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git/builtin/push.c
Junio C Hamano a85b377d04 push: the beginning of "git push --signed" 
While signed tags and commits assert that the objects thusly signed
came from you, who signed these objects, there is not a good way to
assert that you wanted to have a particular object at the tip of a
particular branch.  My signing v2.0.1 tag only means I want to call
the version v2.0.1, and it does not mean I want to push it out to my
'master' branch---it is likely that I only want it in 'maint', so
the signature on the object alone is insufficient.

The only assurance to you that 'maint' points at what I wanted to
place there comes from your trust on the hosting site and my
authentication with it, which cannot easily audited later.

Introduce a mechanism that allows you to sign a "push certificate"
(for the lack of better name) every time you push, asserting that
what object you are pushing to update which ref that used to point
at what other object.  Think of it as a cryptographic protection for
ref updates, similar to signed tags/commits but working on an
orthogonal axis.

The basic flow based on this mechanism goes like this:

 1. You push out your work with "git push --signed".

 2. The sending side learns where the remote refs are as usual,
    together with what protocol extension the receiving end
    supports.  If the receiving end does not advertise the protocol
    extension "push-cert", an attempt to "git push --signed" fails.

    Otherwise, a text file, that looks like the following, is
    prepared in core:

	certificate version 0.1
	pusher Junio C Hamano <gitster@pobox.com> 1315427886 -0700

	7339ca65... 21580ecb... refs/heads/master
	3793ac56... 12850bec... refs/heads/next

    The file begins with a few header lines, which may grow as we
    gain more experience.  The 'pusher' header records the name of
    the signer (the value of user.signingkey configuration variable,
    falling back to GIT_COMMITTER_{NAME|EMAIL}) and the time of the
    certificate generation.  After the header, a blank line follows,
    followed by a copy of the protocol message lines.

    Each line shows the old and the new object name at the tip of
    the ref this push tries to update, in the way identical to how
    the underlying "git push" protocol exchange tells the ref
    updates to the receiving end (by recording the "old" object
    name, the push certificate also protects against replaying).  It
    is expected that new command packet types other than the
    old-new-refname kind will be included in push certificate in the
    same way as would appear in the plain vanilla command packets in
    unsigned pushes.

    The user then is asked to sign this push certificate using GPG,
    formatted in a way similar to how signed tag objects are signed,
    and the result is sent to the other side (i.e. receive-pack).

    In the protocol exchange, this step comes immediately before the
    sender tells what the result of the push should be, which in
    turn comes before it sends the pack data.

 3. When the receiving end sees a push certificate, the certificate
    is written out as a blob.  The pre-receive hook can learn about
    the certificate by checking GIT_PUSH_CERT environment variable,
    which, if present, tells the object name of this blob, and make
    the decision to allow or reject this push.  Additionally, the
    post-receive hook can also look at the certificate, which may be
    a good place to log all the received certificates for later
    audits.

Because a push certificate carry the same information as the usual
command packets in the protocol exchange, we can omit the latter
when a push certificate is in use and reduce the protocol overhead.
This however is not included in this patch to make it easier to
review (in other words, the series at this step should never be
released without the remainder of the series, as it implements an
interim protocol that will be incompatible with the final one).
As such, the documentation update for the protocol is left out of
this step.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-09-15 13:23:20 -07:00

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/*
* "git push"
*/
#include "cache.h"
#include "refs.h"
#include "run-command.h"
#include "builtin.h"
#include "remote.h"
#include "transport.h"
#include "parse-options.h"
#include "submodule.h"
static const char * const push_usage[] = {
N_("git push [<options>] [<repository> [<refspec>...]]"),
NULL,
};
static int thin = 1;
static int deleterefs;
static const char *receivepack;
static int verbosity;
static int progress = -1;
static struct push_cas_option cas;
static const char **refspec;
static int refspec_nr;
static int refspec_alloc;
static void add_refspec(const char *ref)
{
refspec_nr++;
ALLOC_GROW(refspec, refspec_nr, refspec_alloc);
refspec[refspec_nr-1] = ref;
}
static const char *map_refspec(const char *ref,
struct remote *remote, struct ref *local_refs)
{
struct ref *matched = NULL;
/* Does "ref" uniquely name our ref? */
if (count_refspec_match(ref, local_refs, &matched) != 1)
return ref;
if (remote->push) {
struct refspec query;
memset(&query, 0, sizeof(struct refspec));
query.src = matched->name;
if (!query_refspecs(remote->push, remote->push_refspec_nr, &query) &&
query.dst) {
struct strbuf buf = STRBUF_INIT;
strbuf_addf(&buf, "%s%s:%s",
query.force ? "+" : "",
query.src, query.dst);
return strbuf_detach(&buf, NULL);
}
}
if (push_default == PUSH_DEFAULT_UPSTREAM &&
starts_with(matched->name, "refs/heads/")) {
struct branch *branch = branch_get(matched->name + 11);
if (branch->merge_nr == 1 && branch->merge[0]->src) {
struct strbuf buf = STRBUF_INIT;
strbuf_addf(&buf, "%s:%s",
ref, branch->merge[0]->src);
return strbuf_detach(&buf, NULL);
}
}
return ref;
}
static void set_refspecs(const char **refs, int nr, const char *repo)
{
struct remote *remote = NULL;
struct ref *local_refs = NULL;
int i;
for (i = 0; i < nr; i++) {
const char *ref = refs[i];
if (!strcmp("tag", ref)) {
struct strbuf tagref = STRBUF_INIT;
if (nr <= ++i)
die(_("tag shorthand without <tag>"));
ref = refs[i];
if (deleterefs)
strbuf_addf(&tagref, ":refs/tags/%s", ref);
else
strbuf_addf(&tagref, "refs/tags/%s", ref);
ref = strbuf_detach(&tagref, NULL);
} else if (deleterefs) {
struct strbuf delref = STRBUF_INIT;
if (strchr(ref, ':'))
die(_("--delete only accepts plain target ref names"));
strbuf_addf(&delref, ":%s", ref);
ref = strbuf_detach(&delref, NULL);
} else if (!strchr(ref, ':')) {
if (!remote) {
/* lazily grab remote and local_refs */
remote = remote_get(repo);
local_refs = get_local_heads();
}
ref = map_refspec(ref, remote, local_refs);
}
add_refspec(ref);
}
}
static int push_url_of_remote(struct remote *remote, const char ***url_p)
{
if (remote->pushurl_nr) {
*url_p = remote->pushurl;
return remote->pushurl_nr;
}
*url_p = remote->url;
return remote->url_nr;
}
static NORETURN int die_push_simple(struct branch *branch, struct remote *remote) {
/*
* There's no point in using shorten_unambiguous_ref here,
* as the ambiguity would be on the remote side, not what
* we have locally. Plus, this is supposed to be the simple
* mode. If the user is doing something crazy like setting
* upstream to a non-branch, we should probably be showing
* them the big ugly fully qualified ref.
*/
const char *advice_maybe = "";
const char *short_upstream = branch->merge[0]->src;
skip_prefix(short_upstream, "refs/heads/", &short_upstream);
/*
* Don't show advice for people who explicitly set
* push.default.
*/
if (push_default == PUSH_DEFAULT_UNSPECIFIED)
advice_maybe = _("\n"
"To choose either option permanently, "
"see push.default in 'git help config'.");
die(_("The upstream branch of your current branch does not match\n"
"the name of your current branch. To push to the upstream branch\n"
"on the remote, use\n"
"\n"
" git push %s HEAD:%s\n"
"\n"
"To push to the branch of the same name on the remote, use\n"
"\n"
" git push %s %s\n"
"%s"),
remote->name, short_upstream,
remote->name, branch->name, advice_maybe);
}
static const char message_detached_head_die[] =
N_("You are not currently on a branch.\n"
"To push the history leading to the current (detached HEAD)\n"
"state now, use\n"
"\n"
" git push %s HEAD:<name-of-remote-branch>\n");
static void setup_push_upstream(struct remote *remote, struct branch *branch,
int triangular)
{
struct strbuf refspec = STRBUF_INIT;
if (!branch)
die(_(message_detached_head_die), remote->name);
if (!branch->merge_nr || !branch->merge || !branch->remote_name)
die(_("The current branch %s has no upstream branch.\n"
"To push the current branch and set the remote as upstream, use\n"
"\n"
" git push --set-upstream %s %s\n"),
branch->name,
remote->name,
branch->name);
if (branch->merge_nr != 1)
die(_("The current branch %s has multiple upstream branches, "
"refusing to push."), branch->name);
if (triangular)
die(_("You are pushing to remote '%s', which is not the upstream of\n"
"your current branch '%s', without telling me what to push\n"
"to update which remote branch."),
remote->name, branch->name);
if (push_default == PUSH_DEFAULT_SIMPLE) {
/* Additional safety */
if (strcmp(branch->refname, branch->merge[0]->src))
die_push_simple(branch, remote);
}
strbuf_addf(&refspec, "%s:%s", branch->name, branch->merge[0]->src);
add_refspec(refspec.buf);
}
static void setup_push_current(struct remote *remote, struct branch *branch)
{
if (!branch)
die(_(message_detached_head_die), remote->name);
add_refspec(branch->name);
}
static char warn_unspecified_push_default_msg[] =
N_("push.default is unset; its implicit value has changed in\n"
"Git 2.0 from 'matching' to 'simple'. To squelch this message\n"
"and maintain the traditional behavior, use:\n"
"\n"
" git config --global push.default matching\n"
"\n"
"To squelch this message and adopt the new behavior now, use:\n"
"\n"
" git config --global push.default simple\n"
"\n"
"When push.default is set to 'matching', git will push local branches\n"
"to the remote branches that already exist with the same name.\n"
"\n"
"Since Git 2.0, Git defaults to the more conservative 'simple'\n"
"behavior, which only pushes the current branch to the corresponding\n"
"remote branch that 'git pull' uses to update the current branch.\n"
"\n"
"See 'git help config' and search for 'push.default' for further information.\n"
"(the 'simple' mode was introduced in Git 1.7.11. Use the similar mode\n"
"'current' instead of 'simple' if you sometimes use older versions of Git)");
static void warn_unspecified_push_default_configuration(void)
{
static int warn_once;
if (warn_once++)
return;
warning("%s\n", _(warn_unspecified_push_default_msg));
}
static int is_workflow_triangular(struct remote *remote)
{
struct remote *fetch_remote = remote_get(NULL);
return (fetch_remote && fetch_remote != remote);
}
static void setup_default_push_refspecs(struct remote *remote)
{
struct branch *branch = branch_get(NULL);
int triangular = is_workflow_triangular(remote);
switch (push_default) {
default:
case PUSH_DEFAULT_MATCHING:
add_refspec(":");
break;
case PUSH_DEFAULT_UNSPECIFIED:
warn_unspecified_push_default_configuration();
/* fallthru */
case PUSH_DEFAULT_SIMPLE:
if (triangular)
setup_push_current(remote, branch);
else
setup_push_upstream(remote, branch, triangular);
break;
case PUSH_DEFAULT_UPSTREAM:
setup_push_upstream(remote, branch, triangular);
break;
case PUSH_DEFAULT_CURRENT:
setup_push_current(remote, branch);
break;
case PUSH_DEFAULT_NOTHING:
die(_("You didn't specify any refspecs to push, and "
"push.default is \"nothing\"."));
break;
}
}
static const char message_advice_pull_before_push[] =
N_("Updates were rejected because the tip of your current branch is behind\n"
"its remote counterpart. Integrate the remote changes (e.g.\n"
"'git pull ...') before pushing again.\n"
"See the 'Note about fast-forwards' in 'git push --help' for details.");
static const char message_advice_checkout_pull_push[] =
N_("Updates were rejected because a pushed branch tip is behind its remote\n"
"counterpart. Check out this branch and integrate the remote changes\n"
"(e.g. 'git pull ...') before pushing again.\n"
"See the 'Note about fast-forwards' in 'git push --help' for details.");
static const char message_advice_ref_fetch_first[] =
N_("Updates were rejected because the remote contains work that you do\n"
"not have locally. This is usually caused by another repository pushing\n"
"to the same ref. You may want to first integrate the remote changes\n"
"(e.g., 'git pull ...') before pushing again.\n"
"See the 'Note about fast-forwards' in 'git push --help' for details.");
static const char message_advice_ref_already_exists[] =
N_("Updates were rejected because the tag already exists in the remote.");
static const char message_advice_ref_needs_force[] =
N_("You cannot update a remote ref that points at a non-commit object,\n"
"or update a remote ref to make it point at a non-commit object,\n"
"without using the '--force' option.\n");
static void advise_pull_before_push(void)
{
if (!advice_push_non_ff_current || !advice_push_update_rejected)
return;
advise(_(message_advice_pull_before_push));
}
static void advise_checkout_pull_push(void)
{
if (!advice_push_non_ff_matching || !advice_push_update_rejected)
return;
advise(_(message_advice_checkout_pull_push));
}
static void advise_ref_already_exists(void)
{
if (!advice_push_already_exists || !advice_push_update_rejected)
return;
advise(_(message_advice_ref_already_exists));
}
static void advise_ref_fetch_first(void)
{
if (!advice_push_fetch_first || !advice_push_update_rejected)
return;
advise(_(message_advice_ref_fetch_first));
}
static void advise_ref_needs_force(void)
{
if (!advice_push_needs_force || !advice_push_update_rejected)
return;
advise(_(message_advice_ref_needs_force));
}
static int push_with_options(struct transport *transport, int flags)
{
int err;
unsigned int reject_reasons;
transport_set_verbosity(transport, verbosity, progress);
if (receivepack)
transport_set_option(transport,
TRANS_OPT_RECEIVEPACK, receivepack);
transport_set_option(transport, TRANS_OPT_THIN, thin ? "yes" : NULL);
if (!is_empty_cas(&cas)) {
if (!transport->smart_options)
die("underlying transport does not support --%s option",
CAS_OPT_NAME);
transport->smart_options->cas = &cas;
}
if (verbosity > 0)
fprintf(stderr, _("Pushing to %s\n"), transport->url);
err = transport_push(transport, refspec_nr, refspec, flags,
&reject_reasons);
if (err != 0)
error(_("failed to push some refs to '%s'"), transport->url);
err |= transport_disconnect(transport);
if (!err)
return 0;
if (reject_reasons & REJECT_NON_FF_HEAD) {
advise_pull_before_push();
} else if (reject_reasons & REJECT_NON_FF_OTHER) {
advise_checkout_pull_push();
} else if (reject_reasons & REJECT_ALREADY_EXISTS) {
advise_ref_already_exists();
} else if (reject_reasons & REJECT_FETCH_FIRST) {
advise_ref_fetch_first();
} else if (reject_reasons & REJECT_NEEDS_FORCE) {
advise_ref_needs_force();
}
return 1;
}
static int do_push(const char *repo, int flags)
{
int i, errs;
struct remote *remote = pushremote_get(repo);
const char **url;
int url_nr;
if (!remote) {
if (repo)
die(_("bad repository '%s'"), repo);
die(_("No configured push destination.\n"
"Either specify the URL from the command-line or configure a remote repository using\n"
"\n"
" git remote add <name> <url>\n"
"\n"
"and then push using the remote name\n"
"\n"
" git push <name>\n"));
}
if (remote->mirror)
flags |= (TRANSPORT_PUSH_MIRROR|TRANSPORT_PUSH_FORCE);
if ((flags & TRANSPORT_PUSH_ALL) && refspec) {
if (!strcmp(*refspec, "refs/tags/*"))
return error(_("--all and --tags are incompatible"));
return error(_("--all can't be combined with refspecs"));
}
if ((flags & TRANSPORT_PUSH_MIRROR) && refspec) {
if (!strcmp(*refspec, "refs/tags/*"))
return error(_("--mirror and --tags are incompatible"));
return error(_("--mirror can't be combined with refspecs"));
}
if ((flags & (TRANSPORT_PUSH_ALL|TRANSPORT_PUSH_MIRROR)) ==
(TRANSPORT_PUSH_ALL|TRANSPORT_PUSH_MIRROR)) {
return error(_("--all and --mirror are incompatible"));
}
if (!refspec && !(flags & TRANSPORT_PUSH_ALL)) {
if (remote->push_refspec_nr) {
refspec = remote->push_refspec;
refspec_nr = remote->push_refspec_nr;
} else if (!(flags & TRANSPORT_PUSH_MIRROR))
setup_default_push_refspecs(remote);
}
errs = 0;
url_nr = push_url_of_remote(remote, &url);
if (url_nr) {
for (i = 0; i < url_nr; i++) {
struct transport *transport =
transport_get(remote, url[i]);
if (push_with_options(transport, flags))
errs++;
}
} else {
struct transport *transport =
transport_get(remote, NULL);
if (push_with_options(transport, flags))
errs++;
}
return !!errs;
}
static int option_parse_recurse_submodules(const struct option *opt,
const char *arg, int unset)
{
int *flags = opt->value;
if (*flags & (TRANSPORT_RECURSE_SUBMODULES_CHECK |
TRANSPORT_RECURSE_SUBMODULES_ON_DEMAND))
die("%s can only be used once.", opt->long_name);
if (arg) {
if (!strcmp(arg, "check"))
*flags |= TRANSPORT_RECURSE_SUBMODULES_CHECK;
else if (!strcmp(arg, "on-demand"))
*flags |= TRANSPORT_RECURSE_SUBMODULES_ON_DEMAND;
else
die("bad %s argument: %s", opt->long_name, arg);
} else
die("option %s needs an argument (check|on-demand)",
opt->long_name);
return 0;
}
int cmd_push(int argc, const char **argv, const char *prefix)
{
int flags = 0;
int tags = 0;
int rc;
const char *repo = NULL; /* default repository */
struct option options[] = {
OPT__VERBOSITY(&verbosity),
OPT_STRING( 0 , "repo", &repo, N_("repository"), N_("repository")),
OPT_BIT( 0 , "all", &flags, N_("push all refs"), TRANSPORT_PUSH_ALL),
OPT_BIT( 0 , "mirror", &flags, N_("mirror all refs"),
(TRANSPORT_PUSH_MIRROR|TRANSPORT_PUSH_FORCE)),
OPT_BOOL( 0, "delete", &deleterefs, N_("delete refs")),
OPT_BOOL( 0 , "tags", &tags, N_("push tags (can't be used with --all or --mirror)")),
OPT_BIT('n' , "dry-run", &flags, N_("dry run"), TRANSPORT_PUSH_DRY_RUN),
OPT_BIT( 0, "porcelain", &flags, N_("machine-readable output"), TRANSPORT_PUSH_PORCELAIN),
OPT_BIT('f', "force", &flags, N_("force updates"), TRANSPORT_PUSH_FORCE),
{ OPTION_CALLBACK,
0, CAS_OPT_NAME, &cas, N_("refname>:<expect"),
N_("require old value of ref to be at this value"),
PARSE_OPT_OPTARG, parseopt_push_cas_option },
{ OPTION_CALLBACK, 0, "recurse-submodules", &flags, N_("check"),
N_("control recursive pushing of submodules"),
PARSE_OPT_OPTARG, option_parse_recurse_submodules },
OPT_BOOL( 0 , "thin", &thin, N_("use thin pack")),
OPT_STRING( 0 , "receive-pack", &receivepack, "receive-pack", N_("receive pack program")),
OPT_STRING( 0 , "exec", &receivepack, "receive-pack", N_("receive pack program")),
OPT_BIT('u', "set-upstream", &flags, N_("set upstream for git pull/status"),
TRANSPORT_PUSH_SET_UPSTREAM),
OPT_BOOL(0, "progress", &progress, N_("force progress reporting")),
OPT_BIT(0, "prune", &flags, N_("prune locally removed refs"),
TRANSPORT_PUSH_PRUNE),
OPT_BIT(0, "no-verify", &flags, N_("bypass pre-push hook"), TRANSPORT_PUSH_NO_HOOK),
OPT_BIT(0, "follow-tags", &flags, N_("push missing but relevant tags"),
TRANSPORT_PUSH_FOLLOW_TAGS),
OPT_BIT(0, "signed", &flags, N_("GPG sign the push"), TRANSPORT_PUSH_CERT),
OPT_END()
};
packet_trace_identity("push");
git_config(git_default_config, NULL);
argc = parse_options(argc, argv, prefix, options, push_usage, 0);
if (deleterefs && (tags || (flags & (TRANSPORT_PUSH_ALL | TRANSPORT_PUSH_MIRROR))))
die(_("--delete is incompatible with --all, --mirror and --tags"));
if (deleterefs && argc < 2)
die(_("--delete doesn't make sense without any refs"));
if (tags)
add_refspec("refs/tags/*");
if (argc > 0) {
repo = argv[0];
set_refspecs(argv + 1, argc - 1, repo);
}
rc = do_push(repo, flags);
if (rc == -1)
usage_with_options(push_usage, options);
else
return rc;
}
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