Rewrite iconv option parsing [BZ #19519]

This commit replaces string manipulation during `iconv_open' and iconv_prog
option parsing with a structured, flag based conversion specification.  In
doing so, it alters the internal `__gconv_open' interface and accordingly
adjusts its uses.

This change fixes several hangs in the iconv program and therefore includes
a new test to exercise iconv_prog options that originally led to these hangs.
It also includes a new regression test for option handling in the iconv
function.

Reviewed-by: Florian Weimer <fweimer@redhat.com>
Reviewed-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
Reviewed-by: Carlos O'Donell <carlos@redhat.com>

1 files changed, 218 insertions, 0 deletions

diff --git a/iconv/gconv_charset.c b/iconv/gconv_charset.c
new file mode 100644
index 0000000..6ccd077
--- /dev/null
+++ b/iconv/gconv_charset.c
@@ -0,0 +1,218 @@
+/* Charset name normalization.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library 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.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+
+#include <stdlib.h>
+#include <ctype.h>
+#include <locale.h>
+#include <stdbool.h>
+#include <string.h>
+#include <sys/stat.h>
+#include "gconv_int.h"
+#include "gconv_charset.h"
+
+
+/* This function returns a pointer to the last suffix in a conversion code
+   string.  Valid suffixes matched by this function are of the form: '/' or ','
+   followed by arbitrary text that doesn't contain '/' or ','.  It does not
+   edit the string in any way.  The caller is expected to parse the suffix and
+   remove it (by e.g. truncating the string) before the next call.  */
+static char *
+find_suffix (char *s)
+{
+  /* The conversion code is in the form of a triplet, separated by '/' chars.
+     The third component of the triplet contains suffixes. If we don't have two
+     slashes, we don't have a suffix.  */
+
+  int slash_count = 0;
+  char *suffix_term = NULL;
+
+  for (int i = 0; s[i] != '\0'; i++)
+    switch (s[i])
+      {
+        case '/':
+          slash_count++;
+          /* Fallthrough */
+        case ',':
+          suffix_term = &s[i];
+      }
+
+  if (slash_count >= 2)
+    return suffix_term;
+
+  return NULL;
+}
+
+
+struct gconv_parsed_code
+{
+  char *code;
+  bool translit;
+  bool ignore;
+};
+
+
+/* This function parses an iconv_open encoding PC.CODE, strips any suffixes
+   (such as TRANSLIT or IGNORE) from it and sets corresponding flags in it.  */
+static void
+gconv_parse_code (struct gconv_parsed_code *pc)
+{
+  pc->translit = false;
+  pc->ignore = false;
+
+  while (1)
+    {
+      /* First drop any trailing whitespaces and separators.  */
+      size_t len = strlen (pc->code);
+      while ((len > 0)
+             && (isspace (pc->code[len - 1])
+                 || pc->code[len - 1] == ','
+                 || pc->code[len - 1] == '/'))
+        len--;
+
+      pc->code[len] = '\0';
+
+      if (len == 0)
+        return;
+
+      char * suffix = find_suffix (pc->code);
+      if (suffix == NULL)
+        {
+          /* At this point, we have processed and removed all suffixes from the
+             code and what remains of the code is suffix free.  */
+          return;
+        }
+      else
+        {
+          /* A suffix is processed from the end of the code array going
+             backwards, one suffix at a time.  The suffix is an index into the
+             code character array and points to: one past the end of the code
+             and any unprocessed suffixes, and to the beginning of the suffix
+             currently being processed during this iteration.  We must process
+             this suffix and then drop it from the code by terminating the
+             preceding text with NULL.
+
+             We want to allow and recognize suffixes such as:
+
+             "/TRANSLIT"         i.e. single suffix
+             "//TRANSLIT"        i.e. single suffix and multiple separators
+             "//TRANSLIT/IGNORE" i.e. suffixes separated by "/"
+             "/TRANSLIT//IGNORE" i.e. suffixes separated by "//"
+             "//IGNORE,TRANSLIT" i.e. suffixes separated by ","
+             "//IGNORE,"         i.e. trailing ","
+             "//TRANSLIT/"       i.e. trailing "/"
+             "//TRANSLIT//"      i.e. trailing "//"
+             "/"                 i.e. empty suffix.
+
+             Unknown suffixes are silently discarded and ignored.  */
+
+          if ((__strcasecmp_l (suffix,
+                               GCONV_TRIPLE_SEPARATOR
+                               GCONV_TRANSLIT_SUFFIX,
+                               _nl_C_locobj_ptr) == 0)
+              || (__strcasecmp_l (suffix,
+                                  GCONV_SUFFIX_SEPARATOR
+                                  GCONV_TRANSLIT_SUFFIX,
+                                  _nl_C_locobj_ptr) == 0))
+            pc->translit = true;
+
+          if ((__strcasecmp_l (suffix,
+                               GCONV_TRIPLE_SEPARATOR
+                               GCONV_IGNORE_ERRORS_SUFFIX,
+                               _nl_C_locobj_ptr) == 0)
+              || (__strcasecmp_l (suffix,
+                                  GCONV_SUFFIX_SEPARATOR
+                                  GCONV_IGNORE_ERRORS_SUFFIX,
+                                  _nl_C_locobj_ptr) == 0))
+            pc->ignore = true;
+
+          /* We just processed this suffix.  We can now drop it from the
+             code string by truncating it at the suffix's position.  */
+          suffix[0] = '\0';
+        }
+    }
+}
+
+
+/* This function accepts the charset names of the source and destination of the
+   conversion and populates *conv_spec with an equivalent conversion
+   specification that may later be used by __gconv_open.  The charset names
+   might contain options in the form of suffixes that alter the conversion,
+   e.g. "ISO-10646/UTF-8/TRANSLIT".  It processes the charset names, ignoring
+   and truncating any suffix options in fromcode, and processing and truncating
+   any suffix options in tocode.  Supported suffix options ("TRANSLIT" or
+   "IGNORE") when found in tocode lead to the corresponding flag in *conv_spec
+   to be set to true.  Unrecognized suffix options are silently discarded.  If
+   the function succeeds, it returns conv_spec back to the caller.  It returns
+   NULL upon failure.  conv_spec must be allocated and freed by the caller.  */
+struct gconv_spec *
+__gconv_create_spec (struct gconv_spec *conv_spec, const char *fromcode,
+                   const char *tocode)
+{
+  struct gconv_parsed_code pfc, ptc;
+  struct gconv_spec *ret = NULL;
+
+  pfc.code = __strdup (fromcode);
+  ptc.code = __strdup (tocode);
+
+  if ((pfc.code == NULL)
+      || (ptc.code == NULL))
+    goto out;
+
+  gconv_parse_code (&pfc);
+  gconv_parse_code (&ptc);
+
+  /* We ignore suffixes in the fromcode because that is how the current
+     implementation has always handled them.  Only suffixes in the tocode are
+     processed and handled.  The reality is that invalid input in the input
+     character set should only be ignored if the fromcode specifies IGNORE.
+     The current implementation ignores invalid intput in the input character
+     set if the tocode contains IGNORE.  We preserve this behavior for
+     backwards compatibility.  In the future we may split the handling of
+     IGNORE to allow a finer grained specification of ignorning invalid input
+     and/or ignoring invalid output.  */
+  conv_spec->translit = ptc.translit;
+  conv_spec->ignore = ptc.ignore;
+
+  /* 3 extra bytes because 1 extra for '\0', and 2 extra so strip might
+     be able to add one or two trailing '/' characters if necessary.  */
+  conv_spec->fromcode = malloc (strlen (fromcode) + 3);
+  if (conv_spec->fromcode == NULL)
+    goto out;
+
+  conv_spec->tocode = malloc (strlen (tocode) + 3);
+  if (conv_spec->tocode == NULL)
+    {
+      free (conv_spec->fromcode);
+      conv_spec->fromcode = NULL;
+      goto out;
+    }
+
+  /* Strip unrecognized characters and ensure that the code has two '/'
+     characters as per conversion code triplet specification.  */
+  strip (conv_spec->fromcode, pfc.code);
+  strip (conv_spec->tocode, ptc.code);
+  ret = conv_spec;
+
+out:
+  free (pfc.code);
+  free (ptc.code);
+
+  return ret;
+}
+libc_hidden_def (__gconv_create_spec)