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"
79 #include "private/svn_auth_private.h"
81 #include "svn_private_config.h"
83 #ifdef SVN_HAVE_GPG_AGENT
85 #define BUFFER_SIZE 1024
86 #define ATTEMPT_PARAMETER "svn.simple.gpg_agent.attempt"
88 /* Modify STR in-place such that blanks are escaped as required by the
89 * gpg-agent protocol. Return a pointer to STR. */
91 escape_blanks(char *str)
105 /* Generate the string CACHE_ID_P based on the REALMSTRING allocated in
106 * RESULT_POOL using SCRATCH_POOL for temporary allocations. This is similar
107 * to other password caching mechanisms. */
109 get_cache_id(const char **cache_id_p, const char *realmstring,
110 apr_pool_t *scratch_pool, apr_pool_t *result_pool)
112 const char *cache_id = NULL;
113 svn_checksum_t *digest = NULL;
115 SVN_ERR(svn_checksum(&digest, svn_checksum_md5, realmstring,
116 strlen(realmstring), scratch_pool));
117 cache_id = svn_checksum_to_cstring(digest, result_pool);
118 *cache_id_p = cache_id;
123 /* Attempt to read a gpg-agent response message from the socket SD into
124 * buffer BUF. Buf is assumed to be N bytes large. Return TRUE if a response
125 * message could be read that fits into the buffer. Else return FALSE.
126 * If a message could be read it will always be NUL-terminated and the
127 * trailing newline is retained. */
129 receive_from_gpg_agent(int sd, char *buf, size_t n)
135 /* Clear existing buffer content before reading response. */
139 /* Require the message to fit into the buffer and be terminated
143 recvd = read(sd, &c, 1);
148 if (i < n && c == '\n')
158 /* Using socket SD, send the option OPTION with the specified VALUE
159 * to the gpg agent. Store the response in BUF, assumed to be N bytes
160 * in size, and evaluate the response. Return TRUE if the agent liked
161 * the smell of the option, if there is such a thing, and doesn't feel
162 * saturated by it. Else return FALSE.
163 * Do temporary allocations in scratch_pool. */
165 send_option(int sd, char *buf, size_t n, const char *option, const char *value,
166 apr_pool_t *scratch_pool)
170 request = apr_psprintf(scratch_pool, "OPTION %s=%s\n", option, value);
172 if (write(sd, request, strlen(request)) == -1)
175 if (!receive_from_gpg_agent(sd, buf, n))
178 return (strncmp(buf, "OK", 2) == 0);
181 /* Send the BYE command and disconnect from the gpg-agent. Doing this avoids
182 * gpg-agent emitting a "Connection reset by peer" log message with some
183 * versions of gpg-agent. */
185 bye_gpg_agent(int sd)
187 /* don't bother to check the result of the write, it either worked or it
188 * didn't, but either way we're closing. */
189 write(sd, "BYE\n", 4);
193 /* Locate a running GPG Agent, and return an open file descriptor
194 * for communication with the agent in *NEW_SD. If no running agent
195 * can be found, set *NEW_SD to -1. */
197 find_running_gpg_agent(int *new_sd, apr_pool_t *pool)
200 char *gpg_agent_info = NULL;
201 const char *socket_name = NULL;
202 const char *request = NULL;
203 const char *p = NULL;
209 /* This implements the method of finding the socket as described in
210 * the gpg-agent man page under the --use-standard-socket option.
211 * The manage page misleadingly says the standard socket is
212 * "named 'S.gpg-agent' located in the home directory." The standard
213 * socket path is actually in the .gnupg directory in the home directory,
214 * i.e. ~/.gnupg/S.gpg-agent */
215 gpg_agent_info = getenv("GPG_AGENT_INFO");
216 if (gpg_agent_info != NULL)
218 apr_array_header_t *socket_details;
220 /* For reference GPG_AGENT_INFO consists of 3 : separated fields.
221 * The path to the socket, the pid of the gpg-agent process and
222 * finally the version of the protocol the agent talks. */
223 socket_details = svn_cstring_split(gpg_agent_info, ":", TRUE,
225 socket_name = APR_ARRAY_IDX(socket_details, 0, const char *);
229 const char *homedir = svn_user_get_homedir(pool);
234 socket_name = svn_dirent_join_many(pool, homedir, ".gnupg",
235 "S.gpg-agent", NULL);
238 if (socket_name != NULL)
240 struct sockaddr_un addr;
242 addr.sun_family = AF_UNIX;
243 strncpy(addr.sun_path, socket_name, sizeof(addr.sun_path) - 1);
244 addr.sun_path[sizeof(addr.sun_path) - 1] = '\0';
246 sd = socket(AF_UNIX, SOCK_STREAM, 0);
250 if (connect(sd, (struct sockaddr *)&addr, sizeof(addr)) == -1)
259 /* Receive the connection status from the gpg-agent daemon. */
260 buffer = apr_palloc(pool, BUFFER_SIZE);
261 if (!receive_from_gpg_agent(sd, buffer, BUFFER_SIZE))
267 if (strncmp(buffer, "OK", 2) != 0)
273 /* The GPG-Agent documentation says:
274 * "Clients should deny to access an agent with a socket name which does
275 * not match its own configuration". */
276 request = "GETINFO socket_name\n";
277 if (write(sd, request, strlen(request)) == -1)
282 if (!receive_from_gpg_agent(sd, buffer, BUFFER_SIZE))
287 if (strncmp(buffer, "D", 1) == 0)
294 ep = strchr(p, '\n');
297 if (strcmp(socket_name, p) != 0)
302 /* The agent will terminate its response with "OK". */
303 if (!receive_from_gpg_agent(sd, buffer, BUFFER_SIZE))
308 if (strncmp(buffer, "OK", 2) != 0)
319 send_options(int sd, char *buf, size_t n, apr_pool_t *scratch_pool)
321 const char *tty_name;
322 const char *tty_type;
323 const char *lc_ctype;
326 /* Send TTY_NAME to the gpg-agent daemon. */
327 tty_name = getenv("GPG_TTY");
328 if (tty_name != NULL)
330 if (!send_option(sd, buf, n, "ttyname", tty_name, scratch_pool))
334 /* Send TTY_TYPE to the gpg-agent daemon. */
335 tty_type = getenv("TERM");
336 if (tty_type != NULL)
338 if (!send_option(sd, buf, n, "ttytype", tty_type, scratch_pool))
342 /* Compute LC_CTYPE. */
343 lc_ctype = getenv("LC_ALL");
344 if (lc_ctype == NULL)
345 lc_ctype = getenv("LC_CTYPE");
346 if (lc_ctype == NULL)
347 lc_ctype = getenv("LANG");
349 /* Send LC_CTYPE to the gpg-agent daemon. */
350 if (lc_ctype != NULL)
352 if (!send_option(sd, buf, n, "lc-ctype", lc_ctype, scratch_pool))
356 /* Send DISPLAY to the gpg-agent daemon. */
357 display = getenv("DISPLAY");
360 if (!send_option(sd, buf, n, "display", display, scratch_pool))
367 /* Implementation of svn_auth__password_get_t that retrieves the password
370 password_get_gpg_agent(svn_boolean_t *done,
371 const char **password,
373 const char *realmstring,
374 const char *username,
375 apr_hash_t *parameters,
376 svn_boolean_t non_interactive,
380 const char *p = NULL;
383 const char *request = NULL;
384 const char *cache_id = NULL;
385 char *password_prompt;
392 attempt = svn_hash_gets(parameters, ATTEMPT_PARAMETER);
394 SVN_ERR(find_running_gpg_agent(&sd, pool));
398 buffer = apr_palloc(pool, BUFFER_SIZE);
400 if (!send_options(sd, buffer, BUFFER_SIZE, pool))
406 SVN_ERR(get_cache_id(&cache_id, realmstring, pool, pool));
408 password_prompt = apr_psprintf(pool, _("Password for '%s': "), username);
409 realm_prompt = apr_psprintf(pool, _("Enter your Subversion password for %s"),
412 /* X means no error to the gpg-agent protocol */
413 error_prompt = apr_pstrdup(pool, "X");
415 error_prompt = apr_pstrdup(pool, _("Authentication failed"));
417 request = apr_psprintf(pool,
418 "GET_PASSPHRASE --data %s"
420 non_interactive ? "--no-ask " : "",
422 escape_blanks(error_prompt),
423 escape_blanks(password_prompt),
424 escape_blanks(realm_prompt));
426 if (write(sd, request, strlen(request)) == -1)
431 if (!receive_from_gpg_agent(sd, buffer, BUFFER_SIZE))
439 if (strncmp(buffer, "ERR", 3) == 0)
443 if (strncmp(buffer, "D", 1) == 0)
449 ep = strchr(p, '\n');
460 /* Implementation of svn_auth__password_set_t that would store the
461 password in GPG Agent if that's how this particular integration
462 worked. But it isn't. GPG Agent stores the password provided by
463 the user via the pinentry program immediately upon its provision
464 (and regardless of its accuracy as passwords go), so we just need
465 to check if a running GPG Agent exists. */
467 password_set_gpg_agent(svn_boolean_t *done,
469 const char *realmstring,
470 const char *username,
471 const char *password,
472 apr_hash_t *parameters,
473 svn_boolean_t non_interactive,
480 SVN_ERR(find_running_gpg_agent(&sd, pool));
491 /* An implementation of svn_auth_provider_t::first_credentials() */
493 simple_gpg_agent_first_creds(void **credentials,
495 void *provider_baton,
496 apr_hash_t *parameters,
497 const char *realmstring,
501 int *attempt = apr_palloc(pool, sizeof(*attempt));
504 svn_hash_sets(parameters, ATTEMPT_PARAMETER, attempt);
505 err = svn_auth__simple_creds_cache_get(credentials, iter_baton,
506 provider_baton, parameters,
507 realmstring, password_get_gpg_agent,
508 SVN_AUTH__GPG_AGENT_PASSWORD_TYPE,
510 *iter_baton = attempt;
515 /* An implementation of svn_auth_provider_t::next_credentials() */
517 simple_gpg_agent_next_creds(void **credentials,
519 void *provider_baton,
520 apr_hash_t *parameters,
521 const char *realmstring,
524 int *attempt = (int *)iter_baton;
527 const char *cache_id = NULL;
528 const char *request = NULL;
532 /* The users previous credentials failed so first remove the cached entry,
533 * before trying to retrieve them again. Because gpg-agent stores cached
534 * credentials immediately upon retrieving them, this gives us the
535 * opportunity to remove the invalid credentials and prompt the
536 * user again. While it's possible that server side issues could trigger
537 * this, this cache is ephemeral so at worst we're just speeding up
538 * when the user would need to re-enter their password. */
540 if (svn_hash_gets(parameters, SVN_AUTH_PARAM_NON_INTERACTIVE))
542 /* In this case since we're running non-interactively we do not
543 * want to clear the cache since the user was never prompted by
544 * gpg-agent to set a password. */
548 *attempt = *attempt + 1;
550 SVN_ERR(find_running_gpg_agent(&sd, pool));
554 buffer = apr_palloc(pool, BUFFER_SIZE);
556 if (!send_options(sd, buffer, BUFFER_SIZE, pool))
562 SVN_ERR(get_cache_id(&cache_id, realmstring, pool, pool));
564 request = apr_psprintf(pool, "CLEAR_PASSPHRASE %s\n", cache_id);
566 if (write(sd, request, strlen(request)) == -1)
572 if (!receive_from_gpg_agent(sd, buffer, BUFFER_SIZE))
578 if (strncmp(buffer, "OK\n", 3) != 0)
584 /* TODO: This attempt limit hard codes it at 3 attempts (or 2 retries)
585 * which matches svn command line client's retry_limit as set in
586 * svn_cmdline_create_auth_baton(). It would be nice to have that
587 * limit reflected here but that violates the boundry between the
588 * prompt provider and the cache provider. gpg-agent is acting as
589 * both here due to the peculiarties of their design so we'll have to
590 * live with this for now. Note that when these failures get exceeded
591 * it'll eventually fall back on the retry limits of whatever prompt
592 * provider is in effect, so this effectively doubles the limit. */
594 return svn_auth__simple_creds_cache_get(credentials, &iter_baton,
595 provider_baton, parameters,
597 password_get_gpg_agent,
598 SVN_AUTH__GPG_AGENT_PASSWORD_TYPE,
605 /* An implementation of svn_auth_provider_t::save_credentials() */
607 simple_gpg_agent_save_creds(svn_boolean_t *saved,
609 void *provider_baton,
610 apr_hash_t *parameters,
611 const char *realmstring,
614 return svn_auth__simple_creds_cache_set(saved, credentials,
615 provider_baton, parameters,
616 realmstring, password_set_gpg_agent,
617 SVN_AUTH__GPG_AGENT_PASSWORD_TYPE,
622 static const svn_auth_provider_t gpg_agent_simple_provider = {
623 SVN_AUTH_CRED_SIMPLE,
624 simple_gpg_agent_first_creds,
625 simple_gpg_agent_next_creds,
626 simple_gpg_agent_save_creds
632 svn_auth_get_gpg_agent_simple_provider(svn_auth_provider_object_t **provider,
635 svn_auth_provider_object_t *po = apr_pcalloc(pool, sizeof(*po));
637 po->vtable = &gpg_agent_simple_provider;
641 #endif /* SVN_HAVE_GPG_AGENT */