Adding upstream version 2.2.40.upstream/2.2.40

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 762 insertions, 0 deletions

diff --git a/common/ksba-io-support.c b/common/ksba-io-support.c
new file mode 100644
index 0000000..2832a4f
--- /dev/null
+++ b/common/ksba-io-support.c
@@ -0,0 +1,762 @@
+/* kska-io-support.c - Supporting functions for ksba reader and writer
+ * Copyright (C) 2001-2005, 2007, 2010-2011, 2017  Werner Koch
+ * Copyright (C) 2006  g10 Code GmbH
+ *
+ * This file is part of GnuPG.
+ *
+ * This file is free software; you can redistribute it and/or modify
+ * it under the terms of either
+ *
+ *   - the GNU Lesser General Public License as published by the Free
+ *     Software Foundation; either version 3 of the License, or (at
+ *     your option) any later version.
+ *
+ * or
+ *
+ *   - the GNU General Public License as published by the Free
+ *     Software Foundation; either version 2 of the License, or (at
+ *     your option) any later version.
+ *
+ * or both in parallel, as here.
+ *
+ * This file 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 <https://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <time.h>
+#include <assert.h>
+#include <ksba.h>
+
+#include "util.h"
+#include "i18n.h"
+#include "ksba-io-support.h"
+
+
+#ifdef HAVE_DOSISH_SYSTEM
+  #define LF "\r\n"
+#else
+  #define LF "\n"
+#endif
+
+
+/* Data used by the reader callbacks.  */
+struct reader_cb_parm_s
+{
+  estream_t fp;
+
+  unsigned char line[1024];
+  int linelen;
+  int readpos;
+  int have_lf;
+  unsigned long line_counter;
+
+  int allow_multi_pem;  /* Allow processing of multiple PEM objects. */
+  int autodetect;       /* Try to detect the input encoding. */
+  int assume_pem;       /* Assume input encoding is PEM. */
+  int assume_base64;    /* Assume input is base64 encoded. */
+
+  int identified;
+  int is_pem;
+  int is_base64;
+  int stop_seen;
+  int might_be_smime;
+
+  int eof_seen;
+
+  struct {
+    int idx;
+    unsigned char val;
+    int stop_seen;
+  } base64;
+};
+
+
+/* Data used by the writer callbacks.  */
+struct writer_cb_parm_s
+{
+  estream_t stream;    /* Output stream.  */
+
+  char *pem_name;      /* Malloced.  */
+
+  int wrote_begin;
+  int did_finish;
+
+  struct {
+    int idx;
+    int quad_count;
+    unsigned char radbuf[4];
+  } base64;
+
+};
+
+
+/* Context for this module's functions.  */
+struct gnupg_ksba_io_s {
+  union {
+    struct reader_cb_parm_s rparm;
+    struct writer_cb_parm_s wparm;
+  } u;
+
+  union {
+    ksba_reader_t reader;
+    ksba_writer_t writer;
+  } u2;
+};
+
+
+/* The base-64 character list */
+static char bintoasc[64] =
+       "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+       "abcdefghijklmnopqrstuvwxyz"
+       "0123456789+/";
+/* The reverse base-64 list */
+static unsigned char asctobin[256] = {
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0x3e, 0xff, 0xff, 0xff, 0x3f,
+  0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06,
+  0x07, 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, 0x10, 0x11, 0x12,
+  0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, 0x20, 0x21, 0x22, 0x23, 0x24,
+  0x25, 0x26, 0x27, 0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, 0x30,
+  0x31, 0x32, 0x33, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff,
+  0xff, 0xff, 0xff, 0xff
+};
+
+
+static int
+has_only_base64 (const unsigned char *line, int linelen)
+{
+  if (linelen < 20)
+    return 0;
+  for (; linelen; line++, linelen--)
+    {
+      if (*line == '\n' || (linelen > 1 && *line == '\r' && line[1] == '\n'))
+          break;
+      if ( !strchr (bintoasc, *line) )
+        return 0;
+    }
+  return 1;  /* yes */
+}
+
+static int
+is_empty_line (const unsigned char *line, int linelen)
+{
+  if (linelen >= 2 && *line == '\r' && line[1] == '\n')
+    return 1;
+  if (linelen >= 1 && *line == '\n')
+    return 1;
+  return 0;
+}
+
+
+static int
+base64_reader_cb (void *cb_value, char *buffer, size_t count, size_t *nread)
+{
+  struct reader_cb_parm_s *parm = cb_value;
+  size_t n;
+  int c, c2;
+
+  *nread = 0;
+  if (!buffer)
+    return -1; /* not supported */
+
+ next:
+  if (!parm->linelen)
+    {
+      /* read an entire line or up to the size of the buffer */
+      parm->line_counter++;
+      parm->have_lf = 0;
+      for (n=0; n < DIM(parm->line);)
+        {
+          c = es_getc (parm->fp);
+          if (c == EOF)
+            {
+              parm->eof_seen = 1;
+              if (es_ferror (parm->fp))
+                return -1;
+              break;
+            }
+          parm->line[n++] = c;
+          if (c == '\n')
+            {
+              parm->have_lf = 1;
+              /* Fixme: we need to skip overlong lines while detecting
+                 the dashed lines */
+              break;
+            }
+        }
+      parm->linelen = n;
+      if (!n)
+        return -1; /* eof */
+      parm->readpos = 0;
+    }
+
+  if (!parm->identified)
+    {
+      if (!parm->autodetect)
+        {
+          if (parm->assume_pem)
+            {
+              /* wait for the header line */
+              parm->linelen = parm->readpos = 0;
+              if (!parm->have_lf
+                  || strncmp ((char*)parm->line, "-----BEGIN ", 11)
+                  || !strncmp ((char*)parm->line+11, "PGP ", 4))
+                goto next;
+              parm->is_pem = 1;
+            }
+          else if (parm->assume_base64)
+            parm->is_base64 = 1;
+        }
+      else if (parm->line_counter == 1 && !parm->have_lf)
+        {
+          /* first line too long - assume DER encoding */
+          parm->is_pem = 0;
+        }
+      else if (parm->line_counter == 1 && parm->linelen && *parm->line == 0x30)
+        {
+          /* the very first byte does pretty much look like a SEQUENCE tag*/
+          parm->is_pem = 0;
+        }
+      else if ( parm->have_lf
+                && !strncmp ((char*)parm->line, "-----BEGIN ", 11)
+                && strncmp ((char *)parm->line+11, "PGP ", 4) )
+        {
+          /* Fixme: we must only compare if the line really starts at
+             the beginning */
+          parm->is_pem = 1;
+          parm->linelen = parm->readpos = 0;
+        }
+      else if ( parm->have_lf && parm->line_counter == 1
+                && parm->linelen >= 13
+                && !ascii_memcasecmp (parm->line, "Content-Type:", 13))
+        { /* might be a S/MIME body */
+          parm->might_be_smime = 1;
+          parm->linelen = parm->readpos = 0;
+          goto next;
+        }
+      else if (parm->might_be_smime == 1
+               && is_empty_line (parm->line, parm->linelen))
+        {
+          parm->might_be_smime = 2;
+          parm->linelen = parm->readpos = 0;
+          goto next;
+        }
+      else if (parm->might_be_smime == 2)
+        {
+          parm->might_be_smime = 0;
+          if ( !has_only_base64 (parm->line, parm->linelen))
+            {
+              parm->linelen = parm->readpos = 0;
+              goto next;
+            }
+          parm->is_pem = 1;
+        }
+      else
+        {
+          parm->linelen = parm->readpos = 0;
+          goto next;
+        }
+      parm->identified = 1;
+      parm->base64.stop_seen = 0;
+      parm->base64.idx = 0;
+    }
+
+
+  n = 0;
+  if (parm->is_pem || parm->is_base64)
+    {
+      if (parm->is_pem && parm->have_lf
+          && !strncmp ((char*)parm->line, "-----END ", 9))
+        {
+          parm->identified = 0;
+          parm->linelen = parm->readpos = 0;
+
+          /* If the caller want to read multiple PEM objects from one
+             file, we have to reset our internal state and return a
+             EOF immediately. The caller is the expected to use
+             ksba_reader_clear to clear the EOF condition and continue
+             to read.  If we don't want to do that we just return 0
+             bytes which will force the ksba_reader to skip until
+             EOF. */
+          if (parm->allow_multi_pem)
+            {
+              parm->identified = 0;
+              parm->autodetect = 0;
+              parm->assume_pem = 1;
+              parm->stop_seen = 0;
+              return -1; /* Send EOF now. */
+            }
+        }
+      else if (parm->stop_seen)
+        { /* skip the rest of the line */
+          parm->linelen = parm->readpos = 0;
+        }
+      else
+        {
+          int idx = parm->base64.idx;
+          unsigned char val = parm->base64.val;
+
+          while (n < count && parm->readpos < parm->linelen )
+            {
+              c = parm->line[parm->readpos++];
+              if (c == '\n' || c == ' ' || c == '\r' || c == '\t')
+                continue;
+              if ((c = asctobin[(c2=c)]) == 255)
+                {
+                  if (c2 == '=')
+                    { /* pad character: stop */
+                      if (idx == 1)
+                        buffer[n++] = val;
+                      parm->stop_seen = 1;
+                      break;
+                    }
+                  else if (c2 == '-'
+                           && parm->readpos == 1
+                           && parm->readpos-1+9 < parm->linelen
+                           && !strncmp ((char*)parm->line + parm->readpos-1,
+                                        "-----END ", 9))
+                    { /* END line seen (padding was not needed). */
+                      parm->stop_seen = 1;
+                      break;
+                    }
+                  log_error (_("invalid radix64 character %02x skipped\n"),
+                             c2);
+                  continue;
+                }
+              switch (idx)
+                {
+                case 0:
+                  val = c << 2;
+                  break;
+                case 1:
+                  val |= (c>>4)&3;
+                  buffer[n++] = val;
+                  val = (c<<4)&0xf0;
+                  break;
+                case 2:
+                  val |= (c>>2)&15;
+                  buffer[n++] = val;
+                  val = (c<<6)&0xc0;
+                  break;
+                case 3:
+                  val |= c&0x3f;
+                  buffer[n++] = val;
+                  break;
+                }
+              idx = (idx+1) % 4;
+            }
+          if (parm->readpos == parm->linelen)
+            parm->linelen = parm->readpos = 0;
+
+          parm->base64.idx = idx;
+          parm->base64.val = val;
+        }
+    }
+  else
+    { /* DER encoded */
+      while (n < count && parm->readpos < parm->linelen)
+          buffer[n++] = parm->line[parm->readpos++];
+      if (parm->readpos == parm->linelen)
+        parm->linelen = parm->readpos = 0;
+    }
+
+  *nread = n;
+  return 0;
+}
+
+
+
+static int
+simple_reader_cb (void *cb_value, char *buffer, size_t count, size_t *nread)
+{
+  struct reader_cb_parm_s *parm = cb_value;
+  size_t n;
+  int c = 0;
+
+  *nread = 0;
+  if (!buffer)
+    return -1; /* not supported */
+
+  for (n=0; n < count; n++)
+    {
+      c = es_getc (parm->fp);
+      if (c == EOF)
+        {
+          parm->eof_seen = 1;
+          if (es_ferror (parm->fp))
+            return -1;
+          if (n)
+            break; /* Return what we have before an EOF.  */
+          return -1;
+        }
+      *(byte *)buffer++ = c;
+    }
+
+  *nread = n;
+  return 0;
+}
+
+
+
+
+static int
+base64_writer_cb (void *cb_value, const void *buffer, size_t count)
+{
+  struct writer_cb_parm_s *parm = cb_value;
+  unsigned char radbuf[4];
+  int i, c, idx, quad_count;
+  const unsigned char *p;
+  estream_t stream = parm->stream;
+
+  if (!count)
+    return 0;
+
+  if (!parm->wrote_begin)
+    {
+      if (parm->pem_name)
+        {
+          es_fputs ("-----BEGIN ", stream);
+          es_fputs (parm->pem_name, stream);
+          es_fputs ("-----\n", stream);
+        }
+      parm->wrote_begin = 1;
+      parm->base64.idx = 0;
+      parm->base64.quad_count = 0;
+    }
+
+  idx = parm->base64.idx;
+  quad_count = parm->base64.quad_count;
+  for (i=0; i < idx; i++)
+    radbuf[i] = parm->base64.radbuf[i];
+
+  for (p=buffer; count; p++, count--)
+    {
+      radbuf[idx++] = *p;
+      if (idx > 2)
+        {
+          idx = 0;
+          c = bintoasc[(*radbuf >> 2) & 077];
+          es_putc (c, stream);
+          c = bintoasc[(((*radbuf<<4)&060)|((radbuf[1] >> 4)&017))&077];
+          es_putc (c, stream);
+          c = bintoasc[(((radbuf[1]<<2)&074)|((radbuf[2]>>6)&03))&077];
+          es_putc (c, stream);
+          c = bintoasc[radbuf[2]&077];
+          es_putc (c, stream);
+          if (++quad_count >= (64/4))
+            {
+              es_fputs (LF, stream);
+              quad_count = 0;
+            }
+        }
+    }
+  for (i=0; i < idx; i++)
+    parm->base64.radbuf[i] = radbuf[i];
+  parm->base64.idx = idx;
+  parm->base64.quad_count = quad_count;
+
+  return es_ferror (stream)? gpg_error_from_syserror () : 0;
+}
+
+
+/* This callback is only used in stream mode.  However, we don't
+   restrict it to this.  */
+static int
+plain_writer_cb (void *cb_value, const void *buffer, size_t count)
+{
+  struct writer_cb_parm_s *parm = cb_value;
+  estream_t stream = parm->stream;
+
+  if (!count)
+    return 0;
+
+  es_write (stream, buffer, count, NULL);
+
+  return es_ferror (stream)? gpg_error_from_syserror () : 0;
+}
+
+
+static int
+base64_finish_write (struct writer_cb_parm_s *parm)
+{
+  unsigned char *radbuf;
+  int c, idx, quad_count;
+  estream_t stream = parm->stream;
+
+  if (!parm->wrote_begin)
+    return 0; /* Nothing written or we are not called in base-64 mode. */
+
+  /* flush the base64 encoding */
+  idx = parm->base64.idx;
+  quad_count = parm->base64.quad_count;
+  if (idx)
+    {
+      radbuf = parm->base64.radbuf;
+
+      c = bintoasc[(*radbuf>>2)&077];
+      es_putc (c, stream);
+      if (idx == 1)
+        {
+          c = bintoasc[((*radbuf << 4) & 060) & 077];
+          es_putc (c, stream);
+          es_putc ('=', stream);
+          es_putc ('=', stream);
+        }
+      else
+        {
+          c = bintoasc[(((*radbuf<<4)&060)|((radbuf[1]>>4)&017))&077];
+          es_putc (c, stream);
+          c = bintoasc[((radbuf[1] << 2) & 074) & 077];
+          es_putc (c, stream);
+          es_putc ('=', stream);
+
+        }
+      if (++quad_count >= (64/4))
+        {
+          es_fputs (LF, stream);
+          quad_count = 0;
+        }
+    }
+
+  if (quad_count)
+    es_fputs (LF, stream);
+
+  if (parm->pem_name)
+    {
+      es_fputs ("-----END ", stream);
+      es_fputs (parm->pem_name, stream);
+      es_fputs ("-----\n", stream);
+    }
+
+  return es_ferror (stream)? gpg_error_from_syserror () : 0;
+}
+
+
+
+
+/* Create a reader for the stream FP.  FLAGS can be used to specify
+ * the expected input encoding.
+ *
+ * The function returns a gnupg_ksba_io_t object which must be passed to
+ * the gpgme_destroy_reader function.  The created ksba_reader_t
+ * object is stored at R_READER - the caller must not call the
+ * ksba_reader_release function on.
+ *
+ * The supported flags are:
+ *
+ * GNUPG_KSBA_IO_PEM        - Assume the input is PEM encoded
+ * GNUPG_KSBA_IO_BASE64     - Assume the input is Base64 encoded.
+ * GNUPG_KSBA_IO_AUTODETECT - The reader tries to detect the encoding.
+ * GNUPG_KSBA_IO_MULTIPEM   - The reader expects that the caller uses
+ *                            ksba_reader_clear after EOF until no more
+ *                            objects were found.
+ *
+ * Note that the PEM flag has a higher priority than the BASE64 flag
+ * which in turn has a gight priority than the AUTODETECT flag.
+ */
+gpg_error_t
+gnupg_ksba_create_reader (gnupg_ksba_io_t *ctx,
+                          unsigned int flags, estream_t fp,
+                          ksba_reader_t *r_reader)
+{
+  int rc;
+  ksba_reader_t r;
+
+  *r_reader = NULL;
+  *ctx = xtrycalloc (1, sizeof **ctx);
+  if (!*ctx)
+    return out_of_core ();
+  (*ctx)->u.rparm.allow_multi_pem = !!(flags & GNUPG_KSBA_IO_MULTIPEM);
+
+  rc = ksba_reader_new (&r);
+  if (rc)
+    {
+      xfree (*ctx); *ctx = NULL;
+      return rc;
+    }
+
+  (*ctx)->u.rparm.fp = fp;
+  if ((flags & GNUPG_KSBA_IO_PEM))
+    {
+      (*ctx)->u.rparm.assume_pem = 1;
+      (*ctx)->u.rparm.assume_base64 = 1;
+      rc = ksba_reader_set_cb (r, base64_reader_cb, &(*ctx)->u.rparm);
+    }
+  else if ((flags & GNUPG_KSBA_IO_BASE64))
+    {
+      (*ctx)->u.rparm.assume_base64 = 1;
+      rc = ksba_reader_set_cb (r, base64_reader_cb, &(*ctx)->u.rparm);
+    }
+  else if ((flags & GNUPG_KSBA_IO_AUTODETECT))
+    {
+      (*ctx)->u.rparm.autodetect = 1;
+      rc = ksba_reader_set_cb (r, base64_reader_cb, &(*ctx)->u.rparm);
+    }
+  else
+      rc = ksba_reader_set_cb (r, simple_reader_cb, &(*ctx)->u.rparm);
+
+  if (rc)
+    {
+      ksba_reader_release (r);
+      xfree (*ctx); *ctx = NULL;
+      return rc;
+    }
+
+  (*ctx)->u2.reader = r;
+  *r_reader = r;
+  return 0;
+}
+
+
+/* Return True if an EOF as been seen.  */
+int
+gnupg_ksba_reader_eof_seen (gnupg_ksba_io_t ctx)
+{
+  return ctx && ctx->u.rparm.eof_seen;
+}
+
+
+/* Destroy a reader object.  */
+void
+gnupg_ksba_destroy_reader (gnupg_ksba_io_t ctx)
+{
+  if (!ctx)
+    return;
+
+  ksba_reader_release (ctx->u2.reader);
+  xfree (ctx);
+}
+
+
+
+/* Create a writer for the given STREAM.  Depending on FLAGS an output
+ * encoding is chosen.  In PEM mode PEM_NAME is used for the header
+ * and footer lines; if PEM_NAME is NULL the string "CMS OBJECT" is
+ * used.
+ *
+ * The function returns a gnupg_ksba_io_t object which must be passed to
+ * the gpgme_destroy_writer function.  The created ksba_writer_t
+ * object is stored at R_WRITER - the caller must not call the
+ * ksba_reader_release function on it.
+ *
+ * The supported flags are:
+ *
+ * GNUPG_KSBA_IO_PEM    - Write output as PEM
+ * GNUPG_KSBA_IO_BASE64 - Write output as plain Base64; note that the PEM
+ *                        flag overrides this flag.
+ *
+ */
+gpg_error_t
+gnupg_ksba_create_writer (gnupg_ksba_io_t *ctx, unsigned int flags,
+                          const char *pem_name, estream_t stream,
+                          ksba_writer_t *r_writer)
+{
+  int rc;
+  ksba_writer_t w;
+
+  *r_writer = NULL;
+  *ctx = xtrycalloc (1, sizeof **ctx);
+  if (!*ctx)
+    return gpg_error_from_syserror ();
+
+  rc = ksba_writer_new (&w);
+  if (rc)
+    {
+      xfree (*ctx); *ctx = NULL;
+      return rc;
+    }
+
+  if ((flags & GNUPG_KSBA_IO_PEM) || (flags & GNUPG_KSBA_IO_BASE64))
+    {
+      (*ctx)->u.wparm.stream = stream;
+      if ((flags & GNUPG_KSBA_IO_PEM))
+        {
+          (*ctx)->u.wparm.pem_name = xtrystrdup (pem_name
+                                                 ? pem_name
+                                                 : "CMS OBJECT");
+          if (!(*ctx)->u.wparm.pem_name)
+            {
+              rc = gpg_error_from_syserror ();
+              ksba_writer_release (w);
+              xfree (*ctx); *ctx = NULL;
+              return rc;
+            }
+        }
+      rc = ksba_writer_set_cb (w, base64_writer_cb, &(*ctx)->u.wparm);
+    }
+  else if (stream)
+    {
+      (*ctx)->u.wparm.stream = stream;
+      rc = ksba_writer_set_cb (w, plain_writer_cb, &(*ctx)->u.wparm);
+    }
+  else
+    rc = gpg_error (GPG_ERR_INV_ARG);
+
+  if (rc)
+    {
+      ksba_writer_release (w);
+      xfree (*ctx); *ctx = NULL;
+      return rc;
+    }
+
+  (*ctx)->u2.writer = w;
+  *r_writer = w;
+  return 0;
+}
+
+
+/* Flush a writer.  This is for example required to write the padding
+ * or the PEM footer.  */
+gpg_error_t
+gnupg_ksba_finish_writer (gnupg_ksba_io_t ctx)
+{
+  struct writer_cb_parm_s *parm;
+
+  if (!ctx)
+    return gpg_error (GPG_ERR_INV_VALUE);
+  parm = &ctx->u.wparm;
+  if (parm->did_finish)
+    return 0; /* Already done. */
+  parm->did_finish = 1;
+  if (!parm->stream)
+    return 0; /* Callback was not used.  */
+  return base64_finish_write (parm);
+}
+
+
+/* Destroy a writer object.  */
+void
+gnupg_ksba_destroy_writer (gnupg_ksba_io_t ctx)
+{
+  if (!ctx)
+    return;
+
+  ksba_writer_release (ctx->u2.writer);
+  xfree (ctx->u.wparm.pem_name);
+  xfree (ctx);
+}