From 820b0cceef0b67b041973da4041ea53d5e276363 Mon Sep 17 00:00:00 2001
From: Mark Andrews <marka@isc.org>
Date: Tue, 20 Jun 2023 15:21:36 +1000
Subject: [PATCH] Limit isccc_cc_fromwire recursion depth

Named and rndc do not need a lot of recursion so the depth is
set to 10.

---
 lib/isccc/cc.c                   | 39 ++++++++++++++++++++++++--------
 lib/isccc/include/isccc/result.h |  4 +++-
 lib/isccc/result.c               |  4 +++-
 3 files changed, 35 insertions(+), 12 deletions(-)

diff --git a/lib/isccc/cc.c b/lib/isccc/cc.c
index 0be28b9..3744d0f 100644
--- a/lib/isccc/cc.c
+++ b/lib/isccc/cc.c
@@ -50,6 +50,10 @@
 
 #define MAX_TAGS     256
 #define DUP_LIFETIME 900
+#ifndef ISCCC_MAXDEPTH
+#define ISCCC_MAXDEPTH \
+	10 /* Big enough for rndc which just sends a string each way. */
+#endif
 
 typedef isccc_sexpr_t *sexpr_ptr;
 
@@ -480,19 +484,25 @@ verify(isccc_sexpr_t *alist, unsigned char *data, unsigned int length,
 
 static isc_result_t
 table_fromwire(isccc_region_t *source, isccc_region_t *secret,
-	       uint32_t algorithm, isccc_sexpr_t **alistp);
+	       uint32_t algorithm, unsigned int depth, isccc_sexpr_t **alistp);
 
 static isc_result_t
-list_fromwire(isccc_region_t *source, isccc_sexpr_t **listp);
+list_fromwire(isccc_region_t *source, unsigned int depth,
+	      isccc_sexpr_t **listp);
 
 static isc_result_t
-value_fromwire(isccc_region_t *source, isccc_sexpr_t **valuep) {
+value_fromwire(isccc_region_t *source, unsigned int depth,
+	       isccc_sexpr_t **valuep) {
 	unsigned int msgtype;
 	uint32_t len;
 	isccc_sexpr_t *value;
 	isccc_region_t active;
 	isc_result_t result;
 
+	if (depth > ISCCC_MAXDEPTH) {
+		return (ISCCC_R_MAXDEPTH);
+	}
+
 	if (REGION_SIZE(*source) < 1 + 4) {
 		return (ISC_R_UNEXPECTEDEND);
 	}
@@ -513,9 +523,9 @@ value_fromwire(isccc_region_t *source, isccc_sexpr_t **valuep) {
 			result = ISC_R_NOMEMORY;
 		}
 	} else if (msgtype == ISCCC_CCMSGTYPE_TABLE) {
-		result = table_fromwire(&active, NULL, 0, valuep);
+		result = table_fromwire(&active, NULL, 0, depth + 1, valuep);
 	} else if (msgtype == ISCCC_CCMSGTYPE_LIST) {
-		result = list_fromwire(&active, valuep);
+		result = list_fromwire(&active, depth + 1, valuep);
 	} else {
 		result = ISCCC_R_SYNTAX;
 	}
@@ -525,7 +535,7 @@ value_fromwire(isccc_region_t *source, isccc_sexpr_t **valuep) {
 
 static isc_result_t
 table_fromwire(isccc_region_t *source, isccc_region_t *secret,
-	       uint32_t algorithm, isccc_sexpr_t **alistp) {
+	       uint32_t algorithm, unsigned int depth, isccc_sexpr_t **alistp) {
 	char key[256];
 	uint32_t len;
 	isc_result_t result;
@@ -535,6 +545,10 @@ table_fromwire(isccc_region_t *source, isccc_region_t *secret,
 
 	REQUIRE(alistp != NULL && *alistp == NULL);
 
+	if (depth > ISCCC_MAXDEPTH) {
+		return (ISCCC_R_MAXDEPTH);
+	}
+
 	checksum_rstart = NULL;
 	first_tag = true;
 	alist = isccc_alist_create();
@@ -551,7 +565,7 @@ table_fromwire(isccc_region_t *source, isccc_region_t *secret,
 		GET_MEM(key, len, source->rstart);
 		key[len] = '\0'; /* Ensure NUL termination. */
 		value = NULL;
-		result = value_fromwire(source, &value);
+		result = value_fromwire(source, depth + 1, &value);
 		if (result != ISC_R_SUCCESS) {
 			goto bad;
 		}
@@ -589,14 +603,19 @@ bad:
 }
 
 static isc_result_t
-list_fromwire(isccc_region_t *source, isccc_sexpr_t **listp) {
+list_fromwire(isccc_region_t *source, unsigned int depth,
+	      isccc_sexpr_t **listp) {
 	isccc_sexpr_t *list, *value;
 	isc_result_t result;
 
+	if (depth > ISCCC_MAXDEPTH) {
+		return (ISCCC_R_MAXDEPTH);
+	}
+
 	list = NULL;
 	while (!REGION_EMPTY(*source)) {
 		value = NULL;
-		result = value_fromwire(source, &value);
+		result = value_fromwire(source, depth + 1, &value);
 		if (result != ISC_R_SUCCESS) {
 			isccc_sexpr_free(&list);
 			return (result);
@@ -628,7 +647,7 @@ isccc_cc_fromwire(isccc_region_t *source, isccc_sexpr_t **alistp,
 		return (ISCCC_R_UNKNOWNVERSION);
 	}
 
-	return (table_fromwire(source, secret, algorithm, alistp));
+	return (table_fromwire(source, secret, algorithm, 0, alistp));
 }
 
 static isc_result_t
diff --git a/lib/isccc/include/isccc/result.h b/lib/isccc/include/isccc/result.h
index 5346bab..5b6a876 100644
--- a/lib/isccc/include/isccc/result.h
+++ b/lib/isccc/include/isccc/result.h
@@ -46,8 +46,10 @@
 #define ISCCC_R_CLOCKSKEW (ISC_RESULTCLASS_ISCCC + 4)
 /*% Duplicate */
 #define ISCCC_R_DUPLICATE (ISC_RESULTCLASS_ISCCC + 5)
+/*% Maximum recursion depth */
+#define ISCCC_R_MAXDEPTH (ISC_RESULTCLASS_ISCCC + 6)
 
-#define ISCCC_R_NRESULTS 6 /*%< Number of results */
+#define ISCCC_R_NRESULTS 7 /*%< Number of results */
 
 ISC_LANG_BEGINDECLS
 
diff --git a/lib/isccc/result.c b/lib/isccc/result.c
index 9285435..1956cb1 100644
--- a/lib/isccc/result.c
+++ b/lib/isccc/result.c
@@ -36,12 +36,14 @@ static const char *text[ISCCC_R_NRESULTS] = {
 	"bad auth",	   /* 3 */
 	"expired",	   /* 4 */
 	"clock skew",	   /* 5 */
-	"duplicate"	   /* 6 */
+	"duplicate",	   /* 6 */
+	"max depth"	   /* 7 */
 };
 
 static const char *ids[ISCCC_R_NRESULTS] = {
 	"ISCCC_R_UNKNOWNVERSION", "ISCCC_R_SYNTAX",    "ISCCC_R_BADAUTH",
 	"ISCCC_R_EXPIRED",	  "ISCCC_R_CLOCKSKEW", "ISCCC_R_DUPLICATE",
+	"ISCCC_R_MAXDEPTH"
 };
 
 #define ISCCC_RESULT_RESULTSET 2
-- 
2.33.0

