net: ip: account for the size in the inet_ntop code path

The code was writing to the dst without a verification check on
size which is not appropriate. The guard on the arguements should
be enforced and so just ensure the size is larger then the
definition of the strings from POSIX and return an error in those
cases.

Signed-off-by: Charles Hardin <[email protected]>

Author: ckhardin

drivers/modem/hl7800.c

@@ -286,7 +286,7 @@ struct xmodem_packet {
 #define MAX_PROFILE_LINE_LENGTH                                                \
 	MAX(sizeof(PROFILE_LINE_1), sizeof(PROFILE_LINE_2))
 
-#define IPV6_ADDR_FORMAT "####:####:####:####:####:####:####:####"
+#define IPV6_ADDR_FORMAT "####:####:####:####:####:####:xxx.xxx.xxx.xxx"
 #define HL7800_IPV6_ADDR_LEN                                                                       \
 	sizeof("a01.a02.a03.a04.a05.a06.a07.a08.a09.a10.a11.a12.a13.a14.a15.a16")
 

include/zephyr/net/net_ip.h

@@ -479,7 +479,7 @@ extern const struct in6_addr in6addr_loopback;
 /** @cond INTERNAL_HIDDEN */
 
 /* These are for internal usage of the stack */
-#define NET_IPV6_ADDR_LEN sizeof("xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx")
+#define NET_IPV6_ADDR_LEN sizeof("xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxx.xxx.xxx.xxx")
 #define NET_IPV4_ADDR_LEN sizeof("xxx.xxx.xxx.xxx")
 
 /** @endcond */

subsys/net/ip/utils.c

@@ -174,7 +174,13 @@ char *z_impl_net_addr_ntop(sa_family_t family, const void *src,
 	bool needcolon = false;
 	bool mapped = false;
 
-	if (family == AF_INET6) {
+	switch (family) {
+	case AF_INET6:
+		if (size < INET6_ADDRSTRLEN) {
+			/* POSIX definition is the size - includes nil */
+			return NULL;
+		}
+
 		net_ipv6_addr_copy_raw(addr6.s6_addr, src);
 		w = (uint16_t *)addr6.s6_addr16;
 		len = 8;
@@ -203,12 +209,20 @@ char *z_impl_net_addr_ntop(sa_family_t family, const void *src,
 		if (longest == 1U) {
 			pos = -1;
 		}
+		break;
+
+	case AF_INET:
+		if (size < INET_ADDRSTRLEN) {
+			/* POSIX definition is the size - includes nil */
+			return NULL;
+		}
 
-	} else if (family == AF_INET) {
 		net_ipv4_addr_copy_raw(addr.s4_addr, src);
 		len = 4;
 		delim = '.';
-	} else {
+		break;
+
+	default:
 		return NULL;
 	}
 
@@ -281,10 +295,6 @@ char *z_impl_net_addr_ntop(sa_family_t family, const void *src,
 		needcolon = true;
 	}
 
-	if (!(ptr - dst)) {
-		return NULL;
-	}
-
 	if (family == AF_INET) {
 		*(ptr - 1) = '\0';
 	} else {