sepolgen: Support latest refpolicy interfaces

Some refpolicy interfaces use:

* "$" character in paths, for example in kernel/selinux.if:

    genfscon selinuxfs /booleans/$2 gen_context(system_u:object_r:$1,s0)

* empty members in ifelse statement, for example in system/init.if:

    ifelse(`$5',`',`',`
        ...
    ')

Modify sepolgen/refparser grammar accordingly.

This fixes the following syntax errors reported by sepolgen-ifgen:

    /usr/share/selinux/refpolicy/include/kernel/selinux.if: Syntax error
    on line 43 gen_context [type=GEN_CONTEXT]
    /usr/share/selinux/refpolicy/include/system/init.if: Syntax error on
    line 1416 ' [type=SQUOTE]
    /usr/share/selinux/refpolicy/include/system/init.if: Syntax error on
    line 1422 ' [type=SQUOTE]

Signed-off-by: Nicolas Iooss <[email protected]>

sepolgen/src/sepolgen/refparser.py

@@ -219,7 +219,7 @@
 t_EXPL = r'\!'
 t_EQUAL = r'\='
 t_NUMBER = r'[0-9\.]+'
-t_PATH = r'/[a-zA-Z0-9)_\.\*/]*'
+t_PATH = r'/[a-zA-Z0-9)_\.\*/\$]*'
 #t_IPV6_ADDR = r'[a-fA-F0-9]{0,4}:[a-fA-F0-9]{0,4}:([a-fA-F0-9]{0,4}:)*'
 
 # Ignore whitespace - this is a special token for ply that more efficiently
@@ -417,6 +417,7 @@ def p_tunable_policy(p):
 def p_ifelse(p):
  '''ifelse : IFELSE OPAREN TICK IDENTIFIER SQUOTE COMMA COMMA TICK IDENTIFIER SQUOTE COMMA TICK interface_stmts SQUOTE CPAREN optional_semi
  | IFELSE OPAREN TICK IDENTIFIER SQUOTE COMMA TICK IDENTIFIER SQUOTE COMMA TICK interface_stmts SQUOTE COMMA TICK interface_stmts SQUOTE CPAREN optional_semi
+ | IFELSE OPAREN TICK IDENTIFIER SQUOTE COMMA TICK SQUOTE COMMA TICK interface_stmts SQUOTE COMMA TICK interface_stmts SQUOTE CPAREN optional_semi
  '''
 # x = refpolicy.IfDef(p[4])
 # v = True