Escape/unescape commas when serializing/deserializing a stringlist.

MANIFEST

@@ -799,6 +799,7 @@ plugins/sudoers/regress/parser/check_digest.out.ok
 plugins/sudoers/regress/parser/check_fill.c
 plugins/sudoers/regress/parser/check_gentime.c
 plugins/sudoers/regress/parser/check_hexchar.c
+plugins/sudoers/regress/serialize_list/check_serialize_list.c
 plugins/sudoers/regress/starttime/check_starttime.c
 plugins/sudoers/regress/sudoers/test1.in
 plugins/sudoers/regress/sudoers/test1.json.ok
@@ -1011,6 +1012,7 @@ plugins/sudoers/regress/visudo/test8.out.ok
 plugins/sudoers/regress/visudo/test8.sh
 plugins/sudoers/regress/visudo/test9.out.ok
 plugins/sudoers/regress/visudo/test9.sh
+plugins/sudoers/serialize_list.c
 plugins/sudoers/set_perms.c
 plugins/sudoers/solaris_audit.c
 plugins/sudoers/solaris_audit.h
@@ -1047,6 +1049,7 @@ plugins/sudoers/toke_util.c
 plugins/sudoers/tsdump.c
 plugins/sudoers/tsgetgrpw.c
 plugins/sudoers/tsgetgrpw.h
+plugins/sudoers/unesc_str.c
 plugins/sudoers/visudo.c
 plugins/system_group/Makefile.in
 plugins/system_group/system_group.c

plugins/sudoers/Makefile.in

@@ -158,8 +158,8 @@ PROGS = sudoers.la visudo sudoreplay cvtsudoers testsudoers
 # Regression tests
 TEST_PROGS = check_addr check_base64 check_digest check_editor \
 	     check_env_pattern check_exptilde check_fill check_gentime \
-	     check_hexchar check_iolog_plugin check_starttime \
+	     check_hexchar check_iolog_plugin check_serialize_list \
-	     check_unesc @SUDOERS_TEST_PROGS@
+	     check_starttime check_unesc @SUDOERS_TEST_PROGS@
 
 # Fuzzers
 LIB_FUZZING_ENGINE = @FUZZ_ENGINE@
@@ -185,9 +185,9 @@ SUDOERS_OBJS = $(AUTH_OBJS) audit.lo boottime.lo check.lo editor.lo env.lo \
 	       sudoers_hooks.lo env_pattern.lo file.lo find_path.lo \
 	       fmtsudoers.lo gc.lo goodpath.lo group_plugin.lo interfaces.lo \
 	       iolog.lo iolog_path_escapes.lo locale.lo log_client.lo \
-	       logging.lo parse.lo policy.lo prompt.lo set_perms.lo \
+	       logging.lo parse.lo policy.lo prompt.lo serialize_list.lo \
-	       starttime.lo strlcpy_unesc.lo strvec_join.lo sudo_nss.lo \
+	       set_perms.lo starttime.lo strlcpy_unesc.lo strvec_join.lo \
-	       sudoers.lo timestamp.lo @SUDOERS_OBJS@
+	       sudo_nss.lo sudoers.lo timestamp.lo unesc_str.lo @SUDOERS_OBJS@
 
 SUDOERS_IOBJS = $(SUDOERS_OBJS:.lo=.i)
 
@@ -241,17 +241,22 @@ CHECK_HEXCHAR_OBJS = check_hexchar.o hexchar.lo sudoers_debug.lo
 
 CHECK_IOLOG_PLUGIN_OBJS = check_iolog_plugin.o iolog.lo log_client.lo \
 			  locale.lo pwutil.lo pwutil_impl.lo redblack.lo \
-			  strlist.lo sudoers_debug.lo
+			  strlist.lo sudoers_debug.lo unesc_str.lo
 
 CHECK_SYMBOLS_OBJS = check_symbols.o
 
 CHECK_STARTTIME_OBJS = check_starttime.o starttime.lo sudoers_debug.lo
 
-CHECK_UNESC_OBJS = check_unesc.o strlcpy_unesc.lo strvec_join.lo sudoers_debug.lo
+CHECK_UNESC_OBJS = check_unesc.o strlcpy_unesc.lo strvec_join.lo \
+		   sudoers_debug.lo unesc_str.lo
+
+CHECK_SERIALIZE_LIST_OBJS = check_serialize_list.lo serialize_list.lo \
+			    sudoers_debug.lo
 
 FUZZ_POLICY_OBJS = editor.lo env.lo env_pattern.lo fuzz_policy.o fuzz_stubs.o \
 		   gc.lo iolog_path_escapes.lo locale.lo policy.lo \
-		   strlcpy_unesc.lo strvec_join.lo sudoers.lo sudoers_hooks.lo
+		   serialize_list.lo strlcpy_unesc.lo strvec_join.lo \
+		   sudoers.lo sudoers_hooks.lo
 
 FUZZ_POLICY_CORPUS = $(srcdir)/regress/corpus/seed/policy/policy.*
 
@@ -386,6 +391,9 @@ check_hexchar: $(CHECK_HEXCHAR_OBJS) $(LIBUTIL)
 check_iolog_plugin: $(CHECK_IOLOG_PLUGIN_OBJS) $(LIBUTIL) $(LIBIOLOG) $(LIBLOGSRV)
 	$(LIBTOOL) $(LTFLAGS) --mode=link $(CC) -o $@ $(CHECK_IOLOG_PLUGIN_OBJS) $(LDFLAGS) $(ASAN_LDFLAGS) $(PIE_LDFLAGS) $(SSP_LDFLAGS) $(LIBIOLOG) $(LIBLOGSRV) @LIBTLS@
 
+check_serialize_list: $(CHECK_SERIALIZE_LIST_OBJS) $(LIBUTIL)
+	$(LIBTOOL) $(LTFLAGS) --mode=link $(CC) -o $@ $(CHECK_SERIALIZE_LIST_OBJS) $(LDFLAGS) $(ASAN_LDFLAGS) $(PIE_LDFLAGS) $(SSP_LDFLAGS) $(LIBS)
+
 check_starttime: $(CHECK_STARTTIME_OBJS) $(LIBUTIL)
 	$(LIBTOOL) $(LTFLAGS) --mode=link $(CC) -o $@ $(CHECK_STARTTIME_OBJS) $(LDFLAGS) $(ASAN_LDFLAGS) $(PIE_LDFLAGS) $(SSP_LDFLAGS) $(LIBS)
 
@@ -659,6 +667,7 @@ check: $(TEST_PROGS) visudo testsudoers cvtsudoers check-fuzzer
 	    ./check_hexchar || rval=`expr $$rval + $$?`; \
 	    mkdir -p regress/iolog_plugin; \
 	    ./check_iolog_plugin regress/iolog_plugin/iolog || rval=`expr $$rval + $$?`; \
+	    ./check_serialize_list || rval=`expr $$rval + $$?`; \
 	    ./check_starttime || rval=`expr $$rval + $$?`; \
 	    ./check_unesc || rval=`expr $$rval + $$?`; \
 	    if test -f check_symbols; then \
@@ -1259,6 +1268,34 @@ check_iolog_plugin.i: $(srcdir)/regress/iolog_plugin/check_iolog_plugin.c \
 	$(CC) -E -o $@ $(CPPFLAGS) $<
 check_iolog_plugin.plog: check_iolog_plugin.i
 	rm -f $@; pvs-studio --cfg $(PVS_CFG) --sourcetree-root $(top_srcdir) --skip-cl-exe yes --source-file $(srcdir)/regress/iolog_plugin/check_iolog_plugin.c --i-file $< --output-file $@
+check_serialize_list.lo: \
+                         $(srcdir)/regress/serialize_list/check_serialize_list.c \
+                         $(devdir)/def_data.h $(incdir)/compat/stdbool.h \
+                         $(incdir)/sudo_compat.h $(incdir)/sudo_conf.h \
+                         $(incdir)/sudo_debug.h $(incdir)/sudo_eventlog.h \
+                         $(incdir)/sudo_fatal.h $(incdir)/sudo_gettext.h \
+                         $(incdir)/sudo_plugin.h $(incdir)/sudo_queue.h \
+                         $(incdir)/sudo_util.h $(srcdir)/defaults.h \
+                         $(srcdir)/logging.h $(srcdir)/parse.h \
+                         $(srcdir)/sudo_nss.h $(srcdir)/sudoers.h \
+                         $(srcdir)/sudoers_debug.h $(top_builddir)/config.h \
+                         $(top_builddir)/pathnames.h
+	$(LIBTOOL) $(LTFLAGS) --mode=compile $(CC) -c $(CPPFLAGS) $(CFLAGS) $(ASAN_CFLAGS) $(PIE_CFLAGS) $(SSP_CFLAGS) $(srcdir)/regress/serialize_list/check_serialize_list.c
+check_serialize_list.i: \
+                         $(srcdir)/regress/serialize_list/check_serialize_list.c \
+                         $(devdir)/def_data.h $(incdir)/compat/stdbool.h \
+                         $(incdir)/sudo_compat.h $(incdir)/sudo_conf.h \
+                         $(incdir)/sudo_debug.h $(incdir)/sudo_eventlog.h \
+                         $(incdir)/sudo_fatal.h $(incdir)/sudo_gettext.h \
+                         $(incdir)/sudo_plugin.h $(incdir)/sudo_queue.h \
+                         $(incdir)/sudo_util.h $(srcdir)/defaults.h \
+                         $(srcdir)/logging.h $(srcdir)/parse.h \
+                         $(srcdir)/sudo_nss.h $(srcdir)/sudoers.h \
+                         $(srcdir)/sudoers_debug.h $(top_builddir)/config.h \
+                         $(top_builddir)/pathnames.h
+	$(CC) -E -o $@ $(CPPFLAGS) $<
+check_serialize_list.plog: check_serialize_list.i
+	rm -f $@; pvs-studio --cfg $(PVS_CFG) --sourcetree-root $(top_srcdir) --skip-cl-exe yes --source-file $(srcdir)/regress/serialize_list/check_serialize_list.c --i-file $< --output-file $@
 check_starttime.o: $(srcdir)/regress/starttime/check_starttime.c \
                    $(incdir)/compat/stdbool.h $(incdir)/sudo_compat.h \
                    $(incdir)/sudo_fatal.h $(incdir)/sudo_plugin.h \
@@ -2671,6 +2708,30 @@ securid5.i: $(authdir)/securid5.c $(authdir)/sudo_auth.h $(devdir)/def_data.h \
 	$(CC) -E -o $@ $(CPPFLAGS) $<
 securid5.plog: securid5.i
 	rm -f $@; pvs-studio --cfg $(PVS_CFG) --sourcetree-root $(top_srcdir) --skip-cl-exe yes --source-file $(authdir)/securid5.c --i-file $< --output-file $@
+serialize_list.lo: $(srcdir)/serialize_list.c $(devdir)/def_data.h \
+                   $(incdir)/compat/stdbool.h $(incdir)/sudo_compat.h \
+                   $(incdir)/sudo_conf.h $(incdir)/sudo_debug.h \
+                   $(incdir)/sudo_eventlog.h $(incdir)/sudo_fatal.h \
+                   $(incdir)/sudo_gettext.h $(incdir)/sudo_plugin.h \
+                   $(incdir)/sudo_queue.h $(incdir)/sudo_util.h \
+                   $(srcdir)/defaults.h $(srcdir)/logging.h $(srcdir)/parse.h \
+                   $(srcdir)/sudo_nss.h $(srcdir)/sudoers.h \
+                   $(srcdir)/sudoers_debug.h $(top_builddir)/config.h \
+                   $(top_builddir)/pathnames.h
+	$(LIBTOOL) $(LTFLAGS) --mode=compile $(CC) -c $(CPPFLAGS) $(CFLAGS) $(ASAN_CFLAGS) $(PIE_CFLAGS) $(SSP_CFLAGS) $(srcdir)/serialize_list.c
+serialize_list.i: $(srcdir)/serialize_list.c $(devdir)/def_data.h \
+                   $(incdir)/compat/stdbool.h $(incdir)/sudo_compat.h \
+                   $(incdir)/sudo_conf.h $(incdir)/sudo_debug.h \
+                   $(incdir)/sudo_eventlog.h $(incdir)/sudo_fatal.h \
+                   $(incdir)/sudo_gettext.h $(incdir)/sudo_plugin.h \
+                   $(incdir)/sudo_queue.h $(incdir)/sudo_util.h \
+                   $(srcdir)/defaults.h $(srcdir)/logging.h $(srcdir)/parse.h \
+                   $(srcdir)/sudo_nss.h $(srcdir)/sudoers.h \
+                   $(srcdir)/sudoers_debug.h $(top_builddir)/config.h \
+                   $(top_builddir)/pathnames.h
+	$(CC) -E -o $@ $(CPPFLAGS) $<
+serialize_list.plog: serialize_list.i
+	rm -f $@; pvs-studio --cfg $(PVS_CFG) --sourcetree-root $(top_srcdir) --skip-cl-exe yes --source-file $(srcdir)/serialize_list.c --i-file $< --output-file $@
 set_perms.lo: $(srcdir)/set_perms.c $(devdir)/def_data.h \
               $(incdir)/compat/stdbool.h $(incdir)/sudo_compat.h \
               $(incdir)/sudo_conf.h $(incdir)/sudo_debug.h \
@@ -3213,6 +3274,12 @@ tsgetgrpw.i: $(srcdir)/tsgetgrpw.c $(devdir)/def_data.h \
 	$(CC) -E -o $@ $(CPPFLAGS) $<
 tsgetgrpw.plog: tsgetgrpw.i
 	rm -f $@; pvs-studio --cfg $(PVS_CFG) --sourcetree-root $(top_srcdir) --skip-cl-exe yes --source-file $(srcdir)/tsgetgrpw.c --i-file $< --output-file $@
+unesc_str.lo: $(srcdir)/unesc_str.c 
+	$(LIBTOOL) $(LTFLAGS) --mode=compile $(CC) -c $(CPPFLAGS) $(CFLAGS) $(ASAN_CFLAGS) $(PIE_CFLAGS) $(SSP_CFLAGS) $(srcdir)/unesc_str.c
+unesc_str.i: $(srcdir)/unesc_str.c 
+	$(CC) -E -o $@ $(CPPFLAGS) $<
+unesc_str.plog: unesc_str.i
+	rm -f $@; pvs-studio --cfg $(PVS_CFG) --sourcetree-root $(top_srcdir) --skip-cl-exe yes --source-file $(srcdir)/unesc_str.c --i-file $< --output-file $@
 visudo.o: $(srcdir)/visudo.c $(devdir)/def_data.h $(devdir)/gram.h \
           $(incdir)/compat/getopt.h $(incdir)/compat/stdbool.h \
           $(incdir)/sudo_compat.h $(incdir)/sudo_conf.h $(incdir)/sudo_debug.h \

plugins/sudoers/iolog.c

@@ -211,7 +211,6 @@ free_iolog_details(void)
 
 /*
  * Convert a comma-separated list to a string list.
- * XXX - handle escaped commas
  */
 static struct sudoers_str_list *
 deserialize_stringlist(const char *s)
@@ -235,6 +234,7 @@ deserialize_stringlist(const char *s)
 	    free(str);
 	    goto bad;
 	}
+	unescape_string(str->str);
 	STAILQ_INSERT_TAIL(strlist, str, entries);
     }
     if (STAILQ_EMPTY(strlist))
@@ -265,9 +265,9 @@ set_passprompt_regex(const char *cstr)
 	goto bad;
     }
 
-    /* XXX - handle escaped commas */
     for ((cp = strtok_r(str, ",", &last)); cp != NULL;
 	    (cp = strtok_r(NULL, ",", &last))) {
+	unescape_string(cp);
 	if (!iolog_pwfilt_add(handle, cp))
 	    goto bad;
     }

plugins/sudoers/policy.c

@@ -572,46 +572,6 @@ bad:
     debug_return_int(MODE_ERROR);
 }
 
-/*
- * Convert struct list_members to a comma-separated string with
- * the given variable name.
- * XXX - escape commas in member values
- */
-static char *
-serialize_list(const char *varname, struct list_members *members)
-{
-    struct list_member *lm, *next;
-    size_t len, result_size;
-    char *result;
-    debug_decl(serialize_list, SUDOERS_DEBUG_PLUGIN);
-
-    result_size = strlen(varname) + 1;
-    SLIST_FOREACH(lm, members, entries) {
-	result_size += strlen(lm->value) + 1;
-    }
-    if ((result = malloc(result_size)) == NULL)
-	goto bad;
-    /* No need to check len for overflow here. */
-    len = strlcpy(result, varname, result_size);
-    result[len++] = '=';
-    result[len] = '\0';
-    SLIST_FOREACH_SAFE(lm, members, entries, next) {
-	len = strlcat(result, lm->value, result_size);
-	if (len + (next != NULL) >= result_size) {
-	    sudo_warnx(U_("internal error, %s overflow"), __func__);
-	    goto bad;
-	}
-	if (next != NULL) {
-	    result[len++] = ',';
-	    result[len] = '\0';
-	}
-    }
-    debug_return_str(result);
-bad:
-    free(result);
-    debug_return_str(NULL);
-}
-
 /*
  * Store the execution environment and other front-end settings.
  * Builds up the command_info list and sets argv and envp.

plugins/sudoers/regress/serialize_list/check_serialize_list.c

@@ -0,0 +1,82 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2022 Todd C. Miller <Todd.Miller@sudo.ws>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define SUDO_ERROR_WRAP 0
+
+#include "sudoers.h"
+
+sudo_dso_public int main(int argc, char *argv[]);
+
+static void
+test_serialize_list(int *ntests_out, int *errors_out)
+{
+    int ntests = *ntests_out;
+    int errors = *errors_out;
+    const char *expected = "myvar=a value with spaces,this\\,and\\,that,\\,";
+    struct list_members members = SLIST_HEAD_INITIALIZER(members);
+    struct list_member lm1, lm2, lm3;
+    char *result;
+
+    lm1.value = "a value with spaces";
+    lm2.value = "this,and,that";
+    lm3.value = ",";
+    SLIST_INSERT_HEAD(&members, &lm3, entries);
+    SLIST_INSERT_HEAD(&members, &lm2, entries);
+    SLIST_INSERT_HEAD(&members, &lm1, entries);
+
+    ntests++;
+    result = serialize_list("myvar", &members);
+    if (result == NULL) {
+	sudo_warnx("serialize_list returns NULL");
+	++errors;
+	goto done;
+    }
+    ntests++;
+    if (strcmp(result, expected) != 0) {
+	sudo_warnx("got \"%s\", expected \"%s\"", result, expected);
+	++errors;
+	goto done;
+    }
+
+done:
+    *ntests_out = ntests;
+    *errors_out = errors;
+}
+
+int
+main(int argc, char *argv[])
+{
+    int ntests = 0, errors = 0;
+
+    initprogname(argc > 0 ? argv[0] : "check_serialize_list");
+
+    test_serialize_list(&ntests, &errors);
+
+    if (ntests != 0) {
+	printf("%s: %d tests run, %d errors, %d%% success rate\n",
+	    getprogname(), ntests, errors, (ntests - errors) * 100 / ntests);
+    }
+
+    exit(errors);
+}

plugins/sudoers/regress/unescape/check_unesc.c

@@ -1,7 +1,7 @@
 /*
  * SPDX-License-Identifier: ISC
  *
- * Copyright (c) 2021 Todd C. Miller <Todd.Miller@sudo.ws>
+ * Copyright (c) 2021-2022 Todd C. Miller <Todd.Miller@sudo.ws>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -31,7 +31,10 @@ struct test_data {
     char *result;
     size_t result_len;
     size_t bufsize;
-} test_data[] = {
+};
+
+/* strlcpy_unescape() does not unescape whitespace */
+static struct test_data strlcpy_unescape_test_data[] = {
     { "\\\0ABC", "\\", 1, 2 },			/* 1 */
     { "\\ \\;", "\\ ;", 3, 4 },			/* 2 */
     { "\\\t\\;", "\\\t;", 3, 4 },		/* 3 */
@@ -43,6 +46,20 @@ struct test_data {
     { NULL }
 };
 
+/* unescape_string() _does_ unescape whitespace */
+static struct test_data unescape_string_test_data[] = {
+    { "foo\\ bar", "foo bar", 7, 8 },		/* 1 */
+    { "foo\\,bar", "foo,bar", 7, 8 },		/* 2 */
+    { "baz \\", "baz \\", 5, 5 },		/* 3 */
+    { "\\foo", "foo", 3, 4 },			/* 4 */
+    { "var=aaa,b\\,b", "var=aaa,b,b", 11, 12 },	/* 5 */
+    { "\\a\\ b\\ c\\\\", "a b c\\", 6, 10 },	/* 6 */
+    { "\\", "\\", 1, 1 },			/* 7 */
+    { "foo", "foo", 3, 3 },			/* 8 */
+    { "", "", 0, 0 },				/* 9 */
+    { NULL }
+};
+
 sudo_dso_public int main(int argc, char *argv[]);
 
 static void
@@ -54,7 +71,7 @@ test_strlcpy_unescape(int *ntests_out, int *errors_out)
     char buf[1024];
     size_t len;
 
-    for (td = test_data; td->input != NULL; td++) {
+    for (td = strlcpy_unescape_test_data; td->input != NULL; td++) {
 	ntests++;
 	memset(buf, 'A', sizeof(buf));
 	len = strlcpy_unescape(buf, td->input, td->bufsize);
@@ -85,6 +102,31 @@ test_strlcpy_unescape(int *ntests_out, int *errors_out)
     *errors_out = errors;
 }
 
+static void
+test_unescape_string(int *ntests_out, int *errors_out)
+{
+    int ntests = *ntests_out;
+    int errors = *errors_out;
+    struct test_data *td;
+    char buf[1024];
+
+    for (td = unescape_string_test_data; td->input != NULL; td++) {
+	ntests++;
+	memset(buf, 'A', sizeof(buf));
+	memcpy(buf, td->input, td->bufsize);
+	buf[td->bufsize] = '\0';
+	unescape_string(buf);
+	if (strcmp(td->result, buf) != 0) {
+	    sudo_warnx("%d: \"%s\": got \"%s\", expected \"%s\"",
+		ntests, td->input, buf, td->result);
+	    errors++;
+	}
+    }
+
+    *ntests_out = ntests;
+    *errors_out = errors;
+}
+
 static void
 test_strvec_join(char sep, int *ntests_out, int *errors_out)
 {
@@ -132,6 +174,9 @@ main(int argc, char *argv[])
     /* strlcpy_unescape tests */
     test_strlcpy_unescape(&ntests, &errors);
 
+    /* unescape_string test */
+    test_unescape_string(&ntests, &errors);
+
     /* strvec_join test */
     test_strvec_join(' ', &ntests, &errors);
     test_strvec_join('\n', &ntests, &errors);

plugins/sudoers/serialize_list.c

@@ -0,0 +1,82 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2019, 2022 Todd C. Miller <Todd.Miller@sudo.ws>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * This is an open source non-commercial project. Dear PVS-Studio, please check it.
+ * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
+ */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "sudoers.h"
+
+/*
+ * Convert struct list_members to a comma-separated string with
+ * the given variable name.  Escapes backslashes and commas.
+ */
+char *
+serialize_list(const char *varname, struct list_members *members)
+{
+    struct list_member *lm, *next;
+    size_t len, result_size;
+    char *cp, *result;
+    debug_decl(serialize_list, SUDOERS_DEBUG_PLUGIN);
+
+    result_size = strlen(varname) + 1;
+    SLIST_FOREACH(lm, members, entries) {
+	for (cp = lm->value; *cp != '\0'; cp++) {
+	    result_size++;
+	    if (*cp == '\\' || *cp == ',')
+		result_size++;
+	}
+	result_size++;
+    }
+    if ((result = malloc(result_size)) == NULL)
+	goto bad;
+    /* No need to check len for overflow here. */
+    len = strlcpy(result, varname, result_size);
+    result[len++] = '=';
+    SLIST_FOREACH_SAFE(lm, members, entries, next) {
+	for (cp = lm->value; *cp != '\0'; cp++) {
+	    bool escape = (*cp == '\\' || *cp == ',');
+	    if (len + 1 + escape >= result_size) {
+		sudo_warnx(U_("internal error, %s overflow"), __func__);
+		goto bad;
+	    }
+	    if (escape)
+		result[len++] = '\\';
+	    result[len++] = *cp;
+	}
+	if (next != NULL) {
+	    if (len + 1 >= result_size) {
+		sudo_warnx(U_("internal error, %s overflow"), __func__);
+		goto bad;
+	    }
+	    result[len++] = ',';
+	}
+	result[len] = '\0';
+    }
+    debug_return_str(result);
+bad:
+    free(result);
+    debug_return_str(NULL);
+}

plugins/sudoers/sudoers.h

@@ -467,4 +467,10 @@ size_t strlcpy_unescape(char *dst, const char *src, size_t size);
 /* strvec_join.c */
 char *strvec_join(char *const argv[], char sep, size_t (*cpy)(char *, const char *, size_t));
 
+/* unesc_str.c */
+void unescape_string(char *str);
+
+/* serialize_list.c */
+char *serialize_list(const char *varname, struct list_members *members);
+
 #endif /* SUDOERS_SUDOERS_H */

plugins/sudoers/unesc_str.c

@@ -0,0 +1,42 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2022 Todd C. Miller <Todd.Miller@sudo.ws>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * This is an open source non-commercial project. Dear PVS-Studio, please check it.
+ * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
+ */
+
+#include <string.h>
+
+/*
+ * Remove backslash escape chars.
+ */
+void
+unescape_string(char *str)
+{
+    char *cp = str;
+    char *ep = str + strlen(str);
+
+    while ((cp = strchr(cp, '\\')) != NULL) {
+	if (cp[1] == '\0')
+	    break;
+	memmove(cp, cp + 1, (size_t)(ep - cp));
+	cp++;
+	ep--;
+    }
+}