expression: cleanup expr_ops_by_type() and handle u32 input

Make fewer assumptions about the underlying integer type of the enum.
Instead, be clear about where we have an untrusted uint32_t from netlink
and an enum. Rename expr_ops_by_type() to expr_ops_by_type_u32() to make
this clearer. Later we might make the enum as packed, when this starts
to matter more.

Also, only the code path expr_ops() wants strict validation and assert
against valid enum values. Move the assertion out of
__expr_ops_by_type(). Then expr_ops_by_type_u32() does not need to
duplicate the handling of EXPR_INVALID. We still need to duplicate the
check against EXPR_MAX, to ensure that the uint32_t value can be cast to
an enum value.

[ Remove cast on EXPR_MAX. --pablo ]

Signed-off-by: Thomas Haller <thaller@redhat.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/include/expression.h b/include/expression.h
index 469f41ecd61359711128d0066eaf04c052e2a1cb..aede223db7418c85bfc482284c929cc44d514ff9 100644 (file)
--- a/include/expression.h
+++ b/include/expression.h
@@ -189,7 +189,7 @@ struct expr_ops {
 };
 
 const struct expr_ops *expr_ops(const struct expr *e);
-const struct expr_ops *expr_ops_by_type(enum expr_types etype);
+const struct expr_ops *expr_ops_by_type_u32(uint32_t value);
 
 /**
  * enum expr_flags

diff --git a/src/expression.c b/src/expression.c
index 87d5a9fcbe09ad70dd4b639e344dd689a1296912..c914795041e6fe3a3d3234d624a90f84cb1e6a57 100644 (file)
--- a/src/expression.c
+++ b/src/expression.c
@@ -995,7 +995,7 @@ static struct expr *concat_expr_parse_udata(const struct nftnl_udata *attr)
                        goto err_free;
 
                etype = nftnl_udata_get_u32(nest_ud[NFTNL_UDATA_SET_KEY_CONCAT_SUB_TYPE]);
-               ops = expr_ops_by_type(etype);
+               ops = expr_ops_by_type_u32(etype);
                if (!ops || !ops->parse_udata)
                        goto err_free;
 
@@ -1509,9 +1509,7 @@ void range_expr_value_high(mpz_t rop, const struct expr *expr)
 static const struct expr_ops *__expr_ops_by_type(enum expr_types etype)
 {
        switch (etype) {
-       case EXPR_INVALID:
-               BUG("Invalid expression ops requested");
-               break;
+       case EXPR_INVALID: break;
        case EXPR_VERDICT: return &verdict_expr_ops;
        case EXPR_SYMBOL: return &symbol_expr_ops;
        case EXPR_VARIABLE: return &variable_expr_ops;
@@ -1543,20 +1541,23 @@ static const struct expr_ops *__expr_ops_by_type(enum expr_types etype)
        case EXPR_FLAGCMP: return &flagcmp_expr_ops;
        }
 
-       BUG("Unknown expression type %d\n", etype);
+       return NULL;
 }
 
 const struct expr_ops *expr_ops(const struct expr *e)
 {
-       return __expr_ops_by_type(e->etype);
+       const struct expr_ops *ops;
+
+       ops = __expr_ops_by_type(e->etype);
+       if (!ops)
+               BUG("Unknown expression type %d\n", e->etype);
+
+       return ops;
 }
 
-const struct expr_ops *expr_ops_by_type(enum expr_types value)
+const struct expr_ops *expr_ops_by_type_u32(uint32_t value)
 {
-       /* value might come from unreliable source, such as "udata"
-        * annotation of set keys.  Avoid BUG() assertion.
-        */
-       if (value == EXPR_INVALID || value > EXPR_MAX)
+       if (value > EXPR_MAX)
                return NULL;
 
        return __expr_ops_by_type(value);

diff --git a/src/netlink.c b/src/netlink.c
index 70ebf382b14f73d535177253c85ccfedb796cbd6..8af579c7b77862c027cf573cec2e312b494dab8a 100644 (file)
--- a/src/netlink.c
+++ b/src/netlink.c
@@ -878,8 +878,8 @@ static struct expr *set_make_key(const struct nftnl_udata *attr)
 {
        const struct nftnl_udata *ud[NFTNL_UDATA_SET_TYPEOF_MAX + 1] = {};
        const struct expr_ops *ops;
-       enum expr_types etype;
        struct expr *expr;
+       uint32_t etype;
        int err;
 
        if (!attr)
@@ -895,7 +895,7 @@ static struct expr *set_make_key(const struct nftnl_udata *attr)
                return NULL;
 
        etype = nftnl_udata_get_u32(ud[NFTNL_UDATA_SET_TYPEOF_EXPR]);
-       ops = expr_ops_by_type(etype);
+       ops = expr_ops_by_type_u32(etype);
        if (!ops)
                return NULL;