{base,dir}name: add -z/--zero | arith: fix buffer overflow (#800)

src/cmd/ksh93/sh/arith.c: sh_mathstdfun():
- Fixed small buffer overflow: The check for null termination needs
  to happen after ensuring the name matches because the strncmp
  will return false if the name is shorter than fsize.
- Remove a condition for breaking the loop that is never true;
  *tp->fname is a nonprintable byte that is never greater than c,
  which stores a printable character. See shtab_math in
  arch/*/src/cmd/ksh93/FEATURE/math.

src/lib/libcmd/basename.c:
- Added support for -z|--zero argument for compatiblity with GNU
  basename.
- Implement the behavior described in the usage string regarding
  PATH_LEADING_SLASHES (which it had not supported at all).

src/lib/libcmd/dirname.c:
- Fix handling of initial // where 'getconf PATH_LEADING_SLASHES'
  is 1 (i.e. Cygwin).
- Added support for -z|--zero argument for compatiblity with GNU
  basename.
- Handle multiple operands.

Co-authored-by: Martijn Dekker <martijn@inlv.org>

NEWS

@@ -2,6 +2,19 @@ This documents significant changes in the dev branch of ksh 93u+m.
 For full details, see the git log at: https://github.com/ksh93/ksh
 Uppercase BUG_* IDs are shell bug IDs as used by the Modernish shell library.
 
+2024-12-25:
+
+- The dirname path-bound built-in now accepts multiple operands.
+
+- The basename and dirname path-bound built-ins now have a -z/--zero option
+  for compatibility with the GNU versions of these utilities. It causes the
+  line terminator to be a zero byte instead of a newline.
+
+- Fixed bugs related to the handling of an initial double slash in the
+  basename and dirname path-bound built-ins when used on Windows (Cygwin).
+
+- Fixed a buffer overflow problem in the handling of arithmetic functions.
+
 2024-12-24:
 
 - [v1.1] The fc/hist command has a new -E option. If this option is given,

src/cmd/ksh93/include/version.h

@@ -18,7 +18,7 @@
 #include <ast_release.h>
 #include "git.h"
 
-#define SH_RELEASE_DATE	"2024-12-24"	/* must be in this format for $((.sh.version)) */
+#define SH_RELEASE_DATE	"2024-12-25"	/* must be in this format for $((.sh.version)) */
 /*
  * This comment keeps SH_RELEASE_DATE a few lines away from SH_RELEASE_SVER to avoid
  * merge conflicts when cherry-picking dev branch commits onto a release branch.

src/cmd/ksh93/sh/arith.c

@@ -198,15 +198,15 @@ static Namval_t *scope(Namval_t *np,struct lval *lvalue,int assign)
 	return np;
 }
 
+/* look up a function in the standard math function table */
 static Math_f sh_mathstdfun(const char *fname, size_t fsize, short * nargs)
 {
 	const struct mathtab *tp;
 	char c = fname[0];
+	/* first byte of tp->fname is num. args and return type, unless empty */
 	for(tp=shtab_math; *tp->fname; tp++)
 	{
-		if(*tp->fname > c)
-			break;
-		if(tp->fname[1]==c && tp->fname[fsize+1]==0 && strncmp(&tp->fname[1],fname,fsize)==0)
+		if(tp->fname[1]==c && strncmp(&tp->fname[1],fname,fsize)==0 && tp->fname[fsize+1]==0)
 		{
 			if(nargs)
 				*nargs = *tp->fname;

src/cmd/ksh93/tests/libcmd.sh

@@ -630,6 +630,14 @@ if builtin basename 2> /dev/null; then
 	got=$(basename "$tmp/.bar")
 	exp=".bar"
 	[[ $got == "$exp" ]] || err_exit "basename failed (expected $(printf %q "$exp"), got $(printf %q "$got"))"
+
+	# PATH_LEADING_SLASHES handling
+	case $(builtin getconf 2>/dev/null && getconf PATH_LEADING_SLASHES 2>/dev/null) in
+	1)	exp=$'/\n//\n//\n//' ;;
+	*)	exp=$'/\n/\n/\n/' ;;
+	esac
+	got=$(basename -a / // /// ////)
+	[[ $got == "$exp" ]] || err_exit "PATH_LEADING_SLASHES handling (expected $(printf %q "$exp"), got $(printf %q "$got"))"
 fi
 
 # ======
@@ -840,6 +848,12 @@ if builtin dirname 2> /dev/null; then
 	#  Print the $PATH relative executable file path for string.
 	got=$(dirname -x cat)
 	[[ $got == "$exp" ]] || err_exit "dirname -x failed (expected $(printf %q "$exp"), got $(printf %q "$got"))"
+
+	# PATH_LEADING_SLASHES handling; multiple operands
+	exp=$'/\n//\n//\n//\n//\n//server\n//server'
+	got=$(export _AST_FEATURES='PATH_LEADING_SLASHES - 1'
+	      "$SHELL" -c 'builtin dirname && dirname / // // //server ///server //server/name ///server//name' 2>&1)
+	[[ $got == "$exp" ]] || err_exit "PATH_LEADING_SLASHES handling (expected $(printf %q "$exp"), got $(printf %q "$got"))"
 fi
 
 # ======

src/lib/libcmd/basename.c

@@ -26,7 +26,7 @@
  */
 
 static const char usage[] =
-"[-?\n@(#)$Id: basename (ksh 93u+m) 2022-08-30 $\n]"
+"[-?\n@(#)$Id: basename (ksh 93u+m) 2024-12-05 $\n]"
 "[--catalog?" ERROR_CATALOG "]"
 "[+NAME?basename - strip directory and suffix from filenames]"
 "[+DESCRIPTION?\bbasename\b removes all leading directory components "
@@ -48,6 +48,8 @@ static const char usage[] =
 "[s:suffix?All operands are treated as \astring\a and each modified "
     "pathname, with \asuffix\a removed if it exists, is printed on a "
     "separate line on the standard output.]:[suffix]"
+"[z:zero?Each line of output is terminated with a NUL character instead "
+    "of a newline.]"
 "\n"
 "\n string [suffix]\n"
 "string ...\n"
@@ -63,23 +65,27 @@ static const char usage[] =
 
 #include <cmd.h>
 
-static void namebase(Sfio_t *outfile, char *pathname, char *suffix)
+static void namebase(Sfio_t *outfile, char *pathname, char *suffix, char termch)
 {
 	char *first, *last;
 	int n=0;
+	/* go to end of path */
 	for(first=last=pathname; *last; last++);
 	/* back over trailing '/' */
 	if(last>first)
 		while(*--last=='/' && last > first);
+	/* only slash(es)? */
 	if(last==first && *last=='/')
 	{
-		/* all '/' or "" */
-		if(*first=='/')
-			if(*++last=='/')	/* keep leading // */
-				last++;
+		/* advance back over first '/' */
+		last++;
+		/* keep leading '//' if PATH_LEADING_SLASHES is set */
+		if(*last=='/' && *astconf("PATH_LEADING_SLASHES",NULL,NULL)=='1')
+			last++;
 	}
 	else
 	{
+		/* set to first / from end */
 		for(first=last++;first>pathname && *first!='/';first--);
 		if(*first=='/')
 			first++;
@@ -92,7 +98,7 @@ static void namebase(Sfio_t *outfile, char *pathname, char *suffix)
 	}
 	if(last>first)
 		sfwrite(outfile,first,last-first);
-	sfputc(outfile,'\n');
+	sfputc(outfile,termch);
 }
 
 int
@@ -101,6 +107,7 @@ b_basename(int argc, char** argv, Shbltin_t* context)
 	char*	string;
 	char*	suffix = 0;
 	int	all = 0;
+	char    termch = '\n';
 
 	cmdinit(argc, argv, context, ERROR_CATALOG, 0);
 	for (;;)
@@ -114,6 +121,9 @@ b_basename(int argc, char** argv, Shbltin_t* context)
 			all = 1;
 			suffix = opt_info.arg;
 			continue;
+		case 'z':
+			termch = '\0';
+			continue;
 		case ':':
 			error(2, "%s", opt_info.arg);
 			break;
@@ -131,9 +141,9 @@ b_basename(int argc, char** argv, Shbltin_t* context)
 		UNREACHABLE();
 	}
 	if (!all)
-		namebase(sfstdout, argv[0], argv[1]);
+		namebase(sfstdout, argv[0], argv[1], termch);
 	else
 		while (string = *argv++)
-			namebase(sfstdout, string, suffix);
+			namebase(sfstdout, string, suffix, termch);
 	return 0;
 }

src/lib/libcmd/dirname.c

@@ -26,10 +26,10 @@
  */
 
 static const char usage[] =
-"[-?\n@(#)$Id: dirname (AT&T Research) 2009-01-31 $\n]"
+"[-?\n@(#)$Id: dirname (ksh 93u+m) 2024-12-25 $\n]"
 "[--catalog?" ERROR_CATALOG "]"
 "[+NAME?dirname - return directory portion of file name]"
-"[+DESCRIPTION?\bdirname\b treats \astring\a as a file name and returns "
+"[+DESCRIPTION?\bdirname\b treats each \astring\a as a file name and outputs "
 	"the name of the directory containing the file name by deleting "
 	"the last component from \astring\a.]"
 "[+?If \astring\a consists solely of \b/\b characters the output will "
@@ -48,8 +48,10 @@ static const char usage[] =
 "[f:file?Print the \b$PATH\b relative regular file path for \astring\a.]"
 "[r:relative?Print the \b$PATH\b relative readable file path for \astring\a.]"
 "[x:executable?Print the \b$PATH\b relative executable file path for \astring\a.]"
+"[z:zero?Each line of output is terminated with a NUL character instead "
+    "of a newline.]"
 "\n"
-"\nstring\n"
+"\nstring ...\n"
 "\n"
 "[+EXIT STATUS?]{"
 	"[+0?Successful completion.]"
@@ -60,7 +62,7 @@ static const char usage[] =
 
 #include <cmd.h>
 
-static void l_dirname(Sfio_t *outfile, const char *pathname)
+static void l_dirname(Sfio_t *outfile, const char *pathname, char termch)
 {
 	const char  *last;
 	/* go to end of path */
@@ -80,23 +82,29 @@ static void l_dirname(Sfio_t *outfile, const char *pathname)
 		/* back over trailing '/' */
 		for(;*last=='/' && last > pathname; last--);
 	}
-	/* preserve // */
+	/* preserve leading '//' */
+	if(last==pathname && pathname[0]=='/')
+		while(last[1]=='/')
+			last++;
 	if(last!=pathname && pathname[0]=='/' && pathname[1]=='/')
 	{
+		/* skip any '/' until last two */
 		while(pathname[2]=='/' && pathname<last)
 			pathname++;
+		/* skip first '/' if PATH_LEADING_SLASHES not set */
 		if(last!=pathname && pathname[0]=='/' && pathname[1]=='/' && *astconf("PATH_LEADING_SLASHES",NULL,NULL)!='1')
 			pathname++;
 	}
 	sfwrite(outfile,pathname,last+1-pathname);
-	sfputc(outfile,'\n');
+	sfputc(outfile,termch);
 }
 
 int
 b_dirname(int argc, char** argv, Shbltin_t* context)
 {
 	int	mode = 0;
 	char	buf[PATH_MAX];
+	char	termch = '\n';
 
 	cmdinit(argc, argv, context, ERROR_CATALOG, 0);
 	for (;;)
@@ -113,6 +121,9 @@ b_dirname(int argc, char** argv, Shbltin_t* context)
 		case 'x':
 			mode |= PATH_EXECUTE;
 			continue;
+		case 'z':
+			termch = '\0';
+			continue;
 		case ':':
 			error(2, "%s", opt_info.arg);
 			break;
@@ -124,16 +135,19 @@ b_dirname(int argc, char** argv, Shbltin_t* context)
 	}
 	argv += opt_info.index;
 	argc -= opt_info.index;
-	if(error_info.errors || argc != 1)
+	if(error_info.errors || argc < 1)
 	{
 		error(ERROR_usage(2),"%s", optusage(NULL));
 		UNREACHABLE();
 	}
-	if(!mode)
-		l_dirname(sfstdout,argv[0]);
-	else if(pathpath(argv[0], "", mode, buf, sizeof(buf)))
-		sfputr(sfstdout, buf, '\n');
-	else
-		error(1|ERROR_WARNING, "%s: relative path not found", argv[0]);
+	for(; argv[0]; argv++)
+	{
+		if(!mode)
+			l_dirname(sfstdout,argv[0],termch);
+		else if(pathpath(argv[0], "", mode, buf, sizeof(buf)))
+			sfputr(sfstdout, buf, termch);
+		else
+			error(1|ERROR_WARNING, "%s: relative path not found", argv[0]);
+	}
 	return 0;
 }