diff --git a/common/tlv-parser.c b/common/tlv-parser.c
new file mode 100644
index 000000000..b52cc7a21
--- /dev/null
+++ b/common/tlv-parser.c
@@ -0,0 +1,827 @@
+/* tlv-parser.c - Parse BER encoded objects
+ * Copyright (C) 2023, 2024 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 the GNU Lesser General Public License as
+ * published by the Free Software Foundation; either version 2.1 of
+ * the License, or (at your option) any later version.
+ *
+ * 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 Lesser General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses/>.
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <gpg-error.h>
+
+#include "util.h"
+#include "tlv.h"
+
+
+#define TLV_MAX_DEPTH 25
+
+
+
+/* An object to control the ASN.1 parsing.  */
+struct tlv_parser_s
+{
+  /* The original buffer with the entire pkcs#12 object and its length.  */
+  unsigned char *origbuffer;
+  size_t origbufsize;
+
+  /* The original offset for debugging.  */
+  size_t origoff;
+
+  /* Here we keep a copy of the former TLV.  This is returned by
+   * tlv_parser_release.  */
+  tlv_parser_t lasttlv;
+
+  /* The current buffer we are working on and its length. */
+  unsigned char *buffer;
+  size_t bufsize;
+
+  size_t crammed;      /* 0 or actual length of crammed octet strings.  */
+  int in_ndef;         /* Flag indicating that we are in a NDEF. */
+  int pending;         /* The last tlv_next has not yet been processed.  */
+
+  struct tag_info ti;  /* The current tag.  */
+  gpg_error_t lasterr; /* Last error from tlv function.  */
+  const char *lastfunc;/* Name of last called function.  */
+  int verbosity;       /* Arg from tlv_parser_new.       */
+
+  unsigned int stacklen; /* Used size of the stack.  */
+  struct {
+    unsigned char *buffer;        /* Saved value of BUFFER.   */
+    size_t bufsize;               /* Saved value of BUFSIZE.  */
+    size_t length;                /* Length of the container (ti.length). */
+    size_t crammed;               /* Saved CRAMMED value.                 */
+    int    in_ndef;               /* Saved IN_NDEF flag (ti.ndef).        */
+  } stack[TLV_MAX_DEPTH];
+};
+
+
+static size_t cram_octet_string (tlv_parser_t tlv, int testmode);
+
+
+
+void
+_tlv_parser_dump_tag (const char *text, int lno, tlv_parser_t tlv)
+{
+  struct tag_info *ti;
+
+  if (!tlv || tlv->verbosity < 2)
+    return;
+
+  ti = &tlv->ti;
+
+  log_debug ("%s:%d: %zu@%04zu class=%d tag=%lu %c len=%zu%s nhdr=%zu\n",
+             text, lno, tlv->origoff, tlv_parser_offset (tlv) - ti->nhdr,
+             ti->class, ti->tag, ti->is_constructed?'c':'p',
+             ti->length,ti->ndef?" ndef":"", ti->nhdr);
+}
+
+
+void
+_tlv_parser_dump_state (const char *text, const char *text2,
+                        int lno, tlv_parser_t tlv)
+{
+  if (!tlv || tlv->verbosity < 2)
+    return;
+
+  log_debug ("p12_parse:%s%s%s:%d: %zu@%04zu lvl=%u %s\n",
+             text,
+             text2? "/":"", text2? text2:"",
+             lno, tlv->origoff, tlv_parser_offset (tlv),
+             tlv->stacklen,
+             tlv->in_ndef? " in-ndef":"");
+}
+
+
+static void
+dump_to_file (const void *s, size_t n, const char *name)
+{
+#if 0
+  FILE *fp;
+  char fname[100];
+  static int fcount;
+
+  snprintf (fname, sizeof fname, "tmp-%03d-%s", ++fcount, name);
+  log_debug ("dumping %zu bytes to '%s'\n", n, fname);
+  fp = fopen (fname, "wb");
+  if (!fp || fwrite (s, n, 1, fp) != 1)
+    exit (2);
+  fclose (fp);
+#else
+  (void)s;
+  (void)n;
+  (void)name;
+#endif
+}
+
+
+/* Parse the buffer at the address BUFFER which is of SIZE and return
+ * the tag and the length part from the TLV triplet.  Update BUFFER
+ * and SIZE on success.  Checks that the encoded length does not
+ * exhaust the length of the provided buffer.  */
+static int
+parse_tag (unsigned char const **buffer, size_t *size, struct tag_info *ti)
+{
+  gpg_error_t err;
+  int tag;
+
+  err = parse_ber_header (buffer, size,
+                          &ti->class, &tag,
+                          &ti->is_constructed, &ti->ndef,
+                          &ti->length, &ti->nhdr);
+  if (err)
+    return err;
+  if (tag < 0)
+    return gpg_error (GPG_ERR_EOVERFLOW);
+  ti->tag = tag;
+
+  if (ti->length > *size)
+    {
+      /* data larger than buffer. */
+      log_debug ("%s: ti->length=%zu for a buffer of size=%zu\n",
+                 __func__, ti->length, *size);
+      return gpg_error (GPG_ERR_BUFFER_TOO_SHORT);
+    }
+
+  return 0;
+}
+
+/* Public version of parse_tag.  */
+gpg_error_t
+tlv_parse_tag (unsigned char const **buffer, size_t *size, struct tag_info *ti)
+{
+  return parse_tag (buffer, size, ti);
+}
+
+
+/* Create a new TLV object.  */
+tlv_parser_t
+_tlv_parser_new (const unsigned char *buffer, size_t bufsize,
+                int verbosity, tlv_parser_t lasttlv, int lno)
+{
+  tlv_parser_t tlv;
+
+  if (verbosity > 1)
+    log_debug ("%s:%d: %zu@%zu (%p,%zu)\n", __func__, lno,
+               lasttlv?lasttlv->origoff:0, tlv_parser_offset (lasttlv),
+               buffer, bufsize);
+
+  tlv = xtrycalloc (1, sizeof *tlv);
+  if (tlv)
+    {
+      char *mybuf = xtrymalloc ( bufsize + 1);
+      if (!mybuf)
+        {
+          xfree (tlv);
+          return NULL;
+        }
+      memcpy (mybuf, buffer, bufsize);
+      mybuf[bufsize] = 0;
+      tlv->origbuffer = mybuf;
+      tlv->origbufsize = bufsize;
+      tlv->origoff = tlv_parser_offset (lasttlv);
+      tlv->buffer = mybuf;
+      tlv->bufsize = bufsize;
+      tlv->crammed = 0;
+      tlv->verbosity = verbosity;
+      tlv->lasttlv = lasttlv;
+      dump_to_file (mybuf, bufsize, "context");
+    }
+  return tlv;
+}
+
+
+/* Free the TLV object and returns the last TLV object stored in this
+ * TLV.  */
+tlv_parser_t
+_tlv_parser_release (tlv_parser_t tlv, int lno)
+{
+  tlv_parser_t result;
+
+  if (!tlv)
+    return NULL;
+  result = tlv->lasttlv;
+  if (tlv->verbosity > 1)
+    {
+      if (result)
+        log_debug ("%s:%d: done; returning last TLV %zu@%zu (%p,%zu)\n",
+                   __func__, lno, result->origoff,
+                   tlv_parser_offset (result), result->buffer, result->bufsize);
+      else
+        log_debug ("%s:%d: done\n", __func__, lno);
+    }
+  xfree (tlv->origbuffer);
+  xfree (tlv);
+  return result;
+}
+
+
+/* Helper for tlv_expect_sequence and tlv_expect_context_tag.  */
+static gpg_error_t
+_tlv_push (tlv_parser_t tlv)
+{
+
+  /* Right now our pointer is at the value of the current container.
+   * We push that info onto the stack.  */
+  if (tlv->stacklen >= TLV_MAX_DEPTH)
+    return (tlv->lasterr = gpg_error (GPG_ERR_TOO_MANY));
+  tlv->stack[tlv->stacklen].buffer  = tlv->buffer;
+  tlv->stack[tlv->stacklen].bufsize = tlv->bufsize;
+  tlv->stack[tlv->stacklen].in_ndef = tlv->in_ndef;
+  tlv->stack[tlv->stacklen].length  = tlv->ti.length;
+  tlv->stack[tlv->stacklen].crammed = tlv->crammed;
+  tlv->stacklen++;
+
+  tlv->in_ndef = tlv->ti.ndef;
+
+  /* We set the size of the buffer to the TLV length if it is known or
+   * else to the size of the remaining entire buffer.  */
+  if (tlv->in_ndef)
+    {
+      if ((tlv->buffer - tlv->origbuffer) > tlv->origbufsize)
+        return (tlv->lasterr = gpg_error (GPG_ERR_BUG));
+      tlv->bufsize = tlv->origbufsize - (tlv->buffer - tlv->origbuffer);
+    }
+  else
+    tlv->bufsize = tlv->ti.length;
+
+  _tlv_parser_dump_state (__func__, NULL, 0, tlv);
+  return 0;
+}
+
+
+/* Helper for tlv_next.  */
+static gpg_error_t
+_tlv_pop (tlv_parser_t tlv)
+{
+  size_t length;
+
+  /* We reached the end of a container, either due to the size limit
+   * or due to an end tag.  Now we pop the last container so that we
+   * are positioned at the value of the last container. */
+  if (!tlv->stacklen)
+    return gpg_error (GPG_ERR_EOF);
+
+  tlv->stacklen--;
+  tlv->in_ndef = tlv->stack[tlv->stacklen].in_ndef;
+  length = tlv->ti.length = tlv->stack[tlv->stacklen].length;
+  tlv->crammed = tlv->stack[tlv->stacklen].crammed;
+  if (tlv->in_ndef)
+    {
+      /* We keep buffer but adjust bufsize to the end of the origbuffer. */
+      if ((tlv->buffer - tlv->origbuffer) > tlv->origbufsize)
+        return (tlv->lasterr = gpg_error (GPG_ERR_BUG));
+      tlv->bufsize = tlv->origbufsize - (tlv->buffer - tlv->origbuffer);
+    }
+  else
+    {
+      tlv->buffer  = tlv->stack[tlv->stacklen].buffer;
+      tlv->bufsize = tlv->stack[tlv->stacklen].bufsize;
+      if (length > tlv->bufsize)
+        {
+          if (tlv->verbosity > 1)
+            log_debug ("%s: container larger than buffer (%zu/%zu)\n",
+                       __func__, length, tlv->bufsize);
+          return gpg_error (GPG_ERR_INV_BER);
+        }
+      tlv->buffer += length;
+      tlv->bufsize -= length;
+
+    }
+  _tlv_parser_dump_state (__func__, NULL, 0, tlv);
+  return 0;
+}
+
+
+/* Parse the next tag and value.  Also detect the end of a
+ * container.  The caller should use the tlv_next macro. */
+gpg_error_t
+_tlv_parser_next (tlv_parser_t tlv, unsigned int flag, int lno)
+{
+  gpg_error_t err;
+  const unsigned char *buffer;
+  size_t save_bufsize;
+  const unsigned char *save_buffer;
+  int i;
+
+  tlv->lasterr = 0;
+  tlv->lastfunc = __func__;
+
+  if (tlv->pending)
+    {
+      tlv->pending = 0;
+      if (tlv->verbosity > 1)
+        log_debug ("%s:%d: skipped\n", __func__, lno);
+      return 0;
+    }
+
+  if (tlv->verbosity > 1)
+    log_debug ("%s:%d: called (%p,%zu)\n", __func__, lno,
+               tlv->buffer, tlv->bufsize);
+  /* If we are at the end of an ndef container pop the stack.  */
+  if (!tlv->in_ndef && !tlv->bufsize)
+    {
+      if (tlv->verbosity > 1)
+        for (i=0; i < tlv->stacklen; i++)
+          log_debug ("%s: stack[%d] (%p,@%zu,%zu) len=%zu (%zu) %s\n",
+                     __func__, i,
+                     tlv->stack[i].buffer,
+                     tlv->stack[i].buffer - tlv->origbuffer,
+                     tlv->stack[i].bufsize,
+                     tlv->stack[i].length,
+                     tlv->stack[i].crammed,
+                     tlv->stack[i].in_ndef? " ndef":"");
+      do
+        err = _tlv_pop (tlv);
+      while (!err && !tlv->in_ndef && !tlv->bufsize);
+
+      if (err)
+        return (tlv->lasterr = err);
+      if (tlv->verbosity > 1)
+        log_debug ("%s: container(s) closed due to size (lvl=%d)\n",
+                   __func__, tlv->stacklen);
+    }
+
+ again:
+  /* Get the next tag.  */
+  save_buffer = buffer = tlv->buffer;
+  save_bufsize = tlv->bufsize;
+  err = parse_tag (&buffer, &tlv->bufsize, &tlv->ti);
+  tlv->buffer = (unsigned char *)buffer;
+  if (err)
+    {
+      if (tlv->verbosity > 1)
+        {
+          log_debug ("%s: reading tag returned err=%d\n", __func__, err);
+          log_printhex (save_buffer, save_bufsize > 40? 40: save_bufsize,
+                        "%s: data was\n", __func__);
+          dump_to_file (tlv->origbuffer, save_buffer - tlv->origbuffer,
+                        "parseerr");
+        }
+      return err;
+    }
+
+  if ( ( (tlv->ti.class == CLASS_UNIVERSAL && tlv->ti.tag == TAG_OCTET_STRING)
+         || ((flag & TLV_PARSER_FLAG_T5793)
+             && tlv->ti.class == CLASS_CONTEXT && tlv->ti.tag == 0))
+       && tlv->ti.is_constructed && cram_octet_string (tlv, 1))
+    {
+      if (tlv->verbosity > 1)
+        log_debug ("%s: cramming %s\n", __func__,
+                   tlv->ti.tag? "constructed octet strings":"for Mozilla bug");
+      if (!cram_octet_string (tlv, 0))
+        return (tlv->lasterr = gpg_error (GPG_ERR_BAD_BER));
+    }
+
+  /* If there is an end tag in an ndef container pop the stack.  Also
+   * pop other containers which are fully consumed. */
+  if (tlv->in_ndef && (tlv->ti.class == CLASS_UNIVERSAL
+                       && !tlv->ti.tag && !tlv->ti.is_constructed))
+    {
+      do
+        err = _tlv_pop (tlv);
+      while (!err && !tlv->in_ndef && !tlv->bufsize);
+      if (err)
+        return (tlv->lasterr = err);
+      if (tlv->verbosity > 1)
+        log_debug ("%s: container(s) closed due to end tag (lvl=%d)\n",
+                   __func__, tlv->stacklen);
+      goto again;
+    }
+
+  _tlv_parser_dump_tag (__func__, lno, tlv);
+  return 0;
+}
+
+
+/* Return the current neting level of the TLV object.  */
+unsigned int
+tlv_parser_level (tlv_parser_t tlv)
+{
+  return tlv? tlv->stacklen : 0;
+}
+
+/* Returns the current offset of the parser.  */
+size_t
+tlv_parser_offset (tlv_parser_t tlv)
+{
+  return tlv? (size_t)(tlv->buffer - tlv->origbuffer) : 0;
+}
+
+
+/* Return a string with the last function used.  If TLV is NULL an
+ * empty string is returned.  */
+const char *
+tlv_parser_lastfunc (tlv_parser_t tlv)
+{
+  return tlv? tlv->lastfunc:"";
+}
+
+
+const char *
+tlv_parser_lasterrstr (tlv_parser_t tlv)
+{
+  return tlv? gpg_strerror (tlv->lasterr) : "tlv parser not yet initialized";
+}
+
+
+/* Set a flag to indicate that the last tlv_next has not yet been
+ * consumed.  */
+void
+tlv_parser_set_pending (tlv_parser_t tlv)
+{
+  tlv->pending = 1;
+}
+
+
+/* Return the length of the last read tag.  If with_header is 1 the
+ * lengtb of the header is added to the returned length.  */
+size_t
+tlv_parser_tag_length (tlv_parser_t tlv, int with_header)
+{
+  if (with_header)
+    return tlv->ti.length + tlv->ti.nhdr;
+  else
+    return tlv->ti.length;
+}
+
+
+/* Skip over the value of the current tag.  Does not yet work for ndef
+ * containers.  */
+void
+tlv_parser_skip (tlv_parser_t tlv)
+{
+  tlv->lastfunc = __func__;
+  log_assert (tlv->bufsize >= tlv->ti.length);
+  tlv->buffer += tlv->ti.length;
+  tlv->bufsize -= tlv->ti.length;
+}
+
+
+/* Expect that the current tag is a sequence and setup the context for
+ * processing.  */
+gpg_error_t
+tlv_expect_sequence (tlv_parser_t tlv)
+{
+  tlv->lastfunc = __func__;
+  if (!(tlv->ti.class == CLASS_UNIVERSAL && tlv->ti.tag == TAG_SEQUENCE
+        && tlv->ti.is_constructed))
+    return (tlv->lasterr = gpg_error (GPG_ERR_INV_OBJ));
+  return _tlv_push (tlv);
+}
+
+
+/* Expect that the current tag is a context tag and setup the context
+ * for processing.  The tag of the context is returned at R_TAG.  */
+gpg_error_t
+tlv_expect_context_tag (tlv_parser_t tlv, int *r_tag)
+{
+  tlv->lastfunc = __func__;
+  if (!(tlv->ti.class == CLASS_CONTEXT && tlv->ti.is_constructed))
+    return (tlv->lasterr = gpg_error (GPG_ERR_INV_OBJ));
+  *r_tag = tlv->ti.tag;
+  return _tlv_push (tlv);
+}
+
+
+/* Expect that the current tag is a SET and setup the context for
+ * processing.  */
+gpg_error_t
+tlv_expect_set (tlv_parser_t tlv)
+{
+  tlv->lastfunc = __func__;
+  if (!(tlv->ti.class == CLASS_UNIVERSAL && tlv->ti.tag == TAG_SET
+        && tlv->ti.is_constructed))
+    return (tlv->lasterr = gpg_error (GPG_ERR_INV_OBJ));
+  return _tlv_push (tlv);
+}
+
+
+/* Expect an object of CLASS with TAG and store its value at
+ * (R_DATA,R_DATALEN).  Then skip over its value to the next tag.
+ * Note that the stored value is not allocated but points into
+ * TLV.  */
+gpg_error_t
+tlv_expect_object (tlv_parser_t tlv, int class, int tag,
+                   unsigned char const **r_data, size_t *r_datalen)
+{
+  const unsigned char *p;
+  size_t n;
+  int needpush = 0;
+
+  tlv->lastfunc = __func__;
+  /* Note that the parser has already crammed the octet strings for a
+   * [0] to workaround the Mozilla bug.  */
+  if (!(tlv->ti.class == class && tlv->ti.tag == tag))
+    return (tlv->lasterr = gpg_error (GPG_ERR_INV_OBJ));
+  p = tlv->buffer;
+  n = tlv->ti.length;
+  if (!n && tlv->ti.ndef)
+    {
+      n = tlv->bufsize;
+      needpush = 1;
+    }
+  else if (!tlv->ti.length)
+    return (tlv->lasterr = gpg_error (GPG_ERR_TOO_SHORT));
+
+  if (tlv->verbosity > 1)
+    log_debug ("%s: %zu@%zu %c len=%zu (%zu) bufsize=%zu of %zu\n",
+               __func__,
+               tlv->origoff, tlv_parser_offset (tlv),
+               tlv->ti.is_constructed? 'c':'p',
+               n, tlv->crammed,
+               tlv->bufsize, tlv->origbufsize);
+
+  if (r_data)
+    *r_data = p;
+  if (r_datalen)
+    *r_datalen = tlv->crammed? tlv->crammed : n;
+
+  if (needpush)
+    return _tlv_push (tlv);
+
+  if (!(tlv->bufsize >= n))
+    return (tlv->lasterr = gpg_error (GPG_ERR_TOO_SHORT));
+  tlv->buffer += n;
+  tlv->bufsize -= n;
+  tlv->crammed = 0;
+  return 0;
+}
+
+
+/* Expect that the current tag is an object string and store its value
+ * at (R_DATA,R_DATALEN).  Then skip over its value to the next tag.
+ * Note that the stored value are not allocated but point into TLV. */
+gpg_error_t
+tlv_expect_octet_string (tlv_parser_t tlv,
+                         unsigned char const **r_data, size_t *r_datalen)
+{
+  size_t n;
+
+  tlv->lastfunc = __func__;
+  /* The parser has already crammed constructed octet strings.  */
+  if (!(tlv->ti.class == CLASS_UNIVERSAL && tlv->ti.tag == TAG_OCTET_STRING))
+    return (tlv->lasterr = gpg_error (GPG_ERR_INV_OBJ));
+  if (!(n=tlv->ti.length) || tlv->ti.ndef )
+    return (tlv->lasterr = gpg_error (GPG_ERR_TOO_SHORT));
+
+  if (tlv->verbosity > 1)
+    log_debug ("%s: %zu@%zu %c len=%zu (%zu) bufsize=%zu of %zu\n",
+               __func__,
+               tlv->origoff, tlv_parser_offset (tlv),
+               tlv->ti.is_constructed? 'c':'p',
+               n, tlv->crammed,
+               tlv->bufsize, tlv->origbufsize);
+
+  if (r_data)
+    *r_data = tlv->buffer;
+  if (r_datalen)
+    *r_datalen = tlv->crammed? tlv->crammed : tlv->ti.length;
+
+  if (!(tlv->bufsize >= tlv->ti.length))
+    return (tlv->lasterr = gpg_error (GPG_ERR_TOO_SHORT));
+  tlv->buffer += tlv->ti.length;
+  tlv->bufsize -= tlv->ti.length;
+  tlv->crammed = 0;
+  return 0;
+}
+
+
+/* Expect that the current tag is an integer and return its value at
+ * R_VALUE.  Then skip over its value to the next tag. */
+gpg_error_t
+tlv_expect_integer (tlv_parser_t tlv, int *r_value)
+{
+  const unsigned char *p;
+  size_t n;
+  int value;
+
+  tlv->lastfunc = __func__;
+  if (!(tlv->ti.class == CLASS_UNIVERSAL && tlv->ti.tag == TAG_INTEGER
+        && !tlv->ti.is_constructed))
+    return (tlv->lasterr = gpg_error (GPG_ERR_INV_OBJ));
+  p = tlv->buffer;
+  if (!(n=tlv->ti.length))
+    return (tlv->lasterr = gpg_error (GPG_ERR_TOO_SHORT));
+
+  /* We currently support only positive values.  */
+  if ((*p & 0x80))
+    return (tlv->lasterr = gpg_error (GPG_ERR_ERANGE));
+
+  for (value = 0; n; n--)
+    {
+      value <<= 8;
+      value |= (*p++) & 0xff;
+      if (value < 0)
+        return (tlv->lasterr = gpg_error (GPG_ERR_EOVERFLOW));
+    }
+  *r_value = value;
+  if (!(tlv->bufsize >= tlv->ti.length))
+    return (tlv->lasterr = gpg_error (GPG_ERR_TOO_SHORT));
+  tlv->buffer += tlv->ti.length;
+  tlv->bufsize -= tlv->ti.length;
+  return 0;
+}
+
+
+/* Variant of tlv_expect_integer which returns an MPI.  If IGNORE_ZERO
+ * is set a value of 0 is ignored and R_VALUE not changed and the
+ * function returns GPG_ERR_FALSE.  No check for negative encoded
+ * integers is done because the old code here worked the same and we
+ * can't foreclose invalid encoded PKCS#12 stuff - after all it is
+ * PKCS#12 see https://www.cs.auckland.ac.nz/~pgut001/pubs/pfx.html */
+#ifdef GCRYPT_VERSION
+gpg_error_t
+tlv_expect_mpinteger (tlv_parser_t tlv, int ignore_zero,
+                      gcry_mpi_t *r_value)
+{
+  const unsigned char *p;
+  size_t n;
+
+  tlv->lastfunc = __func__;
+  if (!(tlv->ti.class == CLASS_UNIVERSAL && tlv->ti.tag == TAG_INTEGER
+        && !tlv->ti.is_constructed))
+    return (tlv->lasterr = gpg_error (GPG_ERR_INV_OBJ));
+  p = tlv->buffer;
+  if (!(n=tlv->ti.length))
+    return (tlv->lasterr = gpg_error (GPG_ERR_TOO_SHORT));
+
+  if (!(tlv->bufsize >= tlv->ti.length))
+    return (tlv->lasterr = gpg_error (GPG_ERR_TOO_SHORT));
+  tlv->buffer += tlv->ti.length;
+  tlv->bufsize -= tlv->ti.length;
+  if (ignore_zero && n == 1 && !*p)
+    return gpg_error (GPG_ERR_FALSE);
+
+  return gcry_mpi_scan (r_value, GCRYMPI_FMT_USG, p, n, NULL);
+}
+#endif /*GCRYPT_VERSION*/
+
+
+/* Expect that the current tag is an object id and store its value at
+ * (R_OID,R_OIDLEN).  Then skip over its value to the next tag.  Note
+ * that the stored value is not allocated but points into TLV. */
+gpg_error_t
+tlv_expect_object_id (tlv_parser_t tlv,
+                      unsigned char const **r_oid, size_t *r_oidlen)
+{
+  const unsigned char *p;
+  size_t n;
+
+  tlv->lastfunc = __func__;
+  if (!(tlv->ti.class == CLASS_UNIVERSAL && tlv->ti.tag == TAG_OBJECT_ID
+        && !tlv->ti.is_constructed))
+    return (tlv->lasterr = gpg_error (GPG_ERR_INV_OBJ));
+  p = tlv->buffer;
+  if (!(n=tlv->ti.length))
+    return (tlv->lasterr = gpg_error (GPG_ERR_TOO_SHORT));
+
+  *r_oid = p;
+  *r_oidlen = tlv->ti.length;
+  if (!(tlv->bufsize >= tlv->ti.length))
+    return (tlv->lasterr = gpg_error (GPG_ERR_TOO_SHORT));
+  tlv->buffer += tlv->ti.length;
+  tlv->bufsize -= tlv->ti.length;
+  return 0;
+}
+
+
+/* Expect a NULL tag.  */
+gpg_error_t
+tlv_expect_null (tlv_parser_t tlv)
+{
+  tlv->lastfunc = __func__;
+  if (!(tlv->ti.class == CLASS_UNIVERSAL && tlv->ti.tag == TAG_NULL
+        && !tlv->ti.is_constructed && !tlv->ti.length))
+    return (tlv->lasterr = gpg_error (GPG_ERR_INV_OBJ));
+  return 0;
+}
+
+
+/* Given a BER encoded constructed octet string like the example below
+ * from Mozilla Firefox 1.0.4 (which actually exports certs as single
+ * byte chunks of octet strings) in the buffer described by TLV.
+ * Although the example uses an ndef for the length of the constructed
+ * octet string, a fixed length is also allowed.
+ *
+ *   24 NDEF:       OCTET STRING
+ *   04    1:         OCTET STRING  -- TLV->buffer points to here
+ *          :           30
+ *   04    1:         OCTET STRING
+ *          :           80
+ *        [...]
+ *   04    2:         OCTET STRING
+ *          :           00 00
+ *          :         } -- This denotes a Null tag and are the last
+ *                      -- two bytes in INPUT.
+ *
+ * Turn it into a primitive octet string of this form:
+ *
+ *   24    2:       OCTET STRING
+ *          :         30 80
+ *
+ * and fill it up with FE to the original length.  Unless TESTMODE is
+ * true the TLV object including the the member and the data is
+ * adjusted accordingly; however the intiial tag is not changed (in
+ * the example the "24 NDEF") because this is not needed anymore.
+ *
+ * On error 0 is returned and in this case the buffer might have
+ * already been modified and thus the caller should better stop
+ * parsing - unless TESTMODE was used.  */
+static size_t
+cram_octet_string (tlv_parser_t tlv, int testmode)
+{
+  gpg_error_t err;
+  size_t totallen;    /* Length of the non-crammed octet strings.  */
+  size_t crammedlen;  /* Length of the crammed octet strings.  */
+  const unsigned char *s, *save_s;
+  unsigned char *d;
+  size_t n, save_n;
+  struct tag_info ti;
+
+  if (tlv->ti.class == CLASS_UNIVERSAL && tlv->ti.tag == TAG_OCTET_STRING)
+    ;  /* Okay.  */
+  else if (tlv->ti.class == CLASS_CONTEXT && tlv->ti.tag == 0)
+    ;  /* Workaround for Mozilla bug; see T5793  */
+  else
+    return 0;  /* Oops - we should not have been called.  */
+  if (!tlv->ti.is_constructed)
+    return 0;  /* Oops - Not a constructed octet string.  */
+  if (!tlv->ti.ndef && tlv->ti.length < 4)
+    return 0;  /* Fixed length but too short.  */
+
+  /* Let S point to the first octet string chunk.  */
+  s = tlv->buffer;
+  n = tlv->ti.ndef? tlv->bufsize : tlv->ti.length;
+
+  d = (unsigned char *)s;
+  totallen = crammedlen = 0;
+  while (n)
+    {
+      save_s = s;
+      save_n = n;
+      if ((err=parse_tag (&s, &n, &ti)))
+        {
+          if (tlv->verbosity > 1)
+            {
+              log_debug ("%s: parse_tag(n=%zu) failed : %s\n",
+                         __func__, save_n, gpg_strerror (err));
+              log_printhex (save_s, save_n > 40? 40:save_n, "%s: data was",
+                            __func__);
+            }
+          return 0;
+        }
+      if (tlv->verbosity > 1)
+        log_debug ("%s:%s ti.ndef=%d ti.tag=%lu ti.length=%zu (n %zu->%zu)\n",
+                   __func__, testmode?"test:":"",
+                   ti.ndef, ti.tag, ti.length, save_n, n);
+      if (ti.class == CLASS_UNIVERSAL && ti.tag == TAG_OCTET_STRING
+          && !ti.ndef && !ti.is_constructed)
+        {
+          if (!testmode)
+            memmove (d, s, ti.length);
+          d += ti.length;  /* Update destination */
+          totallen += ti.length + ti.nhdr;
+          crammedlen += ti.length;
+          s += ti.length;  /* Skip to next tag.  */
+          n -= ti.length;
+        }
+      else if (ti.class == CLASS_UNIVERSAL && !ti.tag && !ti.is_constructed)
+        {
+          totallen += ti.nhdr;
+          break; /* EOC - Ready */
+        }
+      else
+        return 0; /* Invalid data.  */
+    }
+  if (!testmode)
+    {
+      memset (d, '\xfe', totallen - crammedlen);
+      tlv->ti.length = totallen;
+      tlv->ti.is_constructed = 0;
+      tlv->ti.ndef = 0;
+      tlv->crammed = crammedlen;
+      if (tlv->verbosity > 1)
+        {
+          log_debug ("%s: crammed length is %zu\n", __func__, crammedlen);
+          log_debug ("%s:   total length is %zu\n", __func__, totallen);
+        }
+      dump_to_file (tlv->buffer, totallen, "crammed");
+    }
+  return totallen;
+}