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|
/*
* Copyright (C) the libgit2 contributors. All rights reserved.
*
* This file is part of libgit2, distributed under the GNU GPL v2 with
* a Linking Exception. For full terms see the included COPYING file.
*/
#ifdef GIT_SSH
#include <libssh2.h>
#endif
#include "git2.h"
#include "buffer.h"
#include "netops.h"
#include "smart.h"
#include "cred.h"
#ifdef GIT_SSH
#define OWNING_SUBTRANSPORT(s) ((ssh_subtransport *)(s)->parent.subtransport)
static const char prefix_ssh[] = "ssh://";
static const char cmd_uploadpack[] = "git-upload-pack";
static const char cmd_receivepack[] = "git-receive-pack";
typedef struct {
git_smart_subtransport_stream parent;
gitno_socket socket;
LIBSSH2_SESSION *session;
LIBSSH2_CHANNEL *channel;
const char *cmd;
char *url;
unsigned sent_command : 1;
} ssh_stream;
typedef struct {
git_smart_subtransport parent;
transport_smart *owner;
ssh_stream *current_stream;
git_cred *cred;
char *cmd_uploadpack;
char *cmd_receivepack;
} ssh_subtransport;
static int list_auth_methods(int *out, LIBSSH2_SESSION *session, const char *username);
static void ssh_error(LIBSSH2_SESSION *session, const char *errmsg)
{
char *ssherr;
libssh2_session_last_error(session, &ssherr, NULL, 0);
giterr_set(GITERR_SSH, "%s: %s", errmsg, ssherr);
}
/*
* Create a git protocol request.
*
* For example: git-upload-pack '/libgit2/libgit2'
*/
static int gen_proto(git_buf *request, const char *cmd, const char *url)
{
char *repo;
int len;
if (!git__prefixcmp(url, prefix_ssh)) {
url = url + strlen(prefix_ssh);
repo = strchr(url, '/');
} else {
repo = strchr(url, ':');
if (repo) repo++;
}
if (!repo) {
giterr_set(GITERR_NET, "Malformed git protocol URL");
return -1;
}
len = strlen(cmd) + 1 /* Space */ + 1 /* Quote */ + strlen(repo) + 1 /* Quote */ + 1;
git_buf_grow(request, len);
git_buf_printf(request, "%s '%s'", cmd, repo);
git_buf_putc(request, '\0');
if (git_buf_oom(request))
return -1;
return 0;
}
static int send_command(ssh_stream *s)
{
int error;
git_buf request = GIT_BUF_INIT;
error = gen_proto(&request, s->cmd, s->url);
if (error < 0)
goto cleanup;
error = libssh2_channel_exec(s->channel, request.ptr);
if (error < LIBSSH2_ERROR_NONE) {
ssh_error(s->session, "SSH could not execute request");
goto cleanup;
}
s->sent_command = 1;
cleanup:
git_buf_free(&request);
return error;
}
static int ssh_stream_read(
git_smart_subtransport_stream *stream,
char *buffer,
size_t buf_size,
size_t *bytes_read)
{
int rc;
ssh_stream *s = (ssh_stream *)stream;
*bytes_read = 0;
if (!s->sent_command && send_command(s) < 0)
return -1;
if ((rc = libssh2_channel_read(s->channel, buffer, buf_size)) < LIBSSH2_ERROR_NONE) {
ssh_error(s->session, "SSH could not read data");;
return -1;
}
*bytes_read = rc;
return 0;
}
static int ssh_stream_write(
git_smart_subtransport_stream *stream,
const char *buffer,
size_t len)
{
ssh_stream *s = (ssh_stream *)stream;
size_t off = 0;
ssize_t ret = 0;
if (!s->sent_command && send_command(s) < 0)
return -1;
do {
ret = libssh2_channel_write(s->channel, buffer + off, len - off);
if (ret < 0)
break;
off += ret;
} while (off < len);
if (ret < 0) {
ssh_error(s->session, "SSH could not write data");
return -1;
}
return 0;
}
static void ssh_stream_free(git_smart_subtransport_stream *stream)
{
ssh_stream *s = (ssh_stream *)stream;
ssh_subtransport *t = OWNING_SUBTRANSPORT(s);
int ret;
GIT_UNUSED(ret);
t->current_stream = NULL;
if (s->channel) {
libssh2_channel_close(s->channel);
libssh2_channel_free(s->channel);
s->channel = NULL;
}
if (s->session) {
libssh2_session_free(s->session);
s->session = NULL;
}
if (s->socket.socket) {
(void)gitno_close(&s->socket);
/* can't do anything here with error return value */
}
git__free(s->url);
git__free(s);
}
static int ssh_stream_alloc(
ssh_subtransport *t,
const char *url,
const char *cmd,
git_smart_subtransport_stream **stream)
{
ssh_stream *s;
assert(stream);
s = git__calloc(sizeof(ssh_stream), 1);
GITERR_CHECK_ALLOC(s);
s->parent.subtransport = &t->parent;
s->parent.read = ssh_stream_read;
s->parent.write = ssh_stream_write;
s->parent.free = ssh_stream_free;
s->cmd = cmd;
s->url = git__strdup(url);
if (!s->url) {
git__free(s);
return -1;
}
*stream = &s->parent;
return 0;
}
static int git_ssh_extract_url_parts(
char **host,
char **username,
const char *url)
{
char *colon, *at;
const char *start;
colon = strchr(url, ':');
at = strchr(url, '@');
if (at) {
start = at + 1;
*username = git__substrdup(url, at - url);
GITERR_CHECK_ALLOC(*username);
} else {
start = url;
*username = NULL;
}
if (colon == NULL || (colon < start)) {
giterr_set(GITERR_NET, "Malformed URL");
return -1;
}
*host = git__substrdup(start, colon - start);
GITERR_CHECK_ALLOC(*host);
return 0;
}
static int ssh_agent_auth(LIBSSH2_SESSION *session, git_cred_ssh_key *c) {
int rc = LIBSSH2_ERROR_NONE;
struct libssh2_agent_publickey *curr, *prev = NULL;
LIBSSH2_AGENT *agent = libssh2_agent_init(session);
if (agent == NULL)
return -1;
rc = libssh2_agent_connect(agent);
if (rc != LIBSSH2_ERROR_NONE)
goto shutdown;
rc = libssh2_agent_list_identities(agent);
if (rc != LIBSSH2_ERROR_NONE)
goto shutdown;
while (1) {
rc = libssh2_agent_get_identity(agent, &curr, prev);
if (rc < 0)
goto shutdown;
if (rc == 1)
goto shutdown;
rc = libssh2_agent_userauth(agent, c->username, curr);
if (rc == 0)
break;
prev = curr;
}
shutdown:
if (rc != LIBSSH2_ERROR_NONE)
ssh_error(session, "error authenticating");
libssh2_agent_disconnect(agent);
libssh2_agent_free(agent);
return rc;
}
static int _git_ssh_authenticate_session(
LIBSSH2_SESSION* session,
git_cred* cred)
{
int rc;
do {
giterr_clear();
switch (cred->credtype) {
case GIT_CREDTYPE_USERPASS_PLAINTEXT: {
git_cred_userpass_plaintext *c = (git_cred_userpass_plaintext *)cred;
rc = libssh2_userauth_password(session, c->username, c->password);
break;
}
case GIT_CREDTYPE_SSH_KEY: {
git_cred_ssh_key *c = (git_cred_ssh_key *)cred;
if (c->privatekey)
rc = libssh2_userauth_publickey_fromfile(
session, c->username, c->publickey,
c->privatekey, c->passphrase);
else
rc = ssh_agent_auth(session, c);
break;
}
case GIT_CREDTYPE_SSH_CUSTOM: {
git_cred_ssh_custom *c = (git_cred_ssh_custom *)cred;
rc = libssh2_userauth_publickey(
session, c->username, (const unsigned char *)c->publickey,
c->publickey_len, c->sign_callback, &c->payload);
break;
}
case GIT_CREDTYPE_SSH_INTERACTIVE: {
void **abstract = libssh2_session_abstract(session);
git_cred_ssh_interactive *c = (git_cred_ssh_interactive *)cred;
/* ideally, we should be able to set this by calling
* libssh2_session_init_ex() instead of libssh2_session_init().
* libssh2's API is inconsistent here i.e. libssh2_userauth_publickey()
* allows you to pass the `abstract` as part of the call, whereas
* libssh2_userauth_keyboard_interactive() does not!
*
* The only way to set the `abstract` pointer is by calling
* libssh2_session_abstract(), which will replace the existing
* pointer as is done below. This is safe for now (at time of writing),
* but may not be valid in future.
*/
*abstract = c->payload;
rc = libssh2_userauth_keyboard_interactive(
session, c->username, c->prompt_callback);
break;
}
default:
rc = LIBSSH2_ERROR_AUTHENTICATION_FAILED;
}
} while (LIBSSH2_ERROR_EAGAIN == rc || LIBSSH2_ERROR_TIMEOUT == rc);
if (rc == LIBSSH2_ERROR_PASSWORD_EXPIRED || rc == LIBSSH2_ERROR_AUTHENTICATION_FAILED)
return GIT_EAUTH;
if (rc != LIBSSH2_ERROR_NONE) {
if (!giterr_last())
ssh_error(session, "Failed to authenticate SSH session");
return -1;
}
return 0;
}
static int request_creds(git_cred **out, ssh_subtransport *t, const char *user, int auth_methods)
{
int error, no_callback = 0;
git_cred *cred = NULL;
if (!t->owner->cred_acquire_cb) {
no_callback = 1;
} else {
error = t->owner->cred_acquire_cb(&cred, t->owner->url, user, auth_methods,
t->owner->cred_acquire_payload);
if (error == GIT_PASSTHROUGH)
no_callback = 1;
else if (error < 0)
return error;
else if (!cred) {
giterr_set(GITERR_SSH, "Callback failed to initialize SSH credentials");
return -1;
}
}
if (no_callback) {
giterr_set(GITERR_SSH, "authentication required but no callback set");
return -1;
}
if (!(cred->credtype & auth_methods)) {
cred->free(cred);
giterr_set(GITERR_SSH, "callback returned unsupported credentials type");
return -1;
}
*out = cred;
return 0;
}
static int _git_ssh_session_create(
LIBSSH2_SESSION** session,
gitno_socket socket)
{
int rc = 0;
LIBSSH2_SESSION* s;
assert(session);
s = libssh2_session_init();
if (!s) {
giterr_set(GITERR_NET, "Failed to initialize SSH session");
return -1;
}
do {
rc = libssh2_session_startup(s, socket.socket);
} while (LIBSSH2_ERROR_EAGAIN == rc || LIBSSH2_ERROR_TIMEOUT == rc);
if (rc != LIBSSH2_ERROR_NONE) {
ssh_error(s, "Failed to start SSH session");
libssh2_session_free(s);
return -1;
}
libssh2_session_set_blocking(s, 1);
*session = s;
return 0;
}
static int _git_ssh_setup_conn(
ssh_subtransport *t,
const char *url,
const char *cmd,
git_smart_subtransport_stream **stream)
{
char *host=NULL, *port=NULL, *path=NULL, *user=NULL, *pass=NULL;
const char *default_port="22";
int auth_methods, error = 0;
ssh_stream *s;
git_cred *cred = NULL;
LIBSSH2_SESSION* session=NULL;
LIBSSH2_CHANNEL* channel=NULL;
*stream = NULL;
if (ssh_stream_alloc(t, url, cmd, stream) < 0)
return -1;
s = (ssh_stream *)*stream;
if (!git__prefixcmp(url, prefix_ssh)) {
if ((error = gitno_extract_url_parts(&host, &port, &path, &user, &pass, url, default_port)) < 0)
goto on_error;
} else {
if ((error = git_ssh_extract_url_parts(&host, &user, url)) < 0)
goto on_error;
port = git__strdup(default_port);
GITERR_CHECK_ALLOC(port);
}
if ((error = gitno_connect(&s->socket, host, port, 0)) < 0)
goto on_error;
if ((error = _git_ssh_session_create(&session, s->socket)) < 0)
goto on_error;
if (t->owner->certificate_check_cb != NULL) {
git_cert_hostkey cert = { 0 };
const char *key;
cert.cert_type = GIT_CERT_HOSTKEY_LIBSSH2;
key = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_SHA1);
if (key != NULL) {
cert.type |= GIT_CERT_SSH_SHA1;
memcpy(&cert.hash_sha1, key, 20);
}
key = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_MD5);
if (key != NULL) {
cert.type |= GIT_CERT_SSH_MD5;
memcpy(&cert.hash_md5, key, 16);
}
if (cert.type == 0) {
giterr_set(GITERR_SSH, "unable to get the host key");
return -1;
}
/* We don't currently trust any hostkeys */
giterr_clear();
error = t->owner->certificate_check_cb((git_cert *) &cert, 0, host, t->owner->message_cb_payload);
if (error < 0) {
if (!giterr_last())
giterr_set(GITERR_NET, "user cancelled hostkey check");
goto on_error;
}
}
/* we need the username to ask for auth methods */
if (!user) {
if ((error = request_creds(&cred, t, NULL, GIT_CREDTYPE_USERNAME)) < 0)
goto on_error;
user = git__strdup(((git_cred_username *) cred)->username);
cred->free(cred);
cred = NULL;
if (!user)
goto on_error;
} else if (user && pass) {
if ((error = git_cred_userpass_plaintext_new(&cred, user, pass)) < 0)
goto on_error;
}
if ((error = list_auth_methods(&auth_methods, session, user)) < 0)
goto on_error;
error = GIT_EAUTH;
/* if we already have something to try */
if (cred && auth_methods & cred->credtype)
error = _git_ssh_authenticate_session(session, cred);
while (error == GIT_EAUTH) {
if (cred) {
cred->free(cred);
cred = NULL;
}
if ((error = request_creds(&cred, t, user, auth_methods)) < 0)
goto on_error;
if (strcmp(user, git_cred__username(cred))) {
giterr_set(GITERR_SSH, "username does not match previous request");
error = -1;
goto on_error;
}
error = _git_ssh_authenticate_session(session, cred);
}
if (error < 0)
goto on_error;
channel = libssh2_channel_open_session(session);
if (!channel) {
error = -1;
ssh_error(session, "Failed to open SSH channel");
goto on_error;
}
libssh2_channel_set_blocking(channel, 1);
s->session = session;
s->channel = channel;
t->current_stream = s;
if (cred)
cred->free(cred);
git__free(host);
git__free(port);
git__free(path);
git__free(user);
git__free(pass);
return 0;
on_error:
s->session = NULL;
s->channel = NULL;
t->current_stream = NULL;
if (*stream)
ssh_stream_free(*stream);
if (cred)
cred->free(cred);
git__free(host);
git__free(port);
git__free(user);
git__free(pass);
if (session)
libssh2_session_free(session);
return error;
}
static int ssh_uploadpack_ls(
ssh_subtransport *t,
const char *url,
git_smart_subtransport_stream **stream)
{
const char *cmd = t->cmd_uploadpack ? t->cmd_uploadpack : cmd_uploadpack;
return _git_ssh_setup_conn(t, url, cmd, stream);
}
static int ssh_uploadpack(
ssh_subtransport *t,
const char *url,
git_smart_subtransport_stream **stream)
{
GIT_UNUSED(url);
if (t->current_stream) {
*stream = &t->current_stream->parent;
return 0;
}
giterr_set(GITERR_NET, "Must call UPLOADPACK_LS before UPLOADPACK");
return -1;
}
static int ssh_receivepack_ls(
ssh_subtransport *t,
const char *url,
git_smart_subtransport_stream **stream)
{
const char *cmd = t->cmd_receivepack ? t->cmd_receivepack : cmd_receivepack;
return _git_ssh_setup_conn(t, url, cmd, stream);
}
static int ssh_receivepack(
ssh_subtransport *t,
const char *url,
git_smart_subtransport_stream **stream)
{
GIT_UNUSED(url);
if (t->current_stream) {
*stream = &t->current_stream->parent;
return 0;
}
giterr_set(GITERR_NET, "Must call RECEIVEPACK_LS before RECEIVEPACK");
return -1;
}
static int _ssh_action(
git_smart_subtransport_stream **stream,
git_smart_subtransport *subtransport,
const char *url,
git_smart_service_t action)
{
ssh_subtransport *t = (ssh_subtransport *) subtransport;
switch (action) {
case GIT_SERVICE_UPLOADPACK_LS:
return ssh_uploadpack_ls(t, url, stream);
case GIT_SERVICE_UPLOADPACK:
return ssh_uploadpack(t, url, stream);
case GIT_SERVICE_RECEIVEPACK_LS:
return ssh_receivepack_ls(t, url, stream);
case GIT_SERVICE_RECEIVEPACK:
return ssh_receivepack(t, url, stream);
}
*stream = NULL;
return -1;
}
static int _ssh_close(git_smart_subtransport *subtransport)
{
ssh_subtransport *t = (ssh_subtransport *) subtransport;
assert(!t->current_stream);
GIT_UNUSED(t);
return 0;
}
static void _ssh_free(git_smart_subtransport *subtransport)
{
ssh_subtransport *t = (ssh_subtransport *) subtransport;
assert(!t->current_stream);
git__free(t->cmd_uploadpack);
git__free(t->cmd_receivepack);
git__free(t);
}
#define SSH_AUTH_PUBLICKEY "publickey"
#define SSH_AUTH_PASSWORD "password"
#define SSH_AUTH_KEYBOARD_INTERACTIVE "keyboard-interactive"
static int list_auth_methods(int *out, LIBSSH2_SESSION *session, const char *username)
{
const char *list, *ptr;
*out = 0;
list = libssh2_userauth_list(session, username, strlen(username));
/* either error, or the remote accepts NONE auth, which is bizarre, let's punt */
if (list == NULL && !libssh2_userauth_authenticated(session))
return -1;
ptr = list;
while (ptr) {
if (*ptr == ',')
ptr++;
if (!git__prefixcmp(ptr, SSH_AUTH_PUBLICKEY)) {
*out |= GIT_CREDTYPE_SSH_KEY;
*out |= GIT_CREDTYPE_SSH_CUSTOM;
ptr += strlen(SSH_AUTH_PUBLICKEY);
continue;
}
if (!git__prefixcmp(ptr, SSH_AUTH_PASSWORD)) {
*out |= GIT_CREDTYPE_USERPASS_PLAINTEXT;
ptr += strlen(SSH_AUTH_PASSWORD);
continue;
}
if (!git__prefixcmp(ptr, SSH_AUTH_KEYBOARD_INTERACTIVE)) {
*out |= GIT_CREDTYPE_SSH_INTERACTIVE;
ptr += strlen(SSH_AUTH_KEYBOARD_INTERACTIVE);
continue;
}
/* Skipt it if we don't know it */
ptr = strchr(ptr, ',');
}
return 0;
}
#endif
int git_smart_subtransport_ssh(
git_smart_subtransport **out, git_transport *owner)
{
#ifdef GIT_SSH
ssh_subtransport *t;
assert(out);
t = git__calloc(sizeof(ssh_subtransport), 1);
GITERR_CHECK_ALLOC(t);
t->owner = (transport_smart *)owner;
t->parent.action = _ssh_action;
t->parent.close = _ssh_close;
t->parent.free = _ssh_free;
*out = (git_smart_subtransport *) t;
return 0;
#else
GIT_UNUSED(owner);
assert(out);
*out = NULL;
giterr_set(GITERR_INVALID, "Cannot create SSH transport. Library was built without SSH support");
return -1;
#endif
}
int git_transport_ssh_with_paths(git_transport **out, git_remote *owner, void *payload)
{
#ifdef GIT_SSH
git_strarray *paths = (git_strarray *) payload;
git_transport *transport;
transport_smart *smart;
ssh_subtransport *t;
int error;
git_smart_subtransport_definition ssh_definition = {
git_smart_subtransport_ssh,
0, /* no RPC */
};
if (paths->count != 2) {
giterr_set(GITERR_SSH, "invalid ssh paths, must be two strings");
return GIT_EINVALIDSPEC;
}
if ((error = git_transport_smart(&transport, owner, &ssh_definition)) < 0)
return error;
smart = (transport_smart *) transport;
t = (ssh_subtransport *) smart->wrapped;
t->cmd_uploadpack = git__strdup(paths->strings[0]);
GITERR_CHECK_ALLOC(t->cmd_uploadpack);
t->cmd_receivepack = git__strdup(paths->strings[1]);
GITERR_CHECK_ALLOC(t->cmd_receivepack);
*out = transport;
return 0;
#else
GIT_UNUSED(owner);
GIT_UNUSED(payload);
assert(out);
*out = NULL;
giterr_set(GITERR_INVALID, "Cannot create SSH transport. Library was built without SSH support");
return -1;
#endif
}
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