() > 0) {
argv_array_pushf(&conn->env_array, GIT_PROTOCOL_ENVIRONMENT "=version=%d",
get_protocol_version_config());
}
}
argv_array_push(&conn->args, cmd.buf);