Question Problems with looking at 2.mob/object.

Barnes
Topic Author
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11 Apr 2023 19:39 #10306 by Barnes

Problems with looking at 2.mob/object. was created by Barnes

I'm running on latest Mac OS. I thought the problem was with changes in my src but I think it's how Mac is handling the configure and compile/architecture that is causing this problem. After downloading a fresh copy of tba, the mud crashes when I try to look at 2.guard, 2.dandelion, or any number of anything in a room.

Based on the information in the stack trace, the error occurred in the

Code:

__strcpy_chk

function of the C standard library, which is called by the

Code:

generic_find

function in the

Code:

handler.c

file.The program was trying to copy a string to a destination buffer using

Code:

strcpy

, but the buffer was not large enough to hold the entire string, leading to a buffer overflow and a segmentation fault.

Does anyone here have a suggestion? Tia.

* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0) * frame #0: 0x00007ff8012e7d5c libsystem_c.dylib`__chk_fail_overlap + 16 frame #1: 0x00007ff8012710b6 libsystem_c.dylib`__chk_overlap + 34 frame #2: 0x00007ff80127968b libsystem_c.dylib`__strcpy_chk + 64 frame #3: 0x0000000100089d7e circle`generic_find [inlined] get_number(name=<unavailable>) at handler.c:602:5 [opt] frame #4: 0x0000000100089d1c circle`generic_find(arg=<unavailable>, bitvector=45, ch=0x0000000104b0f8b0, tar_ch=0x00007ff7bfef28a8, tar_obj=0x00007ff7bfef2888) at handler.c:1355:18 [opt] frame #5: 0x00000001000061e6 circle`look_at_target(ch=0x0000000104b0f8b0, arg=<unavailable>) at act.informative.c:639:10 [opt] frame #6: 0x0000000100005f7b circle`do_look(ch=0x0000000104b0f8b0, argument=" 2.dandelion", cmd=<unavailable>, subcmd=0) at act.informative.c:0:11 [opt] frame #7: 0x0000000100098ff1 circle`command_interpreter(ch=0x0000000104b0f8b0, argument=<unavailable>) at interpreter.c:582:6 [opt]

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thomas
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11 Apr 2023 20:23 #10307 by thomas

Replied by thomas on topic Problems with looking at 2.mob/object.

I see you posted this multiple places, let's just answer here.

The code in question looks like this:

Code:

int get_number(char **name)
{
  int i;
  char *ppos;
  char number[MAX_INPUT_LENGTH];

  *number = '\0';

  if ((ppos = strchr(*name, '.')) != NULL) {
    *ppos++ = '\0';
    strlcpy(number, *name, sizeof(number));
    strcpy(*name, ppos);	/* strcpy: OK (always smaller) */ // line 602

    for (i = 0; *(number + i); i++)
      if (!isdigit(*(number + i)))
	return (0);

    return (atoi(number));
  }
  return (1);
}

The code is failing because we are doing naughty stuff here; we are copying a char array over itself (ppos is *name+2 in this case). In most versions of C, this is not really a problem, but apparently Apple dislikes when you do that. The solution is to copy to a temporary char array first:

Code:

int get_number(char **name)
{
  int i;
  char *ppos;
  char number[MAX_INPUT_LENGTH];
  char tmp[MAX_INPUT_LENGTH];

  *number = '\0';

  if ((ppos = strchr(*name, '.')) != NULL) {
    *ppos++ = '\0';
    strlcpy(number, *name, sizeof(number));
    strlcpy(tmp, ppos, sizeof(tmp));
    strcpy(*name, tmp);	/* strcpy: OK (always smaller) */

    for (i = 0; *(number + i); i++)
      if (!isdigit(*(number + i)))
	return (0);

    return (atoi(number));
  }
  return (1);
}

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thomas
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11 Apr 2023 20:24 #10308 by thomas

Replied by thomas on topic Problems with looking at 2.mob/object.

of course, the above is browser code, so it may or may not compile

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