navigate: Fix buffer overrun for impossibly long paths taken

When a player moves more than 1023 sectors in a single navigate
command, we overrun the buffer holding the path taken.  Remote hole,
but it requires a ship that can go that far, and even a ship with
speed 1000 would need a tech level well in excess of 1000 for that.
Thus, the hole is purely theoretical for even remotely sane game
configurations.

First known version with the flaw is 4.0.0.

Fix by going back the older behavior: don't print the total path
taken, but do print what the path finder does.  Context diff of an
example:

     [0:634] Command : nav 3 6,0
     Flagship is od   oil derrick (#3)
    +Using path 'n'
      h =
     k . .
      j d
     <67.2:67.2: 6,0> h
     od   oil derrick (#3) stopped at 6,0
    -Path taken: n

This is how march works.

Removes the only use of shp_nav_one_sector()'s unusual return value 2.
Return 1 instead.

Signed-off-by: Markus Armbruster <armbru@pond.sub.org>

src/lib/commands/navi.c

@@ -29,7 +29,7 @@
  *  Known contributors to this file:
  *     Ken Stevens, 1995 (rewritten)
  *     Ron Koenderink, 2006-2007
- *     Markus Armbruster, 2006-2011
+ *     Markus Armbruster, 2006-2014
  */
 
 #include <config.h>
@@ -76,8 +76,6 @@ do_unit_move(struct emp_qelem *ulist, int *together,
     int skip = 0;
     char buf[1024];
     char prompt[128];
-    char pathtaken[1024];  /* Doubtful we'll have a path longer than this */
-    char *pt = pathtaken;
     char bmap_flag;
     int ac;
     int type;
@@ -94,7 +92,6 @@ do_unit_move(struct emp_qelem *ulist, int *together,
 	cp = unit_path(*together, leader, buf, sizeof(buf));
     }
 
-    *pt = '\0';
     while (!QEMPTY(ulist)) {
 	char dp[80];
 
@@ -106,10 +103,6 @@ do_unit_move(struct emp_qelem *ulist, int *together,
 		lnd_mar(ulist, minmob, maxmob, together, player->cnum);
 	    if (QEMPTY(ulist)) {
 		pr("No %s left\n", type == EF_SHIP ? "ships" : "lands");
-		if (type == EF_SHIP && strlen(pathtaken) > 1) {
-		    pathtaken[strlen(pathtaken) - 1] = '\0';
-		    pr("Path taken: %s\n", pathtaken);
-		}
 		return RET_OK;
 	    }
 	    leader = get_leader(ulist);
@@ -137,10 +130,6 @@ do_unit_move(struct emp_qelem *ulist, int *together,
 		lnd_mar(ulist, minmob, maxmob, together, player->cnum);
 	    if (QEMPTY(ulist)) {
 		pr("No %s left\n", type == EF_SHIP ? "ships" : "lands");
-		if (type == EF_SHIP && strlen(pathtaken) > 1) {
-		    pathtaken[strlen(pathtaken) - 1] = '\0';
-		    pr("Path taken: %s\n", pathtaken);
-		}
 		return RET_OK;
 	    }
 	    leader = get_leader(ulist);
@@ -161,14 +150,10 @@ do_unit_move(struct emp_qelem *ulist, int *together,
 	    cp = &dirch[DIR_STOP];
 	dir = chkdir(*cp, DIR_STOP, DIR_LAST);
 	if (dir >= 0) {
-	    if (type == EF_SHIP) {
+	    if (type == EF_SHIP)
 		stopping |= shp_nav_one_sector(ulist, dir,
 					       player->cnum, *together);
-		if (stopping != 2) {
+	    else
-		    *pt++ = dirch[dir];
-		    *pt = '\0';
-		}
-	    } else
 		stopping |=
 		    lnd_mar_one_sector(ulist, dir, player->cnum,
 				       *together);
@@ -262,10 +247,6 @@ do_unit_move(struct emp_qelem *ulist, int *together,
 	pr("`d' to drop mines, and `m' to minesweep\n");
 	stopping = 1;
     }
-    if (type == EF_SHIP && strlen(pathtaken) > 1) {
-	pathtaken[strlen(pathtaken) - 1] = '\0';
-	pr("Path taken: %s\n", pathtaken);
-    }
     return RET_OK;
 }
 

src/lib/subs/shpsub.c

@@ -806,7 +806,7 @@ shp_nav_one_sector(struct emp_qelem *list, int dir, natid actor,
 		sprintf(dp, "can't go to %s", xyas(newx, newy, actor));
 	    if (together) {
 		mpr(actor, "%s\n", dp);
-		return 2;
+		return 1;
 	    } else {
 		shp_stays(actor, dp, mlp);
 		continue;

src/lib/subs/unitsub.c

@@ -173,8 +173,7 @@ unit_path(int together, struct empobj *unit, char *buf, size_t bufsz)
 	   xyas(destx, desty, player->cnum));
 	return NULL;
     }
-    if (unit->ef_type == EF_LAND)
+    pr("Using path '%s'\n", buf);
-	pr("Using path '%s'\n", buf);
     return buf;
 }
 

tests/fire/journal.log

@@ -635,7 +635,6 @@
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is bb   battleship (#3)
     Play#1 output Play#1 1 bb   battleship (#3) stopped at 5,1
-    Play#1 output Play#1 1 Path taken: j
     Play#1 output Play#1 6 0 565
     Play#1 input fire sh 3 0,2
     Play#1 command fire
@@ -648,7 +647,6 @@
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is bb   battleship (#3)
     Play#1 output Play#1 1 bb   battleship (#3) stopped at 3,1
-    Play#1 output Play#1 1 Path taken: g
     Play#1 output Play#1 6 0 563
     Play#1 input load s 3 2
     Play#1 command load
@@ -659,7 +657,6 @@
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is bb   battleship (#3)
     Play#1 output Play#1 1 bb   battleship (#3) stopped at 5,1
-    Play#1 output Play#1 1 Path taken: j
     Play#1 output Play#1 6 0 561
     Play#1 input fire sh 3 0,2
     Play#1 command fire
@@ -672,7 +669,6 @@
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is bb   battleship (#3)
     Play#1 output Play#1 1 bb   battleship (#3) stopped at 3,1
-    Play#1 output Play#1 1 Path taken: g
     Play#1 output Play#1 6 0 559
     Play#1 input load s 3 169
     Play#1 command load
@@ -768,7 +764,6 @@
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is dd   destroyer (#5)
     Play#1 output Play#1 1 dd   destroyer (#5) stopped at 10,0
-    Play#1 output Play#1 1 Path taken: j
     Play#1 output Play#1 6 0 544
     Play#1 input fire sh 5 24
     Play#1 command fire

tests/navi-march/journal.log

@@ -73,13 +73,11 @@
     Play#1 output Play#1 4 <127.0:127.0: 0,0>
     Play#1 input yh
     Play#1 output Play#1 1 pt   patrol boat (#10) stopped at -1,-1
-    Play#1 output Play#1 1 Path taken: y
     Play#1 output Play#1 6 0 637
     Play#1 input navi 20 yh
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is pt   patrol boat (#20)
     Play#1 output Play#1 1 pt   patrol boat (#20) stopped at 0,0
-    Play#1 output Play#1 1 Path taken: y
     Play#1 output Play#1 6 0 636
     Play#1 input navi 21 h
     Play#1 command navigate
@@ -91,7 +89,6 @@
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is pt   patrol boat (#22)
     Play#1 output Play#1 1 pt   patrol boat (#22) stopped at 3,-1
-    Play#1 output Play#1 1 Path taken: u
     Play#1 output Play#1 6 0 634
     Play#1 input navi 23 h
     Play#1 command navigate
@@ -104,7 +101,6 @@
     Play#1 output Play#1 1 cs   cargo ship (#26) is landlocked & stays in 2,2
     Play#1 output Play#1 1 Flagship is pt   patrol boat (#24)
     Play#1 output Play#1 1 pt   patrol boat (#24) stopped at 1,1
-    Play#1 output Play#1 1 Path taken: y
     Play#1 output Play#1 6 0 632
     Play#1 input navi 25 h
     Play#1 command navigate
@@ -133,7 +129,6 @@
     Play#1 output Play#1 1 shp#     ship type       x,y   fl  eff mil  sh gun pn he xl ln mob tech
     Play#1 output Play#1 1   30 pt   patrol boat   11,-5     100%   2   0   0  0  0  0  0 117  40
     Play#1 output Play#1 1 pt   patrol boat (#30) stopped at 10,-6
-    Play#1 output Play#1 1 Path taken: jy
     Play#1 output Play#1 6 0 629
     Play#1 input navi 32/33/34/35/36/37/38/39 jiyh
     Play#1 command navigate
@@ -169,13 +164,11 @@
     Play#1 output Play#1 1 pt   patrol boat (#37) stopped at 10,-6
     Play#1 output Play#1 1 pt   patrol boat (#38) stopped at 10,-6
     Play#1 output Play#1 1 pt   patrol boat (#39) stopped at 10,-6
-    Play#1 output Play#1 1 Path taken: jy
     Play#1 output Play#1 6 0 628
     Play#1 input navi 50 nh
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is pt   patrol boat (#50)
     Play#1 output Play#1 1 pt   patrol boat (#50) stopped at 1,1
-    Play#1 output Play#1 1 Path taken: n
     Play#1 output Play#1 6 0 627
     Play#1 input navi 51 bX
     Play#1 command navigate
@@ -192,7 +185,6 @@
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is pt   patrol boat (#52)
     Play#1 output Play#1 1 pt   patrol boat (#52) stopped at 2,0
-    Play#1 output Play#1 1 Path taken: g
     Play#1 output Play#1 6 0 625
     Play#1 input navi 53 jX
     Play#1 command navigate
@@ -219,7 +211,6 @@
     Play#1 output Play#1 1   55 cs   cargo ship     1,1      100%   5   0   0  0  0  0  0 127  20
     Play#1 output Play#1 1 pt   patrol boat (#54) stopped at 0,0
     Play#1 output Play#1 1 cs   cargo ship (#55) stopped at -1,-1
-    Play#1 output Play#1 1 Path taken: yy
     Play#1 output Play#1 6 0 623
     Play#1 input navi 57/56 n
     Play#1 command navigate
@@ -235,7 +226,6 @@
     Play#1 output Play#1 1   56 pt   patrol boat    1,1      100%   2   0   0  0  0  0  0 127  40
     Play#1 output Play#1 1 cs   cargo ship (#57) stopped at -1,-1
     Play#1 output Play#1 1 pt   patrol boat (#56) stopped at -1,-1
-    Play#1 output Play#1 1 Path taken: yy
     Play#1 output Play#1 6 0 622
     Play#1 input navi 58/59 nX
     Play#1 command navigate
@@ -275,13 +265,11 @@
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is pt   patrol boat (#62)
     Play#1 output Play#1 1 pt   patrol boat (#62) stopped at -13,1
-    Play#1 output Play#1 1 Path taken: b
     Play#1 output Play#1 6 0 618
     Play#1 input navi 63 bh
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is pt   patrol boat (#63)
     Play#1 output Play#1 1 pt   patrol boat (#63) stopped at -5,1
-    Play#1 output Play#1 1 Path taken: b
     Play#1 output Play#1 6 0 617
     Play#1 input navi 64 bX
     Play#1 command navigate
@@ -309,13 +297,11 @@
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is pt   patrol boat (#70)
     Play#1 output Play#1 1 pt   patrol boat (#70) stopped at -14,0
-    Play#1 output Play#1 1 Path taken: g
     Play#1 output Play#1 6 0 614
     Play#1 input navi 71 gh
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is pt   patrol boat (#71)
     Play#1 output Play#1 1 pt   patrol boat (#71) stopped at -6,0
-    Play#1 output Play#1 1 Path taken: g
     Play#1 output Play#1 6 0 613
     Play#1 input navi 72 gX
     Play#1 command navigate
@@ -347,16 +333,17 @@
     Play#1 input h
     Play#1 output Play#1 1 cs   cargo ship (#80) stopped at -4,-4
     Play#1 output Play#1 1 cs   cargo ship (#81) stopped at -4,-4
-    Play#1 output Play#1 1 Path taken: yyyy
     Play#1 output Play#1 6 0 611
     Play#1 input navi 90 -3,-3
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is pt   patrol boat (#90)
+    Play#1 output Play#1 1 Using path 'yyy'
     Play#1 output Play#1 1  . .
     Play#1 output Play#1 1 . . .
     Play#1 output Play#1 1  . .
     Play#1 output Play#1 4 <99.4:99.4: -3,-3>
     Play#1 input 0,-4
+    Play#1 output Play#1 1 Using path 'uj'
     Play#1 output Play#1 1  . .
     Play#1 output Play#1 1 . . .
     Play#1 output Play#1 1  . i
@@ -364,7 +351,6 @@
     Play#1 input 1,-1
     Play#1 output Play#1 1 Can't get to '1,-1' right now.
     Play#1 output Play#1 1 pt   patrol boat (#90) stopped at 0,-4
-    Play#1 output Play#1 1 Path taken: yyyuj
     Play#1 output Play#1 6 0 610
     Play#1 input navi 90 1,-1
     Play#1 command navigate
@@ -380,13 +366,13 @@
     Play#1 input navi 91 -3,1
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is pt   patrol boat (#91)
+    Play#1 output Play#1 1 Using path 'gb'
     Play#1 output Play#1 1  . .
     Play#1 output Play#1 1 h h h
     Play#1 output Play#1 1  c c
     Play#1 output Play#1 4 <108.6:108.6: -3,1>
     Play#1 input h
     Play#1 output Play#1 1 pt   patrol boat (#91) stopped at -3,1
-    Play#1 output Play#1 1 Path taken: gb
     Play#1 output Play#1 6 0 608
     Play#1 input navi 92 2,2
     Play#1 command navigate
@@ -544,7 +530,6 @@
     Play#1 output Play#1 1 ft   fishing trawler (#101) stopped at 3,-1
     Play#1 output Play#1 1 dd   destroyer (#100) stopped at 3,-1
     Play#1 output Play#1 1 oe   oil exploration boat (#102) stopped at 3,-1
-    Play#1 output Play#1 1 Path taken: ygg
     Play#1 output Play#1 6 0 599
     Play#1 input navi 110/111 d
     Play#1 command navigate
@@ -561,7 +546,6 @@
     Play#1 input h
     Play#1 output Play#1 1 ms   minesweeper (#110) stopped at 10,-2
     Play#1 output Play#1 1 ms   minesweeper (#111) stopped at 10,-2
-    Play#1 output Play#1 1 Path taken: n
     Play#1 output Play#1 6 0 595
     Play#1 input navi 0/1 mh
     Play#1 command navigate
@@ -603,7 +587,6 @@
     Play#1 output Play#1 1 ms   minesweeper (#128) is out of mobility & stays in 11,-3
     Play#1 output Play#1 1 ms   minesweeper (#121) stopped at 13,-3
     Play#1 output Play#1 1 ms   minesweeper (#122) stopped at 13,-3
-    Play#1 output Play#1 1 Path taken: jj
     Play#1 output Play#1 6 0 592
     Play#1 input __cmd added -1 0 0
     Play#1 command __cmd
@@ -618,7 +601,6 @@
     Play#1 output Play#1 1 Sweep...
     Play#1 output Play#1 1 Sweep...
     Play#1 output Play#1 1 ms   minesweeper (#129) stopped at 10,-2
-    Play#1 output Play#1 1 Path taken: n
     Play#1 output Play#1 6 0 591
     Play#1 input navi 135/130/131/136/137/138/139
     Play#1 command navigate
@@ -707,7 +689,6 @@
     Play#1 output Play#1 1 pt   patrol boat (#137) stopped at 11,-5
     Play#1 output Play#1 1 pt   patrol boat (#138) stopped at 11,-5
     Play#1 output Play#1 1 pt   patrol boat (#139) stopped at 11,-5
-    Play#1 output Play#1 1 Path taken: j
     Play#1 output Play#1 6 0 590
     Play#1 input ctld
     Play#1 output Play#1 1 Bye-bye

tests/retreat/journal.log

@@ -278,7 +278,6 @@
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is dd   destroyer (#5)
     Play#1 output Play#1 1 dd   destroyer (#5) stopped at -5,-1
-    Play#1 output Play#1 1 Path taken: gyu
     Play#1 output Play#1 6 0 610
     Play#1 input fire sh 5 53
     Play#1 command fire
@@ -731,13 +730,11 @@
     Play#1 output Play#1 1    . . . .
     Play#1 output Play#1 1
     Play#1 output Play#1 1 dd   destroyer (#5) stopped at -6,0
-    Play#1 output Play#1 1 Path taken: b
     Play#1 output Play#1 6 0 573
     Play#1 input navi 5 nh
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is dd   destroyer (#5)
     Play#1 output Play#1 1 dd   destroyer (#5) stopped at -5,1
-    Play#1 output Play#1 1 Path taken: n
     Play#1 output Play#1 6 0 572
     Play#1 input board 130 5
     Play#1 command board

tests/smoke/journal.log

@@ -4186,7 +4186,6 @@
     Play#1 output Play#1 4 <59.3:59.3: 9,-1>
     Play#1 input h
     Play#1 output Play#1 1 frg  frigate (#0) stopped at 9,-1
-    Play#1 output Play#1 1 Path taken: jj
     Play#1 output Play#1 6 0 547
     Play#1 input assault 11,-1 0
     Play#1 command assault
@@ -5083,7 +5082,6 @@
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is frg  frigate (#0)
     Play#1 output Play#1 1 frg  frigate (#0) stopped at 13,1
-    Play#1 output Play#1 1 Path taken: njn
     Play#1 output Play#1 6 0 518
     Play#1 input look 0
     Play#1 command lookout
@@ -10786,7 +10784,6 @@
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is cs   cargo ship (#2)
     Play#1 output Play#1 1 cs   cargo ship (#2) stopped at 6,0
-    Play#1 output Play#1 1 Path taken: n
     Play#1 output Play#1 6 0 608
     Play#1 input scrap l 1
     Play#1 command scrap
@@ -14497,13 +14494,13 @@
     Play#1 input nav 3 6,0
     Play#1 command navigate
     Play#1 output Play#1 1 Flagship is od   oil derrick (#3)
+    Play#1 output Play#1 1 Using path 'n'
     Play#1 output Play#1 1  h =
     Play#1 output Play#1 1 k . .
     Play#1 output Play#1 1  j d
     Play#1 output Play#1 4 <67.2:67.2: 6,0>
     Play#1 input h
     Play#1 output Play#1 1 od   oil derrick (#3) stopped at 6,0
-    Play#1 output Play#1 1 Path taken: n
     Play#1 output Play#1 6 0 633
     Play#1 input nav 3 vh
     Play#1 command navigate
@@ -14524,7 +14521,6 @@
     Play#1 output Play#1 1 Flagship is ft   fishing trawler (#4)
     Play#1 output Play#1 1 [fert:84] ft   fishing trawler (#4) @ 6,0 0% sea
     Play#1 output Play#1 1 ft   fishing trawler (#4) stopped at 6,0
-    Play#1 output Play#1 1 Path taken: n
     Play#1 output Play#1 6 0 629
     Play#1 input order 4 des 5,-1 6,0
     Play#1 command order