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netdb/dns: validate nameserver input in dns_add_nameserver #18670

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Merged
anchao merged 1 commit into from
Apr 7, 2026
+81 −21
Merged

netdb/dns: validate nameserver input in dns_add_nameserver #18670

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102 changes: 81 additions & 21 deletions libs/libc/netdb/lib_dnsaddserver.c
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Original file line number Diff line number Diff line change
Expand Up @@ -104,6 +104,46 @@ static int dns_check_nameserver(FAR void *arg, FAR struct sockaddr *addr,
return OK;
}

#ifdef CONFIG_NETDB_RESOLVCONF
static int dns_is_valid_nameserver(FAR const struct sockaddr *addr)
{
#ifdef CONFIG_NET_IPv4
if (addr->sa_family == AF_INET)
{
FAR const struct sockaddr_in *in4 =
(FAR const struct sockaddr_in *)addr;

if (net_ipv4addr_cmp(in4->sin_addr.s_addr, INADDR_ANY) ||
net_ipv4addr_cmp(in4->sin_addr.s_addr, INADDR_BROADCAST) ||
IN_MULTICAST(NTOHL(in4->sin_addr.s_addr)))
{
return -EINVAL;
}

return OK;
}
#endif

#ifdef CONFIG_NET_IPv6
if (addr->sa_family == AF_INET6)
{
FAR const struct sockaddr_in6 *in6 =
(FAR const struct sockaddr_in6 *)addr;

if (IN6_IS_ADDR_UNSPECIFIED(&in6->sin6_addr) ||
IN6_IS_ADDR_MULTICAST(&in6->sin6_addr))
{
return -EINVAL;
}

return OK;
}
#endif

return -ENOSYS;
}
#endif

/****************************************************************************
* Public Functions
****************************************************************************/
Expand All @@ -119,7 +159,7 @@ static int dns_check_nameserver(FAR void *arg, FAR struct sockaddr *addr,
#ifdef CONFIG_NETDB_RESOLVCONF
int dns_add_nameserver(FAR const struct sockaddr *addr, socklen_t addrlen)
{
FAR FILE *stream;
FAR FILE *stream = NULL;
char addrstr[DNS_MAX_ADDRSTR];
union dns_addr_u dns_addr;
FAR uint16_t *pport;
Expand All @@ -131,32 +171,30 @@ int dns_add_nameserver(FAR const struct sockaddr *addr, socklen_t addrlen)
#endif
int ret;

stream = fopen(CONFIG_NETDB_RESOLVCONF_PATH, "a+");
if (stream == NULL)
if (addr == NULL)
{
ret = -get_errno();
nerr("ERROR: Failed to open %s: %d\n",
CONFIG_NETDB_RESOLVCONF_PATH, ret);
DEBUGASSERT(ret < 0);
return ret;
return -EINVAL;
}

dns_lock();

#ifdef CONFIG_NET_IPv4
/* Check for an IPv4 address */

if (addr->sa_family == AF_INET)
{
if (addrlen < sizeof(struct sockaddr_in))
{
ret = -EINVAL;
goto errout;
return -EINVAL;
}
else
{
FAR struct sockaddr_in *in4 = (FAR struct sockaddr_in *)addr;

ret = dns_is_valid_nameserver(addr);
if (ret < 0)
{
return ret;
}

copylen = sizeof(struct sockaddr_in);
pport = &dns_addr.ipv4.sin_port;
if (inet_ntop(AF_INET, &in4->sin_addr, addrstr,
Expand All @@ -165,7 +203,7 @@ int dns_add_nameserver(FAR const struct sockaddr *addr, socklen_t addrlen)
ret = -get_errno();
nerr("ERROR: inet_ntop failed: %d\n", ret);
DEBUGASSERT(ret < 0);
goto errout;
return ret;
}
}
}
Expand All @@ -179,13 +217,18 @@ int dns_add_nameserver(FAR const struct sockaddr *addr, socklen_t addrlen)
{
if (addrlen < sizeof(struct sockaddr_in6))
{
ret = -EINVAL;
goto errout;
return -EINVAL;
}
else
{
FAR struct sockaddr_in6 *in6 = (FAR struct sockaddr_in6 *)addr;

ret = dns_is_valid_nameserver(addr);
if (ret < 0)
{
return ret;
}

copylen = sizeof(struct sockaddr_in6);
pport = &dns_addr.ipv6.sin6_port;
if (inet_ntop(AF_INET6, &in6->sin6_addr, addrstr,
Expand All @@ -194,18 +237,29 @@ int dns_add_nameserver(FAR const struct sockaddr *addr, socklen_t addrlen)
ret = -get_errno();
nerr("ERROR: inet_ntop failed: %d\n", ret);
DEBUGASSERT(ret < 0);
goto errout;
return ret;
}
}
}
else
#endif
{
nerr("ERROR: Unsupported family: %d\n", addr->sa_family);
ret = -ENOSYS;
goto errout;
return -ENOSYS;
}

stream = fopen(CONFIG_NETDB_RESOLVCONF_PATH, "a+");
if (stream == NULL)
{
ret = -get_errno();
nerr("ERROR: Failed to open %s: %d\n",
CONFIG_NETDB_RESOLVCONF_PATH, ret);
DEBUGASSERT(ret < 0);
return ret;
}

dns_lock();

memcpy(&dns_addr.addr, addr, copylen);

/* A port number of zero means to use the default DNS server port number */
Expand All @@ -227,9 +281,7 @@ int dns_add_nameserver(FAR const struct sockaddr *addr, socklen_t addrlen)
ret = OK;
}

dns_unlock();
fclose(stream);
return ret;
goto errout;
}

#if CONFIG_NETDB_DNSSERVER_NAMESERVERS > 1
Expand All @@ -246,6 +298,14 @@ int dns_add_nameserver(FAR const struct sockaddr *addr, socklen_t addrlen)

fclose(stream);
stream = fopen(CONFIG_NETDB_RESOLVCONF_PATH, "w");
if (stream == NULL)
{
ret = -get_errno();
nerr("ERROR: Failed to open %s: %d\n",
CONFIG_NETDB_RESOLVCONF_PATH, ret);
DEBUGASSERT(ret < 0);
goto errout;
}

/* Write the new record to the head of the resolv.conf file. */

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