From f60ef911f1e05a88fae650c487965e7b85d17d2a Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Fri, 17 Mar 2023 10:16:45 +0100 Subject: evaluate: honor statement length in bitwise evaluation Get length from statement, instead infering it from the expression that is used to set the value. In the particular case of {ct|meta} mark, this is 32 bits. Otherwise, bytecode generation is not correct: # nft -c --debug=netlink 'add rule ip6 x y ct mark set ip6 dscp << 2 | 0x10' [ payload load 2b @ network header + 0 => reg 1 ] [ bitwise reg 1 = ( reg 1 & 0x0000c00f ) ^ 0x00000000 ] [ bitwise reg 1 = ( reg 1 >> 0x00000006 ) ] [ byteorder reg 1 = ntoh(reg 1, 2, 1) ] [ bitwise reg 1 = ( reg 1 << 0x00000002 ) ] [ bitwise reg 1 = ( reg 1 & 0x00000fef ) ^ 0x00000010 ] <--- incorrect! [ ct set mark with reg 1 ] the previous bitwise shift already upgraded to 32-bits (not visible from the netlink debug output above). After this patch, the last | 0x10 uses 32-bits: [ bitwise reg 1 = ( reg 1 & 0xffffffef ) ^ 0x00000010 ] note that mask 0xffffffef is used instead of 0x00000fef. Patch ("evaluate: support shifts larger than the width of the left operand") provides the statement length through eval context. Use it to evaluate the bitwise expression accordingly, otherwise bytecode is incorrect: # nft --debug=netlink add rule ip x y 'ct mark set ip dscp & 0x0f << 1 | 0xff000000' ip x y [ payload load 1b @ network header + 1 => reg 1 ] [ bitwise reg 1 = ( reg 1 & 0x000000fc ) ^ 0x00000000 ] [ bitwise reg 1 = ( reg 1 >> 0x00000002 ) ] [ bitwise reg 1 = ( reg 1 & 0x1e000000 ) ^ 0x000000ff ] <-- incorrect byteorder for OR [ byteorder reg 1 = ntoh(reg 1, 4, 4) ] <-- no needed for single ip dscp byte [ ct set mark with reg 1 ] Correct bytecode: # nft --debug=netlink add rule ip x y 'ct mark set ip dscp & 0x0f << 1 | 0xff000000 ip x y [ payload load 1b @ network header + 1 => reg 1 ] [ bitwise reg 1 = ( reg 1 & 0x000000fc ) ^ 0x00000000 ] [ bitwise reg 1 = ( reg 1 >> 0x00000002 ) ] [ bitwise reg 1 = ( reg 1 & 0x0000001e ) ^ 0xff000000 ] [ ct set mark with reg 1 ] Signed-off-by: Pablo Neira Ayuso --- src/evaluate.c | 27 +++++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-) (limited to 'src/evaluate.c') diff --git a/src/evaluate.c b/src/evaluate.c index 4178be4e..c4ddb007 100644 --- a/src/evaluate.c +++ b/src/evaluate.c @@ -1326,13 +1326,32 @@ static int expr_evaluate_shift(struct eval_ctx *ctx, struct expr **expr) static int expr_evaluate_bitwise(struct eval_ctx *ctx, struct expr **expr) { struct expr *op = *expr, *left = op->left; + const struct datatype *dtype; + unsigned int max_len; + int byteorder; + + if (ctx->stmt_len > left->len) { + max_len = ctx->stmt_len; + byteorder = BYTEORDER_HOST_ENDIAN; + dtype = &integer_type; + + /* Both sides need to be in host byte order */ + if (byteorder_conversion(ctx, &op->left, BYTEORDER_HOST_ENDIAN) < 0) + return -1; + + left = op->left; + } else { + max_len = left->len; + byteorder = left->byteorder; + dtype = left->dtype; + } - if (byteorder_conversion(ctx, &op->right, left->byteorder) < 0) + if (byteorder_conversion(ctx, &op->right, byteorder) < 0) return -1; - op->dtype = left->dtype; - op->byteorder = left->byteorder; - op->len = left->len; + datatype_set(op, dtype); + op->byteorder = byteorder; + op->len = max_len; if (expr_is_constant(left)) return constant_binop_simplify(ctx, expr); -- cgit v1.2.3