5480 CVE-2012-3165 mailx(1) buffer overflow vulnerability

Reviewed by: Dan McDonald <danmcd@omniti.com>
Reviewed by: Robert Mustacchi <rm@joyent.com>
Reviewed by: Richard Lowe <richlowe@richlowe.net>
Approved by: Dan McDonald <danmcd@omniti.com>

13 files changed, 421 insertions, 111 deletions

diff --git a/usr/src/cmd/Makefile b/usr/src/cmd/Makefile
index c59e370d47..6f5a277510 100644
--- a/usr/src/cmd/Makefile
+++ b/usr/src/cmd/Makefile
@@ -829,6 +829,7 @@ fs.d: fstyp
 ksh:	shcomp isaexec
 mdb:	terminfo
 print:	lp
+fmt:	mailx
 
 $(FIRST_SUBDIRS) $(BWOSDIRS) $(SUBDIRS) $(AUDITSUBDIRS): FRC
 	@if [ -f $@/Makefile  ]; then \
diff --git a/usr/src/cmd/fmt/Makefile b/usr/src/cmd/fmt/Makefile
index 21938536d6..cecd4e3c2a 100644
--- a/usr/src/cmd/fmt/Makefile
+++ b/usr/src/cmd/fmt/Makefile
@@ -33,6 +33,7 @@ SRCS= $(OBJS:%.o=%.c)
 
 include ../Makefile.cmd
 
+LDLIBS += -lcmdutils
 CERRWARN += -_gcc=-Wno-switch
 CERRWARN += -_gcc=-Wno-parentheses
 
diff --git a/usr/src/cmd/fmt/fmt.c b/usr/src/cmd/fmt/fmt.c
index 52d4676172..b5fbee6e13 100644
--- a/usr/src/cmd/fmt/fmt.c
+++ b/usr/src/cmd/fmt/fmt.c
@@ -86,7 +86,7 @@ int 	h_lines;		/* index into lines of hdrbuf */
 
 void (*(split))(wchar_t []);
 extern int scrwidth(wchar_t);
-extern int ishead(char []);
+extern boolean_t is_headline(const char *);
 
 
 static void fill_hdrbuf(wchar_t []);
@@ -240,13 +240,13 @@ fmt(FILE *fi)
 			}
 			/*
 			 * Need to convert string from wchar_t to char,
-			 * since this is what ishead() expects.  Since we
+			 * since this is what is_headline() expects.  Since we
 			 * only want to make sure cp points to a "From" line
 			 * of the email, we don't have to alloc
 			 * BUFSIZ * MB_LEN_MAX to cbuf.
 			 */
 			wcstombs(cbuf, cp, (BUFSIZ - 1));
-			if (ishead(cbuf)) {
+			if (is_headline(cbuf) == B_TRUE) {
 				hdr_state = in_hdr;
 				fill_hdrbuf(canonb);
 			} else {
diff --git a/usr/src/cmd/mailx/Makefile b/usr/src/cmd/mailx/Makefile
index 93b527b72a..4fb19334f2 100644
--- a/usr/src/cmd/mailx/Makefile
+++ b/usr/src/cmd/mailx/Makefile
@@ -22,6 +22,8 @@
 # Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
 # Use is subject to license terms.
 #
+# Copyright 2014 Joyent, Inc.
+#
 # cmd/mailx/Makefile
 
 PROG= mailx
@@ -67,7 +69,7 @@ CERRWARN +=	-_gcc=-Wno-uninitialized
 CERRWARN +=	-_gcc=-Wno-unused-variable
 CERRWARN +=	-_gcc=-Wno-clobbered
 LINTFLAGS= 	-hb
-LDLIBS +=	-lmail
+LDLIBS +=	-lmail -lcmdutils
 LDFLAGS +=	$(MAPFILE.NGB:%=-M%)
 
 CLOBBERFILES += $(MAILXHELP)
diff --git a/usr/src/cmd/mailx/cmd1.c b/usr/src/cmd/mailx/cmd1.c
index 5cdb7ae465..38c9b7ab9b 100644
--- a/usr/src/cmd/mailx/cmd1.c
+++ b/usr/src/cmd/mailx/cmd1.c
@@ -19,6 +19,11 @@
  *
  * CDDL HEADER END
  */
+
+/*
+ * Copyright 2014 Joyent, Inc.
+ */
+
 /*
  * Copyright 2001 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
@@ -37,8 +42,7 @@
  * contributors.
  */
 
-#pragma ident	"%Z%%M%	%I%	%E% SMI"
-
+#include <err.h>
 #include "rcv.h"
 #include <locale.h>
 
@@ -213,10 +217,14 @@ printhead(int mesg)
 	char *fromline;
 	char pbuf[LINESIZE];
 	char name[LINESIZE];
-	struct headline hl;
+	headline_t *hl;
 	register char *cp;
 	int showto;
 
+	if (headline_alloc(&hl) != 0) {
+		err(1, "could not allocate memory");
+	}
+
 	mp = &message[mesg-1];
 	ibuf = setinput(mp);
 	readline(ibuf, headline);
@@ -248,9 +256,14 @@ printhead(int mesg)
 			dispc = 'H';
 	if (mp->m_flag & MBOX)
 		dispc = 'M';
-	parse(headline, &hl, pbuf);
-	if (hl.l_date == NOSTR)
-		hl.l_date = "<Unknown date>";
+	if (parse_headline(headline, hl) == -1) {
+		headline_reset(hl);
+	}
+	if (custr_len(hl->hl_date) == 0) {
+		if (custr_append(hl->hl_date, "<Unknown date>") != 0) {
+			err(1, "could not print header");
+		}
+	}
 
 	/*
 	 * Netnews interface?
@@ -299,11 +312,14 @@ printhead(int mesg)
 	}
 	if (mp->m_text) {
 		printf("%16.16s %4ld/%-5ld %-.25s\n",
-			hl.l_date, mp->m_lines, mp->m_size, subjline);
-	} else {
-		printf("%16.16s binary/%-5ld %-.25s\n", hl.l_date, mp->m_size,
+		    custr_cstr(hl->hl_date), mp->m_lines, mp->m_size,
 		    subjline);
+	} else {
+		printf("%16.16s binary/%-5ld %-.25s\n", custr_cstr(hl->hl_date),
+		    mp->m_size, subjline);
 	}
+
+	headline_free(hl);
 }
 
 /*
diff --git a/usr/src/cmd/mailx/fio.c b/usr/src/cmd/mailx/fio.c
index 818860d7ae..59eceb519f 100644
--- a/usr/src/cmd/mailx/fio.c
+++ b/usr/src/cmd/mailx/fio.c
@@ -21,6 +21,10 @@
  */
 
 /*
+ * Copyright 2014 Joyent, Inc.
+ */
+
+/*
  * Copyright 1999 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
  */
@@ -28,8 +32,6 @@
 /*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
 /*	  All Rights Reserved  	*/
 
-#pragma	ident	"%Z%%M%	%I%	%E% SMI"
-
 #include "rcv.h"
 #include <locale.h>
 #include <wordexp.h>
@@ -174,7 +176,7 @@ setptr(register FILE *ibuf)
 		}
 
 		/* Look for a From line that starts a new message */
-		if (blankline && linebuf[0] == 'F' && ishead(linebuf)) {
+		if (blankline && linebuf[0] == 'F' && is_headline(linebuf)) {
 			if (msgCount > 0 && !newmail) {
 				message[msgCount-1].m_size = s;
 				message[msgCount-1].m_lines = l;
diff --git a/usr/src/cmd/mailx/hdr/def.h b/usr/src/cmd/mailx/hdr/def.h
index d0e48820ea..7453b24f97 100644
--- a/usr/src/cmd/mailx/hdr/def.h
+++ b/usr/src/cmd/mailx/hdr/def.h
@@ -20,6 +20,10 @@
  */
 
 /*
+ * Copyright 2014 Joyent, Inc.
+ */
+
+/*
  * Copyright (c) 1985, 2010, Oracle and/or its affiliates. All rights reserved.
  */
 
@@ -60,6 +64,7 @@ extern "C" {
 #include <stdlib.h>
 #include <ulimit.h>
 #include <wait.h>
+#include <libcmdutils.h>
 #endif
 #ifdef VMUNIX
 #include <sys/wait.h>
@@ -204,11 +209,11 @@ struct cmd {
  * line
  */
 
-struct headline {
-	char	*l_from;	/* The name of the sender */
-	char	*l_tty;		/* His tty string (if any) */
-	char	*l_date;	/* The entire date string */
-};
+typedef struct headline {
+	custr_t	*hl_from;	/* The name of the sender */
+	custr_t	*hl_tty;	/* His tty string (if any) */
+	custr_t	*hl_date;	/* The entire date string */
+} headline_t;
 
 #define	GTO	1		/* Grab To: line */
 #define	GSUBJECT 2		/* Likewise, Subject: line */
@@ -486,6 +491,9 @@ extern int	hash(char name[]);
 extern char	*hcontents(char hfield[]);
 extern int	headerp(register char *line);
 extern int	headers(int *msgvec);
+extern int	headline_alloc(headline_t **);
+extern void	headline_free(headline_t *);
+extern void	headline_reset(headline_t *);
 extern int	help(void);
 extern char	*helppath(char *file);
 extern char	*hfield(char field[], struct message *mp,
@@ -497,7 +505,7 @@ extern int	igfield(char *list[]);
 extern int	inc(void);
 extern void	inithost(void);
 extern int	isdir(char name[]);
-extern int	ishead(char linebuf[]);
+extern boolean_t is_headline(const char *);
 extern int	ishfield(char linebuf[], char field[]);
 extern int	ishost(char *sys, char *rest);
 extern int	isign(char *field, int saving);
@@ -533,7 +541,7 @@ extern int	null(char *e);
 extern int	outof(struct name *names, FILE *fo);
 extern struct name	*outpre(struct name *to);
 extern void	panic(char *str);
-extern void	parse(char line[], struct headline *hl, char pbuf[]);
+extern int	parse_headline(const char *, headline_t *);
 extern int	pcmdlist(void);
 extern int	pdot(void);
 extern int	preserve(int *msgvec);
diff --git a/usr/src/cmd/mailx/head.c b/usr/src/cmd/mailx/head.c
index 3f833ab14e..b6d09f0767 100644
--- a/usr/src/cmd/mailx/head.c
+++ b/usr/src/cmd/mailx/head.c
@@ -19,6 +19,11 @@
  *
  * CDDL HEADER END
  */
+
+/*
+ * Copyright 2014 Joyent, Inc.
+ */
+
 /*
  * Copyright 1995 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
@@ -38,7 +43,7 @@
  * contributors.
  */
 
-#pragma ident	"%Z%%M%	%I%	%E% SMI"
+#include <err.h>
 
 #include "rcv.h"
 
@@ -49,115 +54,188 @@
  * Routines for processing and detecting headlines.
  */
 
-static char	*copyin(char src[], char **space);
-static char	*nextword(char wp[], char wbuf[]);
+static int nextword(const char *, custr_t *, const char **);
 
 /*
  * See if the passed line buffer is a mail header.
  * Return true if yes.
  */
-
-int 
-ishead(char linebuf[])
+boolean_t
+is_headline(const char *linebuf)
 {
-	register char *cp;
-	struct headline hl;
-	char parbuf[BUFSIZ];
-
-	cp = linebuf;
-	if (strncmp("From ", cp, 5) != 0)
-		return(0);
-	parse(cp, &hl, parbuf);
-	if (hl.l_from == NOSTR) {
-		return(0);
+	headline_t *hl;
+	boolean_t ret;
+
+	if (strncmp("From ", linebuf, 5) != 0) {
+		return (B_FALSE);
+	}
+
+	if (headline_alloc(&hl) != 0 || parse_headline(linebuf, hl) != 0) {
+		err(1, "could not parse headline");
 	}
-	return(1);
+
+	ret = custr_len(hl->hl_from) > 0 ? B_TRUE : B_FALSE;
+
+	headline_free(hl);
+	return (ret);
 }
 
 /*
- * Split a headline into its useful components.
- * Copy the line into dynamic string space, then set
- * pointers into the copied line in the passed headline
- * structure.  Actually, it scans.
+ * Manage headline_t objects:
  */
-void 
-parse(char line[], struct headline *hl, char pbuf[])
+void
+headline_free(headline_t *hl)
+{
+	custr_free(hl->hl_from);
+	custr_free(hl->hl_tty);
+	custr_free(hl->hl_date);
+	free(hl);
+}
+
+int
+headline_alloc(headline_t **hl)
 {
-	register char *cp, *dp;
-	char *sp;
-	char word[LINESIZE];
+	int en;
+	headline_t *t;
+
+	if ((t = calloc(1, sizeof (*t))) == NULL) {
+		return (-1);
+	}
 
-	hl->l_from = NOSTR;
-	hl->l_date = NOSTR;
-	cp = line;
-	sp = pbuf;
+	if (custr_alloc(&t->hl_from) != 0 || custr_alloc(&t->hl_tty) != 0 ||
+	    custr_alloc(&t->hl_date) != 0) {
+		en = errno;
 
-	/*
-	 * Skip the first "word" of the line, which should be "From"
-	 * anyway.
-	 */
+		headline_free(t);
 
-	cp = nextword(cp, word);
-	dp = nextword(cp, word);
-	if (!equal(word, ""))
-		hl->l_from = copyin(word, &sp);
-	if (dp != NOSTR)
-		hl->l_date = copyin(dp, &sp);
+		errno = en;
+		return (-1);
+	}
+
+	*hl = t;
+	return (0);
 }
 
 /*
- * Copy the string on the left into the string on the right
- * and bump the right (reference) string pointer by the length.
- * Thus, dynamically allocate space in the right string, copying
- * the left string into it.
+ * Clear all of the strings in a headline_t:
  */
+void
+headline_reset(headline_t *hl)
+{
+	custr_reset(hl->hl_from);
+	custr_reset(hl->hl_tty);
+	custr_reset(hl->hl_date);
+}
 
-static char *
-copyin(char src[], char **space)
+int
+parse_headline(const char *line, headline_t *hl)
 {
-	register char *cp, *top;
-	register int s;
-
-	s = strlen(src);
-	cp = *space;
-	top = cp;
-	strcpy(cp, src);
-	cp += s + 1;
-	*space = cp;
-	return(top);
+	const char *c = line;
+
+	headline_reset(hl);
+
+	/*
+	 * Load the first word from the line and ensure that it is "From".
+	 */
+	if (nextword(c, hl->hl_from, &c) != 0) {
+		return (-1);
+	}
+	if (strcmp(custr_cstr(hl->hl_from), "From") != 0) {
+		errno = EINVAL;
+		return (-1);
+	}
+	custr_reset(hl->hl_from);
+
+	/*
+	 * The next word will be the From address.
+	 */
+	if (nextword(c, hl->hl_from, &c) != 0) {
+		return (-1);
+	}
+
+	/*
+	 * If there is a next word, the rest of the string is the Date.
+	 */
+	if (c != NULL) {
+		if (custr_append(hl->hl_date, c) != 0) {
+			return (-1);
+		}
+	}
+
+	errno = 0;
+	return (0);
 }
 
 /*
- * Collect a liberal (space, tab delimited) word into the word buffer
- * passed.  Also, return a pointer to the next word following that,
- * or NOSTR if none follow.
+ * Collect a space- or tab-delimited word into the word buffer, if one is
+ * passed.  The double quote character (") can be used to include whitespace
+ * within a word.  Set "nextword" to the location of the first character of the
+ * _next_ word, or NULL if there were no more words.  Returns 0 on success or
+ * -1 otherwise.
  */
-
-static char *
-nextword(char wp[], char wbuf[])
+static int
+nextword(const char *input, custr_t *word, const char **nextword)
 {
-	register char *cp, *cp2;
+	boolean_t in_quotes = B_FALSE;
+	const char *c = input != NULL ? input : "";
+
+	/*
+	 * Collect the first word into the word buffer, if one is provided.
+	 */
+	for (;;) {
+		if (*c == '\0') {
+			/*
+			 * We have reached the end of the string.
+			 */
+			*nextword = NULL;
+			return (0);
+		}
+
+		if (*c == '"') {
+			/*
+			 * Either beginning or ending a quoted string.
+			 */
+			in_quotes = in_quotes ? B_FALSE : B_TRUE;
+		}
+
+		if (!in_quotes && (*c == ' ' || *c == '\t')) {
+			/*
+			 * We have reached a whitespace region.
+			 */
+			break;
+		}
+
+		/*
+		 * Copy this character into the word buffer.
+		 */
+		if (word != NULL) {
+			if (custr_appendc(word, *c) != 0) {
+				return (-1);
+			}
+		}
+		c++;
+	}
+
+	/*
+	 * Find the beginning of the next word, if there is one.
+	 */
+	for (;;) {
+		if (*c == '\0') {
+			/*
+			 * We have reached the end of the string.
+			 */
+			*nextword = NULL;
+			return (0);
 
-	if ((cp = wp) == NOSTR) {
-		copy("", wbuf);
-		return(NOSTR);
+		} else if (*c != ' ' && *c != '\t') {
+			/*
+			 * We have located the next word.
+			 */
+			*nextword = c;
+			return (0);
+		}
+		c++;
 	}
-	cp2 = wbuf;
-	while (!any(*cp, " \t") && *cp != '\0')
-		if (*cp == '"') {
-			*cp2++ = *cp++;
-			while (*cp != '\0' && *cp != '"')
-				*cp2++ = *cp++;
-			if (*cp == '"')
-				*cp2++ = *cp++;
-		} else
-			*cp2++ = *cp++;
-	*cp2 = '\0';
-	while (any(*cp, " \t"))
-		cp++;
-	if (*cp == '\0')
-		return(NOSTR);
-	return(cp);
 }
 
 /*
diff --git a/usr/src/cmd/mailx/receipt.c b/usr/src/cmd/mailx/receipt.c
index 2a128d6a91..0b6b9296fc 100644
--- a/usr/src/cmd/mailx/receipt.c
+++ b/usr/src/cmd/mailx/receipt.c
@@ -19,6 +19,11 @@
  *
  * CDDL HEADER END
  */
+
+/*
+ * Copyright 2014 Joyent, Inc.
+ */
+
 /*
  * Copyright 1998 Sun Microsystems, Inc.  All rights reserved.
  * Use is subject to license terms.
@@ -38,7 +43,7 @@
  * contributors.
  */
 
-#pragma ident	"%Z%%M%	%I%	%E% SMI"
+#include <err.h>
 
 #include "rcv.h"
 
@@ -47,12 +52,12 @@ static int		icsubstr(char *s1, char *s2);
 void 
 receipt(struct message *mp)
 {
-	struct headline	hl;
 	char	head[LINESIZE];
 	char	buf[BUFSIZ];
 	FILE	*pp, *fp;
 	char	*mail, *s;
 
+
 	if ((mail = value("sendmail")) == 0)
 #ifdef SENDMAIL
 		mail = SENDMAIL;
@@ -63,16 +68,27 @@ receipt(struct message *mp)
 	 || icsubstr(hfield(">to", mp, addto), "/receipt")) {
 		snprintf(buf, sizeof (buf), "%s %s", mail, skin(nameof(mp)));
 		if (pp = npopen(buf, "w")) {
+			headline_t *hl;
+
+			if (headline_alloc(&hl) != 0) {
+				err(1, "could not allocate memory");
+			}
+
 			fp = setinput(mp);
 			readline(fp, head);
-			parse(head, &hl, buf);
-			if (hl.l_date != NOSTR)
-				fprintf(pp, "Original-Date: %s\n", hl.l_date);
+			if (parse_headline(head, hl) != 0) {
+				headline_reset(hl);
+			}
+			if (custr_len(hl->hl_date) > 0) {
+				fprintf(pp, "Original-Date: %s\n",
+				    custr_cstr(hl->hl_date));
+			}
 			if (s = hfield("message-id", mp, addone))
 				fprintf(pp, "Original-Message-ID: %s\n", s);
 			s = hfield("subject", mp, addone);
 			fprintf(pp, "Subject: RR: %s\n", s ? s : "(none)");
 			npclose(pp);
+			headline_free(hl);
 		}
 	}
 }
diff --git a/usr/src/lib/libcmdutils/Makefile.com b/usr/src/lib/libcmdutils/Makefile.com
index 2f98fe5f25..ffe3c9cba5 100644
--- a/usr/src/lib/libcmdutils/Makefile.com
+++ b/usr/src/lib/libcmdutils/Makefile.com
@@ -25,7 +25,8 @@
 
 LIBRARY=	libcmdutils.a
 VERS=		.1
-CMD_OBJS=	avltree.o sysattrs.o writefile.o process_xattrs.o uid.o gid.o
+CMD_OBJS=	avltree.o sysattrs.o writefile.o process_xattrs.o uid.o gid.o \
+		custr.o
 COM_OBJS=	list.o
 OBJECTS=	$(CMD_OBJS) $(COM_OBJS)
 
diff --git a/usr/src/lib/libcmdutils/common/custr.c b/usr/src/lib/libcmdutils/common/custr.c
new file mode 100644
index 0000000000..1ec72de9dd
--- /dev/null
+++ b/usr/src/lib/libcmdutils/common/custr.c
@@ -0,0 +1,135 @@
+/*
+ * This file and its contents are supplied under the terms of the
+ * Common Development and Distribution License ("CDDL"), version 1.0.
+ * You may only use this file in accordance with the terms of version
+ * 1.0 of the CDDL.
+ *
+ * A full copy of the text of the CDDL should have accompanied this
+ * source.  A copy of the CDDL is also available via the Internet at
+ * http://www.illumos.org/license/CDDL.
+ */
+
+/*
+ * String utility functions with dynamic memory management.
+ */
+
+/*
+ * Copyright 2014, Joyent, Inc.
+ */
+
+#include <stdlib.h>
+#include <err.h>
+#include <string.h>
+
+#include "libcmdutils.h"
+
+struct custr {
+	size_t cus_strlen;
+	size_t cus_datalen;
+	char *cus_data;
+};
+
+#define	STRING_CHUNK_SIZE	64
+
+void
+custr_reset(custr_t *cus)
+{
+	if (cus->cus_data == NULL)
+		return;
+
+	cus->cus_strlen = 0;
+	cus->cus_data[0] = '\0';
+}
+
+size_t
+custr_len(custr_t *cus)
+{
+	return (cus->cus_strlen);
+}
+
+const char *
+custr_cstr(custr_t *cus)
+{
+	return (cus->cus_data);
+}
+
+int
+custr_appendc(custr_t *cus, char newc)
+{
+	char news[2];
+
+	news[0] = newc;
+	news[1] = '\0';
+
+	return (custr_append(cus, news));
+}
+
+int
+custr_append(custr_t *cus, const char *news)
+{
+	size_t len = strlen(news);
+	size_t chunksz = STRING_CHUNK_SIZE;
+
+	while (chunksz < len) {
+		chunksz *= 2;
+	}
+
+	if (len + cus->cus_strlen + 1 >= cus->cus_datalen) {
+		char *new_data;
+		size_t new_datalen = cus->cus_datalen + chunksz;
+
+		/*
+		 * Allocate replacement memory:
+		 */
+		if ((new_data = malloc(new_datalen)) == NULL) {
+			return (-1);
+		}
+
+		/*
+		 * Copy existing data into replacement memory and free
+		 * the old memory.
+		 */
+		if (cus->cus_data != NULL) {
+			(void) memcpy(new_data, cus->cus_data,
+			    cus->cus_strlen + 1);
+			free(cus->cus_data);
+		}
+
+		/*
+		 * Swap in the replacement buffer:
+		 */
+		cus->cus_data = new_data;
+		cus->cus_datalen = new_datalen;
+	}
+	/*
+	 * Append new string to existing string:
+	 */
+	(void) memcpy(cus->cus_data + cus->cus_strlen, news, len + 1);
+	cus->cus_strlen += len;
+
+	return (0);
+}
+
+int
+custr_alloc(custr_t **cus)
+{
+	custr_t *t;
+
+	if ((t = calloc(1, sizeof (*t))) == NULL) {
+		*cus = NULL;
+		return (-1);
+	}
+
+	*cus = t;
+	return (0);
+}
+
+void
+custr_free(custr_t *cus)
+{
+	if (cus == NULL)
+		return;
+
+	free(cus->cus_data);
+	free(cus);
+}
diff --git a/usr/src/lib/libcmdutils/common/mapfile-vers b/usr/src/lib/libcmdutils/common/mapfile-vers
index e4c5940c31..640959e4b5 100644
--- a/usr/src/lib/libcmdutils/common/mapfile-vers
+++ b/usr/src/lib/libcmdutils/common/mapfile-vers
@@ -42,6 +42,13 @@ $mapfile_version 2
 SYMBOL_VERSION SUNWprivate_1.1 {
     global:
 	add_tnode;
+	custr_alloc;
+	custr_append;
+	custr_appendc;
+	custr_cstr;
+	custr_free;
+	custr_len;
+	custr_reset;
 	destroy_tree;
 	findnextgid;
 	findnextuid;
diff --git a/usr/src/lib/libcmdutils/libcmdutils.h b/usr/src/lib/libcmdutils/libcmdutils.h
index c315e0fbef..a280751c27 100644
--- a/usr/src/lib/libcmdutils/libcmdutils.h
+++ b/usr/src/lib/libcmdutils/libcmdutils.h
@@ -25,6 +25,9 @@
 /*
  * Copyright (c) 2013 RackTop Systems.
  */
+/*
+ * Copyright 2014 Joyent, Inc.
+ */
 
 /*
  * Declarations for the functions in libcmdutils.
@@ -140,6 +143,46 @@ extern int findnextuid(uid_t, uid_t, uid_t *);
  */
 extern int findnextgid(gid_t, gid_t, gid_t *);
 
+
+
+		/* dynamic string utilities */
+
+typedef struct custr custr_t;
+
+/*
+ * Allocate and free a "custr_t" dynamic string object.  Returns 0 on success
+ * and -1 otherwise.
+ */
+extern int custr_alloc(custr_t **);
+extern void custr_free(custr_t *);
+
+/*
+ * Append a single character, or a NUL-terminated string of characters, to a
+ * dynamic string.  Returns 0 on success and -1 otherwise.  The dynamic string
+ * will be unmodified if the function returns -1.
+ */
+extern int custr_appendc(custr_t *, char);
+extern int custr_append(custr_t *, const char *);
+
+/*
+ * Determine the length in bytes, not including the NUL terminator, of the
+ * dynamic string.
+ */
+extern size_t custr_len(custr_t *);
+
+/*
+ * Clear the contents of a dynamic string.  Does not free the underlying
+ * memory.
+ */
+extern void custr_reset(custr_t *);
+
+/*
+ * Retrieve a const pointer to a NUL-terminated string version of the contents
+ * of the dynamic string.  Storage for this string should not be freed, and
+ * the pointer will be invalidated by any mutations to the dynamic string.
+ */
+extern const char *custr_cstr(custr_t *str);
+
 #ifdef	__cplusplus
 }
 #endif