Implement the server comamnd DECRYPT.

Use int instead of gnupg_fd_t in the server.
Comment fixes.
Rename encr-data.c -> decrypt-data.c

1 files changed, 446 insertions, 0 deletions

diff --git a/g10/decrypt-data.c b/g10/decrypt-data.c
new file mode 100644
index 000000000..c9da9be97
--- /dev/null
+++ b/g10/decrypt-data.c
@@ -0,0 +1,446 @@
+/* decrypt-data.c - Decrypt an encrypted data packet
+ * Copyright (C) 1998, 1999, 2000, 2001, 2005,
+ *               2006, 2009 Free Software Foundation, Inc.
+ *
+ * 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.
+ *
+ * GnuPG 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 <http://www.gnu.org/licenses/>.
+ */
+
+#include <config.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+
+#include "gpg.h"
+#include "util.h"
+#include "packet.h"
+#include "cipher.h"
+#include "options.h"
+#include "i18n.h"
+
+
+static int mdc_decode_filter ( void *opaque, int control, IOBUF a,
+                               byte *buf, size_t *ret_len);
+static int decode_filter ( void *opaque, int control, IOBUF a,
+					byte *buf, size_t *ret_len);
+
+typedef struct decode_filter_context_s
+{
+  gcry_cipher_hd_t cipher_hd;
+  gcry_md_hd_t mdc_hash;
+  char defer[22];
+  int  defer_filled;
+  int  eof_seen;
+  int  refcount;
+  int  partial;   /* Working on a partial length packet.  */
+  size_t length;  /* If !partial: Remaining bytes in the packet.  */
+} *decode_filter_ctx_t;
+
+
+/* Helper to release the decode context.  */
+static void
+release_dfx_context (decode_filter_ctx_t dfx)
+{
+  if (!dfx)
+    return;
+
+  assert (dfx->refcount);
+  if ( !--dfx->refcount )
+    {
+      gcry_cipher_close (dfx->cipher_hd);
+      dfx->cipher_hd = NULL;
+      gcry_md_close (dfx->mdc_hash);
+      dfx->mdc_hash = NULL;
+      xfree (dfx);
+    }
+}
+
+
+
+/****************
+ * Decrypt the data, specified by ED with the key DEK.
+ */
+int
+decrypt_data( void *procctx, PKT_encrypted *ed, DEK *dek )
+{
+  decode_filter_ctx_t dfx;
+  byte *p;
+  int rc=0, c, i;
+  byte temp[32];
+  unsigned blocksize;
+  unsigned nprefix;
+  
+  dfx = xtrycalloc (1, sizeof *dfx);
+  if (!dfx)
+    return gpg_error_from_syserror ();
+  dfx->refcount = 1;
+
+  if ( opt.verbose && !dek->algo_info_printed )
+    {
+      if (!openpgp_cipher_test_algo (dek->algo))
+        log_info (_("%s encrypted data\n"), 
+                  openpgp_cipher_algo_name (dek->algo));
+      else
+        log_info (_("encrypted with unknown algorithm %d\n"), dek->algo );
+      dek->algo_info_printed = 1;
+    }
+  rc = openpgp_cipher_test_algo (dek->algo);
+  if (rc)
+    goto leave;
+  blocksize = openpgp_cipher_get_algo_blklen (dek->algo);
+  if ( !blocksize || blocksize > 16 )
+    log_fatal ("unsupported blocksize %u\n", blocksize );
+  nprefix = blocksize;
+  if ( ed->len && ed->len < (nprefix+2) )
+    BUG();
+
+  if ( ed->mdc_method ) 
+    {
+      if (gcry_md_open (&dfx->mdc_hash, ed->mdc_method, 0 ))
+        BUG ();
+      if ( DBG_HASHING )
+        gcry_md_start_debug (dfx->mdc_hash, "checkmdc");
+    }
+
+  rc = openpgp_cipher_open (&dfx->cipher_hd, dek->algo,
+			    GCRY_CIPHER_MODE_CFB,
+			    (GCRY_CIPHER_SECURE
+			     | ((ed->mdc_method || dek->algo >= 100)?
+				0 : GCRY_CIPHER_ENABLE_SYNC)));
+  if (rc)
+    {
+      /* We should never get an error here cause we already checked
+       * that the algorithm is available.  */
+      BUG();
+    }
+
+
+  /* log_hexdump( "thekey", dek->key, dek->keylen );*/
+  rc = gcry_cipher_setkey (dfx->cipher_hd, dek->key, dek->keylen);
+  if ( gpg_err_code (rc) == GPG_ERR_WEAK_KEY )
+    {
+      log_info(_("WARNING: message was encrypted with"
+                 " a weak key in the symmetric cipher.\n"));
+      rc=0;
+    }
+  else if( rc )
+    {
+      log_error("key setup failed: %s\n", g10_errstr(rc) );
+      goto leave;
+    }
+
+  if (!ed->buf) 
+    {
+      log_error(_("problem handling encrypted packet\n"));
+      goto leave;
+    }
+
+  gcry_cipher_setiv (dfx->cipher_hd, NULL, 0);
+
+  if ( ed->len )
+    {
+      for (i=0; i < (nprefix+2) && ed->len; i++, ed->len-- ) 
+        {
+          if ( (c=iobuf_get(ed->buf)) == -1 )
+            break;
+          else
+            temp[i] = c;
+        }
+    }
+  else 
+    {
+      for (i=0; i < (nprefix+2); i++ )
+        if ( (c=iobuf_get(ed->buf)) == -1 )
+          break;
+        else
+          temp[i] = c;
+    }
+  
+  gcry_cipher_decrypt (dfx->cipher_hd, temp, nprefix+2, NULL, 0);
+  gcry_cipher_sync (dfx->cipher_hd);
+  p = temp;
+  /* log_hexdump( "prefix", temp, nprefix+2 ); */
+  if (dek->symmetric
+      && (p[nprefix-2] != p[nprefix] || p[nprefix-1] != p[nprefix+1]) )
+    {
+      rc = gpg_error (GPG_ERR_BAD_KEY);
+      goto leave;
+    }
+  
+  if ( dfx->mdc_hash )
+    gcry_md_write (dfx->mdc_hash, temp, nprefix+2);
+
+  dfx->refcount++;
+  dfx->partial = ed->is_partial;
+  dfx->length = ed->len;
+  if ( ed->mdc_method )
+    iobuf_push_filter ( ed->buf, mdc_decode_filter, dfx );
+  else
+    iobuf_push_filter ( ed->buf, decode_filter, dfx );
+
+  proc_packets ( procctx, ed->buf );
+  ed->buf = NULL;
+  if (dfx->eof_seen > 1 )
+    rc = gpg_error (GPG_ERR_INV_PACKET);
+  else if ( ed->mdc_method )
+    { 
+      /* We used to let parse-packet.c handle the MDC packet but this
+         turned out to be a problem with compressed packets: With old
+         style packets there is no length information available and
+         the decompressor uses an implicit end.  However we can't know
+         this implicit end beforehand (:-) and thus may feed the
+         decompressor with more bytes than actually needed.  It would
+         be possible to unread the extra bytes but due to our weird
+         iobuf system any unread is non reliable due to filters
+         already popped off.  The easy and sane solution is to care
+         about the MDC packet only here and never pass it to the
+         packet parser.  Fortunatley the OpenPGP spec requires a
+         strict format for the MDC packet so that we know that 22
+         bytes are appended.  */
+      int datalen = gcry_md_get_algo_dlen (ed->mdc_method);
+
+      assert (dfx->cipher_hd);
+      assert (dfx->mdc_hash);
+      gcry_cipher_decrypt (dfx->cipher_hd, dfx->defer, 22, NULL, 0);
+      gcry_md_write (dfx->mdc_hash, dfx->defer, 2);
+      gcry_md_final (dfx->mdc_hash);
+
+      if (dfx->defer[0] != '\xd3' || dfx->defer[1] != '\x14' )
+        {
+          log_error("mdc_packet with invalid encoding\n");
+          rc = gpg_error (GPG_ERR_INV_PACKET);
+        }
+      else if (datalen != 20
+               || memcmp (gcry_md_read (dfx->mdc_hash, 0),
+                          dfx->defer+2,datalen ))
+        rc = gpg_error (GPG_ERR_BAD_SIGNATURE);
+      /* log_printhex("MDC message:", dfx->defer, 22); */
+      /* log_printhex("MDC calc:", gcry_md_read (dfx->mdc_hash,0), datalen); */
+    }
+  
+  
+ leave:
+  release_dfx_context (dfx);
+  return rc;
+}
+
+
+
+static int
+mdc_decode_filter (void *opaque, int control, IOBUF a,
+                   byte *buf, size_t *ret_len)
+{
+  decode_filter_ctx_t dfx = opaque;
+  size_t n, size = *ret_len;
+  int rc = 0;
+  int c;
+
+  /* Note: We need to distinguish between a partial and a fixed length
+     packet.  The first is the usual case as created by GPG.  However
+     for short messages the format degrades to a fixed length packet
+     and other implementations might use fixed length as well.  Only
+     looking for the EOF on fixed data works only if the encrypted
+     packet is not followed by other data.  This used to be a long
+     standing bug which was fixed on 2009-10-02.  */
+  
+  if ( control == IOBUFCTRL_UNDERFLOW && dfx->eof_seen )
+    {
+      *ret_len = 0;
+      rc = -1;
+    }
+  else if( control == IOBUFCTRL_UNDERFLOW )
+    {
+      assert (a);
+      assert (size > 44); /* Our code requires at least this size.  */
+      
+      /* Get at least 22 bytes and put it ahead in the buffer.  */
+      if (dfx->partial)
+        {
+          for (n=22; n < 44; n++)
+            {
+              if ( (c = iobuf_get(a)) == -1 )
+                break;
+              buf[n] = c;
+            }
+        }
+      else
+        {
+          for (n=22; n < 44 && dfx->length; n++, dfx->length--)
+            {
+              c = iobuf_get (a);
+              if (c == -1)
+                break; /* Premature EOF.  */
+              buf[n] = c;
+            }
+        }
+      if (n == 44) 
+        {
+          /* We have enough stuff - flush the deferred stuff.  */
+          if ( !dfx->defer_filled )  /* First time. */
+            {
+              memcpy (buf, buf+22, 22);
+              n = 22;
+	    }
+          else
+            {
+              memcpy (buf, dfx->defer, 22);
+	    }
+          /* Fill up the buffer. */
+          if (dfx->partial)
+            {
+              for (; n < size; n++ ) 
+                {
+                  if ( (c = iobuf_get(a)) == -1 )
+                    {
+                      dfx->eof_seen = 1; /* Normal EOF. */
+                      break;
+                    }
+                  buf[n] = c;
+                }
+            }
+          else
+            {
+              for (; n < size && dfx->length; n++, dfx->length--) 
+                {
+                  c = iobuf_get(a);
+                  if (c == -1)
+                    {
+                      dfx->eof_seen = 3; /* Premature EOF. */
+                      break;
+                    }
+                  buf[n] = c;
+                }
+              if (!dfx->length)
+                dfx->eof_seen = 1; /* Normal EOF.  */
+            }
+          
+          /* Move the trailing 22 bytes back to the defer buffer.  We
+             have at least 44 bytes thus a memmove is not needed.  */
+          n -= 22;
+          memcpy (dfx->defer, buf+n, 22 );
+          dfx->defer_filled = 1;
+	}
+      else if ( !dfx->defer_filled )  /* EOF seen but empty defer buffer. */
+        {
+          /* This is bad because it means an incomplete hash. */
+          n -= 22;
+          memcpy (buf, buf+22, n );
+          dfx->eof_seen = 2; /* EOF with incomplete hash.  */
+	}
+      else  /* EOF seen (i.e. read less than 22 bytes). */
+        {
+          memcpy (buf, dfx->defer, 22 );
+          n -= 22;
+          memcpy (dfx->defer, buf+n, 22 );
+          dfx->eof_seen = 1; /* Normal EOF. */
+	}
+
+      if ( n )
+        {
+          if ( dfx->cipher_hd )
+            gcry_cipher_decrypt (dfx->cipher_hd, buf, n, NULL, 0);
+          if ( dfx->mdc_hash )
+            gcry_md_write (dfx->mdc_hash, buf, n);
+	}
+      else
+        {
+          assert ( dfx->eof_seen );
+          rc = -1; /* Return EOF.  */
+	}
+      *ret_len = n;
+    }
+  else if ( control == IOBUFCTRL_FREE ) 
+    {
+      release_dfx_context (dfx);
+    }
+  else if ( control == IOBUFCTRL_DESC ) 
+    {
+      *(char**)buf = "mdc_decode_filter";
+    }
+  return rc;
+}
+
+
+static int
+decode_filter( void *opaque, int control, IOBUF a, byte *buf, size_t *ret_len)
+{
+  decode_filter_ctx_t fc = opaque;
+  size_t size = *ret_len;
+  size_t n;
+  int c, rc = 0;
+
+
+  if ( control == IOBUFCTRL_UNDERFLOW && fc->eof_seen )
+    {
+      *ret_len = 0;
+      rc = -1;
+    }
+  else if ( control == IOBUFCTRL_UNDERFLOW ) 
+    {
+      assert(a);
+      
+      if (fc->partial)
+        {
+          for (n=0; n < size; n++ ) 
+            {
+              c = iobuf_get(a);
+              if (c == -1)
+                {
+                  fc->eof_seen = 1; /* Normal EOF. */
+                  break;
+                }
+              buf[n] = c;
+            }
+        }
+      else
+        {
+          for (n=0; n < size && fc->length; n++, fc->length--) 
+            {
+              c = iobuf_get(a);
+              if (c == -1)
+                {
+                  fc->eof_seen = 3; /* Premature EOF. */
+                  break;
+                }
+              buf[n] = c;
+            }
+          if (!fc->length)
+            fc->eof_seen = 1; /* Normal EOF.  */
+        }
+      if (n)
+        {
+          if (fc->cipher_hd)
+            gcry_cipher_decrypt (fc->cipher_hd, buf, n, NULL, 0);
+        }
+      else
+        {
+          if (!fc->eof_seen)
+            fc->eof_seen = 1;
+          rc = -1; /* Return EOF. */
+        }
+      *ret_len = n;
+    }
+  else if ( control == IOBUFCTRL_FREE ) 
+    {
+      release_dfx_context (fc);
+    }
+  else if ( control == IOBUFCTRL_DESC )
+    {
+      *(char**)buf = "decode_filter";
+    }
+  return rc;
+}
+