retrieving content within XML tags

I've got a ver big XML with lots of information, I'm particularly interested in extracting the content of the following tags (config:tag1)

<config:tag1 var1="a" var2="b" var3="c"
    var4="d">
   <config:tag2 var5="abc" var6="def">
       <config:tag3 var7="foo1" var8="foo2" />
   </config:tag2>
</config:tag1>
<config:tag1 var1="h" var2="i" var3="j"
    var4="y">
   <config:tag2 var5="klm" var6="nop">
       <config:tag3 var7="foo3" var8="foo4" />
   </config:tag2>
</config:tag1>
<config:tag1 var1="m" var2="n" var3="o"
    var4="z">
   <config:tag2 var5="rop" var6="stv">
       <config:tag3 var7="foo5" var8="foo6" />
   </config:tag2>
</config:tag1>

I've tried with sed

sed -n '/config:tag1/{s/.*<config:tag1>//;s/<\/config:tag1.*//;p;}' file.xml

, awk

awk -F "[><]" '/config:tag1/{print $3}' file.xml

and grep

grep -oP '(?<=<config:tag1>).*(?=</config:tag1)' file.xml

with no success, what am I doing wrong?

expected output would be the lines with the all the content

<config:tag1 var1="a" var2="b" var3="c" var4="d">    <config:tag2 var5="abc" var6="def">    <config:tag3 var7="foo1" var8="foo2" /> 
  </config:tag2>    </config:tag1>
<config:tag1 var1="h" var2="i" var3="j" var4="y">    <config:tag2 var5="klm" var6="nop">    <config:tag3 var7="foo3" var8="foo4" /> 
   </config:tag2>    </config:tag1>
<config:tag1 var1="m" var2="n" var3="o" var4="z">    <config:tag2 var5="rop" var6="stv">    <config:tag3 var7="foo5" var8="foo6" /> 
   </config:tag2>    </config:tag1>