common: Add code to execute a helper.

* common/sh-exectool.c: New file.

Signed-off-by: Justus Winter <justus@g10code.com>

common/sh-exectool.c

@@ -0,0 +1,303 @@
+/* sh-exectool.c - Utility functions to execute a helper tool
+ * Copyright (C) 2015 Werner Koch
+ *
+ * This file is part of GnuPG.
+ *
+ * GnuPG is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * GnuPG is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdarg.h>
+#include <errno.h>
+#include <assert.h>
+
+#include "g13-syshelp.h"
+#include <assuan.h>
+#include "i18n.h"
+#include "membuf.h"
+#include "exechelp.h"
+#include "sysutils.h"
+
+typedef struct
+{
+  const char *pgmname;
+  int cont;
+  int used;
+  char buffer[256];
+} read_and_log_buffer_t;
+
+
+static void
+read_and_log_stderr (read_and_log_buffer_t *state, es_poll_t *fderr)
+{
+  gpg_error_t err;
+  int c;
+
+  if (!fderr)
+    {
+      /* Flush internal buffer.  */
+      if (state->used)
+        {
+          const char *pname;
+          int len;
+
+          state->buffer[state->used] = 0;
+          state->used = 0;
+
+          pname = strrchr (state->pgmname, '/');
+          if (pname && pname != state->pgmname && pname[1])
+            pname++;
+          else
+            pname = state->pgmname;
+          /* If our pgmname plus colon is identical to the start of
+             the output, print only the output.  */
+          len = strlen (pname);
+          if (!state->cont
+              && !strncmp (state->buffer, pname, len)
+              && strlen (state->buffer) > strlen (pname)
+              && state->buffer[len] == ':' )
+            log_info ("%s\n", state->buffer);
+          else
+            log_info ("%s%c %s\n",
+                      pname, state->cont? '+':':', state->buffer);
+        }
+      state->cont = 0;
+      return;
+    }
+  for (;;)
+    {
+      c = es_fgetc (fderr->stream);
+      if (c == EOF)
+        {
+          if (es_feof (fderr->stream))
+            {
+              fderr->ignore = 1; /* Not anymore needed.  */
+            }
+          else if (es_ferror (fderr->stream))
+            {
+              err = gpg_error_from_syserror ();
+              log_error ("error reading stderr of '%s': %s\n",
+                         state->pgmname, gpg_strerror (err));
+              fderr->ignore = 1; /* Disable.  */
+            }
+
+          break;
+        }
+      else if (c == '\n')
+        {
+          read_and_log_stderr (state, NULL);
+        }
+      else
+        {
+          if (state->used >= sizeof state->buffer - 1)
+            {
+              read_and_log_stderr (state, NULL);
+              state->cont = 1;
+            }
+          state->buffer[state->used++] = c;
+        }
+    }
+}
+
+
+static gpg_error_t
+read_stdout (membuf_t *mb, es_poll_t *fdout, const char *pgmname)
+{
+  gpg_error_t err = 0;
+  int c;
+
+  for (;;)
+    {
+      c = es_fgetc (fdout->stream);
+      if (c == EOF)
+        {
+          if (es_feof (fdout->stream))
+            {
+              fdout->ignore = 1; /* Ready.  */
+            }
+          else if (es_ferror (fdout->stream))
+            {
+              err = gpg_error_from_syserror ();
+              log_error ("error reading stdout of '%s': %s\n",
+                         pgmname, gpg_strerror (err));
+              fdout->ignore = 1; /* Disable.  */
+            }
+
+          break;
+        }
+      else
+        {
+          char buf[1];
+          *buf = c;
+          put_membuf (mb, buf, 1);
+        }
+    }
+
+  return err;
+}
+
+
+/* Run the program PGMNAME with the command line arguments given in
+   the NULL terminates array ARGV.  If INPUT_STRING is not NULL it
+   will be fed to stdin of the process.  stderr is logged using
+   log_info and the process' stdout is returned in a newly malloced
+   buffer RESULT with the length stored at RESULTLEN if not given as
+   NULL.  A hidden Nul is appended to the output.  On error NULL is
+   stored at RESULT, a diagnostic is printed, and an error code
+   returned.  */
+gpg_error_t
+sh_exec_tool (const char *pgmname, const char *argv[],
+              const char *input_string,
+              char **result, size_t *resultlen)
+{
+  gpg_error_t err;
+  pid_t pid;
+  estream_t infp = NULL;
+  estream_t outfp, errfp;
+  es_poll_t fds[3];
+  int count;
+  read_and_log_buffer_t fderrstate;
+  membuf_t fdout_mb;
+  size_t len, nwritten;
+
+  *result = NULL;
+  if (resultlen)
+    *resultlen = 0;
+  memset (fds, 0, sizeof fds);
+  memset (&fderrstate, 0, sizeof fderrstate);
+  init_membuf (&fdout_mb, 4096);
+
+  err = gnupg_spawn_process (pgmname, argv, GPG_ERR_SOURCE_DEFAULT,
+                             NULL, GNUPG_SPAWN_NONBLOCK,
+                             input_string? &infp : NULL,
+                             &outfp, &errfp, &pid);
+  if (err)
+    {
+      log_error ("error running '%s': %s\n", pgmname, gpg_strerror (err));
+      return err;
+    }
+
+  fderrstate.pgmname = pgmname;
+
+  fds[0].stream = infp;
+  fds[0].want_write = 1;
+  if (!input_string)
+    fds[0].ignore = 1;
+  fds[1].stream = outfp;
+  fds[1].want_read = 1;
+  fds[2].stream = errfp;
+  fds[2].want_read = 1;
+  /* Now read as long as we have something to poll.  We continue
+     reading even after EOF or error on stdout so that we get the
+     other error messages or remaining outout.  */
+  while (!fds[1].ignore && !fds[2].ignore)
+    {
+      count = es_poll (fds, DIM(fds), -1);
+      if (count == -1)
+        {
+          err = gpg_error_from_syserror ();
+          log_error ("error polling '%s': %s\n", pgmname, gpg_strerror (err));
+          goto leave;
+        }
+      if (!count)
+        {
+          log_debug ("unexpected timeout while polling '%s'\n", pgmname);
+          break;
+        }
+
+      if (fds[0].got_write)
+        {
+          len = strlen (input_string);
+          log_debug ("writing '%s'\n", input_string);
+          if (es_write (fds[0].stream, input_string, len, &nwritten))
+	    {
+              if (errno != EAGAIN)
+                {
+                  err = gpg_error_from_syserror ();
+                  log_error ("error writing '%s': %s\n",
+                             pgmname, gpg_strerror (err));
+                  goto leave;
+                }
+              else
+                log_debug ("  .. EAGAIN\n");
+            }
+          else
+            {
+              assert (nwritten <= len);
+              input_string += nwritten;
+	    }
+
+          if (es_fflush (fds[0].stream) && errno != EAGAIN)
+            {
+              err = gpg_error_from_syserror ();
+              log_error ("error writing '%s' (flush): %s\n",
+                         pgmname, gpg_strerror (err));
+              if (gpg_err_code (err) == GPG_ERR_EPIPE && !*input_string)
+                {
+                  /* fixme: How can we tell whether estream has
+                     pending bytes after a HUP - which is an
+                     error?  */
+                }
+              else
+                goto leave;
+            }
+          if (!*input_string)
+            {
+              fds[0].ignore = 1; /* ready.  */
+              es_fclose (infp); infp = NULL;
+            }
+        }
+
+      if (fds[1].got_read)
+        read_stdout (&fdout_mb, fds + 1, pgmname); /* FIXME: Add error
+                                                      handling.  */
+      if (fds[2].got_read)
+        read_and_log_stderr (&fderrstate, fds + 2);
+
+    }
+
+  read_and_log_stderr (&fderrstate, NULL); /* Flush.  */
+  es_fclose (infp); infp = NULL;
+  es_fclose (outfp); outfp = NULL;
+  es_fclose (errfp); errfp = NULL;
+
+  err = gnupg_wait_process (pgmname, pid, 1, NULL);
+  pid = (pid_t)(-1);
+
+ leave:
+  if (err)
+    {
+      gnupg_kill_process (pid);
+      xfree (get_membuf (&fdout_mb, NULL));
+    }
+  else
+    {
+      put_membuf (&fdout_mb, "", 1); /* Make sure it is a string.  */
+      *result = get_membuf (&fdout_mb, resultlen);
+      if (!*result)
+        err = gpg_error_from_syserror ();
+    }
+
+  es_fclose (infp);
+  es_fclose (outfp);
+  es_fclose (errfp);
+  if (pid != (pid_t)(-1))
+    gnupg_wait_process (pgmname, pid, 1, NULL);
+  gnupg_release_process (pid);
+
+  return err;
+}