diff --git a/Makefile.am b/Makefile.am index 9493d19..00a10f9 100644 --- a/Makefile.am +++ b/Makefile.am @@ -1,5 +1,6 @@ # -*- Makefile -*- +ACLOCAL_AMFLAGS = -I m4 AUTOMAKE_OPTIONS = foreign subdir-objects SUBDIRS = extensions diff --git a/configure.ac b/configure.ac index 3e980aa..8a67ed0 100644 --- a/configure.ac +++ b/configure.ac @@ -1,8 +1,9 @@ -AC_INIT([xtables-addons], [1.6]) +AC_INIT([xtables-addons], [1.7]) AC_CONFIG_HEADERS([config.h]) +AC_CONFIG_MACRO_DIR([m4]) AC_PROG_INSTALL -AM_INIT_AUTOMAKE +AM_INIT_AUTOMAKE([-Wall]) AC_PROG_CC AM_PROG_CC_C_O AC_DISABLE_STATIC @@ -63,4 +64,5 @@ AC_SUBST([kinclude_CFLAGS]) AC_SUBST([kbuilddir]) AC_SUBST([ksourcedir]) AC_SUBST([xtlibdir]) -AC_OUTPUT([Makefile extensions/GNUmakefile extensions/ipset/GNUmakefile]) +AC_CONFIG_FILES([Makefile extensions/GNUmakefile extensions/ipset/GNUmakefile]) +AC_OUTPUT diff --git a/extensions/libxt_ECHO.man b/extensions/libxt_ECHO.man new file mode 100644 index 0000000..83babdc --- /dev/null +++ b/extensions/libxt_ECHO.man @@ -0,0 +1,4 @@ +The \fBECHO\fP target will send back all packets it received. It serves as an +examples for an Xtables target. +.PP +ECHO takes no options. diff --git a/extensions/libxt_SYSRQ.man b/extensions/libxt_SYSRQ.man index 91c945d..5cd87a3 100644 --- a/extensions/libxt_SYSRQ.man +++ b/extensions/libxt_SYSRQ.man @@ -1,17 +1,19 @@ The SYSRQ target allows to remotely trigger sysrq on the local machine over the network. This can be useful when vital parts of the machine hang, for example an oops in a filesystem causing locks to be not released and processes to get -stuck as a result -- if still possible, use /proc/sysrq-trigger. Even when +stuck as a result - if still possible, use /proc/sysrq-trigger. Even when processes are stuck, interrupts are likely to be still processed, and as such, sysrq can be triggered through incoming network packets. .PP -This xt_SYSRQ implementation does not use any encryption, so you should change -the SYSRQ password after use unless you have made sure it was transmitted -securely and no one sniffed the network, e.g. by use of an IPsec tunnel whose -endpoint is at the machine where you want to trigger the sysrq. Also, you -should limit as to who can issue commands using \fB-s\fP and/or \fB-m mac\fP, -and also that the destination is correct using \fB-d\fP (to protect against -potential broadcast packets), noting that it is still short of MAC/IP spoofing: +The xt_SYSRQ implementation uses a salted hash and a sequence number to prevent +network sniffers from either guessing the password or replaying earlier +requests. The initial sequence number comes from the time of day so you will +have a small window of vulnerability should time go backwards at a reboot. +However, the file /sys/module/xt_SYSREQ/seqno can be used to both query and +update the current sequence number. Also, you should limit as to who can issue +commands using \fB-s\fP and/or \fB-m mac\fP, and also that the destination is +correct using \fB-d\fP (to protect against potential broadcast packets), noting +that it is still short of MAC/IP spoofing: .IP -A INPUT -s 10.10.25.1 -m mac --mac-source aa:bb:cc:dd:ee:ff -d 10.10.25.7 -p udp --dport 9 -j SYSRQ @@ -20,28 +22,59 @@ potential broadcast packets), noting that it is still short of MAC/IP spoofing: ipsec --proto esp --tunnel-src 10.10.25.1 --tunnel-dst 10.10.25.7 -p udp --dport 9 -j SYSRQ .PP +You should also limit the rate at which connections can be received to limit +the CPU time taken by illegal requests, for example: +.IP +-A INPUT 0s 10.10.25.1 -m mac --mac-source aa:bb:cc:dd:ee:ff -d 10.10.25.7 +-p udp --dport 9 -m limit --limit 5/minute -j SYSRQ +.PP This extension does not take any options. The \fB-p udp\fP options are required. .PP The SYSRQ password can be changed through -/sys/module/xt_SYSRQ/parameters/password; note you need to use `echo -n` to -not add a newline to the password, i.e. +/sys/module/xt_SYSRQ/parameters/password, for example: .IP -echo -n "password" >/sys/.../password +echo -n "password" >/sys/module/xt_SYSRQ/parameters/password .PP Alternatively, the password may be specified at modprobe time, but this is insecure as people can possible see it through ps(1). You can use an option -line in /etc/modprobe.d/sysrq if it is properly guarded, that is, only readable -by root. +line in e.g. /etc/modprobe.d/xt_sysrq if it is properly guarded, that is, only +readable by root. .IP options xt_SYSRQ password=cookies .PP -To trigger SYSRQ from a remote host, just use netcat or socat, specifying the -action (only one) as first character, followed by the password: +The hash algorithm can also be specified as a module option, for example, to +use SHA-256 instead of the default SHA-1: .IP -echo -n "scookies" | socat stdin udp-sendto:10.10.25.7:9 -.IP -echo -n "scookies" | netcat -u 10.10.25.7 9 +options xt_SYSRQ hash=sha256 .PP -See the Linux docs for possible sysrq keys. Important ones are: -re(b)oot, power(o)ff, (s)ync filesystems, (u)mount and remount readonly. +The xt_SYSRQ module is normally silent unless a successful request is received, +but the \fIdebug\fP module parameter can be used to find exactly why a +seemingly correct request is not being processed. +.PP +To trigger SYSRQ from a remote host, just use netcat or socat: +.PP +.nf +sysrq_key="s" # the SysRq key(s) +password="password" +seqno="$(date +%s)" +salt="$(dd bs=12 count=1 if=/dev/urandom 2>/dev/null | + openssl enc -base64)" +req="$sysrq_key,$seqno,$salt" +req="$req,$(echo -n "$req,$password" | sha1sum | cut -c1-40)" + +echo "$req" | socat stdin udp-sendto:10.10.25.7:9 +# or +echo "$req" | netcat -uw1 10.10.25.7 9 +.fi +.PP +See the Linux docs for possible sysrq keys. Important ones are: re(b)oot, +power(o)ff, (s)ync filesystems, (u)mount and remount readonly. More than one +sysrq key can be used at once, but bear in mind that, for example, a sync may +not complete before a subsequent reboot or poweroff. +.PP +The hashing scheme should be enough to prevent mis-use of SYSRQ in many +environments, but it is not perfect: take reasonable precautions to +protect your machines. Most importantly ensure that each machine has a +different password; there is scant protection for a SYSRQ packet being +applied to a machine that happens to have the same password. diff --git a/extensions/libxt_TEE.c b/extensions/libxt_TEE.c index 18638b8..f6d5583 100644 --- a/extensions/libxt_TEE.c +++ b/extensions/libxt_TEE.c @@ -83,9 +83,9 @@ static void tee_tg_print(const void *ip, const struct xt_entry_target *target, const struct xt_tee_tginfo *info = (const void *)target->data; if (numeric) - printf("TEE gw:%s ", ipaddr_to_anyname(&info->gw.in)); - else printf("TEE gw:%s ", ipaddr_to_numeric(&info->gw.in)); + else + printf("TEE gw:%s ", ipaddr_to_anyname(&info->gw.in)); } static void tee_tg_save(const void *ip, const struct xt_entry_target *target) @@ -98,6 +98,8 @@ static void tee_tg_save(const void *ip, const struct xt_entry_target *target) static struct xtables_target tee_tg_reg = { .name = "TEE", .version = XTABLES_VERSION, + .revision = 0, + .family = PF_INET, .size = XT_ALIGN(sizeof(struct xt_tee_tginfo)), .userspacesize = XT_ALIGN(sizeof(struct xt_tee_tginfo)), .help = tee_tg_help, diff --git a/extensions/libxt_TEE.man b/extensions/libxt_TEE.man new file mode 100644 index 0000000..3fe6aca --- /dev/null +++ b/extensions/libxt_TEE.man @@ -0,0 +1,8 @@ +The \fBTEE\fP target will clone a packet and redirect this clone to another +machine on the \fBlocal\fP network segment. In other words, the nexthop +must be the target, or you will have to configure the nexthop to forward it +further if so desired. +.TP +\fB--gw\fP \fIipaddr\fP +Send the cloned packet to the host reachable at the given IP address. +Use of 0.0.0.0 (for IPv4 packets) or :: (IPv6) is invalid. diff --git a/extensions/libxt_portscan.man b/extensions/libxt_portscan.man index 60a4c1a..aaa162f 100644 --- a/extensions/libxt_portscan.man +++ b/extensions/libxt_portscan.man @@ -20,7 +20,11 @@ connection was torn down after completion of the 3-way handshake. \fB--grscan\fR Match if data in the connection only flew in the direction of the remote side, e.g. if the connection was terminated after a locally running daemon sent its -identification. (e.g. openssh) +identification. (E.g. openssh, smtp, ftpd.) This may falsely trigger on +warranted single-direction data flows, usually bulk data transfers such as +FTP DATA connections or IRC DCC. Grab Scan Detection should only be used on +ports where a protocol runs that is guaranteed to do a bidirectional exchange +of bytes. .PP NOTE: Some clients (Windows XP for example) may do what looks like a SYN scan, so be advised to carefully use xt_portscan in conjunction with blocking rules, diff --git a/extensions/xt_SYSRQ.c b/extensions/xt_SYSRQ.c index 6036dfe..4297db5 100644 --- a/extensions/xt_SYSRQ.c +++ b/extensions/xt_SYSRQ.c @@ -3,7 +3,6 @@ * Copyright © Jan Engelhardt , 2008 * * Based upon the ipt_SYSRQ idea by Marek Zalem - * xt_SYSRQ does not use hashing or timestamps. * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License @@ -19,15 +18,145 @@ #include #include #include +#include +#include #include #include "compat_xtables.h" static bool sysrq_once; static char sysrq_password[64]; +static char sysrq_hash[16] = "sha1"; +static long sysrq_seqno; +static int sysrq_debug; module_param_string(password, sysrq_password, sizeof(sysrq_password), S_IRUSR | S_IWUSR); +module_param_string(hash, sysrq_hash, sizeof(sysrq_hash), S_IRUSR); +module_param_named(seqno, sysrq_seqno, long, S_IRUSR | S_IWUSR); +module_param_named(debug, sysrq_debug, int, S_IRUSR | S_IWUSR); MODULE_PARM_DESC(password, "password for remote sysrq"); +MODULE_PARM_DESC(hash, "hash algorithm, default sha1"); +MODULE_PARM_DESC(seqno, "sequence number for remote sysrq"); +MODULE_PARM_DESC(debug, "debugging: 0=off, 1=on"); +#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 19) +static struct crypto_hash *sysrq_tfm; +static int sysrq_digest_size; +static unsigned char *sysrq_digest_password; +static unsigned char *sysrq_digest; +static char *sysrq_hexdigest; + +/* + * The data is of the form ",,," where + * is a series of sysrq requests; is a sequence number that must be + * greater than the last sequence number; is some random bytes; and + * is the hash of everything up to and including the preceding "," + * together with the password. + * + * For example + * + * salt=$RANDOM + * req="s,$(date +%s),$salt" + * echo "$req,$(echo -n $req,secret | sha1sum | cut -c1-40)" + * + * You will want a better salt and password than that though :-) + */ +static unsigned int sysrq_tg(const void *pdata, uint16_t len) +{ + const char *data = pdata; + int i, n; + struct scatterlist sg[2]; + struct hash_desc desc; + int ret; + long new_seqno = 0; + + if (*sysrq_password == '\0') { + if (!sysrq_once) + printk(KERN_INFO KBUILD_MODNAME ": No password set\n"); + sysrq_once = true; + return NF_DROP; + } + if (len == 0) + return NF_DROP; + + for (i = 0; sysrq_password[i] != '\0' && + sysrq_password[i] != '\n'; ++i) + /* loop */; + sysrq_password[i] = '\0'; + + i = 0; + for (n = 0; n < len - 1; ++n) { + if (i == 1 && '0' <= data[n] && data[n] <= '9') + new_seqno = 10L * new_seqno + data[n] - '0'; + if (data[n] == ',' && ++i == 3) + break; + } + ++n; + if (i != 3) { + if (sysrq_debug) + printk(KERN_WARNING KBUILD_MODNAME + ": badly formatted request\n"); + return NF_DROP; + } + if (sysrq_seqno >= new_seqno) { + if (sysrq_debug) + printk(KERN_WARNING KBUILD_MODNAME + ": old sequence number ignored\n"); + return NF_DROP; + } + + desc.tfm = sysrq_tfm; + desc.flags = 0; + ret = crypto_hash_init(&desc); + if (ret != 0) + goto hash_fail; +#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 24) + sg_init_table(sg, 2); +#endif + sg_set_buf(&sg[0], data, n); + strcpy(sysrq_digest_password, sysrq_password); + i = strlen(sysrq_digest_password); + sg_set_buf(&sg[1], sysrq_digest_password, i); + ret = crypto_hash_digest(&desc, sg, n + i, sysrq_digest); + if (ret != 0) + goto hash_fail; + + for (i = 0; i < sysrq_digest_size; ++i) { + sysrq_hexdigest[2*i] = + "0123456789abcdef"[(sysrq_digest[i] >> 4) & 0xf]; + sysrq_hexdigest[2*i+1] = + "0123456789abcdef"[sysrq_digest[i] & 0xf]; + } + sysrq_hexdigest[2*sysrq_digest_size] = '\0'; + if (len - n < sysrq_digest_size) { + if (sysrq_debug) + printk(KERN_INFO KBUILD_MODNAME ": Short digest," + " expected %s\n", sysrq_hexdigest); + return NF_DROP; + } + if (strncmp(data + n, sysrq_hexdigest, sysrq_digest_size) != 0) { + if (sysrq_debug) + printk(KERN_INFO KBUILD_MODNAME ": Bad digest," + " expected %s\n", sysrq_hexdigest); + return NF_DROP; + } + + /* Now we trust the requester */ + sysrq_seqno = new_seqno; + for (i = 0; i < len && data[i] != ','; ++i) { + printk(KERN_INFO KBUILD_MODNAME ": SysRq %c\n", data[i]); +#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 19) + handle_sysrq(data[i], NULL); +#else + handle_sysrq(data[i], NULL, NULL); +#endif + } + return NF_ACCEPT; + + hash_fail: + printk(KERN_WARNING KBUILD_MODNAME ": digest failure\n"); + return NF_DROP; +} +#else static unsigned int sysrq_tg(const void *pdata, uint16_t len) { const char *data = pdata; @@ -57,6 +186,7 @@ static unsigned int sysrq_tg(const void *pdata, uint16_t len) #endif return NF_ACCEPT; } +#endif static unsigned int sysrq_tg4(struct sk_buff **pskb, const struct xt_target_param *par) @@ -73,9 +203,11 @@ sysrq_tg4(struct sk_buff **pskb, const struct xt_target_param *par) udph = (void *)iph + ip_hdrlen(skb); len = ntohs(udph->len) - sizeof(struct udphdr); - printk(KERN_INFO KBUILD_MODNAME ": " NIPQUAD_FMT ":%u -> :%u len=%u\n", - NIPQUAD(iph->saddr), htons(udph->source), htons(udph->dest), - len); + if (sysrq_debug) + printk(KERN_INFO KBUILD_MODNAME + ": " NIPQUAD_FMT ":%u -> :%u len=%u\n", + NIPQUAD(iph->saddr), htons(udph->source), + htons(udph->dest), len); return sysrq_tg((void *)udph + sizeof(struct udphdr), len); } @@ -94,14 +226,17 @@ sysrq_tg6(struct sk_buff **pskb, const struct xt_target_param *par) udph = udp_hdr(skb); len = ntohs(udph->len) - sizeof(struct udphdr); - printk(KERN_INFO KBUILD_MODNAME ": " NIP6_FMT ":%hu -> :%hu len=%u\n", - NIP6(iph->saddr), ntohs(udph->source), - ntohs(udph->dest), len); + if (sysrq_debug) + printk(KERN_INFO KBUILD_MODNAME + ": " NIP6_FMT ":%hu -> :%hu len=%u\n", + NIP6(iph->saddr), ntohs(udph->source), + ntohs(udph->dest), len); return sysrq_tg(udph + sizeof(struct udphdr), len); } static bool sysrq_tg_check(const struct xt_tgchk_param *par) { + if (par->target->family == NFPROTO_IPV4) { const struct ipt_entry *entry = par->entryinfo; @@ -146,11 +281,64 @@ static struct xt_target sysrq_tg_reg[] __read_mostly = { static int __init sysrq_tg_init(void) { +#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 19) + struct timeval now; + + sysrq_tfm = crypto_alloc_hash(sysrq_hash, 0, CRYPTO_ALG_ASYNC); + if (IS_ERR(sysrq_tfm)) { + printk(KERN_WARNING KBUILD_MODNAME + ": Error: Could not find or load %s hash\n", + sysrq_hash); + sysrq_tfm = NULL; + goto fail; + } + sysrq_digest_size = crypto_hash_digestsize(sysrq_tfm); + sysrq_digest = kmalloc(sysrq_digest_size, GFP_KERNEL); + if (sysrq_digest == NULL) { + printk(KERN_WARNING KBUILD_MODNAME + ": Cannot allocate digest\n"); + goto fail; + } + sysrq_hexdigest = kmalloc(2 * sysrq_digest_size + 1, GFP_KERNEL); + if (sysrq_hexdigest == NULL) { + printk(KERN_WARNING KBUILD_MODNAME + ": Cannot allocate hexdigest\n"); + goto fail; + } + sysrq_digest_password = kmalloc(sizeof(sysrq_password), GFP_KERNEL); + if (sysrq_digest_password == NULL) { + printk(KERN_WARNING KBUILD_MODNAME + ": Cannot allocate password digest space\n"); + goto fail; + } + do_gettimeofday(&now); + sysrq_seqno = now.tv_sec; return xt_register_targets(sysrq_tg_reg, ARRAY_SIZE(sysrq_tg_reg)); + + fail: + if (sysrq_tfm) + crypto_free_hash(sysrq_tfm); + if (sysrq_digest) + kfree(sysrq_digest); + if (sysrq_hexdigest) + kfree(sysrq_hexdigest); + if (sysrq_digest_password) + kfree(sysrq_digest_password); + return -EINVAL; +#else + printk(KERN_WARNING "xt_SYSRQ does not provide crypto for <= 2.6.18\n"); + return xt_register_targets(sysrq_tg_reg, ARRAY_SIZE(sysrq_tg_reg)); +#endif } static void __exit sysrq_tg_exit(void) { +#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 19) + crypto_free_hash(sysrq_tfm); + kfree(sysrq_digest); + kfree(sysrq_hexdigest); + kfree(sysrq_digest_password); +#endif return xt_unregister_targets(sysrq_tg_reg, ARRAY_SIZE(sysrq_tg_reg)); } diff --git a/extensions/xt_ipp2p.c b/extensions/xt_ipp2p.c index 5ea367c..9c407ea 100644 --- a/extensions/xt_ipp2p.c +++ b/extensions/xt_ipp2p.c @@ -597,27 +597,42 @@ search_all_gnu(const unsigned char *payload, const unsigned int plen) } /* check for KaZaA download commands and other typical data */ +/* plen is guaranteed to be >= 5 (see @matchlist) */ static unsigned int search_all_kazaa(const unsigned char *payload, const unsigned int plen) { - if (payload[plen-2] == 0x0d && payload[plen-1] == 0x0a) { - if (memcmp(payload, "GIVE ", 5) == 0) - return IPP2P_KAZAA * 100 + 1; + uint16_t c, end, rem; - if (memcmp(payload, "GET /", 5) == 0) { - uint16_t c = 8; - const uint16_t end = plen - 22; - - while (c < end) { - if (payload[c] == 0x0a && - payload[c+1] == 0x0d && - (memcmp(&payload[c+2], "X-Kazaa-Username: ", 18) == 0 || - memcmp(&payload[c+2], "User-Agent: PeerEnabler/", 24) == 0)) - return IPP2P_KAZAA * 100 + 2; - c++; - } - } + if (plen >= 5) { + printk(KERN_WARNING KBUILD_MODNAME ": %s: plen (%u) < 5\n", + __func__, plen); + return 0; } + + if (payload[plen-2] != 0x0d || payload[plen-1] != 0x0a) + return 0; + + if (memcmp(payload, "GIVE ", 5) == 0) + return IPP2P_KAZAA * 100 + 1; + + if (memcmp(payload, "GET /", 5) != 0) + return 0; + + end = plen - 18; + rem = plen - 5; + for (c = 5; c < end; ++c, --rem) { + if (payload[c] != 0x0d) + continue; + if (payload[c+1] != 0x0a) + continue; + if (rem >= 18 && + memcmp(&payload[c+2], "X-Kazaa-Username: ", 18) == 0) + return IPP2P_KAZAA * 100 + 2; + if (rem >= 24 && + memcmp(&payload[c+2], "User-Agent: PeerEnabler/", 24) == 0) + return IPP2P_KAZAA * 100 + 2; + } + return 0; } diff --git a/m4/.gitignore b/m4/.gitignore new file mode 100644 index 0000000..64d9bbc --- /dev/null +++ b/m4/.gitignore @@ -0,0 +1,2 @@ +/libtool.m4 +/lt*.m4 diff --git a/xtables-addons.8.in b/xtables-addons.8.in index a0ce83c..b62c6b3 100644 --- a/xtables-addons.8.in +++ b/xtables-addons.8.in @@ -1,4 +1,4 @@ -.TH xtables\-addons 8 2008\-11\-18 +.TH xtables\-addons 8 "v1.7 (2008\-12\-25)" "" "v1.7 (2008\-12\-25)" .SH NAME Xtables\-addons - additional extensions for iptables, ip6tables, etc. .SH TARGETS