Resolve all IPv4 addresses for domain names (if possible).

Return false in is_ssh_host() if an invalid IP address ([0-9\.]* which is not ^[0-9]+(\.[0-9]+){3}$)
Force lowercase in is_ssh_dest() and add_ssh_dest()

README.md

@@ -147,5 +147,3 @@ I am particually interested in any interesting `[line]` outputs associated with
 - `find ... -readable ...` is used in the script in multiple places. The `-readable` flag is not supported on all versions of `find(1)`.
 
 - The script does not currently look for SSH agent sockets.
-
-- The script does not properly resolve domains with multiple IPv4 addresses.

Snake.nocomments.sh

@@ -994,7 +994,7 @@ local ssh_dest
 declare -A valid_ssh_dests
 declare -A resolved_hosts
 local res
-local mac
+local use_mac
 local to
 if command -v timeout >/dev/null 2>&1; then
 to="timeout 5"
@@ -1003,7 +1003,7 @@ if getent ahostsv4 -- 1.1.1.1 >/dev/null 2>&1; then
 res="$to getent ahostsv4 --"
 elif dscacheutil -q host -a name 1.1.1.1 >/dev/null 2>&1; then
 res="$to dscacheutil -q host -a name"
-mac="1"
+use_mac="1"
 else
 printf "INTERNAL_MSG: command not found: RESOLVE (%s)\n" "$(uname -a 2>/dev/null)"
 fin
@@ -1027,27 +1027,32 @@ is_ssh_dest "$ssh_dest" || continue
 ssh_user="${ssh_dest%%@*}"
 ssh_host="${ssh_dest#*@}"
 if [[ -v 'resolved_hosts["$ssh_host"]' || ${#resolved_hosts["$ssh_host"]} -gt 0 ]]; then
-resolved_ssh_host="${resolved_hosts["$ssh_host"]}"
+:
 else
-if [[ -n "$mac" ]]; then
+local resolved_ssh_hosts
-resolved_ssh_host="$($res "$ssh_host" 2>/dev/null | grep -F 'ip_address:')"
+if [[ -n "$use_mac" ]]; then
-resolved_ssh_host="${resolved_ssh_host#* }"
+resolved_ssh_hosts="$($res "$ssh_host" 2>/dev/null | awk '/ip_address:/{print $NF}')"
 else
-resolved_ssh_host="$($res "$ssh_host" 2>/dev/null)"
+resolved_ssh_hosts="$($res "$ssh_host" 2>/dev/null | awk '/RAW/{print $1}')"
-resolved_ssh_host="${resolved_ssh_host%% *}"
 fi
+for resolved_ssh_host in "${resolved_ssh_hosts[@]}"; do
 if [[ "${resolved_ssh_host:0:1}" =~ [12] ]]; then
 [[ "$resolved_ssh_host" =~ ^127\. ]] && resolved_ssh_host="127.0.0.1"
-resolved_hosts["$ssh_host"]="$resolved_ssh_host"
+[[ -v '_ignored_hosts["$resolved_ssh_host"]' || ${#_ignored_hosts["$resolved_ssh_host"]} -gt 0 ]] && continue
+resolved_hosts["$ssh_host"]+="$resolved_ssh_host "
 else
-_ignored_hosts["$ssh_host"]=1
 [[ -n "$resolved_ssh_host" ]] && _ignored_hosts["$resolved_ssh_host"]=1
+fi
+done
+fi
+if [[ "${#resolved_hosts["$ssh_host"]}" -lt 7 ]]; then
+_ignored_hosts["$ssh_host"]=1
 continue
 fi
-fi
+for resolved_ssh_host in ${resolved_hosts["$ssh_host"]}; do
-[[ -v '_ignored_hosts["$resolved_ssh_host"]' || ${#_ignored_hosts["$resolved_ssh_host"]} -gt 0 ]] && _ignored_hosts["$ssh_host"]=1
 valid_ssh_dests["$ssh_user@$resolved_ssh_host"]=1
 done
+done
 ssh_dests=()
 for ssh_dest in "${!valid_ssh_dests[@]}"; do
 add_ssh_dest "$ssh_dest"
@@ -1088,6 +1093,9 @@ ssh_host="$1"
 [[ -v 'ssh_hosts["$ssh_host"]' || ${#ssh_hosts["$ssh_host"]} -gt 0 ]] && return 0
 [[ "$ssh_host" =~ ^$allowed_host_chars+$ ]] || return 1
 [[ "${ssh_host:0:1}" == "-" || "${ssh_host:0-1}" == "-" || "${ssh_host:0:1}" == "." || "${ssh_host:0-1}" == "." || "$ssh_host" == *"-."* || "$ssh_host" == *"--"* ]] && return 1
+if [[ "$ssh_host" =~ ^[0-9.]+$ ]]; then
+[[ "$ssh_host" =~ ^[0-9]+(\.[0-9]+){3}$ ]] || return 1
+fi
 return 0
 }
 is_ssh_dest() {
@@ -1096,6 +1104,7 @@ local ssh_host
 local ssh_dest
 ssh_dest="$1"
 [[ -z "$ssh_dest" ]] && return 1
+ssh_dest="${ssh_dest,,}"
 [[ -v '_ignored_dests["$ssh_dest"]' || ${#_ignored_dests["$ssh_dest"]} -gt 0 ]] && return 1
 ssh_user="${ssh_dest%%@*}"
 ssh_host="${ssh_dest#*@}"
@@ -1119,6 +1128,7 @@ local ssh_dest
 local ssh_host
 local ssh_user
 ssh_dest="$1"
+ssh_dest="${ssh_dest,,}"
 ssh_user="${ssh_dest%%@*}"
 ssh_host="${ssh_dest#*@}"
 is_ssh_dest "$ssh_dest" && ssh_dests["$ssh_dest"]=1 && ssh_hosts["$ssh_host"]=1 && ssh_users["$ssh_user"]=1 && return 0

Snake.sh

@@ -1672,13 +1672,12 @@ combinate_interesting_users_hosts() {
 }
 
 # Deduplicate ssh_dests by resolving the hosts for each ssh_dest, checking whether the user, host, or resolved dest is ignored, then adding the destinations back to the original ssh_dests array.
-# TODO: doesn't support hosts with multiple hosts (4 ips for 1 domain), and in fact may even break that.
 deduplicate_resolved_hosts_keys() {
   local ssh_dest
   declare -A valid_ssh_dests
   declare -A resolved_hosts
   local res
-  local mac
+  local use_mac
   local to
 
   # DNS timeout of 5 seconds per address (bleh, hack).
@@ -1692,7 +1691,7 @@ deduplicate_resolved_hosts_keys() {
   # Otherwise dscacheutils for mac.
   elif dscacheutil -q host -a name 1.1.1.1 >/dev/null 2>&1; then
     res="$to dscacheutil -q host -a name"
-    mac="1"
+    use_mac="1"
   else
     # If we can't use getent or dscacheutil, we're on an unknown type of system (with bash?!)
     # Use printf instead of chained_print() to be consistent.
@@ -1724,45 +1723,52 @@ deduplicate_resolved_hosts_keys() {
     # Make everything lower case.
     ssh_dest="${ssh_dest,,}"
 
-    is_ssh_dest "$ssh_dest" || continue
+    is_ssh_dest "$ssh_dest" || continue # Checks if the host has been ignored in this loop
 
     ssh_user="${ssh_dest%%@*}"
     ssh_host="${ssh_dest#*@}"
 
     # Check if the host has already been resolved. If it has, use the internally cached answer.
     if [[ -v 'resolved_hosts["$ssh_host"]' || ${#resolved_hosts["$ssh_host"]} -gt 0 ]]; then
-      resolved_ssh_host="${resolved_hosts["$ssh_host"]}"
+      :
     else
       # If the host has not already been resolved, resolve it.
+      # If resolution of ${resolved_hosts["$ssh_host"]} failed before, we won't hit this code path because the host will be added to _ignored_hosts (and will be skipped using is_ssh_dest().
       # macos
-      if [[ -n "$mac" ]]; then
+      local resolved_ssh_hosts # list of ipv4 addresses for a host
-        resolved_ssh_host="$($res "$ssh_host" 2>/dev/null | grep -F 'ip_address:')"
+      if [[ -n "$use_mac" ]]; then
-        resolved_ssh_host="${resolved_ssh_host#* }" # format is 'ip_address: ip'
+        resolved_ssh_hosts="$($res "$ssh_host" 2>/dev/null | awk '/ip_address:/{print $NF}')"
       else
-        resolved_ssh_host="$($res "$ssh_host" 2>/dev/null)"
+      # linux
-        resolved_ssh_host="${resolved_ssh_host%% *}" # format is 'ip\t[junk]
+        resolved_ssh_hosts="$($res "$ssh_host" 2>/dev/null | awk '/RAW/{print $1}')"
       fi
 
+      for resolved_ssh_host in "${resolved_ssh_hosts[@]}"; do
         # Answer must begin with 1 or 2 ($res 0.1.2.3 will respond with 0.1.2.3).
         if [[ "${resolved_ssh_host:0:1}" =~ [12] ]]; then
           [[ "$resolved_ssh_host" =~ ^127\. ]] && resolved_ssh_host="127.0.0.1" # If it's loopback, always use 127.0.0.1
+          [[ -v '_ignored_hosts["$resolved_ssh_host"]' || ${#_ignored_hosts["$resolved_ssh_host"]} -gt 0 ]] && continue
           # Cache the host
-        resolved_hosts["$ssh_host"]="$resolved_ssh_host"
+          resolved_hosts["$ssh_host"]+="$resolved_ssh_host "
         else
-        # Ignore this host
+          # Ignore this RESOLVED host (might save us a few cycles).
-        _ignored_hosts["$ssh_host"]=1
+          # Don't add the ssh_host to _ignored_hosts become it may have non-ignored hosts, too.
-        # Also ignore the resolved host (which may not necessarily be the same as the host).
           [[ -n "$resolved_ssh_host" ]] && _ignored_hosts["$resolved_ssh_host"]=1
+        fi
+      done
+    fi
+
+    # No IPs resolved for the host, add the host to _ignored_host.
+    if [[ "${#resolved_hosts["$ssh_host"]}" -lt 7 ]]; then
+      _ignored_hosts["$ssh_host"]=1
       continue
     fi
-    fi
-
-    # Check whether the resolved host is ignored. If so, also add the unresolved host to _ignored_hosts.
-    [[ -v '_ignored_hosts["$resolved_ssh_host"]' || ${#_ignored_hosts["$resolved_ssh_host"]} -gt 0 ]] && _ignored_hosts["$ssh_host"]=1
-    # add_ssh_dest will check whether the $ssh_user@$resolved_ssh_host is ignored.
 
+    # Loop through each host (which are space-separated now), so no quotation marks.
+    for resolved_ssh_host in ${resolved_hosts["$ssh_host"]}; do
       valid_ssh_dests["$ssh_user@$resolved_ssh_host"]=1
     done
+  done
 
   ssh_dests=()
 
@@ -1834,6 +1840,10 @@ is_ssh_host() {
 
   [[ "${ssh_host:0:1}" == "-" || "${ssh_host:0-1}" == "-" || "${ssh_host:0:1}" == "." || "${ssh_host:0-1}" == "." || "$ssh_host" == *"-."* || "$ssh_host" == *"--"* ]] && return 1
 
+  if [[ "$ssh_host" =~ ^[0-9.]+$ ]]; then
+    [[ "$ssh_host" =~ ^[0-9]+(\.[0-9]+){3}$ ]] || return 1
+  fi
+
   return 0
 }
 
@@ -1847,6 +1857,8 @@ is_ssh_dest() {
 
   [[ -z "$ssh_dest" ]] && return 1
 
+  ssh_dest="${ssh_dest,,}"
+
   # XXX: The below line is intrinsically flawed because even if $ssh_dest is already in ssh_dests, this does not mean $ssh_host has not been added to $_ignored_hosts. We keep it here to remember not to add it again.
   # [[ -v 'ssh_dests["$ssh_dest"]' || ${#ssh_dests["$ssh_dest"]} -gt 0 ]] && return 0
 
@@ -1888,6 +1900,7 @@ add_ssh_dest() {
   local ssh_user
 
   ssh_dest="$1"
+  ssh_dest="${ssh_dest,,}"
   ssh_user="${ssh_dest%%@*}"
   ssh_host="${ssh_dest#*@}"