MDEV-25759: is_local_ip function can come to incorrect conclusion

The is_local_ip function that used in Galera SST scripts now
incorrectly identifies ip-addresses falling under the "127.0.0.0/8"
netmask as non-local ip, although they certainly belong to the
loopback interface. This commit fixes this flaw.

scripts/wsrep_sst_common.sh

@@ -875,7 +875,9 @@ get_openssl()
     readonly OPENSSL_BINARY
 }
 
+#
 # Generate a string equivalent to 16 random bytes
+#
 wsrep_gen_secret()
 {
     get_openssl
@@ -889,16 +891,36 @@ wsrep_gen_secret()
     fi
 }
 
+#
+# Checking if the address passed to us is local.
+# If the second parameter is nonzero, then this function
+# does not check for matches with local domain names:
+#
 is_local_ip()
 {
-    [ "$1" = '127.0.0.1' ]      && return 0
-    [ "$1" = '127.0.0.2' ]      && return 0
-    [ "$1" = 'localhost' ]      && return 0
-    [ "$1" = '[::1]' ]          && return 0
-    [ "$1" = "$(hostname -s)" ] && return 0
-    [ "$1" = "$(hostname -f)" ] && return 0
-    [ "$1" = "$(hostname -d)" ] && return 0
-
+    # Rapid recognition of the most common cases:
+    [ "$1" = '127.0.0.1' -o \
+      "$1" = '127.0.0.2' -o \
+      "$1" = 'localhost' -o \
+      "$1" = '[::1]' ] && return 0
+    # If the address starts with "127." this is probably a local
+    # address, but we need to clarify what follows this prefix:
+    if [ "${1#127.}" != "$1" ]; then
+        # All 127.0.0.0/8 addresses are local:
+        if echo "$1" | grep -q -E '^127\.[0-9]+\.[0-9]+\.[0-9]+$'; then
+            return 0
+        fi
+    fi
+    # If the second parameter is nonzero, then we will skip
+    # the domain name check:
+    if [ "${2:-0}" -eq 0 ]; then
+       # We consider all the names of a given host to be local addresses:
+       [ "$1" = "$(hostname -s)" -o \
+         "$1" = "$(hostname -f)" -o \
+         "$1" = "$(hostname -d)" ] && return 0
+    fi
+    # Now let's check if the given address is assigned to
+    # one of the network cards:
     local ip_util="$(command -v ip)"
     if [ -n "$ip_util" ]; then
         # ip address show ouput format is " inet[6] <address>/<mask>":
@@ -914,7 +936,6 @@ is_local_ip()
                  | grep -F " $1 " >/dev/null && return 0
         fi
     fi
-
     return 1
 }
 

scripts/wsrep_sst_rsync.sh

@@ -250,19 +250,27 @@ else
     CAFILE_OPT=""
 fi
 
+VERIFY_OPT=""
+CHECK_OPT=""
+CHECK_OPT_LOCAL=""
 if [ "${SSLMODE#VERIFY}" != "$SSLMODE" ]
 then
     case "$SSLMODE" in
     'VERIFY_IDENTITY')
         VERIFY_OPT='verifyPeer = yes'
-        CHECK_OPT=""
         ;;
     'VERIFY_CA')
         VERIFY_OPT='verifyChain = yes'
-        if is_local_ip "$WSREP_SST_OPT_HOST_UNESCAPED"; then
-            CHECK_OPT='checkHost = localhost'
+        # check if the address is an ip-address (v4 or v6):
+        if echo "$WSREP_SST_OPT_HOST_UNESCAPED" | \
+           grep -q -E '^([0-9]+(\.[0-9]+){3,3}|[0-9a-fA-F]?(\:[0-9a-fA-F]*)+)$'
+        then
+            CHECK_OPT="checkIP = $WSREP_SST_OPT_HOST_UNESCAPED"
         else
-            CHECK_OPT='checkHost = $WSREP_SST_OPT_HOST_UNESCAPED'
+            CHECK_OPT="checkHost = $WSREP_SST_OPT_HOST"
+        fi
+        if is_local_ip "$WSREP_SST_OPT_HOST_UNESCAPED"; then
+            CHECK_OPT_LOCAL="checkHost = localhost"
         fi
         ;;
     *)
@@ -273,9 +281,6 @@ then
         wsrep_log_error "Can't have ssl-mode='$SSLMODE' without CA file"
         exit 22 # EINVAL
     fi
-else
-    VERIFY_OPT=""
-    CHECK_OPT=""
 fi
 
 STUNNEL=""
@@ -310,6 +315,7 @@ connect = $WSREP_SST_OPT_HOST_UNESCAPED:$WSREP_SST_OPT_PORT
 TIMEOUTclose = 0
 ${VERIFY_OPT}
 ${CHECK_OPT}
+${CHECK_OPT_LOCAL}
 EOF
     fi
 
@@ -566,6 +572,9 @@ foreground = yes
 pid = $STUNNEL_PID
 debug = warning
 client = no
+${VERIFY_OPT}
+${CHECK_OPT}
+${CHECK_OPT_LOCAL}
 [rsync]
 accept = $STUNNEL_ACCEPT
 exec = $(command -v rsync)
@@ -583,6 +592,9 @@ foreground = yes
 pid = $STUNNEL_PID
 debug = warning
 client = no
+${VERIFY_OPT}
+${CHECK_OPT}
+${CHECK_OPT_LOCAL}
 [rsync]
 accept = $STUNNEL_ACCEPT
 exec = $SHELL