- djm@cvs.openbsd.org 2013/10/09 23:42:17

     [sftp-server.8 sftp-server.c]
     Add ability to whitelist and/or blacklist sftp protocol requests by name.
     Refactor dispatch loop and consolidate read-only mode checks.
     Make global variables static, since sftp-server is linked into sshd(8).
     ok dtucker@

3 files changed, 258 insertions, 192 deletions

diff --git a/ChangeLog b/ChangeLog
index 5eb73c9f9..2ab5a2cbf 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+20131015
+ - (djm) OpenBSD CVS Sync
+   - djm@cvs.openbsd.org 2013/10/09 23:42:17
+     [sftp-server.8 sftp-server.c]
+     Add ability to whitelist and/or blacklist sftp protocol requests by name.
+     Refactor dispatch loop and consolidate read-only mode checks.
+     Make global variables static, since sftp-server is linked into sshd(8).
+     ok dtucker@
+
 20131010
  - (dtucker) OpenBSD CVS Sync
    - sthen@cvs.openbsd.org 2013/09/16 11:35:43
diff --git a/sftp-server.8 b/sftp-server.8
index cc925b96e..d7604b28d 100644
--- a/sftp-server.8
+++ b/sftp-server.8
@@ -1,4 +1,4 @@
-.\" $OpenBSD: sftp-server.8,v 1.23 2013/07/16 00:07:52 schwarze Exp $
+.\" $OpenBSD: sftp-server.8,v 1.24 2013/10/09 23:42:17 djm Exp $
 .\"
 .\" Copyright (c) 2000 Markus Friedl.  All rights reserved.
 .\"
@@ -22,7 +22,7 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: July 16 2013 $
+.Dd $Mdocdate: October 9 2013 $
 .Dt SFTP-SERVER 8
 .Os
 .Sh NAME
@@ -30,11 +30,15 @@
 .Nd SFTP server subsystem
 .Sh SYNOPSIS
 .Nm sftp-server
+.Bk -words
 .Op Fl ehR
 .Op Fl d Ar start_directory
 .Op Fl f Ar log_facility
 .Op Fl l Ar log_level
 .Op Fl u Ar umask
+.Ek
+.Nm
+.Fl Q Ar protocol_feature
 .Sh DESCRIPTION
 .Nm
 is a program that speaks the server side of SFTP protocol
@@ -93,6 +97,36 @@ performs on behalf of the client.
 DEBUG and DEBUG1 are equivalent.
 DEBUG2 and DEBUG3 each specify higher levels of debugging output.
 The default is ERROR.
+.It Fl P Ar blacklisted_requests
+Specify a comma-separated list of sftp protocol requests that are banned by
+the server.
+.Nm
+will reply to any blacklisted request with a failure.
+The
+.Fl Q
+flag allows querying
+.Nm
+to determine the supported request types.
+If both a blacklist and a whitelist are specified, then the blacklist is
+applied before the whitelist.
+.It Fl p Ar whitelisted_requests
+Specify a comma-separated list of sftp protocol requests that are permitted
+by the server.
+All request types that are not on the whitelist will be logged and replied
+to with a failure message.
+.Pp
+Care must be taken when using this feature to ensure that requests made
+implicitly by sftp clients are permitted.
+.It Fl Q Ar protocol_feature
+Query protocol features supported by
+.Nm .
+At present the only feature that may be queried is
+.Dq requests ,
+that may be used for whitelisting or blacklisting (flags
+.Fl p
+and
+.Fl P
+respectively.)
 .It Fl R
 Places this instance of
 .Nm
diff --git a/sftp-server.c b/sftp-server.c
index 285f21aaf..ca8335ec7 100644
--- a/sftp-server.c
+++ b/sftp-server.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: sftp-server.c,v 1.97 2013/05/17 00:13:14 djm Exp $ */
+/* $OpenBSD: sftp-server.c,v 1.98 2013/10/09 23:42:17 djm Exp $ */
 /*
  * Copyright (c) 2000-2004 Markus Friedl.  All rights reserved.
  *
@@ -46,6 +46,7 @@
 #include "buffer.h"
 #include "log.h"
 #include "misc.h"
+#include "match.h"
 #include "uidswap.h"
 
 #include "sftp.h"
@@ -57,24 +58,29 @@
 #define get_string(lenp)                buffer_get_string(&iqueue, lenp);
 
 /* Our verbosity */
-LogLevel log_level = SYSLOG_LEVEL_ERROR;
+static LogLevel log_level = SYSLOG_LEVEL_ERROR;
 
 /* Our client */
-struct passwd *pw = NULL;
-char *client_addr = NULL;
+static struct passwd *pw = NULL;
+static char *client_addr = NULL;
 
 /* input and output queue */
-Buffer iqueue;
-Buffer oqueue;
+static Buffer iqueue;
+static Buffer oqueue;
 
 /* Version of client */
-u_int version;
+static u_int version;
+
+/* SSH2_FXP_INIT received */
+static int init_done;
 
 /* Disable writes */
-int readonly;
+static int readonly;
 
-/* portable attributes, etc. */
+/* Requests that are allowed/denied */
+static char *request_whitelist, *request_blacklist;
 
+/* portable attributes, etc. */
 typedef struct Stat Stat;
 
 struct Stat {
@@ -83,6 +89,100 @@ struct Stat {
         Attrib attrib;
 };
 
+/* Packet handlers */
+static void process_open(u_int32_t id);
+static void process_close(u_int32_t id);
+static void process_read(u_int32_t id);
+static void process_write(u_int32_t id);
+static void process_stat(u_int32_t id);
+static void process_lstat(u_int32_t id);
+static void process_fstat(u_int32_t id);
+static void process_setstat(u_int32_t id);
+static void process_fsetstat(u_int32_t id);
+static void process_opendir(u_int32_t id);
+static void process_readdir(u_int32_t id);
+static void process_remove(u_int32_t id);
+static void process_mkdir(u_int32_t id);
+static void process_rmdir(u_int32_t id);
+static void process_realpath(u_int32_t id);
+static void process_rename(u_int32_t id);
+static void process_readlink(u_int32_t id);
+static void process_symlink(u_int32_t id);
+static void process_extended_posix_rename(u_int32_t id);
+static void process_extended_statvfs(u_int32_t id);
+static void process_extended_fstatvfs(u_int32_t id);
+static void process_extended_hardlink(u_int32_t id);
+static void process_extended(u_int32_t id);
+
+struct sftp_handler {
+        const char *name;       /* user-visible name for fine-grained perms */
+        const char *ext_name;   /* extended request name */
+        u_int type;             /* packet type, for non extended packets */
+        void (*handler)(u_int32_t);
+        int does_write;         /* if nonzero, banned for readonly mode */
+};
+
+struct sftp_handler handlers[] = {
+        /* NB. SSH2_FXP_OPEN does the readonly check in the handler itself */
+        { "open", NULL, SSH2_FXP_OPEN, process_open, 0 },
+        { "close", NULL, SSH2_FXP_CLOSE, process_close, 0 },
+        { "read", NULL, SSH2_FXP_READ, process_read, 0 },
+        { "write", NULL, SSH2_FXP_WRITE, process_write, 1 },
+        { "lstat", NULL, SSH2_FXP_LSTAT, process_lstat, 0 },
+        { "fstat", NULL, SSH2_FXP_FSTAT, process_fstat, 0 },
+        { "setstat", NULL, SSH2_FXP_SETSTAT, process_setstat, 1 },
+        { "fsetstat", NULL, SSH2_FXP_FSETSTAT, process_fsetstat, 1 },
+        { "opendir", NULL, SSH2_FXP_OPENDIR, process_opendir, 0 },
+        { "readdir", NULL, SSH2_FXP_READDIR, process_readdir, 0 },
+        { "remove", NULL, SSH2_FXP_REMOVE, process_remove, 1 },
+        { "mkdir", NULL, SSH2_FXP_MKDIR, process_mkdir, 1 },
+        { "rmdir", NULL, SSH2_FXP_RMDIR, process_rmdir, 1 },
+        { "realpath", NULL, SSH2_FXP_REALPATH, process_realpath, 0 },
+        { "stat", NULL, SSH2_FXP_STAT, process_stat, 0 },
+        { "rename", NULL, SSH2_FXP_RENAME, process_rename, 1 },
+        { "readlink", NULL, SSH2_FXP_READLINK, process_readlink, 0 },
+        { "symlink", NULL, SSH2_FXP_SYMLINK, process_symlink, 1 },
+        { NULL, NULL, 0, NULL, 0 }
+};
+
+/* SSH2_FXP_EXTENDED submessages */
+struct sftp_handler extended_handlers[] = {
+        { "posix-rename", "posix-rename@openssh.com", 0,
+           process_extended_posix_rename, 1 },
+        { "statvfs", "statvfs@openssh.com", 0, process_extended_statvfs, 0 },
+        { "fstatvfs", "fstatvfs@openssh.com", 0, process_extended_fstatvfs, 0 },
+        { "hardlink", "hardlink@openssh.com", 0, process_extended_hardlink, 1 },
+        { NULL, NULL, 0, NULL, 0 }
+};
+
+static int
+request_permitted(struct sftp_handler *h)
+{
+        char *result;
+
+        if (readonly && h->does_write) {
+                verbose("Refusing %s request in read-only mode", h->name);
+                return 0;
+        }
+        if (request_blacklist != NULL &&
+            ((result = match_list(h->name, request_blacklist, NULL))) != NULL) {
+                free(result);
+                verbose("Refusing blacklisted %s request", h->name);
+                return 0;
+        }
+        if (request_whitelist != NULL &&
+            ((result = match_list(h->name, request_whitelist, NULL))) != NULL) {
+                free(result);
+                debug2("Permitting whitelisted %s request", h->name);
+                return 1;
+        }
+        if (request_whitelist != NULL) {
+                verbose("Refusing non-whitelisted %s request", h->name);
+                return 0;
+        }
+        return 1;
+}
+
 static int
 errno_to_portable(int unixerrno)
 {
@@ -543,14 +643,13 @@ process_init(void)
 }
 
 static void
-process_open(void)
+process_open(u_int32_t id)
 {
-        u_int32_t id, pflags;
+        u_int32_t pflags;
         Attrib *a;
         char *name;
         int handle, fd, flags, mode, status = SSH2_FX_FAILURE;
 
-        id = get_int();
         name = get_string(NULL);
         pflags = get_int();             /* portable flags */
         debug3("request %u: open flags %d", id, pflags);
@@ -560,9 +659,11 @@ process_open(void)
         logit("open \"%s\" flags %s mode 0%o",
             name, string_from_portable(pflags), mode);
         if (readonly &&
-            ((flags & O_ACCMODE) == O_WRONLY || (flags & O_ACCMODE) == O_RDWR))
-                status = SSH2_FX_PERMISSION_DENIED;
-        else {
+            ((flags & O_ACCMODE) == O_WRONLY ||
+            (flags & O_ACCMODE) == O_RDWR)) {
+                verbose("Refusing open request in read-only mode");
+                status = SSH2_FX_PERMISSION_DENIED;
+        } else {
                 fd = open(name, flags, mode);
                 if (fd < 0) {
                         status = errno_to_portable(errno);
@@ -582,12 +683,10 @@ process_open(void)
 }
 
 static void
-process_close(void)
+process_close(u_int32_t id)
 {
-        u_int32_t id;
         int handle, ret, status = SSH2_FX_FAILURE;
 
-        id = get_int();
         handle = get_handle();
         debug3("request %u: close handle %u", id, handle);
         handle_log_close(handle, NULL);
@@ -597,14 +696,13 @@ process_close(void)
 }
 
 static void
-process_read(void)
+process_read(u_int32_t id)
 {
         char buf[64*1024];
-        u_int32_t id, len;
+        u_int32_t len;
         int handle, fd, ret, status = SSH2_FX_FAILURE;
         u_int64_t off;
 
-        id = get_int();
         handle = get_handle();
         off = get_int64();
         len = get_int();
@@ -638,15 +736,13 @@ process_read(void)
 }
 
 static void
-process_write(void)
+process_write(u_int32_t id)
 {
-        u_int32_t id;
         u_int64_t off;
         u_int len;
         int handle, fd, ret, status;
         char *data;
 
-        id = get_int();
         handle = get_handle();
         off = get_int64();
         data = get_string(&len);
@@ -657,8 +753,6 @@ process_write(void)
         
         if (fd < 0)
                 status = SSH2_FX_FAILURE;
-        else if (readonly)
-                status = SSH2_FX_PERMISSION_DENIED;
         else {
                 if (lseek(fd, off, SEEK_SET) < 0) {
                         status = errno_to_portable(errno);
@@ -683,15 +777,13 @@ process_write(void)
 }
 
 static void
-process_do_stat(int do_lstat)
+process_do_stat(u_int32_t id, int do_lstat)
 {
         Attrib a;
         struct stat st;
-        u_int32_t id;
         char *name;
         int ret, status = SSH2_FX_FAILURE;
 
-        id = get_int();
         name = get_string(NULL);
         debug3("request %u: %sstat", id, do_lstat ? "l" : "");
         verbose("%sstat name \"%s\"", do_lstat ? "l" : "", name);
@@ -709,26 +801,24 @@ process_do_stat(int do_lstat)
 }
 
 static void
-process_stat(void)
+process_stat(u_int32_t id)
 {
-        process_do_stat(0);
+        process_do_stat(id, 0);
 }
 
 static void
-process_lstat(void)
+process_lstat(u_int32_t id)
 {
-        process_do_stat(1);
+        process_do_stat(id, 1);
 }
 
 static void
-process_fstat(void)
+process_fstat(u_int32_t id)
 {
         Attrib a;
         struct stat st;
-        u_int32_t id;
         int fd, ret, handle, status = SSH2_FX_FAILURE;
 
-        id = get_int();
         handle = get_handle();
         debug("request %u: fstat \"%s\" (handle %u)",
             id, handle_to_name(handle), handle);
@@ -760,21 +850,15 @@ attrib_to_tv(const Attrib *a)
 }
 
 static void
-process_setstat(void)
+process_setstat(u_int32_t id)
 {
         Attrib *a;
-        u_int32_t id;
         char *name;
         int status = SSH2_FX_OK, ret;
 
-        id = get_int();
         name = get_string(NULL);
         a = get_attrib();
         debug("request %u: setstat name \"%s\"", id, name);
-        if (readonly) {
-                status = SSH2_FX_PERMISSION_DENIED;
-                a->flags = 0;
-        }
         if (a->flags & SSH2_FILEXFER_ATTR_SIZE) {
                 logit("set \"%s\" size %llu",
                     name, (unsigned long long)a->size);
@@ -811,22 +895,18 @@ process_setstat(void)
 }
 
 static void
-process_fsetstat(void)
+process_fsetstat(u_int32_t id)
 {
         Attrib *a;
-        u_int32_t id;
         int handle, fd, ret;
         int status = SSH2_FX_OK;
 
-        id = get_int();
         handle = get_handle();
         a = get_attrib();
         debug("request %u: fsetstat handle %d", id, handle);
         fd = handle_to_fd(handle);
         if (fd < 0)
                 status = SSH2_FX_FAILURE;
-        else if (readonly)
-                status = SSH2_FX_PERMISSION_DENIED;
         else {
                 char *name = handle_to_name(handle);
 
@@ -878,14 +958,12 @@ process_fsetstat(void)
 }
 
 static void
-process_opendir(void)
+process_opendir(u_int32_t id)
 {
         DIR *dirp = NULL;
         char *path;
         int handle, status = SSH2_FX_FAILURE;
-        u_int32_t id;
 
-        id = get_int();
         path = get_string(NULL);
         debug3("request %u: opendir", id);
         logit("opendir \"%s\"", path);
@@ -908,15 +986,13 @@ process_opendir(void)
 }
 
 static void
-process_readdir(void)
+process_readdir(u_int32_t id)
 {
         DIR *dirp;
         struct dirent *dp;
         char *path;
         int handle;
-        u_int32_t id;
 
-        id = get_int();
         handle = get_handle();
         debug("request %u: readdir \"%s\" (handle %d)", id,
             handle_to_name(handle), handle);
@@ -964,81 +1040,61 @@ process_readdir(void)
 }
 
 static void
-process_remove(void)
+process_remove(u_int32_t id)
 {
         char *name;
-        u_int32_t id;
         int status = SSH2_FX_FAILURE;
         int ret;
 
-        id = get_int();
         name = get_string(NULL);
         debug3("request %u: remove", id);
         logit("remove name \"%s\"", name);
-        if (readonly)
-                status = SSH2_FX_PERMISSION_DENIED;
-        else {
-                ret = unlink(name);
-                status = (ret == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
-        }
+        ret = unlink(name);
+        status = (ret == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
         send_status(id, status);
         free(name);
 }
 
 static void
-process_mkdir(void)
+process_mkdir(u_int32_t id)
 {
         Attrib *a;
-        u_int32_t id;
         char *name;
         int ret, mode, status = SSH2_FX_FAILURE;
 
-        id = get_int();
         name = get_string(NULL);
         a = get_attrib();
         mode = (a->flags & SSH2_FILEXFER_ATTR_PERMISSIONS) ?
             a->perm & 07777 : 0777;
         debug3("request %u: mkdir", id);
         logit("mkdir name \"%s\" mode 0%o", name, mode);
-        if (readonly)
-                status = SSH2_FX_PERMISSION_DENIED;
-        else {
-                ret = mkdir(name, mode);
-                status = (ret == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
-        }
+        ret = mkdir(name, mode);
+        status = (ret == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
         send_status(id, status);
         free(name);
 }
 
 static void
-process_rmdir(void)
+process_rmdir(u_int32_t id)
 {
-        u_int32_t id;
         char *name;
         int ret, status;
 
-        id = get_int();
         name = get_string(NULL);
         debug3("request %u: rmdir", id);
         logit("rmdir name \"%s\"", name);
-        if (readonly)
-                status = SSH2_FX_PERMISSION_DENIED;
-        else {
-                ret = rmdir(name);
-                status = (ret == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
-        }
+        ret = rmdir(name);
+        status = (ret == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
         send_status(id, status);
         free(name);
 }
 
 static void
-process_realpath(void)
+process_realpath(u_int32_t id)
 {
         char resolvedname[MAXPATHLEN];
-        u_int32_t id;
         char *path;
 
-        id = get_int();
         path = get_string(NULL);
         if (path[0] == '\0') {
                 free(path);
@@ -1058,22 +1114,18 @@ process_realpath(void)
 }
 
 static void
-process_rename(void)
+process_rename(u_int32_t id)
 {
-        u_int32_t id;
         char *oldpath, *newpath;
         int status;
         struct stat sb;
 
-        id = get_int();
         oldpath = get_string(NULL);
         newpath = get_string(NULL);
         debug3("request %u: rename", id);
         logit("rename old \"%s\" new \"%s\"", oldpath, newpath);
         status = SSH2_FX_FAILURE;
-        if (readonly)
-                status = SSH2_FX_PERMISSION_DENIED;
-        else if (lstat(oldpath, &sb) == -1)
+        if (lstat(oldpath, &sb) == -1)
                 status = errno_to_portable(errno);
         else if (S_ISREG(sb.st_mode)) {
                 /* Race-free rename of regular files */
@@ -1120,14 +1172,12 @@ process_rename(void)
 }
 
 static void
-process_readlink(void)
+process_readlink(u_int32_t id)
 {
-        u_int32_t id;
         int len;
         char buf[MAXPATHLEN];
         char *path;
 
-        id = get_int();
         path = get_string(NULL);
         debug3("request %u: readlink", id);
         verbose("readlink \"%s\"", path);
@@ -1145,24 +1195,18 @@ process_readlink(void)
 }
 
 static void
-process_symlink(void)
+process_symlink(u_int32_t id)
 {
-        u_int32_t id;
         char *oldpath, *newpath;
         int ret, status;
 
-        id = get_int();
         oldpath = get_string(NULL);
         newpath = get_string(NULL);
         debug3("request %u: symlink", id);
         logit("symlink old \"%s\" new \"%s\"", oldpath, newpath);
         /* this will fail if 'newpath' exists */
-        if (readonly)
-                status = SSH2_FX_PERMISSION_DENIED;
-        else {
-                ret = symlink(oldpath, newpath);
-                status = (ret == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
-        }
+        ret = symlink(oldpath, newpath);
+        status = (ret == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
         send_status(id, status);
         free(oldpath);
         free(newpath);
@@ -1178,12 +1222,8 @@ process_extended_posix_rename(u_int32_t id)
         newpath = get_string(NULL);
         debug3("request %u: posix-rename", id);
         logit("posix-rename old \"%s\" new \"%s\"", oldpath, newpath);
-        if (readonly)
-                status = SSH2_FX_PERMISSION_DENIED;
-        else {
-                ret = rename(oldpath, newpath);
-                status = (ret == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
-        }
+        ret = rename(oldpath, newpath);
+        status = (ret == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
         send_status(id, status);
         free(oldpath);
         free(newpath);
@@ -1235,35 +1275,33 @@ process_extended_hardlink(u_int32_t id)
         newpath = get_string(NULL);
         debug3("request %u: hardlink", id);
         logit("hardlink old \"%s\" new \"%s\"", oldpath, newpath);
-        if (readonly)
-                status = SSH2_FX_PERMISSION_DENIED;
-        else {
-                ret = link(oldpath, newpath);
-                status = (ret == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
-        }
+        ret = link(oldpath, newpath);
+        status = (ret == -1) ? errno_to_portable(errno) : SSH2_FX_OK;
         send_status(id, status);
         free(oldpath);
         free(newpath);
 }
 
 static void
-process_extended(void)
+process_extended(u_int32_t id)
 {
-        u_int32_t id;
         char *request;
+        u_int i;
 
-        id = get_int();
         request = get_string(NULL);
-        if (strcmp(request, "posix-rename@openssh.com") == 0)
-                process_extended_posix_rename(id);
-        else if (strcmp(request, "statvfs@openssh.com") == 0)
-                process_extended_statvfs(id);
-        else if (strcmp(request, "fstatvfs@openssh.com") == 0)
-                process_extended_fstatvfs(id);
-        else if (strcmp(request, "hardlink@openssh.com") == 0)
-                process_extended_hardlink(id);
-        else
+        for (i = 0; extended_handlers[i].handler != NULL; i++) {
+                if (strcmp(request, extended_handlers[i].ext_name) == 0) {
+                        if (!request_permitted(&extended_handlers[i]))
+                                send_status(id, SSH2_FX_PERMISSION_DENIED);
+                        else
+                                extended_handlers[i].handler(id);
+                        break;
+                }
+        }
+        if (extended_handlers[i].handler == NULL) {
+                error("Unknown extended request \"%.100s\"", request);
                 send_status(id, SSH2_FX_OP_UNSUPPORTED);        /* MUST */
+        }
         free(request);
 }
 
@@ -1272,11 +1310,9 @@ process_extended(void)
 static void
 process(void)
 {
-        u_int msg_len;
-        u_int buf_len;
-        u_int consumed;
-        u_int type;
+        u_int msg_len, buf_len, consumed, type, i;
         u_char *cp;
+        u_int32_t id;
 
         buf_len = buffer_len(&iqueue);
         if (buf_len < 5)
@@ -1293,70 +1329,35 @@ process(void)
         buffer_consume(&iqueue, 4);
         buf_len -= 4;
         type = buffer_get_char(&iqueue);
+
         switch (type) {
         case SSH2_FXP_INIT:
                 process_init();
-                break;
-        case SSH2_FXP_OPEN:
-                process_open();
-                break;
-        case SSH2_FXP_CLOSE:
-                process_close();
-                break;
-        case SSH2_FXP_READ:
-                process_read();
-                break;
-        case SSH2_FXP_WRITE:
-                process_write();
-                break;
-        case SSH2_FXP_LSTAT:
-                process_lstat();
-                break;
-        case SSH2_FXP_FSTAT:
-                process_fstat();
-                break;
-        case SSH2_FXP_SETSTAT:
-                process_setstat();
-                break;
-        case SSH2_FXP_FSETSTAT:
-                process_fsetstat();
-                break;
-        case SSH2_FXP_OPENDIR:
-                process_opendir();
-                break;
-        case SSH2_FXP_READDIR:
-                process_readdir();
-                break;
-        case SSH2_FXP_REMOVE:
-                process_remove();
-                break;
-        case SSH2_FXP_MKDIR:
-                process_mkdir();
-                break;
-        case SSH2_FXP_RMDIR:
-                process_rmdir();
-                break;
-        case SSH2_FXP_REALPATH:
-                process_realpath();
-                break;
-        case SSH2_FXP_STAT:
-                process_stat();
-                break;
-        case SSH2_FXP_RENAME:
-                process_rename();
-                break;
-        case SSH2_FXP_READLINK:
-                process_readlink();
-                break;
-        case SSH2_FXP_SYMLINK:
-                process_symlink();
+                init_done = 1;
                 break;
         case SSH2_FXP_EXTENDED:
-                process_extended();
+                if (!init_done)
+                        fatal("Received extended request before init");
+                id = get_int();
+                process_extended(id);
                 break;
         default:
-                error("Unknown message %d", type);
-                break;
+                if (!init_done)
+                        fatal("Received %u request before init", type);
+                id = get_int();
+                for (i = 0; handlers[i].handler != NULL; i++) {
+                        if (type == handlers[i].type) {
+                                if (!request_permitted(&handlers[i])) {
+                                        send_status(id,
+                                            SSH2_FX_PERMISSION_DENIED);
+                                } else {
+                                        handlers[i].handler(id);
+                                }
+                                break;
+                        }
+                }
+                if (handlers[i].handler == NULL)
+                        error("Unknown message %u", type);
         }
         /* discard the remaining bytes from the current packet */
         if (buf_len < buffer_len(&iqueue)) {
@@ -1365,7 +1366,7 @@ process(void)
         }
         consumed = buf_len - buffer_len(&iqueue);
         if (msg_len < consumed) {
-                error("msg_len %d < consumed %d", msg_len, consumed);
+                error("msg_len %u < consumed %u", msg_len, consumed);
                 sftp_server_cleanup_exit(255);
         }
         if (msg_len > consumed)
@@ -1400,7 +1401,7 @@ int
 sftp_server_main(int argc, char **argv, struct passwd *user_pw)
 {
         fd_set *rset, *wset;
-        int in, out, max, ch, skipargs = 0, log_stderr = 0;
+        int i, in, out, max, ch, skipargs = 0, log_stderr = 0;
         ssize_t len, olen, set_size;
         SyslogFacility log_facility = SYSLOG_FACILITY_AUTH;
         char *cp, *homedir = NULL, buf[4*4096];
@@ -1414,8 +1415,20 @@ sftp_server_main(int argc, char **argv, struct passwd *user_pw)
 
         pw = pwcopy(user_pw);
 
-        while (!skipargs && (ch = getopt(argc, argv, "d:f:l:u:cehR")) != -1) {
+        while (!skipargs && (ch = getopt(argc, argv,
+            "d:f:l:P:p:Q:u:cehR")) != -1) {
                 switch (ch) {
+                case 'Q':
+                        if (strcasecmp(optarg, "requests") != 0) {
+                                fprintf(stderr, "Invalid query type\n");
+                                exit(1);
+                        }
+                        for (i = 0; handlers[i].handler != NULL; i++)
+                                printf("%s\n", handlers[i].name);
+                        for (i = 0; extended_handlers[i].handler != NULL; i++)
+                                printf("%s\n", extended_handlers[i].name);
+                        exit(0);
+                        break;
                 case 'R':
                         readonly = 1;
                         break;
@@ -1445,6 +1458,16 @@ sftp_server_main(int argc, char **argv, struct passwd *user_pw)
                             "u", user_pw->pw_name, (char *)NULL);
                         free(cp);
                         break;
+                case 'p':
+                        if (request_whitelist != NULL)
+                                fatal("Permitted requests already set");
+                        request_whitelist = xstrdup(optarg);
+                        break;
+                case 'P':
+                        if (request_blacklist != NULL)
+                                fatal("Refused requests already set");
+                        request_blacklist = xstrdup(optarg);
+                        break;
                 case 'u':
                         errno = 0;
                         mask = strtol(optarg, &cp, 8);