common: Add new function b64decode.

* common/b64dec.c (b64decode): New.
* common/t-b64.c: Change license to LGPL.
(oops): New macro.
(hex2buffer): New.
(test_b64decode): New.
(main): Default to run the new test.
* common/Makefile.am (module_maint_tests): Move t-b64 to ...
(module_tests): here.
--

Sometimes we have a short base64 encoded string we need todecode.
This function makes it simpler.

License change of the test module justified because I am the single
author of the code.

5 files changed, 168 insertions, 18 deletions

diff --git a/common/Makefile.am b/common/Makefile.am
index d5ab038bf..7c78708da 100644
--- a/common/Makefile.am
+++ b/common/Makefile.am
@@ -161,7 +161,7 @@ module_tests = t-stringhelp t-timestuff \
                t-convert t-percent t-gettime t-sysutils t-sexputil \
 	       t-session-env t-openpgp-oid t-ssh-utils \
 	       t-mapstrings t-zb32 t-mbox-util t-iobuf t-strlist \
-	       t-name-value t-ccparray t-recsel t-w32-cmdline
+	       t-name-value t-ccparray t-recsel t-w32-cmdline t-b64
 if HAVE_W32_SYSTEM
 module_tests += t-w32-reg
 else
@@ -169,7 +169,7 @@ module_tests += t-exechelp t-exectool
 endif
 
 if MAINTAINER_MODE
-module_maint_tests = t-helpfile t-b64
+module_maint_tests = t-helpfile
 else
 module_maint_tests =
 endif
diff --git a/common/b64dec.c b/common/b64dec.c
index 6af494b79..2904b0471 100644
--- a/common/b64dec.c
+++ b/common/b64dec.c
@@ -16,6 +16,7 @@
  *
  * 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>
@@ -252,3 +253,47 @@ b64dec_finish (struct b64state *state)
 
   return state->invalid_encoding? gpg_error(GPG_ERR_BAD_DATA): 0;
 }
+
+
+/* Convert STRING consisting of base64 characters into its binary
+ * representation and store the result in a newly allocated buffer at
+ * R_BUFFER with its length at R_BUFLEN.  If TITLE is NULL a plain
+ * base64 decoding is done.  If it is the empty string the decoder
+ * will skip everything until a "-----BEGIN " line has been seen,
+ * decoding then ends at a "----END " line.  On failure the function
+ * returns an error code and sets R_BUFFER to NULL.  If the decoded
+ * data has a length of 0 a dummy buffer will still be allocated and
+ * the length is set to 0. */
+gpg_error_t
+b64decode (const char *string, const char *title,
+           void **r_buffer, size_t *r_buflen)
+{
+  gpg_error_t err;
+  struct b64state state;
+  size_t nbytes;
+  char *buffer;
+
+  *r_buffer = NULL;
+  *r_buflen = 0;
+
+  buffer = xtrystrdup (string);
+  if (!buffer)
+    return gpg_error_from_syserror();
+
+  err = b64dec_start (&state, title);
+  if (err)
+    {
+      xfree (buffer);
+      return err;
+    }
+  b64dec_proc (&state, buffer, strlen (buffer), &nbytes);
+  err = b64dec_finish (&state);
+  if (err)
+    xfree (buffer);
+  else
+    {
+      *r_buffer = buffer;
+      *r_buflen = nbytes;
+    }
+  return err;
+}
diff --git a/common/b64enc.c b/common/b64enc.c
index d633048ea..7846dcb3e 100644
--- a/common/b64enc.c
+++ b/common/b64enc.c
@@ -18,6 +18,7 @@
  *
  * 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>
diff --git a/common/t-b64.c b/common/t-b64.c
index 3b6387246..16c079d1d 100644
--- a/common/t-b64.c
+++ b/common/t-b64.c
@@ -1,30 +1,24 @@
 /* t-b64.c - Module tests for b64enc.c and b64dec.c
- *	Copyright (C) 2008 Free Software Foundation, Inc.
+ * Copyright (C) 2008 Free Software Foundation, Inc.
+ * Copyright (C) 2008, 2023 g10 Code GmbH
  *
  * 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.
+ * 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.
  *
- * GnuPG is distributed in the hope that it will be useful,
+ * 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
+ * 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
  */
 
-/*
-
-   As of now this is only a test program for manual tests.
-
- */
-
-
-
 #include <config.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -36,10 +30,112 @@
                                __FILE__,__LINE__, (a));          \
                      errcount++;                                 \
                    } while(0)
+#define oops()   do { fprintf (stderr, "%s:%d: ooops\n",         \
+                               __FILE__,__LINE__);               \
+                      exit (2);                                  \
+                   } while(0)
 
 static int verbose;
 static int errcount;
 
+
+/* Convert STRING consisting of hex characters into its binary
+ * representation and return it as an allocated buffer. The valid
+ * length of the buffer is returned at R_LENGTH.  The string is
+ * delimited by end of string.  The function returns NULL on
+ * error.  */
+static void *
+hex2buffer (const char *string, size_t *r_length)
+{
+  const char *s;
+  unsigned char *buffer;
+  size_t length;
+
+  buffer = xmalloc (strlen(string)/2+1);
+  length = 0;
+  for (s=string; *s; s +=2 )
+    {
+      if (!hexdigitp (s) || !hexdigitp (s+1))
+        return NULL;           /* Invalid hex digits. */
+      ((unsigned char*)buffer)[length++] = xtoi_2 (s);
+    }
+  *r_length = length;
+  return buffer;
+}
+
+
+static void
+test_b64decode (void)
+{
+  static struct {
+    const char *string;    /* String to test.  */
+    const char *title;     /* title parameter.  */
+    gpg_error_t  err;      /* expected error.  */
+    const char *datastr;   /* Expected data (hex encoded)  */
+  } tests[] = {
+    { "YQ==", NULL, 0,
+      "61" },
+    { "YWE==", NULL, 0,
+      "6161" },
+    { "YWFh", NULL, 0,
+      "616161" },
+    { "YWFhYQ==", NULL, 0,
+      "61616161" },
+    { "YWJjZA==", NULL, 0,
+      "61626364" },
+    { "AA=", NULL, 0,
+      "00" },
+    { "AAEA=", NULL, 0,
+      "000100" },
+    { "/w==", NULL, 0,
+      "ff" },
+    { "oRQwEqADCgEDoQsGCSqGSIL3EgECAg==", NULL, 0,
+      "a1143012a0030a0103a10b06092a864882f712010202" },
+    { "oRQwEqADCgEDoQsGCSqGSIL3EgECA-==", NULL, GPG_ERR_BAD_DATA,
+      "a1143012a0030a0103a10b06092a864882f712010202" },
+    { "oRQwEqADCgEDoQsGCSqGSIL3EgECAg==", "", 0,
+      "" },
+    { "-----BEGIN PGP\n\n"
+      "oRQwEqADCgEDoQsGCSqGSIL3EgECAg==\n"
+      "-----END PGP\n", "", 0,
+      "a1143012a0030a0103a10b06092a864882f712010202" },
+
+    { "", NULL, 0,
+      "" }
+  };
+  int tidx;
+  gpg_error_t err;
+  void *data = NULL;
+  size_t datalen;
+  char *wantdata = NULL;
+  size_t wantdatalen;
+
+  for (tidx = 0; tidx < DIM(tests); tidx++)
+    {
+      xfree (wantdata);
+      if (!(wantdata = hex2buffer (tests[tidx].datastr, &wantdatalen)))
+        oops ();
+      xfree (data);
+      err = b64decode (tests[tidx].string, tests[tidx].title, &data, &datalen);
+      if (verbose)
+        fprintf (stderr, "%s:%d: test %d, err=%d, datalen=%zu\n",
+                 __FILE__, __LINE__, tidx, err, datalen);
+      if (gpg_err_code (err) != tests[tidx].err)
+        fail (tidx);
+      else if (err)
+        pass ();
+      else if (wantdatalen != datalen)
+        fail (tidx);
+      else if (memcmp (wantdata, data, datalen))
+        fail (tidx);
+      else
+        pass ();
+    }
+  xfree (wantdata);
+  xfree (data);
+}
+
+
 static void
 test_b64enc_pgp (const char *string)
 {
@@ -101,6 +197,7 @@ test_b64enc_file (const char *fname)
   pass ();
 }
 
+
 static void
 test_b64dec_file (const char *fname)
 {
@@ -150,6 +247,7 @@ main (int argc, char **argv)
 {
   int do_encode = 0;
   int do_decode = 0;
+  int do_pgpdecode = 0;
 
   if (argc)
     { argc--; argv++; }
@@ -169,13 +267,17 @@ main (int argc, char **argv)
       do_decode = 1;
       argc--; argv++;
     }
+  else if (argc)
+    do_pgpdecode = 1;
 
   if (do_encode)
     test_b64enc_file (argc? *argv: NULL);
   else if (do_decode)
     test_b64dec_file (argc? *argv: NULL);
-  else
+  else if (do_pgpdecode)
     test_b64enc_pgp (argc? *argv: NULL);
+  else
+    test_b64decode ();
 
   return !!errcount;
 }
diff --git a/common/util.h b/common/util.h
index aa24e39e6..83882caf2 100644
--- a/common/util.h
+++ b/common/util.h
@@ -171,6 +171,8 @@ gpg_error_t b64dec_start (struct b64state *state, const char *title);
 gpg_error_t b64dec_proc (struct b64state *state, void *buffer, size_t length,
                          size_t *r_nbytes);
 gpg_error_t b64dec_finish (struct b64state *state);
+gpg_error_t b64decode (const char *string, const char *title,
+                       void **r_buffer, size_t *r_buflen);
 
 /*-- sexputil.c */
 char *canon_sexp_to_string (const unsigned char *canon, size_t canonlen);