From 62ad29e9b778f4419573c6b43fe7a0a00d783fe6 Mon Sep 17 00:00:00 2001 From: Kyle Bowman Date: Fri, 1 Oct 2021 18:41:37 +0100 Subject: extensions: libxt_NFLOG: don't truncate log prefix on print/save When parsing the rule, use a struct with a layout compatible to that of struct xt_nflog_info, but with a buffer large enough to contain the whole 128-character nft prefix. We always send the nflog-group to the kernel since, for nft, log and nflog targets are handled by the same kernel module, and are distinguished by whether they define an nflog-group. Therefore, we must send the group even if it is zero, or the kernel will configure the target as a log, not an nflog. Changes to nft_is_expr_compatible were made since only targets which have an `nflog-group` are compatible. Since nflog targets are distinguished by having an nflog-group, we ignore targets without one. We also set the copy-len flag if the snap-len is set since without this, iptables will mistake `nflog-size` for `nflog-range`. Signed-off-by: Kyle Bowman Signed-off-by: Alex Forster Signed-off-by: Jeremy Sowden Signed-off-by: Florian Westphal --- iptables/nft-shared.c | 52 +++++++++++++++++++++++++++++++++++++++++++++++++++ iptables/nft.c | 4 ++++ 2 files changed, 56 insertions(+) diff --git a/iptables/nft-shared.c b/iptables/nft-shared.c index 4394e8b7..d0d0d558 100644 --- a/iptables/nft-shared.c +++ b/iptables/nft-shared.c @@ -20,8 +20,10 @@ #include +#include #include #include +#include #include #include @@ -580,6 +582,54 @@ static void nft_parse_limit(struct nft_xt_ctx *ctx, struct nftnl_expr *e) ctx->h->ops->parse_match(match, ctx->cs); } +static void nft_parse_log(struct nft_xt_ctx *ctx, struct nftnl_expr *e) +{ + struct xtables_target *target; + struct xt_entry_target *t; + size_t target_size; + /* + * In order to handle the longer log-prefix supported by nft, instead of + * using struct xt_nflog_info, we use a struct with a compatible layout, but + * a larger buffer for the prefix. + */ + struct xt_nflog_info_nft { + __u32 len; + __u16 group; + __u16 threshold; + __u16 flags; + __u16 pad; + char prefix[NF_LOG_PREFIXLEN]; + } info = { + .group = nftnl_expr_get_u16(e, NFTNL_EXPR_LOG_GROUP), + .threshold = nftnl_expr_get_u16(e, NFTNL_EXPR_LOG_QTHRESHOLD), + }; + if (nftnl_expr_is_set(e, NFTNL_EXPR_LOG_SNAPLEN)) { + info.len = nftnl_expr_get_u32(e, NFTNL_EXPR_LOG_SNAPLEN); + info.flags = XT_NFLOG_F_COPY_LEN; + } + if (nftnl_expr_is_set(e, NFTNL_EXPR_LOG_PREFIX)) + snprintf(info.prefix, sizeof(info.prefix), "%s", + nftnl_expr_get_str(e, NFTNL_EXPR_LOG_PREFIX)); + + target = xtables_find_target("NFLOG", XTF_TRY_LOAD); + if (target == NULL) + return; + + target_size = XT_ALIGN(sizeof(struct xt_entry_target)) + + XT_ALIGN(sizeof(struct xt_nflog_info_nft)); + + t = xtables_calloc(1, target_size); + t->u.target_size = target_size; + strcpy(t->u.user.name, target->name); + t->u.user.revision = target->revision; + + target->t = t; + + memcpy(&target->t->data, &info, sizeof(info)); + + ctx->h->ops->parse_target(target, ctx->cs); +} + static void nft_parse_lookup(struct nft_xt_ctx *ctx, struct nft_handle *h, struct nftnl_expr *e) { @@ -629,6 +679,8 @@ void nft_rule_to_iptables_command_state(struct nft_handle *h, nft_parse_limit(&ctx, expr); else if (strcmp(name, "lookup") == 0) nft_parse_lookup(&ctx, h, expr); + else if (strcmp(name, "log") == 0) + nft_parse_log(&ctx, expr); expr = nftnl_expr_iter_next(iter); } diff --git a/iptables/nft.c b/iptables/nft.c index e4932a7a..72f7cf13 100644 --- a/iptables/nft.c +++ b/iptables/nft.c @@ -3542,6 +3542,10 @@ static int nft_is_expr_compatible(struct nftnl_expr *expr, void *data) nftnl_expr_get_u32(expr, NFTNL_EXPR_LIMIT_FLAGS) == 0) return 0; + if (!strcmp(name, "log") && + nftnl_expr_is_set(expr, NFTNL_EXPR_LOG_GROUP)) + return 0; + return -1; } -- cgit v1.2.3