conf: rework allow/deny parser

Refactor the (cmd)allow/deny parser and make it more strict in what
input it accepts. Check the scanned numbers and require whole input to
be processed.

Move the parser to cmdparse to make it available to the client.

cmdparse.c

@@ -181,6 +181,85 @@ CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src)
 
 /* ================================================== */
 
+int
+CPS_ParseAllowDeny(char *line, int *all, IPAddr *ip, int *subnet_bits)
+{
+  char *p, *net, *slash;
+  uint32_t a, b, c;
+  int bits, len, n;
+
+  p = CPS_SplitWord(line);
+
+  if (strcmp(line, "all") == 0) {
+    *all = 1;
+    net = p;
+    p = CPS_SplitWord(p);
+  } else {
+    *all = 0;
+    net = line;
+  }
+
+  /* Make sure there are no other arguments */
+  if (*p)
+    return 0;
+
+  /* No specified address or network means all IPv4 and IPv6 addresses */
+  if (!*net) {
+    ip->family = IPADDR_UNSPEC;
+    *subnet_bits = 0;
+    return 1;
+  }
+
+  slash = strchr(net, '/');
+  if (slash) {
+    if (sscanf(slash + 1, "%d%n", &bits, &len) != 1 || slash[len + 1] || bits < 0)
+      return 0;
+    *slash = '\0';
+  } else {
+    bits = -1;
+  }
+
+  if (UTI_StringToIP(net, ip)) {
+    if (bits >= 0)
+      *subnet_bits = bits;
+    else
+      *subnet_bits = ip->family == IPADDR_INET6 ? 128 : 32;
+    return 1;
+  }
+
+  /* Check for a shortened IPv4 network notation using only 1, 2, or 3 decimal
+     numbers.  This is different than the numbers-and-dots notation accepted
+     by inet_aton()! */
+
+  a = b = c = 0;
+  n = sscanf(net, "%"PRIu32"%n.%"PRIu32"%n.%"PRIu32"%n", &a, &len, &b, &len, &c, &len);
+
+  if (n > 0 && !net[len]) {
+    if (a > 255 || b > 255 || c > 255)
+      return 0;
+
+    ip->family = IPADDR_INET4;
+    ip->addr.in4 = (a << 24) | (b << 16) | (c << 8);
+
+    if (bits >= 0)
+      *subnet_bits = bits;
+    else
+      *subnet_bits = n * 8;
+
+    return 1;
+  }
+
+  /* The last possibility is a hostname */
+  if (bits < 0 && DNS_Name2IPAddress(net, ip, 1) == DNS_Success) {
+    *subnet_bits = ip->family == IPADDR_INET6 ? 128 : 32;
+    return 1;
+  }
+
+  return 0;
+}
+
+/* ================================================== */
+
 int
 CPS_ParseLocal(char *line, int *stratum, int *orphan, double *distance)
 {

cmdparse.h

@@ -39,6 +39,9 @@ typedef struct {
 /* Parse a command to add an NTP server or peer */
 extern int CPS_ParseNTPSourceAdd(char *line, CPS_NTP_Source *src);
   
+/* Parse a command to allow/deny access */
+extern int CPS_ParseAllowDeny(char *line, int *all, IPAddr *ip, int *subnet_bits);
+
 /* Parse a command to enable local reference */
 extern int CPS_ParseLocal(char *line, int *stratum, int *orphan, double *distance);
 

conf.c

@@ -1217,100 +1217,18 @@ parse_ntstrustedcerts(char *line)
 static void
 parse_allow_deny(char *line, ARR_Instance restrictions, int allow)
 {
-  char *p;
-  unsigned long a, b, c, d, n;
-  int all = 0;
-  AllowDeny *new_node = NULL;
-  IPAddr ip_addr;
+  int all, subnet_bits;
+  AllowDeny *node;
+  IPAddr ip;
 
-  p = line;
-
-  if (!strncmp(p, "all", 3)) {
-    all = 1;
-    p = CPS_SplitWord(line);
-  }
-
-  if (!*p) {
-    /* Empty line applies to all addresses */
-    new_node = (AllowDeny *)ARR_GetNewElement(restrictions);
-    new_node->allow = allow;
-    new_node->all = all;
-    new_node->ip.family = IPADDR_UNSPEC;
-    new_node->subnet_bits = 0;
-  } else {
-    char *slashpos;
-    slashpos = strchr(p, '/');
-    if (slashpos) *slashpos = 0;
-
-    check_number_of_args(p, 1);
-    n = 0;
-    if (UTI_StringToIP(p, &ip_addr) ||
-        (n = sscanf(p, "%lu.%lu.%lu.%lu", &a, &b, &c, &d)) >= 1) {
-      new_node = (AllowDeny *)ARR_GetNewElement(restrictions);
-      new_node->allow = allow;
-      new_node->all = all;
-
-      if (n == 0) {
-        new_node->ip = ip_addr;
-        if (ip_addr.family == IPADDR_INET6)
-          new_node->subnet_bits = 128;
-        else
-          new_node->subnet_bits = 32;
-      } else {
-        new_node->ip.family = IPADDR_INET4;
-
-        a &= 0xff;
-        b &= 0xff;
-        c &= 0xff;
-        d &= 0xff;
-        
-        switch (n) {
-          case 1:
-            new_node->ip.addr.in4 = (a<<24);
-            new_node->subnet_bits = 8;
-            break;
-          case 2:
-            new_node->ip.addr.in4 = (a<<24) | (b<<16);
-            new_node->subnet_bits = 16;
-            break;
-          case 3:
-            new_node->ip.addr.in4 = (a<<24) | (b<<16) | (c<<8);
-            new_node->subnet_bits = 24;
-            break;
-          case 4:
-            new_node->ip.addr.in4 = (a<<24) | (b<<16) | (c<<8) | d;
-            new_node->subnet_bits = 32;
-            break;
-          default:
-            assert(0);
-        }
-      }
-      
-      if (slashpos) {
-        int specified_subnet_bits, n;
-        n = sscanf(slashpos+1, "%d", &specified_subnet_bits);
-        if (n == 1) {
-          new_node->subnet_bits = specified_subnet_bits;
-        } else {
+  if (!CPS_ParseAllowDeny(line, &all, &ip, &subnet_bits))
     command_parse_error();
-        }
-      }
 
-    } else {
-      if (!slashpos && DNS_Name2IPAddress(p, &ip_addr, 1) == DNS_Success) {
-        new_node = (AllowDeny *)ARR_GetNewElement(restrictions);
-        new_node->allow = allow;
-        new_node->all = all;
-        new_node->ip = ip_addr;
-        if (ip_addr.family == IPADDR_INET6)
-          new_node->subnet_bits = 128;
-        else
-          new_node->subnet_bits = 32;
-      } else {
-        command_parse_error();
-      }      
-    }
-  }
+  node = ARR_GetNewElement(restrictions);
+  node->allow = allow;
+  node->all = all;
+  node->ip = ip;
+  node->subnet_bits = subnet_bits;
 }
   
 /* ================================================== */