Merge pull request #6 from trekawek/read-only

Support optional read-only mode.

src/Makefile

@@ -32,7 +32,7 @@ ifdef USAGELOG
 endif
 
 CFLAGS=$(FLAGS) $(EXFLAGS) $(LOGFLAGS)
-OBJS=main.o datagram.o event_common.o log.o session.o endian.o directory.o errortable.o tnfs_file.o chroot.o fileinfo.o stats.o $(EXOBJS)
+OBJS=main.o datagram.o event_common.o log.o session.o endian.o directory.o errortable.o tnfs_file.o chroot.o fileinfo.o stats.o auth.o $(EXOBJS)
 
 all:	$(OBJS)
 	$(CC) -o ../bin/$(EXEC) $(OBJS) $(LIBS)

src/auth.c

@@ -0,0 +1,54 @@
+#include "auth.h"
+#include "tnfs.h"
+#include "tnfs_file.h"
+
+int RW_CMDS[] =
+{
+    TNFS_MKDIR,
+    TNFS_RMDIR,
+    TNFS_WRITEBLOCK,
+    TNFS_UNLINKFILE,
+    TNFS_CHMODFILE,
+    TNFS_RENAMEFILE,
+    -1,
+};
+
+int RW_FLAGS =
+    TNFS_O_WRONLY |
+    TNFS_O_RDWR   |
+    TNFS_O_APPEND |
+    TNFS_O_CREAT  |
+    TNFS_O_TRUNC  |
+    TNFS_O_EXCL;
+
+bool read_only;
+
+void auth_init(bool _read_only)
+{
+    read_only = _read_only;
+}
+
+bool is_cmd_allowed(uint8_t cmd)
+{
+    if (!read_only)
+    {
+        return true;
+    }
+    for (int i = 0; RW_CMDS[i] != -1; i++)
+    {
+        if (RW_CMDS[i] == cmd)
+        {
+            return false;
+        }
+    }
+    return true;
+}
+
+bool is_open_allowed(char *filename, int flags)
+{
+    if (!read_only)
+    {
+        return true;
+    }
+    return (flags & RW_FLAGS) == 0;
+}

src/auth.h

@@ -0,0 +1,13 @@
+#ifndef _READONLY_H
+#define _READONLY_H
+
+#include <stdint.h>
+#include <stdbool.h>
+
+void auth_init(bool enable_writes);
+
+bool is_cmd_allowed(uint8_t cmd);
+
+bool is_open_allowed(char *filename, int flags);
+
+#endif

src/datagram.c

@@ -25,6 +25,7 @@ TNFS daemon datagram handler
 */
 
 #include <sys/types.h>
+#include <stdbool.h>
 #include <stdio.h>
 #include <string.h>
 #include <errno.h>
@@ -51,9 +52,11 @@ TNFS daemon datagram handler
 #include "directory.h"
 #include "tnfs_file.h"
 #include "event.h"
+#include "auth.h"
 
-int sockfd;		 /* UDP global socket file descriptor */
-int tcplistenfd; /* TCP listening socket file descriptor */
+int sockfd;         /* UDP global socket file descriptor */
+int tcplistenfd;    /* TCP listening socket file descriptor */
+bool write_support; /* Whether writes should be enabled. */
 
 tnfs_cmdfunc dircmd[NUM_DIRCMDS] =
 	{&tnfs_opendir, &tnfs_readdir, &tnfs_closedir,
@@ -378,6 +381,12 @@ void tnfs_decode(struct sockaddr_in *cliaddr, int cli_fd, int rxbytes, unsigned
 	TNFSMSGLOG(&hdr, "REQUEST cmd=0x%02x %s", hdr.cmd, get_cmd_name(hdr.cmd));
 #endif
 
+	if (!is_cmd_allowed(hdr.cmd))
+	{
+		tnfs_notpermitted(&hdr);
+		return;
+	}
+
 	/* The MOUNT command is the only one that doesn't need an
 	 * established session (since MOUNT is actually what will
 	 * establish the session) */
@@ -463,6 +472,13 @@ void tnfs_badcommand(Header *hdr, Session *sess)
 	tnfs_send(sess, hdr, NULL, 0);
 }
 
+void tnfs_notpermitted(Header *hdr)
+{
+	TNFSMSGLOG(hdr, "Command %s is not permitted", get_cmd_name(hdr->cmd));
+	hdr->status = TNFS_EPERM;
+	tnfs_send(NULL, hdr, NULL, 0);
+}
+
 void tnfs_send(Session *sess, Header *hdr, unsigned char *msg, int msgsz)
 {
 	struct sockaddr_in cliaddr;

src/datagram.h

@@ -54,6 +54,7 @@ void tnfs_decode(struct sockaddr_in *cliaddr, int cli_fd,
 	int rxbytes, unsigned char *rxbuf);
 void tnfs_invalidsession(Header *hdr);
 void tnfs_badcommand(Header *hdr, Session *sess);
+void tnfs_notpermitted(Header *hdr);
 void tnfs_send(Session *sess, Header *hdr, unsigned char *msg, int msgsz);
 void tnfs_resend(Session *sess, struct sockaddr_in *cliaddr, int cli_fd);
 #endif

src/main.c

@@ -24,6 +24,7 @@
  *
  * */
 
+#include <stdbool.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
@@ -35,6 +36,7 @@
 #include "errortable.h"
 #include "chroot.h"
 #include "log.h"
+#include "auth.h"
 
 /* declare the main() - it won't be used elsewhere so I'll not bother
  * with putting it in a .h file */
@@ -47,14 +49,15 @@ int main(int argc, char **argv)
     char *uvalue = NULL;
     char *gvalue = NULL;
 #endif
+    bool read_only = false;
     char *pvalue = NULL;
 
     if(argc >= 2)
     {
         #ifdef ENABLE_CHROOT
-        while((opt = getopt(argc, argv, "u:g:p:")) != -1)
+        while((opt = getopt(argc, argv, "ru:g:p:")) != -1)
         #else
-        while((opt = getopt(argc, argv, "p:")) != -1)
+        while((opt = getopt(argc, argv, "rp:")) != -1)
         #endif
         {
             switch(opt)
@@ -63,6 +66,9 @@ int main(int argc, char **argv)
                 case 'p':
                     pvalue = optarg;
                     break;
+                case 'r':
+                    read_only = true;
+                    break;
                 #ifdef ENABLE_CHROOT
                 case 'u':
                     uvalue = optarg;
@@ -83,9 +89,9 @@ int main(int argc, char **argv)
     else
     {
     #ifdef ENABLE_CHROOT
-    LOG("Usage: tnfsd <root dir> [-u <username> -g <group> -p <port>]\n");
+    LOG("Usage: tnfsd <root dir> [-u <username> -g <group> -p <port>] -r\n");
     #else
-    LOG("Usage: tnfsd <root dir> [-p <port>]\n");
+    LOG("Usage: tnfsd <root dir> [-p <port>] -r\n");
     #endif
     exit(-1);
     }
@@ -139,13 +145,21 @@ int main(int argc, char **argv)
 	const char *version = "24.0522.1";
 
 	LOG("Starting tnfsd version %s on port %d using root directory \"%s\"\n", version, port, argv[optind]);
+    if (read_only)
+    {
+        LOG("The server runs in read-only mode. TNFS clients can only list and download files.\n");
+    }
+    else
+    {
+        LOG("The server runs in read-write mode. TNFS clients can upload and modify files. Use -r to enable read-only mode.\n");
+    }
 
-	tnfs_init();		/* initialize structures etc. */
-	tnfs_init_errtable();	/* initialize error lookup table */
-	tnfs_event_init();
-	tnfs_sockinit(port);	/* initialize communications */
-	tnfs_mainloop();	/* run */
-	tnfs_event_close();
+	tnfs_init();              /* initialize structures etc. */
+	tnfs_init_errtable();     /* initialize error lookup table */
+	tnfs_event_init();        /* initialize event system */
+	tnfs_sockinit(port);      /* initialize communications */
+	auth_init(read_only);     /* initialize authentication */
+	tnfs_mainloop();          /* run */
 
 	return 0;
 }

src/tnfs_file.c

@@ -50,6 +50,7 @@
 #include "endian.h"
 #include "bsdcompat.h"
 #include "log.h"
+#include "auth.h"
 
 char fnbuf[MAX_FILEPATH];
 unsigned char iobuf[MAX_IOSZ + 2]; /* 2 bytes added for the size param */
@@ -95,13 +96,19 @@ void tnfs_open(Header *hdr, Session *s, unsigned char *buf, int bufsz)
 		return;
 	}
 
+	flags = *buf + (*(buf + 1) * 256);
+	mode = *(buf + 2) + (*(buf + 3) * 256);
+
+	if (!is_open_allowed(fnbuf, flags))
+	{
+		tnfs_notpermitted(hdr);
+		return;
+	}
+
 	for (i = 0; i < MAX_FD_PER_CONN; i++)
 	{
 		if (s->fd[i] == 0)
 		{
-			flags = *buf + (*(buf + 1) * 256);
-			mode = *(buf + 2) + (*(buf + 3) * 256);
-
 #ifdef WITH_ZIP
 			fd = zipopen(fnbuf, tnfs_make_mode(flags), mode);
 #else