link-local scope

README.md

@@ -154,3 +154,5 @@ See [Features](FEATURES.md)
   IPv6 address sorting as used by `ares_getaddrinfo()`.
 - [RFC7413](https://datatracker.ietf.org/doc/html/rfc7413).
   TCP FastOpen (TFO) for 0-RTT TCP Connection Resumption.
+- [RFC3986](https://datatracker.ietf.org/doc/html/rfc3986).
+  Uniform Resource Identifier (URI). Used for server configuration.

src/lib/include/ares_str.h

@@ -44,6 +44,7 @@ CARES_EXTERN size_t ares_strlen(const char *str);
 CARES_EXTERN size_t ares_strcpy(char *dest, const char *src, size_t dest_size);
 
 CARES_EXTERN ares_bool_t   ares_str_isnum(const char *str);
+CARES_EXTERN ares_bool_t   ares_str_isalnum(const char *str);
 
 CARES_EXTERN void          ares_str_ltrim(char *str);
 CARES_EXTERN void          ares_str_rtrim(char *str);

src/lib/str/ares_str.c

@@ -101,7 +101,23 @@ ares_bool_t ares_str_isnum(const char *str)
   }
 
   for (i = 0; str[i] != 0; i++) {
-    if (str[i] < '0' || str[i] > '9') {
+    if (!ares_isdigit(str[i])) {
+      return ARES_FALSE;
+    }
+  }
+  return ARES_TRUE;
+}
+
+ares_bool_t ares_str_isalnum(const char *str)
+{
+  size_t i;
+
+  if (str == NULL || *str == 0) {
+    return ARES_FALSE;
+  }
+
+  for (i = 0; str[i] != 0; i++) {
+    if (!ares_isdigit(str[i]) && !ares_isalpha(str[i])) {
       return ARES_FALSE;
     }
   }

src/lib/util/ares_uri.c

@@ -416,16 +416,43 @@ ares_status_t ares_uri_set_host(ares_uri_t *uri, const char *host)
 {
   struct ares_addr addr;
   size_t           addrlen;
+  char             hoststr[256];
+  char            *ll_scope;
 
-  if (uri == NULL || ares_strlen(host) == 0) {
+  if (uri == NULL || ares_strlen(host) == 0 ||
+      ares_strlen(host) >= sizeof(hoststr)) {
     return ARES_EFORMERR;
   }
 
+  ares_strcpy(hoststr, host, sizeof(hoststr));
+
+  /* Look for '%' which could be a link-local scope for ipv6 addresses and
+   * parse it off */
+  ll_scope = strchr(hoststr, '%');
+  if (ll_scope != NULL) {
+    *ll_scope = 0;
+    ll_scope++;
+    if (!ares_str_isalnum(ll_scope)) {
+      return ARES_EBADNAME;
+    }
+  }
+
   /* If its an IP address, normalize it */
   memset(&addr, 0, sizeof(addr));
   addr.family = AF_UNSPEC;
-  if (ares_dns_pton(host, &addr, &addrlen) != NULL) {
-    ares_inet_ntop(addr.family, &addr.addr, uri->host, sizeof(uri->host));
+  if (ares_dns_pton(hoststr, &addr, &addrlen) != NULL) {
+    char ipaddr[256];
+    ares_inet_ntop(addr.family, &addr.addr, ipaddr, sizeof(ipaddr));
+    /* Only IPv6 is allowed to have a scope */
+    if (ll_scope != NULL && addr.family != AF_INET6) {
+      return ARES_EBADNAME;
+    }
+
+    if (ll_scope != NULL) {
+      snprintf(uri->host, sizeof(uri->host), "%s%%%s", ipaddr, ll_scope);
+    } else {
+      ares_strcpy(uri->host, ipaddr, sizeof(uri->host));
+    }
     return ARES_SUCCESS;
   }
 
@@ -647,8 +674,6 @@ static ares_status_t ares_uri_write_scheme(ares_uri_t *uri, ares_buf_t *buf)
 static ares_status_t ares_uri_write_authority(ares_uri_t *uri, ares_buf_t *buf)
 {
   ares_status_t    status;
-  struct ares_addr addr;
-  size_t           addrlen;
   ares_bool_t      is_ipv6 = ARES_FALSE;
 
   if (ares_strlen(uri->username)) {
@@ -678,10 +703,19 @@ static ares_status_t ares_uri_write_authority(ares_uri_t *uri, ares_buf_t *buf)
   }
 
   /* We need to write ipv6 addresses with [ ] */
-  memset(&addr, 0, sizeof(addr));
-  addr.family = AF_INET6;
-  if (ares_dns_pton(uri->host, &addr, &addrlen) != NULL) {
+  if (strchr(uri->host, '%') != NULL) {
+    /* If we have a % in the name, it must be ipv6 link local scope, so we
+     * don't need to check anything else */
     is_ipv6 = ARES_TRUE;
+  } else {
+    /* Parse the host to see if it is an ipv6 address */
+    struct ares_addr addr;
+    size_t           addrlen;
+    memset(&addr, 0, sizeof(addr));
+    addr.family = AF_INET6;
+    if (ares_dns_pton(uri->host, &addr, &addrlen) != NULL) {
+      is_ipv6 = ARES_TRUE;
+    }
   }
 
   if (is_ipv6) {

src/lib/util/ares_uri.h

@@ -113,7 +113,8 @@ const char    *ares_uri_get_password(ares_uri_t *uri);
  */
 ares_status_t  ares_uri_set_host(ares_uri_t *uri, const char *host);
 
-/*! Retrieve the currently configured host (or ip address).
+/*! Retrieve the currently configured host (or ip address).  IPv6 addresses
+ *  May include a link-local scope (e.g. fe80::b542:84df:1719:65e3%en0).
  *
  *  \param[in] uri    Initialized URI object
  *  \return string containing host, maybe NULL if not set.

test/ares-test-fuzz-name.c

@@ -33,6 +33,11 @@
 
 int LLVMFuzzerTestOneInput(const unsigned char *data, unsigned long size);
 
+/* Fuzzing on a query name isn't very useful as its already fuzzed as part
+ * of the normal fuzzing operations.  So we'll disable this by default and
+ * instead use this same fuzzer to validate our URI scheme parsers accessed
+ * via ares_set_servers_csv() */
+#ifdef USE_LEGACY_FUZZERS
 /* Entrypoint for Clang's libfuzzer, exercising query creation. */
 int LLVMFuzzerTestOneInput(const unsigned char *data, unsigned long size)
 {
@@ -48,3 +53,27 @@ int LLVMFuzzerTestOneInput(const unsigned char *data, unsigned long size)
   free(name);
   return 0;
 }
+
+#else
+
+int LLVMFuzzerTestOneInput(const unsigned char *data, unsigned long size)
+{
+  ares_channel_t *channel = NULL;
+  char           *csv;
+
+  ares_library_init(ARES_LIB_INIT_ALL);
+  ares_init(&channel);
+
+  /* Need to null-term data */
+  csv = malloc(size + 1);
+  memcpy(csv, data, size);
+  csv[size] = '\0';
+  ares_set_servers_csv(channel, csv);
+  free(csv);
+
+  ares_destroy(channel);
+  ares_library_cleanup();
+
+  return 0;
+}
+#endif

test/ares-test-fuzz.c

@@ -31,7 +31,7 @@
 
 int LLVMFuzzerTestOneInput(const unsigned char *data, unsigned long size);
 
-#ifdef USE_LEGACY_PARSERS
+#ifdef USE_LEGACY_FUZZERS
 
 /* This implementation calls the legacy c-ares parsers, which historically
  * all used different logic and parsing.  As of c-ares 1.21.0 these are

test/ares-test-internal.cc

@@ -366,6 +366,7 @@ TEST_F(LibraryTest, URI) {
     { ARES_TRUE,  "https://www.example.com?key=%41%61%32%2D%2E%5f%7e%2F%3F%21%24%27%28%29%2a%2C%3b%3a%40", "https://www.example.com?key=Aa2-._~/?!$'()*,;:@" },
     { ARES_TRUE,  "dns+tls://192.168.1.1:53",                                                              NULL },
     { ARES_TRUE,  "dns+tls://[fe80::1]:53",                                                                NULL },
+    { ARES_TRUE,  "dns://[fe80::b542:84df:1719:65e3%en0]",                                                 NULL },
     { ARES_TRUE,  "dns+tls://[fe80:00::00:1]:53",                                                          "dns+tls://[fe80::1]:53" },
     { ARES_TRUE,  "d.n+s-tls://www.example.com",                                                           NULL },
     { ARES_FALSE, "dns*tls://www.example.com",                                                             NULL },