2 * gpg_agent.c: GPG Agent provider for SVN_AUTH_CRED_*
4 * ====================================================================
5 * Licensed to the Apache Software Foundation (ASF) under one
6 * or more contributor license agreements. See the NOTICE file
7 * distributed with this work for additional information
8 * regarding copyright ownership. The ASF licenses this file
9 * to you under the Apache License, Version 2.0 (the
10 * "License"); you may not use this file except in compliance
11 * with the License. You may obtain a copy of the License at
13 * http://www.apache.org/licenses/LICENSE-2.0
15 * Unless required by applicable law or agreed to in writing,
16 * software distributed under the License is distributed on an
17 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
18 * KIND, either express or implied. See the License for the
19 * specific language governing permissions and limitations
21 * ====================================================================
24 /* ==================================================================== */
26 /* This auth provider stores a plaintext password in memory managed by
27 * a running gpg-agent. In contrast to other password store providers
28 * it does not save the password to disk.
30 * Prompting is performed by the gpg-agent using a "pinentry" program
31 * which needs to be installed separately. There are several pinentry
32 * implementations with different front-ends (e.g. qt, gtk, ncurses).
34 * The gpg-agent will let the password time out after a while,
35 * or immediately when it receives the SIGHUP signal.
36 * When the password has timed out it will automatically prompt the
37 * user for the password again. This is transparent to Subversion.
39 * SECURITY CONSIDERATIONS:
41 * Communication to the agent happens over a UNIX socket, which is located
42 * in a directory which only the user running Subversion can access.
43 * However, any program the user runs could access this socket and get
44 * the Subversion password if the program knows the "cache ID" Subversion
45 * uses for the password.
46 * The cache ID is very easy to obtain for programs running as the same user.
47 * Subversion uses the MD5 of the realmstring as cache ID, and these checksums
48 * are also used as filenames within ~/.subversion/auth/svn.simple.
49 * Unlike GNOME Keyring or KDE Wallet, the user is not prompted for
50 * permission if another program attempts to access the password.
52 * Therefore, while the gpg-agent is running and has the password cached,
53 * this provider is no more secure than a file storing the password in
64 #include <sys/socket.h>
67 #include <apr_pools.h>
69 #include "svn_config.h"
70 #include "svn_error.h"
71 #include "svn_pools.h"
72 #include "svn_cmdline.h"
73 #include "svn_checksum.h"
74 #include "svn_string.h"
77 #include "svn_dirent_uri.h"
80 #include "private/svn_auth_private.h"
82 #include "svn_private_config.h"
84 #ifdef SVN_HAVE_GPG_AGENT
86 #define BUFFER_SIZE 1024
87 #define ATTEMPT_PARAMETER "svn.simple.gpg_agent.attempt"
89 /* Modify STR in-place such that blanks are escaped as required by the
90 * gpg-agent protocol. Return a pointer to STR. */
92 escape_blanks(char *str)
106 #define is_hex(c) (((c) >= '0' && (c) <= '9') || ((c) >= 'A' && (c) <= 'F'))
107 #define hex_to_int(c) ((c) < '9' ? (c) - '0' : (c) - 'A' + 10)
109 /* Modify STR in-place. '%', CR and LF are always percent escaped,
110 other characters may be percent escaped, always using uppercase
111 hex, see https://www.gnupg.org/documentation/manuals/assuan.pdf */
113 unescape_assuan(char *str)
119 if (s[0] == '%' && is_hex(s[1]) && is_hex(s[2]))
122 char val = hex_to_int(s[1]) * 16 + hex_to_int(s[2]);
140 /* Generate the string CACHE_ID_P based on the REALMSTRING allocated in
141 * RESULT_POOL using SCRATCH_POOL for temporary allocations. This is similar
142 * to other password caching mechanisms. */
144 get_cache_id(const char **cache_id_p, const char *realmstring,
145 apr_pool_t *result_pool, apr_pool_t *scratch_pool)
147 const char *cache_id = NULL;
148 svn_checksum_t *digest = NULL;
150 SVN_ERR(svn_checksum(&digest, svn_checksum_md5, realmstring,
151 strlen(realmstring), scratch_pool));
152 cache_id = svn_checksum_to_cstring(digest, result_pool);
153 *cache_id_p = cache_id;
158 /* Attempt to read a gpg-agent response message from the socket SD into
159 * buffer BUF. Buf is assumed to be N bytes large. Return TRUE if a response
160 * message could be read that fits into the buffer. Else return FALSE.
161 * If a message could be read it will always be NUL-terminated and the
162 * trailing newline is retained. */
164 receive_from_gpg_agent(int sd, char *buf, size_t n)
170 /* Clear existing buffer content before reading response. */
174 /* Require the message to fit into the buffer and be terminated
178 recvd = read(sd, &c, 1);
183 if (i < n && c == '\n')
193 /* Using socket SD, send the option OPTION with the specified VALUE
194 * to the gpg agent. Store the response in BUF, assumed to be N bytes
195 * in size, and evaluate the response. Return TRUE if the agent liked
196 * the smell of the option, if there is such a thing, and doesn't feel
197 * saturated by it. Else return FALSE.
198 * Do temporary allocations in scratch_pool. */
200 send_option(int sd, char *buf, size_t n, const char *option, const char *value,
201 apr_pool_t *scratch_pool)
205 request = apr_psprintf(scratch_pool, "OPTION %s=%s\n", option, value);
207 if (write(sd, request, strlen(request)) == -1)
210 if (!receive_from_gpg_agent(sd, buf, n))
213 return (strncmp(buf, "OK", 2) == 0);
216 /* Send the BYE command and disconnect from the gpg-agent. Doing this avoids
217 * gpg-agent emitting a "Connection reset by peer" log message with some
218 * versions of gpg-agent. */
220 bye_gpg_agent(int sd)
222 /* don't bother to check the result of the write, it either worked or it
223 * didn't, but either way we're closing. */
224 write(sd, "BYE\n", 4);
228 /* Locate a running GPG Agent, and return an open file descriptor
229 * for communication with the agent in *NEW_SD. If no running agent
230 * can be found, set *NEW_SD to -1. */
232 find_running_gpg_agent(int *new_sd, apr_pool_t *pool)
235 char *gpg_agent_info = NULL;
236 const char *socket_name = NULL;
237 const char *request = NULL;
238 const char *p = NULL;
244 /* This implements the method of finding the socket as described in
245 * the gpg-agent man page under the --use-standard-socket option.
246 * The manage page misleadingly says the standard socket is
247 * "named 'S.gpg-agent' located in the home directory." The standard
248 * socket path is actually in the .gnupg directory in the home directory,
249 * i.e. ~/.gnupg/S.gpg-agent */
250 gpg_agent_info = getenv("GPG_AGENT_INFO");
251 if (gpg_agent_info != NULL)
253 apr_array_header_t *socket_details;
255 /* For reference GPG_AGENT_INFO consists of 3 : separated fields.
256 * The path to the socket, the pid of the gpg-agent process and
257 * finally the version of the protocol the agent talks. */
258 socket_details = svn_cstring_split(gpg_agent_info, ":", TRUE,
260 socket_name = APR_ARRAY_IDX(socket_details, 0, const char *);
264 const char *homedir = svn_user_get_homedir(pool);
269 homedir = svn_dirent_canonicalize(homedir, pool);
270 socket_name = svn_dirent_join_many(pool, homedir, ".gnupg",
271 "S.gpg-agent", SVN_VA_NULL);
274 if (socket_name != NULL)
276 struct sockaddr_un addr;
278 addr.sun_family = AF_UNIX;
279 strncpy(addr.sun_path, socket_name, sizeof(addr.sun_path) - 1);
280 addr.sun_path[sizeof(addr.sun_path) - 1] = '\0';
282 sd = socket(AF_UNIX, SOCK_STREAM, 0);
286 if (connect(sd, (struct sockaddr *)&addr, sizeof(addr)) == -1)
295 /* Receive the connection status from the gpg-agent daemon. */
296 buffer = apr_palloc(pool, BUFFER_SIZE);
297 if (!receive_from_gpg_agent(sd, buffer, BUFFER_SIZE))
303 if (strncmp(buffer, "OK", 2) != 0)
309 /* The GPG-Agent documentation says:
310 * "Clients should deny to access an agent with a socket name which does
311 * not match its own configuration". */
312 request = "GETINFO socket_name\n";
313 if (write(sd, request, strlen(request)) == -1)
318 if (!receive_from_gpg_agent(sd, buffer, BUFFER_SIZE))
323 if (strncmp(buffer, "D", 1) == 0)
330 ep = strchr(p, '\n');
333 if (strcmp(socket_name, p) != 0)
338 /* The agent will terminate its response with "OK". */
339 if (!receive_from_gpg_agent(sd, buffer, BUFFER_SIZE))
344 if (strncmp(buffer, "OK", 2) != 0)
355 send_options(int sd, char *buf, size_t n, apr_pool_t *scratch_pool)
357 const char *tty_name;
358 const char *tty_type;
359 const char *lc_ctype;
362 /* Send TTY_NAME to the gpg-agent daemon. */
363 tty_name = getenv("GPG_TTY");
364 if (tty_name != NULL)
366 if (!send_option(sd, buf, n, "ttyname", tty_name, scratch_pool))
370 /* Send TTY_TYPE to the gpg-agent daemon. */
371 tty_type = getenv("TERM");
372 if (tty_type != NULL)
374 if (!send_option(sd, buf, n, "ttytype", tty_type, scratch_pool))
378 /* Compute LC_CTYPE. */
379 lc_ctype = getenv("LC_ALL");
380 if (lc_ctype == NULL)
381 lc_ctype = getenv("LC_CTYPE");
382 if (lc_ctype == NULL)
383 lc_ctype = getenv("LANG");
385 /* Send LC_CTYPE to the gpg-agent daemon. */
386 if (lc_ctype != NULL)
388 if (!send_option(sd, buf, n, "lc-ctype", lc_ctype, scratch_pool))
392 /* Send DISPLAY to the gpg-agent daemon. */
393 display = getenv("DISPLAY");
396 if (!send_option(sd, buf, n, "display", display, scratch_pool))
403 /* Implementation of svn_auth__password_get_t that retrieves the password
406 password_get_gpg_agent(svn_boolean_t *done,
407 const char **password,
409 const char *realmstring,
410 const char *username,
411 apr_hash_t *parameters,
412 svn_boolean_t non_interactive,
419 const char *request = NULL;
420 const char *cache_id = NULL;
421 char *password_prompt;
428 attempt = svn_hash_gets(parameters, ATTEMPT_PARAMETER);
430 SVN_ERR(find_running_gpg_agent(&sd, pool));
434 buffer = apr_palloc(pool, BUFFER_SIZE);
436 if (!send_options(sd, buffer, BUFFER_SIZE, pool))
442 SVN_ERR(get_cache_id(&cache_id, realmstring, pool, pool));
444 password_prompt = apr_psprintf(pool, _("Password for '%s': "), username);
445 realm_prompt = apr_psprintf(pool, _("Enter your Subversion password for %s"),
448 /* X means no error to the gpg-agent protocol */
449 error_prompt = apr_pstrdup(pool, "X");
451 error_prompt = apr_pstrdup(pool, _("Authentication failed"));
453 request = apr_psprintf(pool,
454 "GET_PASSPHRASE --data %s"
456 non_interactive ? "--no-ask " : "",
458 escape_blanks(error_prompt),
459 escape_blanks(password_prompt),
460 escape_blanks(realm_prompt));
462 if (write(sd, request, strlen(request)) == -1)
467 if (!receive_from_gpg_agent(sd, buffer, BUFFER_SIZE))
475 if (strncmp(buffer, "ERR", 3) == 0)
479 if (strncmp(buffer, "D", 1) == 0)
485 ep = strchr(p, '\n');
489 *password = unescape_assuan(p);
496 /* Implementation of svn_auth__password_set_t that would store the
497 password in GPG Agent if that's how this particular integration
498 worked. But it isn't. GPG Agent stores the password provided by
499 the user via the pinentry program immediately upon its provision
500 (and regardless of its accuracy as passwords go), so we just need
501 to check if a running GPG Agent exists. */
503 password_set_gpg_agent(svn_boolean_t *done,
505 const char *realmstring,
506 const char *username,
507 const char *password,
508 apr_hash_t *parameters,
509 svn_boolean_t non_interactive,
516 SVN_ERR(find_running_gpg_agent(&sd, pool));
527 /* An implementation of svn_auth_provider_t::first_credentials() */
529 simple_gpg_agent_first_creds(void **credentials,
531 void *provider_baton,
532 apr_hash_t *parameters,
533 const char *realmstring,
537 int *attempt = apr_palloc(pool, sizeof(*attempt));
540 svn_hash_sets(parameters, ATTEMPT_PARAMETER, attempt);
541 err = svn_auth__simple_creds_cache_get(credentials, iter_baton,
542 provider_baton, parameters,
543 realmstring, password_get_gpg_agent,
544 SVN_AUTH__GPG_AGENT_PASSWORD_TYPE,
546 *iter_baton = attempt;
551 /* An implementation of svn_auth_provider_t::next_credentials() */
553 simple_gpg_agent_next_creds(void **credentials,
555 void *provider_baton,
556 apr_hash_t *parameters,
557 const char *realmstring,
560 int *attempt = (int *)iter_baton;
563 const char *cache_id = NULL;
564 const char *request = NULL;
568 /* The users previous credentials failed so first remove the cached entry,
569 * before trying to retrieve them again. Because gpg-agent stores cached
570 * credentials immediately upon retrieving them, this gives us the
571 * opportunity to remove the invalid credentials and prompt the
572 * user again. While it's possible that server side issues could trigger
573 * this, this cache is ephemeral so at worst we're just speeding up
574 * when the user would need to re-enter their password. */
576 if (svn_hash_gets(parameters, SVN_AUTH_PARAM_NON_INTERACTIVE))
578 /* In this case since we're running non-interactively we do not
579 * want to clear the cache since the user was never prompted by
580 * gpg-agent to set a password. */
584 *attempt = *attempt + 1;
586 SVN_ERR(find_running_gpg_agent(&sd, pool));
590 buffer = apr_palloc(pool, BUFFER_SIZE);
592 if (!send_options(sd, buffer, BUFFER_SIZE, pool))
598 SVN_ERR(get_cache_id(&cache_id, realmstring, pool, pool));
600 request = apr_psprintf(pool, "CLEAR_PASSPHRASE %s\n", cache_id);
602 if (write(sd, request, strlen(request)) == -1)
608 if (!receive_from_gpg_agent(sd, buffer, BUFFER_SIZE))
614 if (strncmp(buffer, "OK\n", 3) != 0)
620 /* TODO: This attempt limit hard codes it at 3 attempts (or 2 retries)
621 * which matches svn command line client's retry_limit as set in
622 * svn_cmdline_create_auth_baton(). It would be nice to have that
623 * limit reflected here but that violates the boundry between the
624 * prompt provider and the cache provider. gpg-agent is acting as
625 * both here due to the peculiarties of their design so we'll have to
626 * live with this for now. Note that when these failures get exceeded
627 * it'll eventually fall back on the retry limits of whatever prompt
628 * provider is in effect, so this effectively doubles the limit. */
630 return svn_auth__simple_creds_cache_get(credentials, &iter_baton,
631 provider_baton, parameters,
633 password_get_gpg_agent,
634 SVN_AUTH__GPG_AGENT_PASSWORD_TYPE,
641 /* An implementation of svn_auth_provider_t::save_credentials() */
643 simple_gpg_agent_save_creds(svn_boolean_t *saved,
645 void *provider_baton,
646 apr_hash_t *parameters,
647 const char *realmstring,
650 return svn_auth__simple_creds_cache_set(saved, credentials,
651 provider_baton, parameters,
652 realmstring, password_set_gpg_agent,
653 SVN_AUTH__GPG_AGENT_PASSWORD_TYPE,
658 static const svn_auth_provider_t gpg_agent_simple_provider = {
659 SVN_AUTH_CRED_SIMPLE,
660 simple_gpg_agent_first_creds,
661 simple_gpg_agent_next_creds,
662 simple_gpg_agent_save_creds
668 svn_auth__get_gpg_agent_simple_provider(svn_auth_provider_object_t **provider,
671 svn_auth_provider_object_t *po = apr_pcalloc(pool, sizeof(*po));
673 po->vtable = &gpg_agent_simple_provider;
677 #endif /* SVN_HAVE_GPG_AGENT */