thodg/libgit2/src/transports/ssh.c

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• Hash : 6fc6eeb6
  Author :
  Date : 2021-12-24T15:14:38
  

  remote: introduce `git_remote_connect_options` The existing mechanism for providing options to remote fetch/push calls, and subsequently to transports, is unsatisfactory. It requires an options structure to avoid breaking the API and callback signatures. 1. Introduce `git_remote_connect_options` to satisfy those needs. 2. Add a new remote connection API, `git_remote_connect_ext` that will take this new options structure. Existing `git_remote_connect` calls will proxy to that. `git_remote_fetch` and `git_remote_push` will proxy their fetch/push options to that as well. 3. Define the interaction between `git_remote_connect` and fetch/push. Connect _may_ be called before fetch/push, but _need not_ be. The semantics of which options would be used for these operations was not specified if you specify options for both connect _and_ fetch. Now these are defined that the fetch or push options will be used _if_ they were specified. Otherwise, the connect options will be used if they were specified. Otherwise, the library's defaults will be used. 4. Update the transports to understand `git_remote_connect_options`. This is a breaking change to the systems API.

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• src/transports/ssh.c

• /*
   * 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.
   */
  
  #include "ssh.h"
  
  #ifdef GIT_SSH
  #include <libssh2.h>
  #endif
  
  #include "runtime.h"
  #include "net.h"
  #include "netops.h"
  #include "smart.h"
  #include "streams/socket.h"
  
  #include "git2/credential.h"
  #include "git2/sys/credential.h"
  
  #ifdef GIT_SSH
  
  #define OWNING_SUBTRANSPORT(s) ((ssh_subtransport *)(s)->parent.subtransport)
  
  static const char *ssh_prefixes[] = { "ssh://", "ssh+git://", "git+ssh://" };
  
  static const char cmd_uploadpack[] = "git-upload-pack";
  static const char cmd_receivepack[] = "git-receive-pack";
  
  typedef struct {
  	git_smart_subtransport_stream parent;
  	git_stream *io;
  	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_credential *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);
  
  	git_error_set(GIT_ERROR_SSH, "%s: %s", errmsg, ssherr);
  }
  
  /*
   * Create a git protocol request.
   *
   * For example: git-upload-pack '/libgit2/libgit2'
   */
  static int gen_proto(git_str *request, const char *cmd, const char *url)
  {
  	const char *repo;
  	int len;
  	size_t i;
  
  	for (i = 0; i < ARRAY_SIZE(ssh_prefixes); ++i) {
  		const char *p = ssh_prefixes[i];
  
  		if (!git__prefixcmp(url, p)) {
  			url = url + strlen(p);
  			repo = strchr(url, '/');
  			if (repo && repo[1] == '~')
  				++repo;
  
  			goto done;
  		}
  	}
  	repo = strchr(url, ':');
  	if (repo) repo++;
  
  done:
  	if (!repo) {
  		git_error_set(GIT_ERROR_NET, "malformed git protocol URL");
  		return -1;
  	}
  
  	len = strlen(cmd) + 1 /* Space */ + 1 /* Quote */ + strlen(repo) + 1 /* Quote */ + 1;
  
  	git_str_grow(request, len);
  	git_str_puts(request, cmd);
  	git_str_puts(request, " '");
  	git_str_decode_percent(request, repo, strlen(repo));
  	git_str_puts(request, "'");
  
  	if (git_str_oom(request))
  		return -1;
  
  	return 0;
  }
  
  static int send_command(ssh_stream *s)
  {
  	int error;
  	git_str request = GIT_STR_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_str_dispose(&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 = GIT_CONTAINER_OF(stream, ssh_stream, parent);
  
  	*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;
  	}
  
  	/*
  	 * If we can't get anything out of stdout, it's typically a
  	 * not-found error, so read from stderr and signal EOF on
  	 * stderr.
  	 */
  	if (rc == 0) {
  		if ((rc = libssh2_channel_read_stderr(s->channel, buffer, buf_size)) > 0) {
  			git_error_set(GIT_ERROR_SSH, "%*s", rc, buffer);
  			return GIT_EEOF;
  		} else if (rc < LIBSSH2_ERROR_NONE) {
  			ssh_error(s->session, "SSH could not read stderr");
  			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 = GIT_CONTAINER_OF(stream, ssh_stream, parent);
  	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 = GIT_CONTAINER_OF(stream, ssh_stream, parent);
  	ssh_subtransport *t;
  
  	if (!stream)
  		return;
  
  	t = OWNING_SUBTRANSPORT(s);
  	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_disconnect(s->session, "closing transport");
  		libssh2_session_free(s->session);
  		s->session = NULL;
  	}
  
  	if (s->io) {
  		git_stream_close(s->io);
  		git_stream_free(s->io);
  		s->io = NULL;
  	}
  
  	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;
  
  	GIT_ASSERT_ARG(stream);
  
  	s = git__calloc(sizeof(ssh_stream), 1);
  	GIT_ERROR_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(
  	git_net_url *urldata,
  	const char *url)
  {
  	char *colon, *at;
  	const char *start;
  
  	colon = strchr(url, ':');
  
  
  	at = strchr(url, '@');
  	if (at) {
  		start = at + 1;
  		urldata->username = git__substrdup(url, at - url);
  		GIT_ERROR_CHECK_ALLOC(urldata->username);
  	} else {
  		start = url;
  		urldata->username = NULL;
  	}
  
  	if (colon == NULL || (colon < start)) {
  		git_error_set(GIT_ERROR_NET, "malformed URL");
  		return -1;
  	}
  
  	urldata->host = git__substrdup(start, colon - start);
  	GIT_ERROR_CHECK_ALLOC(urldata->host);
  
  	return 0;
  }
  
  static int ssh_agent_auth(LIBSSH2_SESSION *session, git_credential_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;
  
  		/* rc is set to 1 whenever the ssh agent ran out of keys to check.
  		 * Set the error code to authentication failure rather than erroring
  		 * out with an untranslatable error code.
  		 */
  		if (rc == 1) {
  			rc = LIBSSH2_ERROR_AUTHENTICATION_FAILED;
  			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_credential *cred)
  {
  	int rc;
  
  	do {
  		git_error_clear();
  		switch (cred->credtype) {
  		case GIT_CREDENTIAL_USERPASS_PLAINTEXT: {
  			git_credential_userpass_plaintext *c = (git_credential_userpass_plaintext *)cred;
  			rc = libssh2_userauth_password(session, c->username, c->password);
  			break;
  		}
  		case GIT_CREDENTIAL_SSH_KEY: {
  			git_credential_ssh_key *c = (git_credential_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_CREDENTIAL_SSH_CUSTOM: {
  			git_credential_ssh_custom *c = (git_credential_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_CREDENTIAL_SSH_INTERACTIVE: {
  			void **abstract = libssh2_session_abstract(session);
  			git_credential_ssh_interactive *c = (git_credential_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;
  		}
  #ifdef GIT_SSH_MEMORY_CREDENTIALS
  		case GIT_CREDENTIAL_SSH_MEMORY: {
  			git_credential_ssh_key *c = (git_credential_ssh_key *)cred;
  
  			GIT_ASSERT(c->username);
  			GIT_ASSERT(c->privatekey);
  
  			rc = libssh2_userauth_publickey_frommemory(
  				session,
  				c->username,
  				strlen(c->username),
  				c->publickey,
  				c->publickey ? strlen(c->publickey) : 0,
  				c->privatekey,
  				strlen(c->privatekey),
  				c->passphrase);
  			break;
  		}
  #endif
  		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 ||
  		rc == LIBSSH2_ERROR_PUBLICKEY_UNVERIFIED)
  			return GIT_EAUTH;
  
  	if (rc != LIBSSH2_ERROR_NONE) {
  		if (!git_error_last())
  			ssh_error(session, "Failed to authenticate SSH session");
  		return -1;
  	}
  
  	return 0;
  }
  
  static int request_creds(git_credential **out, ssh_subtransport *t, const char *user, int auth_methods)
  {
  	int error, no_callback = 0;
  	git_credential *cred = NULL;
  
  	if (!t->owner->connect_opts.callbacks.credentials) {
  		no_callback = 1;
  	} else {
  		error = t->owner->connect_opts.callbacks.credentials(
  			&cred,
  			t->owner->url,
  			user,
  			auth_methods,
  			t->owner->connect_opts.callbacks.payload);
  
  		if (error == GIT_PASSTHROUGH) {
  			no_callback = 1;
  		} else if (error < 0) {
  			return error;
  		} else if (!cred) {
  			git_error_set(GIT_ERROR_SSH, "callback failed to initialize SSH credentials");
  			return -1;
  		}
  	}
  
  	if (no_callback) {
  		git_error_set(GIT_ERROR_SSH, "authentication required but no callback set");
  		return GIT_EAUTH;
  	}
  
  	if (!(cred->credtype & auth_methods)) {
  		cred->free(cred);
  		git_error_set(GIT_ERROR_SSH, "authentication callback returned unsupported credentials type");
  		return GIT_EAUTH;
  	}
  
  	*out = cred;
  
  	return 0;
  }
  
  static int _git_ssh_session_create(
  	LIBSSH2_SESSION **session,
  	git_stream *io)
  {
  	int rc = 0;
  	LIBSSH2_SESSION *s;
  	git_socket_stream *socket = GIT_CONTAINER_OF(io, git_socket_stream, parent);
  
  	GIT_ASSERT_ARG(session);
  
  	s = libssh2_session_init();
  	if (!s) {
  		git_error_set(GIT_ERROR_NET, "failed to initialize SSH session");
  		return -1;
  	}
  
  	do {
  		rc = libssh2_session_handshake(s, socket->s);
  	} 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;
  }
  
  #define SSH_DEFAULT_PORT "22"
  
  static int _git_ssh_setup_conn(
  	ssh_subtransport *t,
  	const char *url,
  	const char *cmd,
  	git_smart_subtransport_stream **stream)
  {
  	git_net_url urldata = GIT_NET_URL_INIT;
  	int auth_methods, error = 0;
  	size_t i;
  	ssh_stream *s;
  	git_credential *cred = NULL;
  	LIBSSH2_SESSION *session=NULL;
  	LIBSSH2_CHANNEL *channel=NULL;
  
  	t->current_stream = NULL;
  
  	*stream = NULL;
  	if (ssh_stream_alloc(t, url, cmd, stream) < 0)
  		return -1;
  
  	s = (ssh_stream *)*stream;
  	s->session = NULL;
  	s->channel = NULL;
  
  	for (i = 0; i < ARRAY_SIZE(ssh_prefixes); ++i) {
  		const char *p = ssh_prefixes[i];
  
  		if (!git__prefixcmp(url, p)) {
  			if ((error = git_net_url_parse(&urldata, url)) < 0)
  				goto done;
  
  			goto post_extract;
  		}
  	}
  	if ((error = git_ssh_extract_url_parts(&urldata, url)) < 0)
  		goto done;
  
  	if (urldata.port == NULL)
  		urldata.port = git__strdup(SSH_DEFAULT_PORT);
  
  	GIT_ERROR_CHECK_ALLOC(urldata.port);
  
  post_extract:
  	if ((error = git_socket_stream_new(&s->io, urldata.host, urldata.port)) < 0 ||
  	    (error = git_stream_connect(s->io)) < 0)
  		goto done;
  
  	if ((error = _git_ssh_session_create(&session, s->io)) < 0)
  		goto done;
  
  	if (t->owner->connect_opts.callbacks.certificate_check != NULL) {
  		git_cert_hostkey cert = {{ 0 }}, *cert_ptr;
  		const char *key;
  		size_t cert_len;
  		int cert_type;
  
  		cert.parent.cert_type = GIT_CERT_HOSTKEY_LIBSSH2;
  
  		key = libssh2_session_hostkey(session, &cert_len, &cert_type);
  		if (key != NULL) {
  			cert.type |= GIT_CERT_SSH_RAW;
  			cert.hostkey = key;
  			cert.hostkey_len = cert_len;
  			switch (cert_type) {
  				case LIBSSH2_HOSTKEY_TYPE_RSA:
  					cert.raw_type = GIT_CERT_SSH_RAW_TYPE_RSA;
  					break;
  				case LIBSSH2_HOSTKEY_TYPE_DSS:
  					cert.raw_type = GIT_CERT_SSH_RAW_TYPE_DSS;
  					break;
  
  #ifdef LIBSSH2_HOSTKEY_TYPE_ECDSA_256
  				case LIBSSH2_HOSTKEY_TYPE_ECDSA_256:
  					cert.raw_type = GIT_CERT_SSH_RAW_TYPE_KEY_ECDSA_256;
  					break;
  				case LIBSSH2_HOSTKEY_TYPE_ECDSA_384:
  					cert.raw_type = GIT_CERT_SSH_RAW_TYPE_KEY_ECDSA_384;
  					break;
  				case LIBSSH2_KNOWNHOST_KEY_ECDSA_521:
  					cert.raw_type = GIT_CERT_SSH_RAW_TYPE_KEY_ECDSA_521;
  					break;
  #endif
  
  #ifdef LIBSSH2_HOSTKEY_TYPE_ED25519
  				case LIBSSH2_HOSTKEY_TYPE_ED25519:
  					cert.raw_type = GIT_CERT_SSH_RAW_TYPE_KEY_ED25519;
  					break;
  #endif
  				default:
  					cert.raw_type = GIT_CERT_SSH_RAW_TYPE_UNKNOWN;
  			}
  		}
  
  #ifdef LIBSSH2_HOSTKEY_HASH_SHA256
  		key = libssh2_hostkey_hash(session, LIBSSH2_HOSTKEY_HASH_SHA256);
  		if (key != NULL) {
  			cert.type |= GIT_CERT_SSH_SHA256;
  			memcpy(&cert.hash_sha256, key, 32);
  		}
  #endif
  
  		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) {
  			git_error_set(GIT_ERROR_SSH, "unable to get the host key");
  			error = -1;
  			goto done;
  		}
  
  		/* We don't currently trust any hostkeys */
  		git_error_clear();
  
  		cert_ptr = &cert;
  
  		error = t->owner->connect_opts.callbacks.certificate_check(
  			(git_cert *)cert_ptr,
  			0,
  			urldata.host,
  			t->owner->connect_opts.callbacks.payload);
  
  		if (error < 0 && error != GIT_PASSTHROUGH) {
  			if (!git_error_last())
  				git_error_set(GIT_ERROR_NET, "user cancelled hostkey check");
  
  			goto done;
  		}
  	}
  
  	/* we need the username to ask for auth methods */
  	if (!urldata.username) {
  		if ((error = request_creds(&cred, t, NULL, GIT_CREDENTIAL_USERNAME)) < 0)
  			goto done;
  
  		urldata.username = git__strdup(((git_credential_username *) cred)->username);
  		cred->free(cred);
  		cred = NULL;
  		if (!urldata.username)
  			goto done;
  	} else if (urldata.username && urldata.password) {
  		if ((error = git_credential_userpass_plaintext_new(&cred, urldata.username, urldata.password)) < 0)
  			goto done;
  	}
  
  	if ((error = list_auth_methods(&auth_methods, session, urldata.username)) < 0)
  		goto done;
  
  	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, urldata.username, auth_methods)) < 0)
  			goto done;
  
  		if (strcmp(urldata.username, git_credential_get_username(cred))) {
  			git_error_set(GIT_ERROR_SSH, "username does not match previous request");
  			error = -1;
  			goto done;
  		}
  
  		error = _git_ssh_authenticate_session(session, cred);
  
  		if (error == GIT_EAUTH) {
  			/* refresh auth methods */
  			if ((error = list_auth_methods(&auth_methods, session, urldata.username)) < 0)
  				goto done;
  			else
  				error = GIT_EAUTH;
  		}
  	}
  
  	if (error < 0)
  		goto done;
  
  	channel = libssh2_channel_open_session(session);
  	if (!channel) {
  		error = -1;
  		ssh_error(session, "Failed to open SSH channel");
  		goto done;
  	}
  
  	libssh2_channel_set_blocking(channel, 1);
  
  	s->session = session;
  	s->channel = channel;
  
  	t->current_stream = s;
  
  done:
  	if (error < 0) {
  		ssh_stream_free(*stream);
  
  		if (session)
  			libssh2_session_free(session);
  	}
  
  	if (cred)
  		cred->free(cred);
  
  	git_net_url_dispose(&urldata);
  
  	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;
  	}
  
  	git_error_set(GIT_ERROR_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;
  	}
  
  	git_error_set(GIT_ERROR_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 = GIT_CONTAINER_OF(subtransport, ssh_subtransport, parent);
  
  	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 = GIT_CONTAINER_OF(subtransport, ssh_subtransport, parent);
  
  	GIT_ASSERT(!t->current_stream);
  
  	GIT_UNUSED(t);
  
  	return 0;
  }
  
  static void _ssh_free(git_smart_subtransport *subtransport)
  {
  	ssh_subtransport *t = GIT_CONTAINER_OF(subtransport, ssh_subtransport, parent);
  
  	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)) {
  		ssh_error(session, "Failed to retrieve list of SSH authentication methods");
  		return GIT_EAUTH;
  	}
  
  	ptr = list;
  	while (ptr) {
  		if (*ptr == ',')
  			ptr++;
  
  		if (!git__prefixcmp(ptr, SSH_AUTH_PUBLICKEY)) {
  			*out |= GIT_CREDENTIAL_SSH_KEY;
  			*out |= GIT_CREDENTIAL_SSH_CUSTOM;
  #ifdef GIT_SSH_MEMORY_CREDENTIALS
  			*out |= GIT_CREDENTIAL_SSH_MEMORY;
  #endif
  			ptr += strlen(SSH_AUTH_PUBLICKEY);
  			continue;
  		}
  
  		if (!git__prefixcmp(ptr, SSH_AUTH_PASSWORD)) {
  			*out |= GIT_CREDENTIAL_USERPASS_PLAINTEXT;
  			ptr += strlen(SSH_AUTH_PASSWORD);
  			continue;
  		}
  
  		if (!git__prefixcmp(ptr, SSH_AUTH_KEYBOARD_INTERACTIVE)) {
  			*out |= GIT_CREDENTIAL_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, void *param)
  {
  #ifdef GIT_SSH
  	ssh_subtransport *t;
  
  	GIT_ASSERT_ARG(out);
  
  	GIT_UNUSED(param);
  
  	t = git__calloc(sizeof(ssh_subtransport), 1);
  	GIT_ERROR_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);
  	GIT_UNUSED(param);
  
  	GIT_ASSERT_ARG(out);
  	*out = NULL;
  
  	git_error_set(GIT_ERROR_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 */
  		NULL,
  	};
  
  	if (paths->count != 2) {
  		git_error_set(GIT_ERROR_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]);
  	GIT_ERROR_CHECK_ALLOC(t->cmd_uploadpack);
  	t->cmd_receivepack = git__strdup(paths->strings[1]);
  	GIT_ERROR_CHECK_ALLOC(t->cmd_receivepack);
  
  	*out = transport;
  	return 0;
  #else
  	GIT_UNUSED(owner);
  	GIT_UNUSED(payload);
  
  	GIT_ASSERT_ARG(out);
  	*out = NULL;
  
  	git_error_set(GIT_ERROR_INVALID, "cannot create SSH transport. Library was built without SSH support");
  	return -1;
  #endif
  }
  
  #ifdef GIT_SSH
  static void shutdown_ssh(void)
  {
      libssh2_exit();
  }
  #endif
  
  int git_transport_ssh_global_init(void)
  {
  #ifdef GIT_SSH
  	if (libssh2_init(0) < 0) {
  		git_error_set(GIT_ERROR_SSH, "unable to initialize libssh2");
  		return -1;
  	}
  
  	return git_runtime_shutdown_register(shutdown_ssh);
  
  #else
  
  	/* Nothing to initialize */
  	return 0;
  
  #endif
  }
  

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