Only MBR and GPT structures can be edited by fdisk.

If neither are found, restrict user actions to printing basic
information on the disk, reading the man page, initializing an
MBR or GPT, or terminating fdisk without changing anything.

Feedback on earlier attempt by miod@ and brynet@.

diff --git a/sbin/fdisk/cmd.c b/sbin/fdisk/cmd.c
index 3ced91d..dc86989 100644 (file)
--- a/sbin/fdisk/cmd.c
+++ b/sbin/fdisk/cmd.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: cmd.c,v 1.163 2022/07/10 20:34:31 krw Exp $   */
+/*     $OpenBSD: cmd.c,v 1.164 2022/07/25 17:45:16 krw Exp $   */
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -371,8 +371,13 @@ Xprint(const char *args, struct mbr *mbr)
 {
        if (gh.gh_sig == GPTSIGNATURE)
                GPT_print(args, VERBOSE);
-       else
+       else if (MBR_valid_prt(mbr))
                MBR_print(mbr, args);
+       else {
+               DISK_printgeometry("s");
+               printf("Offset: %d\tSignature: 0x%X.\tNo MBR or GPT.\n",
+                   DOSBBSECTOR, (int)mbr->mbr_signature);
+       }
 
        return CMD_CONT;
 }
@@ -430,7 +435,7 @@ Xexit(const char *args, struct mbr *mbr)
 int
 Xhelp(const char *args, struct mbr *mbr)
 {
-       USER_help();
+       USER_help(mbr);
 
        return CMD_CONT;
 }

diff --git a/sbin/fdisk/mbr.c b/sbin/fdisk/mbr.c
index 11308d3..2ef6783 100644 (file)
--- a/sbin/fdisk/mbr.c
+++ b/sbin/fdisk/mbr.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: mbr.c,v 1.119 2022/04/25 17:10:09 krw Exp $   */
+/*     $OpenBSD: mbr.c,v 1.120 2022/07/25 17:45:16 krw Exp $   */
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -180,3 +180,23 @@ MBR_write(const struct mbr *mbr)
 
        return 0;
 }
+
+int
+MBR_valid_prt(const struct mbr *mbr)
+{
+       uint64_t                bs, ns;
+       unsigned int            i, nprt;
+       unsigned char           id;
+
+       nprt = 0;
+       for (i = 0; i < NDOSPART; i++) {
+               bs = mbr->mbr_prt[i].prt_bs;
+               ns = mbr->mbr_prt[i].prt_ns;
+               id = mbr->mbr_prt[i].prt_id;
+               if ((bs == 0 && ns == 0 && id == 0) ||
+                   (bs < DL_GETDSIZE(&dl) && ns > 0 && ns <= DL_GETDSIZE(&dl)))
+                       nprt++;
+       }
+
+       return nprt > 0 && mbr->mbr_signature == DOSMBR_SIGNATURE;
+}

diff --git a/sbin/fdisk/mbr.h b/sbin/fdisk/mbr.h
index ad44908..0c56a3d 100644 (file)
--- a/sbin/fdisk/mbr.h
+++ b/sbin/fdisk/mbr.h
@@ -1,4 +1,4 @@
-/*     $OpenBSD: mbr.h,v 1.42 2021/10/25 13:51:25 krw Exp $    */
+/*     $OpenBSD: mbr.h,v 1.43 2022/07/25 17:45:16 krw Exp $    */
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -30,3 +30,4 @@ void          MBR_print(const struct mbr *, const char *);
 void           MBR_init(struct mbr *);
 int            MBR_read(const uint64_t, const uint64_t, struct mbr *);
 int            MBR_write(const struct mbr *);
+int            MBR_valid_prt(const struct mbr *);

diff --git a/sbin/fdisk/user.c b/sbin/fdisk/user.c
index 50b1d4b..f4389ab 100644 (file)
--- a/sbin/fdisk/user.c
+++ b/sbin/fdisk/user.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: user.c,v 1.83 2022/07/18 15:06:22 krw Exp $   */
+/*     $OpenBSD: user.c,v 1.84 2022/07/25 17:45:16 krw Exp $   */
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -33,31 +33,34 @@
 
 struct cmd {
        char    *cmd_name;
-       int      cmd_gpt;
+       int      cmd_valid;
        int     (*cmd_fcn)(const char *, struct mbr *);
        char    *cmd_help;
 };
 
 const struct cmd               cmd_table[] = {
-       {"help",   1, Xhelp,   "Display summary of available commands"},
-       {"manual", 1, Xmanual, "Display fdisk man page"},
-       {"reinit", 1, Xreinit, "Initialize the partition table"},
+       {"help",   2, Xhelp,   "Display summary of available commands"},
+       {"manual", 2, Xmanual, "Display fdisk man page"},
+       {"reinit", 2, Xreinit, "Initialize the partition table"},
        {"setpid", 1, Xsetpid, "Set identifier of table entry"},
        {"edit",   1, Xedit,   "Edit table entry"},
        {"flag",   1, Xflag,   "Set flag value of table entry"},
        {"update", 0, Xupdate, "Update MBR bootcode"},
        {"select", 0, Xselect, "Select MBR extended table entry"},
        {"swap",   1, Xswap,   "Swap two table entries"},
-       {"print",  1, Xprint,  "Print partition table"},
+       {"print",  2, Xprint,  "Print partition table"},
        {"write",  1, Xwrite,  "Write partition table to disk"},
        {"exit",   1, Xexit,   "Discard changes and exit edit level"},
        {"quit",   1, Xquit,   "Save changes and exit edit level"},
-       {"abort",  1, Xabort,  "Discard changes and terminate fdisk"},
+       {"abort",  2, Xabort,  "Discard changes and terminate fdisk"},
 };
 
+#define        ANY_CMD(_i)     (cmd_table[(_i)].cmd_valid > 1)
+#define        GPT_CMD(_i)     (cmd_table[(_i)].cmd_valid > 0)
+
 int                    modified;
 
-int                    ask_cmd(char **);
+int                    ask_cmd(const struct mbr *, char **);
 
 void
 USER_edit(const uint64_t lba_self, const uint64_t lba_firstembr)
@@ -84,7 +87,7 @@ USER_edit(const uint64_t lba_self, const uint64_t lba_firstembr)
                printf("%s%s: %d> ", disk.dk_name, modified ? "*" : "",
                    editlevel);
                fflush(stdout);
-               i = ask_cmd(&args);
+               i = ask_cmd(&mbr, &args);
                if (i == -1)
                        continue;
 
@@ -121,7 +124,14 @@ USER_print_disk(const int verbosity)
        do {
                if (MBR_read(lba_self, lba_firstembr, &mbr))
                        break;
-               if (lba_self == 0) {
+               if (lba_self == DOSBBSECTOR) {
+                       if (MBR_valid_prt(&mbr) == 0) {
+                               DISK_printgeometry("s");
+                               printf("Offset: %d\tSignature: 0x%X.\t"
+                                   "No MBR or GPT.\n", DOSBBSECTOR,
+                                   (int)mbr.mbr_signature);
+                               return;
+                       }
                        if (GPT_read(ANYGPT)) {
                                if (verbosity == VERBOSE) {
                                        printf("Primary GPT:\nNot Found\n");
@@ -161,20 +171,22 @@ USER_print_disk(const int verbosity)
 }
 
 void
-USER_help(void)
+USER_help(const struct mbr *mbr)
 {
        unsigned int            i;
 
        for (i = 0; i < nitems(cmd_table); i++) {
-               if (gh.gh_sig == GPTSIGNATURE && cmd_table[i].cmd_gpt == 0)
+               if (gh.gh_sig == GPTSIGNATURE && GPT_CMD(i) == 0)
                                continue;
+               if (MBR_valid_prt(mbr) == 0 && ANY_CMD(i) == 0)
+                       continue;
                printf("\t%s\t\t%s\n", cmd_table[i].cmd_name,
                    cmd_table[i].cmd_help);
        }
 }
 
 int
-ask_cmd(char **arg)
+ask_cmd(const struct mbr *mbr, char **arg)
 {
        static char              lbuf[LINEBUFSZ];
        char                    *cmd;
@@ -194,7 +206,9 @@ ask_cmd(char **arg)
                cmd = "help";
 
        for (i = 0; i < nitems(cmd_table); i++) {
-               if (gh.gh_sig == GPTSIGNATURE && cmd_table[i].cmd_gpt == 0)
+               if (gh.gh_sig == GPTSIGNATURE && GPT_CMD(i) == 0)
+                       continue;
+               if (MBR_valid_prt(mbr) == 0 && ANY_CMD(i) == 0)
                        continue;
                if (strstr(cmd_table[i].cmd_name, cmd) == cmd_table[i].cmd_name)
                        return i;

diff --git a/sbin/fdisk/user.h b/sbin/fdisk/user.h
index 11010a1..e358f81 100644 (file)
--- a/sbin/fdisk/user.h
+++ b/sbin/fdisk/user.h
@@ -1,4 +1,4 @@
-/*     $OpenBSD: user.h,v 1.23 2022/07/10 17:46:03 krw Exp $   */
+/*     $OpenBSD: user.h,v 1.24 2022/07/25 17:45:16 krw Exp $   */
 
 /*
  * Copyright (c) 1997 Tobias Weingartner
@@ -21,4 +21,4 @@
 
 void           USER_edit(const uint64_t, const uint64_t);
 void           USER_print_disk(const int);
-void           USER_help(void);
+void           USER_help(const struct mbr *);