common/get-passphrase.c

   1 /* get-passphrase.c - Ask for a passphrase via the agent
   2  * Copyright (C) 2009 Free Software Foundation, Inc.
   3  *
   4  * This file is part of GnuPG.
   5  *
   6  * GnuPG is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * GnuPG is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <config.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <assert.h>
  25 #include <assuan.h>
  26
  27 #include "util.h"
  28 #include "i18n.h"
  29 #include "asshelp.h"
  30 #include "membuf.h"
  31 #include "sysutils.h"
  32 #include "get-passphrase.h"
  33
  34 /* The context used by this process to ask for the passphrase.  */
  35 static assuan_context_t agent_ctx;
  36 static struct
  37 {
  38   gpg_err_source_t errsource;
  39   int verbosity;
  40   const char *homedir;
  41   const char *agent_program;
  42   const char *lc_ctype;
  43   const char *lc_messages;
  44   session_env_t session_env;
  45   const char *pinentry_user_data;
  46 } agentargs;
  47
  48
  49 /* Set local variable to be used for a possible agent startup.  Note
  50    that the strings are just pointers and should not anymore be
  51    modified by the caller. */
  52 void
  53 gnupg_prepare_get_passphrase (gpg_err_source_t errsource,
  54                               int verbosity,
  55                               const char *homedir,
  56                               const char *agent_program,
  57                               const char *opt_lc_ctype,
  58                               const char *opt_lc_messages,
  59                               session_env_t session_env)
  60 {
  61   agentargs.errsource          = errsource;
  62   agentargs.verbosity          = verbosity;
  63   agentargs.homedir            = homedir;
  64   agentargs.agent_program      = agent_program;
  65   agentargs.lc_ctype           = opt_lc_ctype;
  66   agentargs.lc_messages        = opt_lc_messages;
  67   agentargs.session_env        = session_env;
  68 }
  69
  70
  71 /* Try to connect to the agent via socket or fork it off and work by
  72    pipes.  Handle the server's initial greeting.  */
  73 static gpg_error_t
  74 start_agent (void)
  75 {
  76   gpg_error_t err;
  77
  78   /* Fixme: This code is not thread safe, thus we don't build it with
  79      pth.  We will need a context for each thread or serialize the
  80      access to the agent.  */
  81   if (agent_ctx)
  82     return 0;
  83
  84   err = start_new_gpg_agent (&agent_ctx,
  85                              agentargs.errsource,
  86                              agentargs.homedir,
  87                              agentargs.agent_program,
  88                              agentargs.lc_ctype,
  89                              agentargs.lc_messages,
  90                              agentargs.session_env,
  91                              agentargs.verbosity, 0, NULL, NULL);
  92   if (!err)
  93     {
  94       /* Tell the agent that we support Pinentry notifications.  No
  95          error checking so that it will work with older agents.  */
  96       assuan_transact (agent_ctx, "OPTION allow-pinentry-notify",
  97                        NULL, NULL, NULL, NULL, NULL, NULL);
  98     }
  99
 100   return err;
 101 }
 102
 103
 104 /* This is the default inquiry callback.  It merely handles the
 105    Pinentry notification.  */
 106 static int
 107 default_inq_cb (void *opaque, const char *line)
 108 {
 109   (void)opaque;
 110
 111   if (!strncmp (line, "PINENTRY_LAUNCHED", 17) && (line[17]==' '||!line[17]))
 112     {
 113       gnupg_allow_set_foregound_window ((pid_t)strtoul (line+17, NULL, 10));
 114       /* We do not return errors to avoid breaking other code.  */
 115     }
 116   else
 117     log_debug ("ignoring gpg-agent inquiry `%s'\n", line);
 118
 119   return 0;
 120 }
 121
 122
 123 static int
 124 membuf_data_cb (void *opaque, const void *buffer, size_t length)
 125 {
 126   membuf_t *data = opaque;
 127
 128   if (buffer)
 129     put_membuf (data, buffer, length);
 130   return 0;
 131 }
 132
 133
 134 /* Ask for a passphrase via gpg-agent.  On success the caller needs to
 135    free the string stored at R_PASSPHRASE.  On error NULL will be
 136    stored at R_PASSPHRASE and an appropriate gpg error code is
 137    returned.  With REPEAT set to 1, gpg-agent will ask the user to
 138    repeat the just entered passphrase.  CACHE_ID is a gpg-agent style
 139    passphrase cache id or NULL.  ERR_MSG is a error message to be
 140    presented to the user (e.g. "bad passphrase - try again") or NULL.
 141    PROMPT is the prompt string to label the entry box, it may be NULL
 142    for a default one.  DESC_MSG is a longer description to be
 143    displayed above the entry box, if may be NULL for a default one.
 144    If USE_SECMEM is true, the returned passphrase is retruned in
 145    secure memory.  The length of all these strings is limited; they
 146    need to fit in their encoded form into a standard Assuan line (i.e
 147    less then about 950 characters).  All strings shall be UTF-8.  */
 148 gpg_error_t
 149 gnupg_get_passphrase (const char *cache_id,
 150                       const char *err_msg,
 151                       const char *prompt,
 152                       const char *desc_msg,
 153                       int repeat,
 154                       int check_quality,
 155                       int use_secmem,
 156                       char **r_passphrase)
 157 {
 158   gpg_error_t err;
 159   char line[ASSUAN_LINELENGTH];
 160   const char *arg1 = NULL;
 161   char *arg2 = NULL;
 162   char *arg3 = NULL;
 163   char *arg4 = NULL;
 164   membuf_t data;
 165
 166   *r_passphrase = NULL;
 167
 168   err = start_agent ();
 169   if (err)
 170     return err;
 171
 172   /* Check that the gpg-agent understands the repeat option.  */
 173   if (assuan_transact (agent_ctx,
 174                        "GETINFO cmd_has_option GET_PASSPHRASE repeat",
 175                        NULL, NULL, NULL, NULL, NULL, NULL))
 176     return gpg_error (GPG_ERR_NOT_SUPPORTED);
 177
 178   arg1 = cache_id && *cache_id? cache_id:NULL;
 179   if (err_msg && *err_msg)
 180     if (!(arg2 = percent_plus_escape (err_msg)))
 181       goto no_mem;
 182   if (prompt && *prompt)
 183     if (!(arg3 = percent_plus_escape (prompt)))
 184       goto no_mem;
 185   if (desc_msg && *desc_msg)
 186     if (!(arg4 = percent_plus_escape (desc_msg)))
 187       goto no_mem;
 188
 189   snprintf (line, DIM(line)-1,
 190             "GET_PASSPHRASE --data %s--repeat=%d -- %s %s %s %s",
 191             check_quality? "--check ":"",
 192             repeat,
 193             arg1? arg1:"X",
 194             arg2? arg2:"X",
 195             arg3? arg3:"X",
 196             arg4? arg4:"X");
 197   line[DIM(line)-1] = 0;
 198   xfree (arg2);
 199   xfree (arg3);
 200   xfree (arg4);
 201
 202   if (use_secmem)
 203     init_membuf_secure (&data, 64);
 204   else
 205     init_membuf (&data, 64);
 206   err = assuan_transact (agent_ctx, line,
 207                          membuf_data_cb, &data,
 208                          default_inq_cb, NULL, NULL, NULL);
 209
 210   /* Older Pinentries return the old assuan error code for canceled
 211      which gets translated bt libassuan to GPG_ERR_ASS_CANCELED and
 212      not to the code for a user cancel.  Fix this here. */
 213   if (err && gpg_err_source (err)
 214       && gpg_err_code (err) == GPG_ERR_ASS_CANCELED)
 215     err = gpg_err_make (gpg_err_source (err), GPG_ERR_CANCELED);
 216
 217   if (err)
 218     {
 219       void *p;
 220       size_t n;
 221
 222       p = get_membuf (&data, &n);
 223       if (p)
 224         wipememory (p, n);
 225       xfree (p);
 226     }
 227   else
 228     {
 229       put_membuf (&data, "", 1);
 230       *r_passphrase = get_membuf (&data, NULL);
 231       if (!*r_passphrase)
 232         err = gpg_error_from_syserror ();
 233     }
 234   return err;
 235  no_mem:
 236   err = gpg_error_from_syserror ();
 237   xfree (arg2);
 238   xfree (arg3);
 239   xfree (arg4);
 240   return err;
 241 }
 242
 243
 244 /* Flush the passphrase cache with Id CACHE_ID.  */
 245 gpg_error_t
 246 gnupg_clear_passphrase (const char *cache_id)
 247 {
 248   gpg_error_t err;
 249   char line[ASSUAN_LINELENGTH];
 250
 251   if (!cache_id || !*cache_id)
 252     return 0;
 253
 254   err = start_agent ();
 255   if (err)
 256     return err;
 257
 258   snprintf (line, DIM(line)-1, "CLEAR_PASSPHRASE %s", cache_id);
 259   line[DIM(line)-1] = 0;
 260   return assuan_transact (agent_ctx, line, NULL, NULL,
 261                           default_inq_cb, NULL, NULL, NULL);
 262 }