From 632c8ceeff26a7663f939895f77aecb8377773f2 Mon Sep 17 00:00:00 2001 From: Marius Tomaschewski Date: Sun, 27 Mar 2011 13:15:58 +0200 Subject: [PATCH] dhclient: discard incorrect string options Discard string options such as host and domain names containing disallowed characters or beeing too long. This proctive patch limits root-path to the a-zA-Z0-9, space and the #%+-_:.,@~/\[]= characters. Signed-off-by: Marius Tomaschewski --- client/dhclient.c | 186 +++++++++++++++++++++++++++++++++++++++++++++++++---- common/options.c | 3 +- 2 files changed, 175 insertions(+), 14 deletions(-) diff --git a/client/dhclient.c b/client/dhclient.c index dc19e8b..5d96c72 100644 --- a/client/dhclient.c +++ b/client/dhclient.c @@ -91,6 +91,11 @@ static void usage(void); static isc_result_t write_duid(struct data_string *duid); +static int check_domain_name(const char *ptr, size_t len, int dots); +static int check_domain_name_list(const char *ptr, size_t len, int dots); +static int check_option_values(struct universe *universe, unsigned int opt, + const char *ptr, size_t len); + int main(int argc, char **argv) { int fd; @@ -3034,13 +3039,23 @@ void client_option_envadd (struct option_cache *oc, if (data.len) { char name [256]; if (dhcp_option_ev_name (name, sizeof name, - oc -> option)) { - client_envadd (es -> client, es -> prefix, - name, "%s", - (pretty_print_option - (oc -> option, - data.data, data.len, - 0, 0))); + oc->option)) { + const char *value; + value = pretty_print_option(oc->option, + data.data, + data.len, 0, 0); + size_t length = strlen(value); + + if (check_option_values(oc->option->universe, + oc->option->code, + value, length) == 0) { + client_envadd(es->client, es->prefix, + name, "%s", value); + } else { + log_error("suspect value in %s " + "option - discarded", + name); + } data_string_forget (&data, MDL); } } @@ -3118,12 +3133,32 @@ void script_write_params (client, prefix, lease) data_string_forget (&data, MDL); } - if (lease -> filename) - client_envadd (client, - prefix, "filename", "%s", lease -> filename); - if (lease -> server_name) - client_envadd (client, prefix, "server_name", - "%s", lease -> server_name); + if (lease->filename) { + if (check_option_values(NULL, DHO_ROOT_PATH, + lease->filename, + strlen(lease->filename)) == 0) { + client_envadd(client, prefix, "filename", + "%s", lease->filename); + } else { + log_error("suspect value in %s " + "option - discarded", + "filename"); + } + } + + if (lease->server_name) { + if (check_option_values(NULL, DHO_HOST_NAME, + lease->server_name, + strlen(lease->server_name)) == 0 ) { + client_envadd (client, prefix, "server_name", + "%s", lease->server_name); + } else { + log_error("suspect value in %s " + "option - discarded", + "server_name"); + } + } + for (i = 0; i < lease -> options -> universe_count; i++) { option_space_foreach ((struct packet *)0, (struct lease *)0, @@ -4026,3 +4061,128 @@ dhcpv4_client_assignments(void) } else remote_port = htons (ntohs (local_port) - 1); /* XXX */ } + +/* + * The following routines are used to check that certain + * strings are reasonable before we pass them to the scripts. + * This avoids some problems with scripts treating the strings + * as commands - see ticket 23722 + * The domain checking code should be done as part of assembling + * the string but we are doing it here for now due to time + * constraints. + */ + +static int check_domain_name(const char *ptr, size_t len, int dots) +{ + const char *p; + + /* not empty or complete length not over 255 characters */ + if ((len == 0) || (len >= 256)) + return(-1); + + /* consists of [[:alnum:]-]+ labels separated by [.] */ + /* a [_] is against RFC but seems to be "widely used"... */ + for (p=ptr; (*p != 0) && (len-- > 0); p++) { + if ((*p == '-') || (*p == '_')) { + /* not allowed at begin or end of a label */ + if (((p - ptr) == 0) || (len == 0) || (p[1] == '.')) + return(-1); + } else if (*p == '.') { + /* each label has to be 1-63 characters; + we allow [.] at the end ('foo.bar.') */ + size_t d = p - ptr; + if ((d <= 0) || (d >= 64)) + return(-1); + ptr = p + 1; /* jump to the next label */ + if ((dots > 0) && (len > 0)) + dots--; + } else if (isalnum((unsigned char)*p) == 0) { + /* also numbers at the begin are fine */ + return(-1); + } + } + return(dots ? -1 : 0); +} + +static int check_domain_name_list(const char *ptr, size_t len, int dots) +{ + const char *p; + int ret = -1; /* at least one needed */ + + if ((ptr == NULL) || (len == 0)) + return(-1); + + for (p=ptr; (*p != 0) && (len > 0); p++, len--) { + if (*p != ' ') + continue; + if (p > ptr) { + if (check_domain_name(ptr, p - ptr, dots) != 0) + return(-1); + ret = 0; + } + ptr = p + 1; + } + if (p > ptr) + return(check_domain_name(ptr, p - ptr, dots)); + else + return(ret); +} + +static int check_option_values(struct universe *universe, + unsigned int opt, + const char *ptr, + size_t len) +{ + if (ptr == NULL) + return(-1); + + /* just reject options we want to protect, will be escaped anyway */ + if ((universe == NULL) || (universe == &dhcp_universe)) { + switch(opt) { + case DHO_HOST_NAME: + case DHO_DOMAIN_NAME: + case DHO_NIS_DOMAIN: + case DHO_NETBIOS_SCOPE: + return check_domain_name(ptr, len, 0); + break; + case DHO_DOMAIN_SEARCH: + return check_domain_name_list(ptr, len, 0); + break; + case DHO_ROOT_PATH: + if (len == 0) + return(-1); + for (; (*ptr != 0) && (len-- > 0); ptr++) { + if(!(isalnum((unsigned char)*ptr) || + *ptr == '#' || *ptr == '%' || + *ptr == '+' || *ptr == '-' || + *ptr == '_' || *ptr == ':' || + *ptr == '.' || *ptr == ',' || + *ptr == '@' || *ptr == '~' || + *ptr == '\\' || *ptr == '/' || + *ptr == '[' || *ptr == ']' || + *ptr == '=' || *ptr == ' ')) + return(-1); + } + return(0); + break; + } + } + +#ifdef DHCPv6 + if (universe == &dhcpv6_universe) { + switch(opt) { + case D6O_SIP_SERVERS_DNS: + case D6O_DOMAIN_SEARCH: + case D6O_NIS_DOMAIN_NAME: + case D6O_NISP_DOMAIN_NAME: + return check_domain_name_list(ptr, len, 0); + break; + } + } +#endif + + return(0); +} + + + diff --git a/common/options.c b/common/options.c index 28c36e6..3a6cb33 100644 --- a/common/options.c +++ b/common/options.c @@ -3915,7 +3915,8 @@ pretty_escape(char **dst, char *dend, const unsigned char **src, count += 4; } } else if (**src == '"' || **src == '\'' || **src == '$' || - **src == '`' || **src == '\\') { + **src == '`' || **src == '\\' || **src == '|' || + **src == '&' || **src == ';') { if (*dst + 2 > dend) return -1; -- 1.7.3.4