[PATCH v3] wg: Support restricting address family of DNS resolved Endpoint
dxld at darkboxed.org
dxld at darkboxed.org
Tue Nov 1 11:07:26 UTC 2022
Hi,
Just a ping on this patch.
I've actually been able to find a workaround for this issue. We can leave
the peer Endpoints empty and use a PostUp action to fill it in like so:
PostUp = wg set %i peer $PUBKEY endpoint $(getent ahostsv6 host.example.net | sed -n '/^::ffff:/d;s/\s*DGRAM.*$//p'):51820
PostUp = wg set %i peer $PUBKEY endpoint $(getent ahostsv4 host.example.net | sed -n 's/\s*DGRAM.*$//p'):51820
I use `getent ahosts` since that comes with glibc and is thus available on
all my systems as opposed to say `host`.
This does have the quirk that for ahostsv6 we need to remove
ipv6-mapped-ipv4 addresses with a ::ffff: prefix since getent passes
AI_V4MAPPED to getaddrinfo unconditionally, but since it also spits out
DGRAM/STREAM/RAW addresses seperatly that's not toooo much uglyness.
I'd still like to get the proper solution is, especially since there is no
way this workaround will be viable on the mobile apps whereas the
AddressFamily= is easy to support there too.
--Daniel
On Mon, Aug 22, 2022 at 08:32:53PM +0200, Daniel Gröber wrote:
> When using wireguard tunnels for providing IPv6 connectivity to machines it
> can be important to pin which IP address family should be used.
>
> Consider a peer using a DNS name with both A/AAAA records, wg will
> currently blindly follow system policy and use the first address returned
> by getaddrinfo(). In typical deployments this will cause the IPv6 address
> of the peer to be used, however when the whole IPv6 internet is being
> routed over our wireguard all this accomplishes is a traffic black hole.
>
> Naturally this can be worked around by having different DNS names for
> v4-only / dual-stack addresses, however this may not be possible in some
> situations where, say, a dynamic-DNS service is also in use.
>
> To fix this we allow users to control which address family they want using
> the new AddressFamily= config option, see wg.8 for details. We also update
> reresolve-dns to take the AddressFamily option into account.
>
> We would like to note that the not_oif patch[1] would also alleviate this
> problem but since this never got merged it's not a workable solution.
>
> [1]: http://marc.info/?t=145452167200014&r=1&w=2
>
> Signed-off-by: Daniel Gröber <dxld at darkboxed.org>
> ---
> contrib/reresolve-dns/reresolve-dns.sh | 4 ++-
> src/config.c | 41 ++++++++++++++++++++------
> src/config.h | 2 +-
> src/containers.h | 5 ++++
> src/man/wg.8 | 8 ++++-
> src/set.c | 9 +++++-
> src/setconf.c | 2 +-
> 7 files changed, 57 insertions(+), 14 deletions(-)
>
> --
> Changes since v1: reword commit message and add missing sign-off.
>
> diff --git a/contrib/reresolve-dns/reresolve-dns.sh b/contrib/reresolve-dns/reresolve-dns.sh
> index 711c332..bdb47ac 100755
> --- a/contrib/reresolve-dns/reresolve-dns.sh
> +++ b/contrib/reresolve-dns/reresolve-dns.sh
> @@ -17,7 +17,7 @@ process_peer() {
> [[ $PEER_SECTION -ne 1 || -z $PUBLIC_KEY || -z $ENDPOINT ]] && return 0
> [[ $(wg show "$INTERFACE" latest-handshakes) =~ ${PUBLIC_KEY//+/\\+}\ ([0-9]+) ]] || return 0
> (( ($EPOCHSECONDS - ${BASH_REMATCH[1]}) > 135 )) || return 0
> - wg set "$INTERFACE" peer "$PUBLIC_KEY" endpoint "$ENDPOINT"
> + wg set "$INTERFACE" peer "$PUBLIC_KEY" endpoint "$ENDPOINT" address-family "$FAMILY"
> reset_peer_section
> }
>
> @@ -25,6 +25,7 @@ reset_peer_section() {
> PEER_SECTION=0
> PUBLIC_KEY=""
> ENDPOINT=""
> + FAMILY=unspec
> }
>
> reset_peer_section
> @@ -38,6 +39,7 @@ while read -r line || [[ -n $line ]]; do
> case "$key" in
> PublicKey) PUBLIC_KEY="$value"; continue ;;
> Endpoint) ENDPOINT="$value"; continue ;;
> + AddressFamily) FAMILY="$value"; continue ;;
> esac
> fi
> done < "$CONFIG_FILE"
> diff --git a/src/config.c b/src/config.c
> index 81ccb47..e8db900 100644
> --- a/src/config.c
> +++ b/src/config.c
> @@ -192,14 +192,14 @@ static inline int parse_dns_retries(void)
> return (int)ret;
> }
>
> -static inline bool parse_endpoint(struct sockaddr *endpoint, const char *value)
> +static inline bool parse_endpoint(struct sockaddr *endpoint, const char *value, int family)
> {
> char *mutable = strdup(value);
> char *begin, *end;
> int ret, retries = parse_dns_retries();
> struct addrinfo *resolved;
> struct addrinfo hints = {
> - .ai_family = AF_UNSPEC,
> + .ai_family = family,
> .ai_socktype = SOCK_DGRAM,
> .ai_protocol = IPPROTO_UDP
> };
> @@ -279,6 +279,20 @@ static inline bool parse_endpoint(struct sockaddr *endpoint, const char *value)
> return true;
> }
>
> +static inline bool parse_address_family(int *family, const char *value)
> +{
> + if (strcmp(value, "inet") == 0)
> + *family = AF_INET;
> + else if (strcmp(value, "inet6") == 0)
> + *family = AF_INET6;
> + else if (strcmp(value, "unspec") == 0)
> + *family = AF_UNSPEC;
> + else
> + return false;
> +
> + return true;
> +}
> +
> static inline bool parse_persistent_keepalive(uint16_t *interval, uint32_t *flags, const char *value)
> {
> unsigned long ret;
> @@ -454,8 +468,10 @@ static bool process_line(struct config_ctx *ctx, const char *line)
> goto error;
> } else if (ctx->is_peer_section) {
> if (key_match("Endpoint"))
> - ret = parse_endpoint(&ctx->last_peer->endpoint.addr, value);
> - else if (key_match("PublicKey")) {
> + ctx->last_peer->endpoint_value = strdup(value);
> + else if (key_match("AddressFamily")) {
> + ret = parse_address_family(&ctx->last_peer->addr_fam, value);
> + } else if (key_match("PublicKey")) {
> ret = parse_key(ctx->last_peer->public_key, value);
> if (ret)
> ctx->last_peer->flags |= WGPEER_HAS_PUBLIC_KEY;
> @@ -527,19 +543,22 @@ bool config_read_init(struct config_ctx *ctx, bool append)
> return true;
> }
>
> -struct wgdevice *config_read_finish(struct config_ctx *ctx)
> +struct wgdevice *config_read_finish(struct wgdevice *device)
> {
> struct wgpeer *peer;
>
> - for_each_wgpeer(ctx->device, peer) {
> + for_each_wgpeer(device, peer) {
> if (!(peer->flags & WGPEER_HAS_PUBLIC_KEY)) {
> fprintf(stderr, "A peer is missing a public key\n");
> goto err;
> }
> +
> + if (!parse_endpoint(&peer->endpoint.addr, peer->endpoint_value, peer->addr_fam))
> + goto err;
> }
> - return ctx->device;
> + return device;
> err:
> - free_wgdevice(ctx->device);
> + free_wgdevice(device);
> return NULL;
> }
>
> @@ -611,7 +630,11 @@ struct wgdevice *config_read_cmd(const char *argv[], int argc)
> argv += 1;
> argc -= 1;
> } else if (!strcmp(argv[0], "endpoint") && argc >= 2 && peer) {
> - if (!parse_endpoint(&peer->endpoint.addr, argv[1]))
> + peer->endpoint_value = strdup(argv[1]);
> + argv += 2;
> + argc -= 2;
> + } else if (!strcmp(argv[0], "address-family") && argc >= 2 && peer) {
> + if (!parse_address_family(&peer->addr_fam, argv[1]))
> goto error;
> argv += 2;
> argc -= 2;
> diff --git a/src/config.h b/src/config.h
> index 443cf21..6f81da2 100644
> --- a/src/config.h
> +++ b/src/config.h
> @@ -22,6 +22,6 @@ struct config_ctx {
> struct wgdevice *config_read_cmd(const char *argv[], int argc);
> bool config_read_init(struct config_ctx *ctx, bool append);
> bool config_read_line(struct config_ctx *ctx, const char *line);
> -struct wgdevice *config_read_finish(struct config_ctx *ctx);
> +struct wgdevice *config_read_finish(struct wgdevice *device);
>
> #endif
> diff --git a/src/containers.h b/src/containers.h
> index a82e8dd..c111621 100644
> --- a/src/containers.h
> +++ b/src/containers.h
> @@ -52,12 +52,15 @@ struct wgpeer {
> uint8_t public_key[WG_KEY_LEN];
> uint8_t preshared_key[WG_KEY_LEN];
>
> + char *endpoint_value;
> union {
> struct sockaddr addr;
> struct sockaddr_in addr4;
> struct sockaddr_in6 addr6;
> } endpoint;
>
> + int addr_fam;
> +
> struct timespec64 last_handshake_time;
> uint64_t rx_bytes, tx_bytes;
> uint16_t persistent_keepalive_interval;
> @@ -99,6 +102,8 @@ static inline void free_wgdevice(struct wgdevice *dev)
> for (struct wgpeer *peer = dev->first_peer, *np = peer ? peer->next_peer : NULL; peer; peer = np, np = peer ? peer->next_peer : NULL) {
> for (struct wgallowedip *allowedip = peer->first_allowedip, *na = allowedip ? allowedip->next_allowedip : NULL; allowedip; allowedip = na, na = allowedip ? allowedip->next_allowedip : NULL)
> free(allowedip);
> + if (peer->endpoint_value)
> + free(peer->endpoint_value);
> free(peer);
> }
> free(dev);
> diff --git a/src/man/wg.8 b/src/man/wg.8
> index 7984539..fd9fde7 100644
> --- a/src/man/wg.8
> +++ b/src/man/wg.8
> @@ -55,7 +55,7 @@ transfer-rx, transfer-tx, persistent-keepalive.
> Shows the current configuration of \fI<interface>\fP in the format described
> by \fICONFIGURATION FILE FORMAT\fP below.
> .TP
> -\fBset\fP \fI<interface>\fP [\fIlisten-port\fP \fI<port>\fP] [\fIfwmark\fP \fI<fwmark>\fP] [\fIprivate-key\fP \fI<file-path>\fP] [\fIpeer\fP \fI<base64-public-key>\fP [\fIremove\fP] [\fIpreshared-key\fP \fI<file-path>\fP] [\fIendpoint\fP \fI<ip>:<port>\fP] [\fIpersistent-keepalive\fP \fI<interval seconds>\fP] [\fIallowed-ips\fP \fI<ip1>/<cidr1>\fP[,\fI<ip2>/<cidr2>\fP]...] ]...
> +\fBset\fP \fI<interface>\fP [\fIlisten-port\fP \fI<port>\fP] [\fIfwmark\fP \fI<fwmark>\fP] [\fIprivate-key\fP \fI<file-path>\fP] [\fIpeer\fP \fI<base64-public-key>\fP [\fIremove\fP] [\fIpreshared-key\fP \fI<file-path>\fP] [\fIendpoint\fP \fI<ip>:<port>\fP] [\fIaddress-family\fP \fI<family>\fP] [\fIpersistent-keepalive\fP \fI<interval seconds>\fP] [\fIallowed-ips\fP \fI<ip1>/<cidr1>\fP[,\fI<ip2>/<cidr2>\fP]...] ]...
> Sets configuration values for the specified \fI<interface>\fP. Multiple
> \fIpeer\fPs may be specified, and if the \fIremove\fP argument is given
> for a peer, that peer is removed, not configured. If \fIlisten-port\fP
> @@ -163,6 +163,12 @@ port number. This endpoint will be updated automatically to the most recent
> source IP address and port of correctly authenticated packets from the peer.
> Optional.
> .IP \(bu
> +AddressFamily \(em one of \fIinet\fP, \fIinet6\fP or \fIunspec\fP. When a
> +hostname is given for \fIEndpoint\fP, setting this to \fIinet\fP or
> +\fIinet6\fP will allow only addresses of the given family to be
> +used. Defaults to \fIunspec\fP, which causes the first returned address of
> +any type to be used.
> +.IP \(bu
> PersistentKeepalive \(em a seconds interval, between 1 and 65535 inclusive, of
> how often to send an authenticated empty packet to the peer for the purpose of keeping a
> stateful firewall or NAT mapping valid persistently. For example, if the interface
> diff --git a/src/set.c b/src/set.c
> index 75560fd..20ee85e 100644
> --- a/src/set.c
> +++ b/src/set.c
> @@ -18,13 +18,20 @@ int set_main(int argc, const char *argv[])
> int ret = 1;
>
> if (argc < 3) {
> - fprintf(stderr, "Usage: %s %s <interface> [listen-port <port>] [fwmark <mark>] [private-key <file path>] [peer <base64 public key> [remove] [preshared-key <file path>] [endpoint <ip>:<port>] [persistent-keepalive <interval seconds>] [allowed-ips <ip1>/<cidr1>[,<ip2>/<cidr2>]...] ]...\n", PROG_NAME, argv[0]);
> + fprintf(stderr, "Usage: %s %s <interface> [listen-port <port>] [fwmark <mark>] [private-key <file path>] [peer <base64 public key> [remove] [preshared-key <file path>] [endpoint <ip>:<port>] [address-family <family>] [persistent-keepalive <interval seconds>] [allowed-ips <ip1>/<cidr1>[,<ip2>/<cidr2>]...] ]...\n", PROG_NAME, argv[0]);
> return 1;
> }
>
> device = config_read_cmd(argv + 2, argc - 2);
> if (!device)
> goto cleanup;
> +
> + device = config_read_finish(device);
> + if (!device) {
> + fprintf(stderr, "Invalid configuration\n");
> + goto cleanup;
> + }
> +
> strncpy(device->name, argv[1], IFNAMSIZ - 1);
> device->name[IFNAMSIZ - 1] = '\0';
>
> diff --git a/src/setconf.c b/src/setconf.c
> index 1c5b138..c90fd30 100644
> --- a/src/setconf.c
> +++ b/src/setconf.c
> @@ -127,7 +127,7 @@ int setconf_main(int argc, const char *argv[])
> goto cleanup;
> }
> }
> - device = config_read_finish(&ctx);
> + device = config_read_finish(ctx.device);
> if (!device) {
> fprintf(stderr, "Invalid configuration\n");
> goto cleanup;
> --
> 2.30.2
>
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