[Mplayer-dev-eng] [PATCH] FIBMAP as non-root

[Jason Lunz]

I looked at the linux-kernel archive for why FIBMAP isn't allowed as
root. The short answer is that it probably won't be changed until linux
2.5, so I went ahead and moved the FIBMAP ioctl into its own binary so
it can be called from mplayer. Then I patched mplayer to support this.

The spawned command should probably be a configuration option, not
hardcoded as "fibmap". oh well.

Here's the fibmap binary. It needs to be installed suid root. Note that
this means that users can still mess around with FIBMAP, but at least
the rest of mplayer won't be running as root.

======== Makefile ========
CFLAGS=-O2 -Wall
PROG:=fibmap

$(PROG):

clean:
	rm -f $(PROG)

strip: $(PROG)
	strip $(PROG)

======== fibmap.c ========
#include <fcntl.h>
#include <sys/ioctl.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <linux/fs.h>

void usage(char *name) {
	fprintf(stderr, "usage: %s <filename>\n", name);
	exit(EXIT_FAILURE);
}

int main(int argc, char *argv[]) {
	int i;

	if(geteuid() != 0) {
		fprintf(stderr, "must be root to call FIBMAP ioctl\n");
		return EXIT_FAILURE;
	}
	if(argc < 2) {
		usage(argv[0]);
	}
	for(i = 1; i < argc; i++) {
		int fd;
		int lba = 0;

		if((fd = open(argv[i], O_RDONLY)) < 0) {
			perror(argv[i]);
			continue;
		}
		if(ioctl(fd, FIBMAP, &lba) < 0) {
			perror ("ioctl FIBMAP");
			close(fd);
			continue;
		}
		close(fd);
		if(fprintf(stdout, "%d\n", lba) < 0) {
			perror("fprintf(stdout)");
			return EXIT_FAILURE;
		}
	}
	return EXIT_SUCCESS;
}


Now, patch dvdauth.c with this (this patch is against tonight's CVS):


Index: dvdauth.c
===================================================================
RCS file: /cvsroot/mplayer/main/dvdauth.c,v
retrieving revision 1.5
diff -u -r1.5 dvdauth.c
--- dvdauth.c	2001/06/06 21:16:21	1.5
+++ dvdauth.c	2001/06/15 06:10:38
@@ -13,6 +13,7 @@
 #include <sys/types.h>
 #include <sys/ioctl.h>
 #include <sys/stat.h>
+#include <sys/wait.h>
 #include <css.h>
 #if CSS_MAJOR_VERSION > 0 || (CSS_MAJOR_VERSION == 0 && CSS_MINOR_VERSION > 1)
 # include <dvd.h>
@@ -46,8 +47,6 @@
 #define	DVDCloseDevice(hdl)	close(hdl)
 #define	CSSDVDisEncrypted(hdl)	CSSisEncrypted(hdl)
 #define	CSSDVDAuthDisc		CSSAuthDisc
-#define	CSSDVDAuthTitlePath(hdl,key_title,path) \
-		CSSAuthTitle(hdl,key_title,path_to_lba(path))
 
 #else	/*OLD_CSS_API*/
 
@@ -79,22 +78,34 @@
 
 static int path_to_lba (char *path)
 {
-    int fd, lba = 0;
-
+    FILE *fh;
+    int fd;
+    int lba = 0;
+    char cmd[PATH_MAX+8];
+
+    snprintf(cmd, sizeof(cmd), "fibmap %s", path);
+    if(NULL != (fh = popen(cmd, "r"))) {
+	if(1 == fscanf(fh, "%d", &lba)) {
+	    int status = pclose(fh);
+	    if(WIFEXITED(status) && !WEXITSTATUS(status)) {
+		return lba;
+	    }
+	}
+    }
+    perror("attempt to spawn fibmap failed");
     if ((fd = open(path, O_RDONLY)) == -1) {
-        fprintf(stderr, "Cannot open file %s: %s",
+	fprintf(stderr, "Cannot open file %s: %s",
 		path ? path : "(NULL)", strerror(errno));
-        return -1;
+	return -1;
     }
     if (ioctl(fd, FIBMAP, &lba) != 0) {
-        perror ("ioctl FIBMAP");
-	fprintf(stderr,"Hint: run mplayer as root!\n");
-        close(fd);
-        return -1;
+	perror ("ioctl FIBMAP");
+	fprintf(stderr,"Hint: install fibmap or run mplayer as root\n");
+	close(fd);
+	return -1;
     }
 
     close(fd);
-
     return lba;
 }
 #else /*linux*/
@@ -150,6 +161,7 @@
 int dvd_auth ( char *dev , char *filename )
 {
     	DVDHandle dvd;  /* DVD device handle */
+	int lba;
 
 	if ((dvd=DVDOpenDevice(dev)) == DVDOpenFailed) {
 		fprintf(stderr,"DVD: cannot open DVD device \"%s\".\n",dev);
@@ -172,7 +184,10 @@
 		return 1;
 	}
 
-        if (CSSDVDAuthTitlePath(dvd,key_title,filename)) {
+	if((lba = path_to_lba(filename)) < 0) {
+		return 1;
+	}
+        if (CSSAuthTitle(dvd,key_title,lba)) {
 		fprintf(stderr,"DVD: CSSDVDAuthTitle() failed.\n");
 		DVDCloseDevice(dvd);
 		return 1;

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