[PATCH v4 2/5] Import b64dec from gpg-error

[Vladimir Serbinenko <phcoder@gmail.com>]

Base on libgpg-error 1.49 but with modifications to make it compile
in GRUB environment

Signed-off-by: Vladimir Serbinenko <phcoder@gmail.com>
---
 grub-core/lib/b64dec.c | 293 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 293 insertions(+)
 create mode 100644 grub-core/lib/b64dec.c

diff --git a/grub-core/lib/b64dec.c b/grub-core/lib/b64dec.c
new file mode 100644
index 000000000..8aafa9700
--- /dev/null
+++ b/grub-core/lib/b64dec.c
@@ -0,0 +1,293 @@
+/* b64dec.c - Simple Base64 decoder.
+ * Copyright (C) 2008, 2011 Free Software Foundation, Inc.
+ * Copyright (C) 2008, 2011, 2016 g10 Code GmbH
+ *
+ * This file is part of Libgpg-error.
+ *
+ * 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 Lesser 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
+ *
+ * This file was originally a part of GnuPG.
+ */
+
+#include <config.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <grub/crypto.h>
+
+struct _gpgrt_b64state
+{
+  int idx;
+  int quad_count;
+  char *title;
+  unsigned char radbuf[4];
+  unsigned int crc;
+  gpg_err_code_t lasterr;
+  unsigned int flags;
+  unsigned int stop_seen:1;
+  unsigned int invalid_encoding:1;
+  unsigned int using_decoder:1;
+};
+
+
+/* The reverse base-64 list used for base-64 decoding. */
+static unsigned char const asctobin[128] =
+  {
+    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
+  };
+
+enum decoder_states
+  {
+    s_init, s_idle, s_lfseen, s_beginseen, s_waitheader, s_waitblank, s_begin,
+    s_b64_0, s_b64_1, s_b64_2, s_b64_3,
+    s_waitendtitle, s_waitend
+  };
+
+
+
+/* Allocate and initialize the context for the base64 decoder.  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 ends at a "----END " line.  */
+gpgrt_b64state_t
+gpgrt_b64dec_start (const char *title)
+{
+  gpgrt_b64state_t state;
+  char *t = NULL;
+
+  if (title)
+    {
+      t = grub_strdup (title);
+      if (!t)
+        return NULL;
+    }
+
+  state = grub_calloc (1, sizeof (struct _gpgrt_b64state));
+  if (!state)
+    {
+      grub_free (t);
+      return NULL;
+    }
+
+  if (t)
+    {
+      state->title = t;
+      state->idx = s_init;
+    }
+  else
+    state->idx = s_b64_0;
+
+  state->using_decoder = 1;
+
+  return state;
+}
+
+
+/* Do in-place decoding of base-64 data of LENGTH in BUFFER.  Stores the
+   new length of the buffer at R_NBYTES. */
+gpg_err_code_t
+gpgrt_b64dec_proc (gpgrt_b64state_t state, void *buffer, size_t length,
+                    size_t *r_nbytes)
+{
+  enum decoder_states ds = state->idx;
+  unsigned char val = state->radbuf[0];
+  int pos = state->quad_count;
+  char *d, *s;
+
+  if (state->lasterr)
+    return state->lasterr;
+
+  if (state->stop_seen)
+    {
+      *r_nbytes = 0;
+      state->lasterr = GPG_ERR_EOF;
+      grub_free (state->title);
+      state->title = NULL;
+      return state->lasterr;
+    }
+
+  for (s=d=buffer; length && !state->stop_seen; length--, s++)
+    {
+    again:
+      switch (ds)
+        {
+        case s_idle:
+          if (*s == '\n')
+            {
+              ds = s_lfseen;
+              pos = 0;
+            }
+          break;
+        case s_init:
+          ds = s_lfseen;
+          /* Fall through */
+        case s_lfseen:
+          if (*s != "-----BEGIN "[pos])
+            {
+              ds = s_idle;
+              goto again;
+            }
+          else if (pos == 10)
+            {
+              pos = 0;
+              ds = s_beginseen;
+            }
+          else
+            pos++;
+          break;
+        case s_beginseen:
+          if (*s != "PGP "[pos])
+            ds = s_begin; /* Not a PGP armor.  */
+          else if (pos == 3)
+            ds = s_waitheader;
+          else
+            pos++;
+          break;
+        case s_waitheader:
+          if (*s == '\n')
+            ds = s_waitblank;
+          break;
+        case s_waitblank:
+          if (*s == '\n')
+            ds = s_b64_0; /* blank line found.  */
+          else if (*s == ' ' || *s == '\r' || *s == '\t')
+            ; /* Ignore spaces. */
+          else
+            {
+              /* Armor header line.  Note that we don't care that our
+               * FSM accepts a header prefixed with spaces.  */
+              ds = s_waitheader; /* Wait for next header.  */
+            }
+          break;
+        case s_begin:
+          if (*s == '\n')
+            ds = s_b64_0;
+          break;
+        case s_b64_0:
+        case s_b64_1:
+        case s_b64_2:
+        case s_b64_3:
+          {
+            int c;
+
+            if (*s == '-' && state->title)
+              {
+                /* Not a valid Base64 character: assume end
+                   header.  */
+                ds = s_waitend;
+              }
+            else if (*s == '=')
+              {
+                /* Pad character: stop */
+                if (ds == s_b64_1)
+                  *d++ = val;
+                ds = state->title? s_waitendtitle : s_waitend;
+              }
+            else if (*s == '\n' || *s == ' ' || *s == '\r' || *s == '\t')
+              ; /* Skip white spaces. */
+            else if ( (*s & 0x80)
+                      || (c = asctobin[*(unsigned char *)s]) == 255)
+              {
+                /* Skip invalid encodings.  */
+                state->invalid_encoding = 1;
+              }
+            else if (ds == s_b64_0)
+              {
+                val = c << 2;
+                ds = s_b64_1;
+              }
+            else if (ds == s_b64_1)
+              {
+                val |= (c>>4)&3;
+                *d++ = val;
+                val = (c<<4)&0xf0;
+                ds = s_b64_2;
+              }
+            else if (ds == s_b64_2)
+              {
+                val |= (c>>2)&15;
+                *d++ = val;
+                val = (c<<6)&0xc0;
+                ds = s_b64_3;
+              }
+            else
+              {
+                val |= c&0x3f;
+                *d++ = val;
+                ds = s_b64_0;
+              }
+          }
+          break;
+        case s_waitendtitle:
+          if (*s == '-')
+            ds = s_waitend;
+          break;
+        case s_waitend:
+          if ( *s == '\n')
+            state->stop_seen = 1;
+          break;
+        default:
+          grub_fatal ("invalid state");
+        }
+    }
+
+
+  state->idx = ds;
+  state->radbuf[0] = val;
+  state->quad_count = pos;
+  *r_nbytes = (d -(char*) buffer);
+  return 0;
+}
+
+
+/* Return an error code in case an encoding error has been found
+   during decoding. */
+gpg_err_code_t
+gpgrt_b64dec_finish (gpgrt_b64state_t state)
+{
+  gpg_error_t err;
+
+  if (!state)
+    return 0;  /* Already released.  */
+
+  if (!state->using_decoder)
+    err = GPG_ERR_CONFLICT;  /* State was allocated for the encoder.  */
+  else if (state->lasterr)
+    err = state->lasterr;
+  else
+    {
+      grub_free (state->title);
+      err = state->invalid_encoding? GPG_ERR_BAD_DATA : 0;
+    }
+  grub_free (state);
+
+  return err;
+}
-- 
2.39.2


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