2004-07-27 Moritz Schulte <[email protected]>

	* command-ssh.c: Use gcrypt memory allocators, use secure memory
	where necessary.

2004-07-26  Moritz Schulte  <[email protected]>

	* command-ssh.c (data_sign): Do not forget to unsigned char when
	constructing human-readable key grip.

	* Makefile.am (gpg_agent_SOURCES): Removed: buffer.c, buffer.h;
	updated Libgpg-stream.

5 files changed, 571 insertions, 73 deletions

diff --git a/agent/ChangeLog b/agent/ChangeLog
index 1fa81c4be..2c503a5fc 100644
--- a/agent/ChangeLog
+++ b/agent/ChangeLog
@@ -1,3 +1,16 @@
+2004-07-27  Moritz Schulte  <[email protected]>
+
+	* command-ssh.c: Use gcrypt memory allocators, use secure memory
+	where necessary.
+
+2004-07-26  Moritz Schulte  <[email protected]>
+
+	* command-ssh.c (data_sign): Do not forget to unsigned char when
+	constructing human-readable key grip.
+
+	* Makefile.am (gpg_agent_SOURCES): Removed: buffer.c, buffer.h;
+	updated Libgpg-stream.
+
 2004-07-24  Moritz Schulte  <[email protected]>
 
 	* gpg-stream-config.h: New file (was missing before).
diff --git a/agent/Makefile.am b/agent/Makefile.am
index 406b8f33c..6eab1162c 100644
--- a/agent/Makefile.am
+++ b/agent/Makefile.am
@@ -30,7 +30,6 @@ AM_CFLAGS = $(LIBGCRYPT_CFLAGS) $(LIBASSUAN_CFLAGS) $(PTH_CFLAGS)
 gpg_agent_SOURCES = \
 	gpg-agent.c agent.h \
 	gpg-stream.c gpg-stream.h gpg-stream-config.h \
-	buffer.c buffer.h \
 	command.c command-ssh.c \
 	query.c \
 	cache.c \
diff --git a/agent/command-ssh.c b/agent/command-ssh.c
index c877c6ec7..8195b9038 100644
--- a/agent/command-ssh.c
+++ b/agent/command-ssh.c
@@ -26,7 +26,7 @@
 #include <errno.h>
 #include <sys/types.h>
 #include <dirent.h>
-//#include <stdio.h>
+#include <stdio.h>
 
 #include "agent.h"
 
@@ -227,7 +227,7 @@ gpg_stream_write_uint32 (gpg_stream_t stream, uint32_t uint32)
 }
 
 static gpg_err_code_t
-gpg_stream_read_string (gpg_stream_t stream,
+gpg_stream_read_string (gpg_stream_t stream, unsigned int secure,
 			unsigned char **string, uint32_t *string_size)
 {
   gpg_err_code_t err = GPG_ERR_NO_ERROR;
@@ -241,7 +241,10 @@ gpg_stream_read_string (gpg_stream_t stream,
     goto out;
 
   /* Allocate space.  */
-  buffer = malloc (length + 1);
+  if (secure)
+    buffer = gcry_malloc_secure (length + 1);
+  else
+    buffer = gcry_malloc (length + 1);
   if (! buffer)
     {
       err = gpg_err_code_from_errno (errno);
@@ -268,7 +271,7 @@ gpg_stream_read_string (gpg_stream_t stream,
     }
   else
     if (buffer)
-      free (buffer);
+      gcry_free (buffer);
 
   return err;
 }
@@ -303,8 +306,8 @@ gpg_stream_write_cstring (gpg_stream_t stream, char *string)
 }			  
 
 static gpg_err_code_t
-gpg_stream_read_mpint (gpg_stream_t stream, mpint_t *mpint,
-		       unsigned int mpi_type)
+gpg_stream_read_mpint (gpg_stream_t stream, unsigned int secure,
+		       mpint_t *mpint, unsigned int mpi_type)
 {
   gpg_err_code_t err = GPG_ERR_NO_ERROR;
   unsigned char *mpi_data = NULL;
@@ -314,7 +317,8 @@ gpg_stream_read_mpint (gpg_stream_t stream, mpint_t *mpint,
   if (! mpi_type)
     mpi_type = GCRYMPI_FMT_STD;
 
-  err = gpg_stream_read_string (stream, &mpi_data, &mpi_data_size);
+  err = gpg_stream_read_string (stream, secure,
+				&mpi_data, &mpi_data_size);
   if (err)
     goto out;
 
@@ -324,7 +328,7 @@ gpg_stream_read_mpint (gpg_stream_t stream, mpint_t *mpint,
 
  out:
 
-  free (mpi_data);
+  gcry_free (mpi_data);
 
   if (! err)
     *mpint = mpi;
@@ -333,8 +337,8 @@ gpg_stream_read_mpint (gpg_stream_t stream, mpint_t *mpint,
 }
 
 static gpg_err_code_t
-gpg_stream_write_mpint (gpg_stream_t stream, mpint_t mpint,
-			unsigned int mpi_type)
+gpg_stream_write_mpint (gpg_stream_t stream,
+			mpint_t mpint, unsigned int mpi_type)
 {
   gpg_err_code_t err = GPG_ERR_NO_ERROR;
   unsigned char *mpi_buffer = NULL;
@@ -376,7 +380,7 @@ gpg_stream_read_file (const char *filename,
   if (err)
     goto out;
 
-  buffer_new = malloc (buffer_new_n);
+  buffer_new = gcry_malloc (buffer_new_n);
   if (! buffer_new)
     {
       err = gpg_err_code_from_errno (errno);
@@ -436,7 +440,7 @@ ssh_receive_key_secret (gpg_stream_t stream, ssh_key_secret_t *key_secret)
   unsigned char *key_type = NULL;
   gcry_mpi_t mpi_iqmp = NULL;
 	
-  err = gpg_stream_read_string (stream, &key_type, NULL);
+  err = gpg_stream_read_string (stream, 0, &key_type, NULL);
   if (err)
     goto out;
 
@@ -448,22 +452,22 @@ ssh_receive_key_secret (gpg_stream_t stream, ssh_key_secret_t *key_secret)
     {
     case SSH_KEY_TYPE_RSA:
       {
-	err = gpg_stream_read_mpint (stream, &key.material.rsa.n, 0);
+	err = gpg_stream_read_mpint (stream, 0, &key.material.rsa.n, 0);
 	if (err)
 	  break;
-	err = gpg_stream_read_mpint (stream, &key.material.rsa.e, 0);
+	err = gpg_stream_read_mpint (stream, 0, &key.material.rsa.e, 0);
 	if (err)
 	  break;
-	err = gpg_stream_read_mpint (stream, &key.material.rsa.d, 0);
+	err = gpg_stream_read_mpint (stream, 1, &key.material.rsa.d, 0);
 	if (err)
 	  break;
-	err = gpg_stream_read_mpint (stream, &mpi_iqmp, 0);
+	err = gpg_stream_read_mpint (stream, 1, &mpi_iqmp, 0);
 	if (err)
 	  break;
-	err = gpg_stream_read_mpint (stream, &key.material.rsa.p, 0);
+	err = gpg_stream_read_mpint (stream, 1, &key.material.rsa.p, 0);
 	if (err)
 	  break;
-	err = gpg_stream_read_mpint (stream, &key.material.rsa.q, 0);
+	err = gpg_stream_read_mpint (stream, 1, &key.material.rsa.q, 0);
 	if (err)
 	  break;
 
@@ -483,7 +487,7 @@ ssh_receive_key_secret (gpg_stream_t stream, ssh_key_secret_t *key_secret)
 	  {
 	    /* u has to be recomputed.  */
 
-	    key.material.rsa.u = gcry_mpi_new (0);
+	    key.material.rsa.u = gcry_mpi_snew (0);
 	    gcry_mpi_invm (key.material.rsa.u,
 			   key.material.rsa.p, key.material.rsa.q);
 	  }
@@ -501,19 +505,27 @@ ssh_receive_key_secret (gpg_stream_t stream, ssh_key_secret_t *key_secret)
 
  out:
 
-  free (key_type);
+  gcry_free (key_type);
   gcry_mpi_release (mpi_iqmp);
 
   if (! err)
     *key_secret = key;
   else
     {
-      gcry_mpi_release (key.material.rsa.n);
-      gcry_mpi_release (key.material.rsa.e);
-      gcry_mpi_release (key.material.rsa.d);
-      gcry_mpi_release (key.material.rsa.p);
-      gcry_mpi_release (key.material.rsa.q);
-      gcry_mpi_release (key.material.rsa.u);
+      switch (key.type)
+	{
+	case SSH_KEY_TYPE_RSA:
+	  gcry_mpi_release (key.material.rsa.n);
+	  gcry_mpi_release (key.material.rsa.e);
+	  gcry_mpi_release (key.material.rsa.d);
+	  gcry_mpi_release (key.material.rsa.p);
+	  gcry_mpi_release (key.material.rsa.q);
+	  gcry_mpi_release (key.material.rsa.u);
+	  break;
+
+	case SSH_KEY_TYPE_NONE:
+	  break;
+	}
     }
 
   return err;
@@ -558,7 +570,7 @@ ssh_receive_key_public (gpg_stream_t stream, ssh_key_public_t *key_public)
   ssh_key_public_t key = { 0 };
   unsigned char *key_type = NULL;
 
-  err = gpg_stream_read_string (stream, &key_type, NULL);
+  err = gpg_stream_read_string (stream, 0, &key_type, NULL);
   if (err)
     goto out;
 
@@ -570,10 +582,10 @@ ssh_receive_key_public (gpg_stream_t stream, ssh_key_public_t *key_public)
    {
     case SSH_KEY_TYPE_RSA:
       {
-	err = gpg_stream_read_mpint (stream, &key.material.rsa.e, 0);
+	err = gpg_stream_read_mpint (stream, 0, &key.material.rsa.e, 0);
 	if (err)
 	  break;
-	err = gpg_stream_read_mpint (stream, &key.material.rsa.n, 0);
+	err = gpg_stream_read_mpint (stream, 0, &key.material.rsa.n, 0);
 	if (err)
 	  break;
 	break;
@@ -589,7 +601,7 @@ ssh_receive_key_public (gpg_stream_t stream, ssh_key_public_t *key_public)
 
  out:
 
-  free (key_type);
+  gcry_free (key_type);
 
   if (! err)
     *key_public = key;
@@ -670,7 +682,7 @@ ssh_convert_key_to_blob (unsigned char **blob, size_t *blob_size,
   if (err)
     goto out;
 
-  blob_new = malloc (blob_new_size);
+  blob_new = gcry_malloc (blob_new_size);
   if (! blob_new)
     {
       err = gpg_err_code_from_errno (errno);
@@ -721,7 +733,7 @@ ssh_key_grip (ssh_key_public_t *public, ssh_key_secret_t *secret,
 			     : secret->material.rsa.n,
 			     public
 			     ? public->material.rsa.e
-			     : secret->material.rsa.n);
+			     : secret->material.rsa.e);
       break;
 
     case SSH_KEY_TYPE_NONE:
@@ -867,7 +879,7 @@ ssh_handler_request_identities (ctrl_t ctrl,
     }
   key_directory_n = strlen (key_directory);
   
-  key_path = malloc (key_directory_n + 46);
+  key_path = gcry_malloc (key_directory_n + 46);
   if (! key_path)
     {
       err = gpg_err_code_from_errno (errno);
@@ -903,7 +915,7 @@ ssh_handler_request_identities (ctrl_t ctrl,
 
 	      /* Convert it into a public key.   */
 	      err = ssh_key_public_from_stored_key (buffer, buffer_n, &key);
-	      free (buffer);
+	      gcry_free (buffer);
 	      buffer = NULL;
 	      if (err)
 		goto out;
@@ -915,7 +927,7 @@ ssh_handler_request_identities (ctrl_t ctrl,
 
 	      /* Add key blob to buffer stream.  */
 	      err = gpg_stream_write_string (key_blobs, key_blob, key_blob_n);
-	      free (key_blob);
+	      gcry_free (key_blob);
 	      key_blob = NULL;
 	      if (err)
 		goto out;
@@ -949,8 +961,8 @@ ssh_handler_request_identities (ctrl_t ctrl,
   gpg_stream_destroy (key_blobs);
   closedir (dir);
   free (key_directory);
-  free (key_path);
-  free (key_blob);
+  gcry_free (key_path);
+  gcry_free (key_blob);
 }
 
 static gpg_err_code_t
@@ -984,7 +996,7 @@ data_sign (CTRL ctrl, unsigned char **sig, size_t *sig_n)
   unsigned int i = 0;
 
   for (i = 0; i < 20; i++)
-    sprintf (&key_grip[i * 2], "%02X", ctrl->keygrip[i]);
+    sprintf (&key_grip[i * 2], "%02X", (unsigned char) ctrl->keygrip[i]);
   strncpy (strchr (description, '0'), key_grip, 40);
 	   
   err = agent_pksign_do (ctrl, description, &signature_sexp, 0);
@@ -1039,7 +1051,7 @@ data_sign (CTRL ctrl, unsigned char **sig, size_t *sig_n)
   if (err)
     goto out;
 
-  sig_blob = malloc (sig_blob_n);
+  sig_blob = gcry_malloc (sig_blob_n);
   if (! sig_blob)
     {
       err = gpg_err_code_from_errno (errno);
@@ -1048,7 +1060,7 @@ data_sign (CTRL ctrl, unsigned char **sig, size_t *sig_n)
 
   err = gpg_stream_read (stream, sig_blob, sig_blob_n, &bytes_read);
   if ((! err) && (sig_blob_n != bytes_read))
-    err = GPG_ERR_INTERNAL; 	/* violation */
+    err = GPG_ERR_EOF;
   if (err)
     goto out;
 
@@ -1067,7 +1079,7 @@ data_sign (CTRL ctrl, unsigned char **sig, size_t *sig_n)
     {
       gcry_sexp_release (signature_sexp);
       gcry_sexp_release (sublist);
-      free (sig_blob);
+      gcry_free (sig_blob);
     }
 
   return err;
@@ -1095,7 +1107,7 @@ ssh_handler_sign_request (ctrl_t ctrl,
 
   /* Receive key.  */
   
-  err = gpg_stream_read_string (request, &key_blob, &key_blob_size);
+  err = gpg_stream_read_string (request, 0, &key_blob, &key_blob_size);
   if (err)
     goto out;
   
@@ -1105,7 +1117,7 @@ ssh_handler_sign_request (ctrl_t ctrl,
 
   /* Receive data to sign.  */
   
-  err = gpg_stream_read_string (request, &data, &data_size);
+  err = gpg_stream_read_string (request, 0, &data, &data_size);
   if (err)
     goto out;
 
@@ -1161,9 +1173,9 @@ ssh_handler_sign_request (ctrl_t ctrl,
   else
     gpg_stream_write_byte (response, SSH_RESPONSE_FAILURE);
 
-  free (key_blob);
-  free (data);
-  free (sig);
+  gcry_free (key_blob);
+  gcry_free (data);
+  gcry_free (sig);
 }
 
 static gpg_err_code_t
@@ -1194,7 +1206,7 @@ ssh_key_to_sexp_buffer (ssh_key_secret_t *key, const char *passphrase,
     goto out;
 
   buffer_new_n = gcry_sexp_sprint (key_sexp, GCRYSEXP_FMT_CANON, NULL, 0);
-  buffer_new = malloc (buffer_new_n);
+  buffer_new = gcry_malloc (buffer_new_n);
   if (! buffer_new)
     {
       err = gpg_err_code_from_errno (errno);
@@ -1209,10 +1221,8 @@ ssh_key_to_sexp_buffer (ssh_key_secret_t *key, const char *passphrase,
 
  out:
 
-  if (key_sexp)
-    gcry_sexp_release (key_sexp);
-  if (buffer_new)
-    free (buffer_new);
+  gcry_sexp_release (key_sexp);
+  gcry_free (buffer_new);
 
   return err;
 }
@@ -1254,24 +1264,35 @@ static gpg_err_code_t
 ssh_identity_register (ssh_key_secret_t *key, int ttl)
 {
   gpg_err_code_t err = GPG_ERR_NO_ERROR;
-  unsigned char key_grip[21] = { 0 };
+  unsigned char key_grip_raw[21] = { 0 };
   unsigned char *buffer = NULL;
   unsigned int buffer_n = 0;
   char passphrase[100] = { 0 };
+  char description[] =
+    "Please provide the passphrase, which should  "
+    "be used for protecting the received secret key "
+    "`0123456789012345678901234567890123456789':";
+  unsigned int i = 0;
+  char key_grip[41];
   int ret = 0;
 
   if (DBG_COMMAND)
     log_debug ("[ssh-agent] registering identity `%s'\n", key_grip);
 
-  err = ssh_key_grip (NULL, key, key_grip);
+  err = ssh_key_grip (NULL, key, key_grip_raw);
   if (err)
     goto out;
 
-  ret = agent_key_available (key_grip);
+  ret = agent_key_available (key_grip_raw);
   if (! ret)
     goto out;
 
-  err = get_passphrase ("foo", sizeof (passphrase), passphrase);
+  for (i = 0; i < 20; i++)
+    sprintf (&key_grip[i * 2], "%02X", key_grip_raw[i]);
+  strncpy (strchr (description, '0'), key_grip, 40);
+
+  err = get_passphrase (description,
+			sizeof (passphrase), passphrase);
   if (err)
     goto out;
 
@@ -1279,11 +1300,11 @@ ssh_identity_register (ssh_key_secret_t *key, int ttl)
   if (err)
     goto out;
 
-  err = agent_write_private_key (key_grip, buffer, buffer_n, 0);
+  err = agent_write_private_key (key_grip_raw, buffer, buffer_n, 0);
   if (err)
     goto out;
 
-  err = agent_put_cache (key_grip, passphrase, ttl);
+  err = agent_put_cache (key_grip_raw, passphrase, ttl);
   if (err)
     goto out;
 
@@ -1332,7 +1353,7 @@ ssh_handler_add_identity (ctrl_t ctrl,
   if (err)
     goto out;
 
-  err = gpg_stream_read_string (request, &comment, NULL);
+  err = gpg_stream_read_string (request, 0, &comment, NULL);
   if (err)
     goto out;
   
@@ -1382,8 +1403,21 @@ ssh_handler_add_identity (ctrl_t ctrl,
  out:
 
   free (comment);
-  
-  //ssh_key_destroy (key); FIXME
+
+  switch (key.type)
+    {
+    case SSH_KEY_TYPE_RSA:
+      gcry_mpi_release (key.material.rsa.n);
+      gcry_mpi_release (key.material.rsa.e);
+      gcry_mpi_release (key.material.rsa.d);
+      gcry_mpi_release (key.material.rsa.p);
+      gcry_mpi_release (key.material.rsa.q);
+      gcry_mpi_release (key.material.rsa.u);
+      break;
+
+    case SSH_KEY_TYPE_NONE:
+      break;
+    }
 
   gpg_stream_write_byte (response,
 			 err
@@ -1405,7 +1439,7 @@ ssh_handler_remove_identity (ctrl_t ctrl,
   if (DBG_COMMAND)
     log_debug ("[ssh-agent] remove identity\n");
   
-  err = gpg_stream_read_string (request, &key_blob, NULL);
+  err = gpg_stream_read_string (request, 0, &key_blob, NULL);
   if (err)
     goto out;
 
@@ -1419,7 +1453,7 @@ ssh_handler_remove_identity (ctrl_t ctrl,
 
  out:
 
-  free (key_blob);
+  gcry_free (key_blob);
   
   err = gpg_stream_write_byte (response,
 			       err
@@ -1567,9 +1601,25 @@ gpg_stream_eof_p (gpg_stream_t stream, unsigned int *eof)
   return err;
 }
 
+/* FIXME: Libgcrypt should provide this function.  */
+static void *
+gcry_realloc_secure (void *mem, size_t size)
+{
+  if (! mem)
+    return gcry_malloc_secure (size);
+  else
+    return gcry_realloc (mem, size);
+}
+  
 void
 start_command_handler_ssh (int sock_client)
 {
+  gpg_stream_spec_mem_t stream_spec_secure = { NULL, 0, 1,
+					       gcry_realloc_secure,
+					       gcry_free };
+  gpg_stream_spec_mem_t stream_spec = { NULL, 0, 1,
+					gcry_realloc,
+					gcry_free };
   struct server_control_s ctrl =  { NULL };
   gpg_err_code_t err = GPG_ERR_NO_ERROR;
   gpg_stream_t stream_sock = NULL;
@@ -1598,24 +1648,28 @@ start_command_handler_ssh (int sock_client)
       if (err || eof)
 	break;
 
-      /* Create memory streams for request/response data.  */
+      /* Create memory streams for request/response data.  The entire
+	 request will be stored in secure memory, since it might
+	 contain secret key material.  The response does not have to
+	 be stored in secure memory, since we never give out secret
+	 keys.  */
       stream_request = NULL;
-      err = gpg_stream_create (&stream_request, NULL,
+      err = gpg_stream_create (&stream_request, &stream_spec_secure,
 			       GPG_STREAM_FLAG_READ | GPG_STREAM_FLAG_WRITE,
 			       gpg_stream_functions_mem);
       if (err)
 	break;
       stream_response = NULL;
-      err = gpg_stream_create (&stream_response, NULL,
+      err = gpg_stream_create (&stream_response, &stream_spec,
 			       GPG_STREAM_FLAG_READ | GPG_STREAM_FLAG_WRITE,
 			       gpg_stream_functions_mem);
       if (err)
 	break;
 
       /* Retrieve request length.  */
-      free (request);
+      gcry_free (request);
       request = NULL;
-      err = gpg_stream_read_string (stream_sock, &request, &request_size);
+      err = gpg_stream_read_string (stream_sock, 1, &request, &request_size);
       if (err)
 	break;
 
@@ -1666,7 +1720,7 @@ start_command_handler_ssh (int sock_client)
   gpg_stream_destroy (stream_sock);
   gpg_stream_destroy (stream_request);
   gpg_stream_destroy (stream_response);
-  free (request);
+  gcry_free (request);
 
   if (DBG_COMMAND)
     log_debug ("[ssh-agent] Leaving ssh command handler: %s\n", gpg_strerror (err));
diff --git a/agent/gpg-stream.c b/agent/gpg-stream.c
index 1139cbe3d..1fb3c4033 100644
--- a/agent/gpg-stream.c
+++ b/agent/gpg-stream.c
@@ -33,10 +33,430 @@
 
 #include "gpg-stream.h"
 #include "gpg-stream-config.h"
-#include "buffer.h"
 
 
 
+/* Buffer management layer.  */
+
+#define BUFFER_BLOCK_SIZE 1024
+
+
+
+typedef struct buffer *buffer_t;
+
+/* Callbacks, necessary for filling/flushing/seeking.  */
+typedef gpg_error_t (*buffer_func_read_t) (void *handle,
+					   char *buffer,
+					   size_t bytes_to_read,
+					   size_t *bytes_read);
+typedef gpg_error_t (*buffer_func_write_t) (void *handle,
+					    const char *buffer,
+					    size_t bytes_to_write,
+					    size_t *bytes_written);
+typedef gpg_error_t (*buffer_func_seek_t) (void *handle,
+					   off_t offset,
+					   int whence);
+
+typedef gpg_error_t (*buffer_func_stat_t) (void *handle,
+					   size_t *size);
+
+typedef struct buffer_functions
+{
+  buffer_func_read_t  func_read;  /* Read callback.   */
+  buffer_func_write_t func_write; /* Write callback.  */
+  buffer_func_seek_t  func_seek;  /* Seek callback.   */
+  buffer_func_stat_t  func_stat;  /* Stat callback.   */
+} buffer_functions_t;
+
+/* Buffer context.  */
+struct buffer
+{
+  void *handle;			/* Handle, passed to callbacks.     */
+  buffer_functions_t functions;	/* Callback functions.              */
+  unsigned int flags;		/* General flags.                   */
+  struct buffer_in
+  {
+    char *container;		/* Container holding data.          */
+    size_t container_size;	/* Size of CONTAINER.               */
+    size_t data_size;		/* Size of data in CONTAINER.       */
+    off_t data_offset;		/* Offset inside of CONTAINER.      */
+  } buffer_in;
+  struct buffer_out
+  {
+    char *container;		/* Container holding data.          */
+    size_t container_size;	/* Size of CONTAINER.               */
+    size_t data_size;		/* Size of data in CONTAINER.       */
+    off_t data_offset;		/* Offset inside of CONTAINER.      */
+    size_t data_flushed;	/* Amount of data already flushed.  */
+  } buffer_out;
+};
+
+
+
+/* Buffer contains unflushed data.  */
+#define BUFFER_FLAG_DIRTY (1 << 0)
+
+
+
+/* Fill buffer.  */
+static gpg_error_t
+buffer_fill_do (buffer_t buffer)
+{
+  gpg_error_t err = GPG_ERR_NO_ERROR;
+  size_t bytes_read = 0;
+
+  if (! buffer->functions.func_read)
+    err = gpg_error (GPG_ERR_NOT_IMPLEMENTED);
+  else
+    {
+      buffer_func_read_t func_read = buffer->functions.func_read;
+      
+      err = (*func_read) (buffer->handle,
+			  buffer->buffer_in.container,
+			  buffer->buffer_in.container_size,
+			  &bytes_read);
+    }
+
+  buffer->buffer_in.data_offset = 0;
+  buffer->buffer_in.data_size = bytes_read;
+
+  return err;
+}
+
+/* Empty buffer input.  */
+static gpg_error_t
+buffer_empty (buffer_t buffer)
+{
+  gpg_error_t err = GPG_ERR_NO_ERROR;
+
+  buffer->buffer_in.data_size = 0;
+  buffer->buffer_in.data_offset = 0;
+
+  return err;
+}
+
+/* Flush data contained in buffer.  */
+static gpg_error_t
+buffer_flush_do (buffer_t buffer)
+{
+  buffer_func_write_t func_write = buffer->functions.func_write;
+  gpg_error_t err = GPG_ERR_NO_ERROR;
+  size_t bytes_written = 0;
+
+  if (! func_write)
+    err = gpg_error (GPG_ERR_NOT_IMPLEMENTED);
+  else if (buffer->flags & BUFFER_FLAG_DIRTY)
+    while ((buffer->buffer_out.data_size
+	    - buffer->buffer_out.data_flushed) && (! err))
+      {
+	
+	err = (*func_write) (buffer->handle,
+			     buffer->buffer_out.container
+			     + buffer->buffer_out.data_flushed,
+			     buffer->buffer_out.data_size
+			     - buffer->buffer_out.data_flushed,
+			     &bytes_written);
+	if (! err)
+	  {
+	    buffer->buffer_out.data_size = 0;
+	    buffer->buffer_out.data_offset = 0;
+	    buffer->buffer_out.data_flushed = 0;
+	    buffer->flags &= ~BUFFER_FLAG_DIRTY;
+	  }
+	else
+	  buffer->buffer_out.data_flushed += bytes_written;
+      }
+  
+  return err;
+}
+
+static gpg_error_t
+buffer_stat_do (buffer_t buffer,
+		size_t *size)
+{
+  buffer_func_stat_t func_stat = buffer->functions.func_stat;
+  gpg_error_t err = GPG_ERR_NO_ERROR;
+
+  err = (*func_stat) (buffer->handle, size);
+
+  return err;
+}
+
+
+
+/* Read from a buffer.  */
+gpg_error_t
+buffer_read (buffer_t buffer,
+	     char *data,
+	     size_t bytes_to_read,
+	     size_t *bytes_read)
+{
+  gpg_error_t err = GPG_ERR_NO_ERROR;
+  size_t data_read = 0;
+  size_t data_to_copy = 0;
+
+  if (! (buffer->flags & BUFFER_FLAG_DIRTY))
+    err = buffer_flush_do (buffer);
+
+  while ((bytes_to_read - data_read) && (! err))
+    {
+      if (buffer->buffer_in.data_offset == buffer->buffer_in.data_size)
+	{
+	  /* Nothing more to read in current container, try to
+	     fill container with new data.  */
+	  err = buffer_fill_do (buffer);
+	  if (! err)
+	    if (! buffer->buffer_in.data_size)
+	      /* Filling did not result in any data read.  */
+	      break;
+	}
+
+      if (! err)
+	{
+	  if ((bytes_to_read
+	       - data_read) > (buffer->buffer_in.data_size
+			       - buffer->buffer_in.data_offset))
+	    data_to_copy = (buffer->buffer_in.data_size
+			    - buffer->buffer_in.data_offset);
+	  else
+	    data_to_copy = bytes_to_read - data_read;
+
+	  memcpy (data + data_read,
+		  buffer->buffer_in.container + buffer->buffer_in.data_offset,
+		  data_to_copy);
+	  buffer->buffer_in.data_offset += data_to_copy;
+	  data_read += data_to_copy;
+	}
+    }
+
+  if (bytes_read)
+    *bytes_read = data_read;
+
+  return err;
+}
+
+/* Write to a buffer.  */
+gpg_error_t
+buffer_write (buffer_t buffer,
+	      const char *data,
+	      size_t bytes_to_write,
+	      size_t *bytes_written)
+{
+  gpg_error_t err = GPG_ERR_NO_ERROR;
+  size_t data_written = 0;
+  size_t data_to_copy = 0;
+      
+  while ((bytes_to_write - data_written) && (! err))
+    {
+      if (buffer->buffer_out.data_offset == buffer->buffer_out.container_size)
+	/* Container full, flush buffer.  */
+	err = buffer_flush_do (buffer);
+
+      if (! err)
+	{
+	  if ((bytes_to_write
+	       - data_written) > (buffer->buffer_out.container_size
+				  - buffer->buffer_out.data_offset))
+	    data_to_copy = (buffer->buffer_out.container_size
+			    - buffer->buffer_out.data_offset);
+	  else
+	    data_to_copy = bytes_to_write - data_written;
+
+	  memcpy (buffer->buffer_out.container
+		  + buffer->buffer_out.data_offset,
+		  data + data_written,
+		  data_to_copy);
+	  if ((buffer->buffer_out.data_offset
+	       + data_to_copy) > buffer->buffer_out.data_size)
+	    buffer->buffer_out.data_size = (buffer->buffer_out.data_offset
+					    + data_to_copy);
+	  buffer->buffer_out.data_offset += data_to_copy;
+	  data_written += data_to_copy;
+
+	  if (data_written)
+	    if (! (buffer->flags & BUFFER_FLAG_DIRTY))
+	      buffer->flags |= BUFFER_FLAG_DIRTY;
+	}
+    }
+
+  if (bytes_written)
+    *bytes_written = data_written;
+
+  return err;
+}
+
+/* Seek in a buffer.  */
+gpg_error_t
+buffer_seek (buffer_t buffer,
+	     off_t offset,
+	     int whence)
+{
+  buffer_func_seek_t func_seek = buffer->functions.func_seek;
+  gpg_error_t err = GPG_ERR_NO_ERROR;
+
+  if (! func_seek)
+    err = gpg_error (GPG_ERR_NOT_IMPLEMENTED);
+  else
+    {
+      if (buffer->flags & BUFFER_FLAG_DIRTY)
+	/* Flush data first in order to prevent flushing it to the
+	   wrong offset.  */
+	err = buffer_flush_do (buffer);
+      
+      if (! err)
+	err = (*func_seek) (buffer->handle, offset, whence);
+
+      if (! err)
+	err = buffer_empty (buffer);
+    }
+
+  return err;
+}
+
+/* Return the unread data contained in a buffer.  */
+gpg_error_t
+buffer_peek (buffer_t buffer,
+	     char **data,
+	     size_t *data_size)
+{
+  gpg_error_t err = GPG_ERR_NO_ERROR;
+
+  if (buffer->buffer_in.data_offset == buffer->buffer_in.data_size)
+    /* Refill container.  */
+    err = buffer_fill_do (buffer);
+
+  if (! err)
+    {
+      if (data)
+	*data = buffer->buffer_in.container + buffer->buffer_in.data_offset;
+      if (data_size)
+	*data_size = buffer->buffer_in.data_size - buffer->buffer_in.data_offset;
+    }
+  
+  return err;
+}
+
+/* Skip SIZE bytes of input data contained in buffer.  */
+gpg_error_t
+buffer_skip (buffer_t buffer,
+	     size_t size)
+{
+  gpg_error_t err = GPG_ERR_NO_ERROR;
+
+  if (buffer->buffer_in.data_offset + size > buffer->buffer_in.data_size)
+    err = gpg_error (GPG_ERR_INV_ARG);
+  else
+    buffer->buffer_in.data_offset += size;
+
+  return err;
+}
+
+
+
+/* Create a new buffer.  */
+gpg_error_t
+buffer_create (buffer_t *buffer,
+	       void *handle,
+	       buffer_functions_t functions)
+{
+  gpg_error_t err = GPG_ERR_NO_ERROR;
+
+  /* Allocate memory, initialize.  */
+      
+  buffer_t buffer_new = NULL;
+  char *container_in_new = NULL;
+  char *container_out_new = NULL;
+
+  buffer_new = malloc (sizeof (*buffer_new));
+  if (! buffer_new)
+    err = gpg_error_from_errno (errno);
+
+  if (! err)
+    {
+      container_in_new = malloc (BUFFER_BLOCK_SIZE);
+      if (! container_in_new)
+	err = gpg_error_from_errno (errno);
+    }
+  if (! err)
+    {
+      container_out_new = malloc (BUFFER_BLOCK_SIZE);
+      if (! container_out_new)
+	err = gpg_error_from_errno (errno);
+    }
+
+  if (! err)
+    {
+      buffer_new->handle = handle;
+      buffer_new->flags = 0;
+      buffer_new->functions = functions;
+      buffer_new->buffer_in.container = container_in_new;
+      buffer_new->buffer_in.container_size = BUFFER_BLOCK_SIZE;
+      buffer_new->buffer_in.data_size = 0;
+      buffer_new->buffer_in.data_offset = 0;
+      buffer_new->buffer_out.container = container_out_new;
+      buffer_new->buffer_out.container_size = BUFFER_BLOCK_SIZE;
+      buffer_new->buffer_out.data_size = 0;
+      buffer_new->buffer_out.data_offset = 0;
+      buffer_new->buffer_out.data_flushed = 0;
+      *buffer = buffer_new;
+    }
+  else
+    {
+      if (container_in_new)
+	free (container_in_new);
+      if (container_out_new)
+	free (container_out_new);
+      if (buffer_new)
+	free (buffer_new);
+    }
+  
+  return err;
+}
+
+/* Destroy a buffer.  */
+gpg_error_t
+buffer_destroy (buffer_t buffer)
+{
+  gpg_error_t err = GPG_ERR_NO_ERROR;
+  
+  if (buffer)
+    {
+      err = buffer_flush_do (buffer);
+      free (buffer->buffer_in.container);
+      free (buffer->buffer_out.container);
+      free (buffer);
+    }
+
+  return err;
+}
+
+/* Write out unwritten data contained in buffer.  */
+gpg_error_t
+buffer_flush (buffer_t buffer)
+{
+  gpg_error_t err = GPG_ERR_NO_ERROR;
+
+  err = buffer_flush_do (buffer);
+
+  return err;
+}
+
+/* Stat buffer.  */
+gpg_error_t
+buffer_stat (buffer_t buffer,
+	     size_t *size)
+{
+  gpg_error_t err = GPG_ERR_NO_ERROR;
+
+  err = buffer_stat_do (buffer, size);
+
+  return err;
+}
+
+
+
+/* Stream layer.  */
+
 /* A Stream Context.  */
 struct gpg_stream
 {
@@ -66,6 +486,9 @@ struct gpg_stream
 
 /* Implementation of Memory I/O.  */
 
+typedef void *(*mem_func_realloc_t) (void *mem, size_t size);
+typedef void (*mem_func_free_t) (void *mem);
+
 typedef struct gpg_stream_handle_mem
 {
   char *memory;			/* Data.                       */
@@ -73,6 +496,8 @@ typedef struct gpg_stream_handle_mem
   size_t data_size;		/* Size of data in MEMORY.     */
   unsigned int grow: 1;		/* MEMORY is allowed to grow.  */
   size_t offset;		/* Current offset in MEMORY.   */
+  mem_func_realloc_t func_realloc;
+  mem_func_free_t func_free;
 } *gpg_stream_handle_mem_t;
 
 static gpg_error_t
@@ -94,6 +519,10 @@ gpg_stream_func_mem_create (void **handle,
       mem_handle->data_size = 0;
       mem_handle->grow = mem_spec ? mem_spec->grow : 1;
       mem_handle->offset = 0;
+      mem_handle->func_realloc = ((mem_spec && mem_spec->func_realloc)
+				  ? mem_spec->func_realloc : realloc);
+      mem_handle->func_free = ((mem_spec && mem_spec->func_free)
+			       ? mem_spec->func_free : free);
       *handle = mem_handle;
     }
 
@@ -136,8 +565,9 @@ gpg_stream_func_mem_write (void *handle,
 
   while (bytes_to_write > mem_handle->memory_size - mem_handle->offset)
     {
-      memory_new = realloc (mem_handle->memory,
-			    mem_handle->memory_size + BUFFER_BLOCK_SIZE);
+      memory_new = (*mem_handle->func_realloc)
+	(mem_handle->memory,
+	 mem_handle->memory_size + BUFFER_BLOCK_SIZE);
       if (! memory_new)
 	err = gpg_error_from_errno (errno);
       else
@@ -216,7 +646,7 @@ gpg_stream_func_mem_destroy (void *handle)
   gpg_error_t err = GPG_ERR_NO_ERROR;
 
   if (mem_handle->memory)
-    free (mem_handle->memory);
+    (*mem_handle->func_free) (mem_handle->memory);
   free (mem_handle);
 
   return err;
diff --git a/agent/gpg-stream.h b/agent/gpg-stream.h
index c7db5f0b6..464d9ea9b 100644
--- a/agent/gpg-stream.h
+++ b/agent/gpg-stream.h
@@ -129,6 +129,8 @@ typedef struct gpg_stream_spec_mem
   char *memory;
   size_t memory_size;
   unsigned int grow: 1;
+  void *(*func_realloc) (void *mem, size_t size);
+  void (*func_free) (void *mem);
 } gpg_stream_spec_mem_t;
 
 extern gpg_stream_functions_t gpg_stream_functions_mem;