diff options
Diffstat (limited to 'release/src/linux/linux/net/ipv4/netfilter/ipt_layer7.c')
| -rw-r--r-- | release/src/linux/linux/net/ipv4/netfilter/ipt_layer7.c | 570 |
1 files changed, 570 insertions, 0 deletions
diff --git a/release/src/linux/linux/net/ipv4/netfilter/ipt_layer7.c b/release/src/linux/linux/net/ipv4/netfilter/ipt_layer7.c new file mode 100644 index 00000000..567e3847 --- /dev/null +++ b/release/src/linux/linux/net/ipv4/netfilter/ipt_layer7.c @@ -0,0 +1,570 @@ +/* + Kernel module to match application layer (OSI layer 7) + data in connections. + + http://l7-filter.sf.net + + By Matthew Strait and Ethan Sommer, 2003-2005. + + This program is free software; you can redistribute it and/or + modify it under the terms of the GNU General Public License + as published by the Free Software Foundation; either version + 2 of the License, or (at your option) any later version. + http://www.gnu.org/licenses/gpl.txt + + Based on ipt_string.c (C) 2000 Emmanuel Roger <winfield@freegates.be> + and cls_layer7.c (C) 2003 Matthew Strait, Ethan Sommer, Justin Levandoski +*/ + +#include <linux/module.h> +#include <linux/skbuff.h> +#include <linux/netfilter_ipv4/ip_conntrack.h> +#include <linux/proc_fs.h> +#include <linux/ctype.h> +#include <net/ip.h> +#include <net/tcp.h> +#include <linux/netfilter_ipv4/lockhelp.h> + +#include "regexp/regexp.c" + +#include <linux/netfilter_ipv4/ipt_layer7.h> +#include <linux/netfilter_ipv4/ip_tables.h> + +MODULE_AUTHOR("Matthew Strait <quadong@users.sf.net>, Ethan Sommer <sommere@users.sf.net>"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("iptables application layer match module"); + +static int maxdatalen = 2048; // this is the default +MODULE_PARM(maxdatalen,"i"); +MODULE_PARM_DESC(maxdatalen,"maximum bytes of data looked at by l7-filter"); + +#if defined(CONFIG_IP_NF_MATCH_LAYER7_DEBUG) + #define DPRINTK(format,args...) printk(format,##args) +#else + #define DPRINTK(format,args...) +#endif + +#define TOTAL_PACKETS master_conntrack->layer7.numpackets + +/* Number of packets whose data we look at. +This can be modified through /proc/net/layer7_numpackets */ +static int num_packets = 10; + +static struct pattern_cache { + char * regex_string; + regexp * pattern; + struct pattern_cache * next; +} * first_pattern_cache = NULL; + +/* I'm new to locking. Here are my assumptions: + +- No one will write to /proc/net/layer7_numpackets over and over very fast; + if they did, nothing awful would happen. + +- This code will never be processing the same packet twice at the same time, + because iptables rules are traversed in order. + +- It doesn't matter if two packets from different connections are in here at + the same time, because they don't share any data. + +- It _does_ matter if two packets from the same connection are here at the same + time. In this case, we have to protect the conntracks and the list of + compiled patterns. +*/ +DECLARE_RWLOCK(ct_lock); +DECLARE_LOCK(list_lock); + +#if CONFIG_IP_NF_MATCH_LAYER7_DEBUG +/* Converts an unfriendly string into a friendly one by +replacing unprintables with periods and all whitespace with " ". */ +static char * friendly_print(unsigned char * s) +{ + char * f = kmalloc(strlen(s) + 1, GFP_ATOMIC); + int i; + + if(!f) { + if (net_ratelimit()) + printk(KERN_ERR "layer7: out of memory in friendly_print, bailing.\n"); + return NULL; + } + + for(i = 0; i < strlen(s); i++){ + if(isprint(s[i]) && s[i] < 128) f[i] = s[i]; + else if(isspace(s[i])) f[i] = ' '; + else f[i] = '.'; + } + f[i] = '\0'; + return f; +} + +static char dec2hex(int i) +{ + switch (i) { + case 0 ... 9: + return (char)(i + '0'); + break; + case 10 ... 15: + return (char)(i - 10 + 'a'); + break; + default: + if (net_ratelimit()) + printk("Problem in dec2hex\n"); + return '\0'; + } +} + +static char * hex_print(unsigned char * s) +{ + char * g = kmalloc(strlen(s)*3 + 1, GFP_ATOMIC); + int i; + + if(!g) { + if (net_ratelimit()) + printk(KERN_ERR "layer7: out of memory in hex_print, bailing.\n"); + return NULL; + } + + for(i = 0; i < strlen(s); i++) { + g[i*3 ] = dec2hex(s[i]/16); + g[i*3 + 1] = dec2hex(s[i]%16); + g[i*3 + 2] = ' '; + } + g[i*3] = '\0'; + + return g; +} +#endif // DEBUG + +/* Use instead of regcomp. As we expect to be seeing the same regexps over and +over again, it make sense to cache the results. */ +static regexp * compile_and_cache(char * regex_string, char * protocol) +{ + struct pattern_cache * node = first_pattern_cache; + struct pattern_cache * last_pattern_cache = first_pattern_cache; + struct pattern_cache * tmp; + unsigned int len; + + while (node != NULL) { + if (!strcmp(node->regex_string, regex_string)) + return node->pattern; + + last_pattern_cache = node;/* points at the last non-NULL node */ + node = node->next; + } + + /* If we reach the end of the list, then we have not yet cached + the pattern for this regex. Let's do that now. + Be paranoid about running out of memory to avoid list corruption. */ + tmp = kmalloc(sizeof(struct pattern_cache), GFP_ATOMIC); + + if(!tmp) { + if (net_ratelimit()) + printk(KERN_ERR "layer7: out of memory in compile_and_cache, bailing.\n"); + return NULL; + } + + tmp->regex_string = kmalloc(strlen(regex_string) + 1, GFP_ATOMIC); + tmp->pattern = kmalloc(sizeof(struct regexp), GFP_ATOMIC); + tmp->next = NULL; + + if(!tmp->regex_string || !tmp->pattern) { + if (net_ratelimit()) + printk(KERN_ERR "layer7: out of memory in compile_and_cache, bailing.\n"); + kfree(tmp->regex_string); + kfree(tmp->pattern); + kfree(tmp); + return NULL; + } + + /* Ok. The new node is all ready now. */ + node = tmp; + + if(first_pattern_cache == NULL) /* list is empty */ + first_pattern_cache = node; /* make node the beginning */ + else + last_pattern_cache->next = node; /* attach node to the end */ + + /* copy the string and compile the regex */ + len = strlen(regex_string); + DPRINTK("About to compile this: \"%s\"\n", regex_string); + node->pattern = regcomp(regex_string, &len); + if ( !node->pattern ) { + if (net_ratelimit()) + printk(KERN_ERR "layer7: Error compiling regexp \"%s\" (%s)\n", regex_string, protocol); + /* pattern is now cached as NULL, so we won't try again. */ + } + + strcpy(node->regex_string, regex_string); + return node->pattern; +} + +static int can_handle(const struct sk_buff *skb) +{ + if(!skb->nh.iph) /* not IP */ + return 0; + if(skb->nh.iph->protocol != IPPROTO_TCP && + skb->nh.iph->protocol != IPPROTO_UDP && + skb->nh.iph->protocol != IPPROTO_ICMP) + return 0; + return 1; +} + +/* Returns offset the into the skb->data that the application data starts */ +static int app_data_offset(const struct sk_buff *skb) +{ + /* In case we are ported somewhere (ebtables?) where skb->nh.iph + isn't set, this can be gotten from 4*(skb->data[0] & 0x0f) as well. */ + int ip_hl = 4*skb->nh.iph->ihl; + + if( skb->nh.iph->protocol == IPPROTO_TCP ) { + /* 12 == offset into TCP header for the header length field. + Can't get this with skb->h.th->doff because the tcphdr + struct doesn't get set when routing (this is confirmed to be + true in Netfilter as well as QoS.) */ + int tcp_hl = 4*(skb->data[ip_hl + 12] >> 4); + + return ip_hl + tcp_hl; + } else if( skb->nh.iph->protocol == IPPROTO_UDP ) { + return ip_hl + 8; /* UDP header is always 8 bytes */ + } else if( skb->nh.iph->protocol == IPPROTO_ICMP ) { + return ip_hl + 8; /* ICMP header is 8 bytes */ + } else { + if (net_ratelimit()) + printk(KERN_ERR "layer7: tried to handle unknown protocol!\n"); + return ip_hl + 8; /* something reasonable */ + } +} + +/* handles whether there's a match when we aren't appending data anymore */ +static int match_no_append(struct ip_conntrack * conntrack, struct ip_conntrack * master_conntrack, + enum ip_conntrack_info ctinfo, enum ip_conntrack_info master_ctinfo, + struct ipt_layer7_info * info) +{ + /* If we're in here, throw the app data away */ + WRITE_LOCK(&ct_lock); + if(master_conntrack->layer7.app_data != NULL) { + + #ifdef CONFIG_IP_NF_MATCH_LAYER7_DEBUG + if(!master_conntrack->layer7.app_proto) { + char * f = friendly_print(master_conntrack->layer7.app_data); + char * g = hex_print(master_conntrack->layer7.app_data); + DPRINTK("\nl7-filter gave up after %d bytes (%d packets):\n%s\n", + strlen(f), + TOTAL_PACKETS, f); + kfree(f); + DPRINTK("In hex: %s\n", g); + kfree(g); + } + #endif + + kfree(master_conntrack->layer7.app_data); + master_conntrack->layer7.app_data = NULL; /* don't free again */ + } + WRITE_UNLOCK(&ct_lock); + + if(master_conntrack->layer7.app_proto){ + /* Here child connections set their .app_proto (for /proc/net/ip_conntrack) */ + WRITE_LOCK(&ct_lock); + if(!conntrack->layer7.app_proto) { + conntrack->layer7.app_proto = kmalloc(strlen(master_conntrack->layer7.app_proto)+1, GFP_ATOMIC); + if(!conntrack->layer7.app_proto){ + if (net_ratelimit()) + printk(KERN_ERR "layer7: out of memory in match_no_append, bailing.\n"); + WRITE_UNLOCK(&ct_lock); + return 1; + } + strcpy(conntrack->layer7.app_proto, master_conntrack->layer7.app_proto); + } + WRITE_UNLOCK(&ct_lock); + + return (!strcmp(master_conntrack->layer7.app_proto, info->protocol)); + } + else { + /* If not classified, set to "unknown" to distinguish from + connections that are still being tested. */ + WRITE_LOCK(&ct_lock); + master_conntrack->layer7.app_proto = kmalloc(strlen("unknown")+1, GFP_ATOMIC); + if(!master_conntrack->layer7.app_proto){ + if (net_ratelimit()) + printk(KERN_ERR "layer7: out of memory in match_no_append, bailing.\n"); + WRITE_UNLOCK(&ct_lock); + return 1; + } + strcpy(master_conntrack->layer7.app_proto, "unknown"); + WRITE_UNLOCK(&ct_lock); + return 0; + } +} + +/* add the new app data to the conntrack. Return number of bytes added. */ +static int add_data(struct ip_conntrack * master_conntrack, + char * app_data, int appdatalen) +{ + int length = 0, i; + int oldlength = master_conntrack->layer7.app_data_len; + + /* Strip nulls. Make everything lower case (our regex lib doesn't + do case insensitivity). Add it to the end of the current data. */ + for(i = 0; i < maxdatalen-oldlength-1 && i < appdatalen; i++) { + if(app_data[i] != '\0') { + master_conntrack->layer7.app_data[length+oldlength] = + /* the kernel version of tolower mungs 'upper ascii' */ + isascii(app_data[i])? tolower(app_data[i]) : app_data[i]; + length++; + } + } + + master_conntrack->layer7.app_data[length+oldlength] = '\0'; + master_conntrack->layer7.app_data_len = length + oldlength; + + return length; +} + +/* Returns true on match and false otherwise. */ +static int match(/* const */struct sk_buff *skb, const struct net_device *in, + const struct net_device *out, const void *matchinfo, + int offset, int *hotdrop) +{ + struct ipt_layer7_info * info = (struct ipt_layer7_info *)matchinfo; + enum ip_conntrack_info master_ctinfo, ctinfo; + struct ip_conntrack *master_conntrack, *conntrack; + unsigned char * app_data; + unsigned int pattern_result, appdatalen; + regexp * comppattern; + + if(!can_handle(skb)){ + DPRINTK("layer7: This is some protocol I can't handle.\n"); + return info->invert; + } + + /* Treat the parent and all its children together as one connection, + except for the purpose of setting conntrack->layer7.app_proto in the + actual connection. This makes /proc/net/ip_conntrack somewhat more + satisfying. */ + if(!(conntrack = ip_conntrack_get((struct sk_buff *)skb, &ctinfo)) || + !(master_conntrack = ip_conntrack_get((struct sk_buff *)skb, &master_ctinfo))) { + DPRINTK("layer7: packet is not from a known connection, giving up.\n"); + return info->invert; + } + + /* Try to get a master conntrack (and its master etc) for FTP, etc. */ + while (master_ct(master_conntrack) != NULL) + master_conntrack = master_ct(master_conntrack); + + if(!skb->cb[0]){ + WRITE_LOCK(&ct_lock); + master_conntrack->layer7.numpackets++;/*starts at 0 via memset*/ + WRITE_UNLOCK(&ct_lock); + } + + /* if we've classified it or seen too many packets */ + if(TOTAL_PACKETS > num_packets || + master_conntrack->layer7.app_proto) { + + pattern_result = match_no_append(conntrack, master_conntrack, ctinfo, master_ctinfo, info); + + /* skb->cb[0] == seen. Avoid doing things twice if there are two l7 + rules. I'm not sure that using cb for this purpose is correct, although + it says "put your private variables there". But it doesn't look like it + is being used for anything else in the skbs that make it here. How can + I write to cb without making the compiler angry? */ + skb->cb[0] = 1; /* marking it seen here is probably irrelevant, but consistant */ + + return (pattern_result ^ info->invert); + } + + if(skb_is_nonlinear(skb)){ + if(skb_linearize(skb, GFP_ATOMIC) != 0){ + if (net_ratelimit()) + printk(KERN_ERR "layer7: failed to linearize packet, bailing.\n"); + return info->invert; + } + } + + /* now that the skb is linearized, it's safe to set these. */ + app_data = skb->data + app_data_offset(skb); + appdatalen = skb->tail - app_data; + + LOCK_BH(&list_lock); + /* the return value gets checked later, when we're ready to use it */ + comppattern = compile_and_cache(info->pattern, info->protocol); + UNLOCK_BH(&list_lock); + + /* On the first packet of a connection, allocate space for app data */ + WRITE_LOCK(&ct_lock); + if(TOTAL_PACKETS == 1 && !skb->cb[0] && !master_conntrack->layer7.app_data) { + master_conntrack->layer7.app_data = kmalloc(maxdatalen, GFP_ATOMIC); + if(!master_conntrack->layer7.app_data){ + if (net_ratelimit()) + printk(KERN_ERR "layer7: out of memory in match, bailing.\n"); + WRITE_UNLOCK(&ct_lock); + return info->invert; + } + + master_conntrack->layer7.app_data[0] = '\0'; + } + WRITE_UNLOCK(&ct_lock); + + /* Can be here, but unallocated, if numpackets is increased near + the beginning of a connection */ + if(master_conntrack->layer7.app_data == NULL) + return (info->invert); /* unmatched */ + + if(!skb->cb[0]){ + int newbytes; + WRITE_LOCK(&ct_lock); + newbytes = add_data(master_conntrack, app_data, appdatalen); + WRITE_UNLOCK(&ct_lock); + + if(newbytes == 0) { /* didn't add any data */ + skb->cb[0] = 1; + /* Didn't match before, not going to match now */ + return info->invert; + } + } + + /* If looking for "unknown", then never match. "Unknown" means that + we've given up; we're still trying with these packets. */ + if(!strcmp(info->protocol, "unknown")) { + pattern_result = 0; + /* If the regexp failed to compile, don't bother running it */ + } else if(comppattern && regexec(comppattern, master_conntrack->layer7.app_data)) { + DPRINTK("layer7: regexec positive: %s!\n", info->protocol); + pattern_result = 1; + } else pattern_result = 0; + + if(pattern_result) { + WRITE_LOCK(&ct_lock); + master_conntrack->layer7.app_proto = kmalloc(strlen(info->protocol)+1, GFP_ATOMIC); + if(!master_conntrack->layer7.app_proto){ + if (net_ratelimit()) + printk(KERN_ERR "layer7: out of memory in match, bailing.\n"); + WRITE_UNLOCK(&ct_lock); + return (pattern_result ^ info->invert); + } + strcpy(master_conntrack->layer7.app_proto, info->protocol); + WRITE_UNLOCK(&ct_lock); + } + + /* mark the packet seen */ + skb->cb[0] = 1; + + return (pattern_result ^ info->invert); +} + +static int checkentry(const char *tablename, const struct ipt_ip *ip, + void *matchinfo, unsigned int matchsize, unsigned int hook_mask) +{ + if (matchsize != IPT_ALIGN(sizeof(struct ipt_layer7_info))) + return 0; + return 1; +} + +static struct ipt_match layer7_match = { + .name = "layer7", + .match = &match, + .checkentry = &checkentry, + .me = THIS_MODULE +}; + +/* taken from drivers/video/modedb.c */ +static int my_atoi(const char *s) +{ + int val = 0; + + for (;; s++) { + switch (*s) { + case '0'...'9': + val = 10*val+(*s-'0'); + break; + default: + return val; + } + } +} + +/* write out num_packets to userland. */ +static int layer7_read_proc(char* page, char ** start, off_t off, int count, + int* eof, void * data) +{ + if(num_packets > 99 && net_ratelimit()) + printk(KERN_ERR "layer7: NOT REACHED. num_packets too big\n"); + + page[0] = num_packets/10 + '0'; + page[1] = num_packets%10 + '0'; + page[2] = '\n'; + page[3] = '\0'; + + *eof=1; + + return 3; +} + +/* Read in num_packets from userland */ +static int layer7_write_proc(struct file* file, const char* buffer, + unsigned long count, void *data) +{ + char * foo = kmalloc(count, GFP_ATOMIC); + + if(!foo){ + if (net_ratelimit()) + printk(KERN_ERR "layer7: out of memory, bailing. num_packets unchanged.\n"); + return count; + } + + copy_from_user(foo, buffer, count); + + num_packets = my_atoi(foo); + kfree (foo); + + /* This has an arbitrary limit to make the math easier. I'm lazy. + But anyway, 99 is a LOT! If you want more, you're doing it wrong! */ + if(num_packets > 99) { + printk(KERN_WARNING "layer7: num_packets can't be > 99.\n"); + num_packets = 99; + } else if(num_packets < 1) { + printk(KERN_WARNING "layer7: num_packets can't be < 1.\n"); + num_packets = 1; + } + + return count; +} + +/* register the proc file */ +static void layer7_init_proc(void) +{ + struct proc_dir_entry* entry; + entry = create_proc_entry("layer7_numpackets", 0644, proc_net); + entry->read_proc = layer7_read_proc; + entry->write_proc = layer7_write_proc; +} + +static void layer7_cleanup_proc(void) +{ + remove_proc_entry("layer7_numpackets", proc_net); +} + +static int __init init(void) +{ + layer7_init_proc(); + if(maxdatalen < 1) { + printk(KERN_WARNING "layer7: maxdatalen can't be < 1, using 1\n"); + maxdatalen = 1; + } + /* This is not a hard limit. It's just here to prevent people from + bringing their slow machines to a grinding halt. */ + else if(maxdatalen > 65536) { + printk(KERN_WARNING "layer7: maxdatalen can't be > 65536, using 65536\n"); + maxdatalen = 65536; + } + return ipt_register_match(&layer7_match); +} + +static void __exit fini(void) +{ + layer7_cleanup_proc(); + ipt_unregister_match(&layer7_match); +} + +module_init(init); +module_exit(fini); |