--- httpd-2.4.25/modules/metadata/mod_unique_id.c.uniqueid 2011-12-05 02:08:01.000000000 +0200 +++ httpd-2.4.25/modules/metadata/mod_unique_id.c 2016-12-24 15:43:18.060602927 +0200 @@ -14,304 +14,212 @@ * limitations under the License. */ /* * mod_unique_id.c: generate a unique identifier for each request * * Original author: Dean Gaudet <dgaudet@arctic.org> * UUencoding modified by: Alvaro Martinez Echevarria <alvaro@lander.es> */ #define APR_WANT_BYTEFUNC /* for htons() et al */ #include "apr_want.h" #include "apr_general.h" /* for APR_OFFSETOF */ #include "apr_network_io.h" #include "httpd.h" #include "http_config.h" #include "http_log.h" #include "http_protocol.h" /* for ap_hook_post_read_request */ -#if APR_HAVE_UNISTD_H -#include <unistd.h> /* for getpid() */ -#endif +#define ROOT_SIZE 10 typedef struct { unsigned int stamp; - unsigned int in_addr; - unsigned int pid; + char root[ROOT_SIZE]; unsigned short counter; unsigned int thread_index; } unique_id_rec; /* We are using thread_index (the index into the scoreboard), because we * cannot guarantee the thread_id will be an integer. * * This code looks like it won't give a unique ID with the new thread logic. * It will. The reason is, we don't increment the counter in a thread_safe * manner. Because the thread_index is also in the unique ID now, this does * not matter. In order for the id to not be unique, the same thread would * have to get the same counter twice in the same second. */ /* Comments: * * We want an identifier which is unique across all hits, everywhere. * "everywhere" includes multiple httpd instances on the same machine, or on * multiple machines. Essentially "everywhere" should include all possible * httpds across all servers at a particular "site". We make some assumptions * that if the site has a cluster of machines then their time is relatively * synchronized. We also assume that the first address returned by a * gethostbyname (gethostname()) is unique across all the machines at the * "site". * - * We also further assume that pids fit in 32-bits. If something uses more - * than 32-bits, the fix is trivial, but it requires the unrolled uuencoding - * loop to be extended. * A similar fix is needed to support multithreaded - * servers, using a pid/tid combo. - * - * Together, the in_addr and pid are assumed to absolutely uniquely identify - * this one child from all other currently running children on all servers - * (including this physical server if it is running multiple httpds) from each + * The root is assumed to absolutely uniquely identify this one child + * from all other currently running children on all servers (including + * this physical server if it is running multiple httpds) from each * other. * - * The stamp and counter are used to distinguish all hits for a particular - * (in_addr,pid) pair. The stamp is updated using r->request_time, - * saving cpu cycles. The counter is never reset, and is used to permit up to - * 64k requests in a single second by a single child. + * The stamp and counter are used to distinguish all hits for a + * particular root. The stamp is updated using r->request_time, + * saving cpu cycles. The counter is never reset, and is used to + * permit up to 64k requests in a single second by a single child. * * The 144-bits of unique_id_rec are encoded using the alphabet * [A-Za-z0-9@-], resulting in 24 bytes of printable characters. That is then * stuffed into the environment variable UNIQUE_ID so that it is available to * other modules. The alphabet choice differs from normal base64 encoding * [A-Za-z0-9+/] because + and / are special characters in URLs and we want to * make it easy to use UNIQUE_ID in URLs. * * Note that UNIQUE_ID should be considered an opaque token by other * applications. No attempt should be made to dissect its internal components. * It is an abstraction that may change in the future as the needs of this * module change. * * It is highly desirable that identifiers exist for "eternity". But future - * needs (such as much faster webservers, moving to 64-bit pids, or moving to a + * needs (such as much faster webservers, or moving to a * multithreaded server) may dictate a need to change the contents of * unique_id_rec. Such a future implementation should ensure that the first * field is still a time_t stamp. By doing that, it is possible for a site to * have a "flag second" in which they stop all of their old-format servers, * wait one entire second, and then start all of their new-servers. This * procedure will ensure that the new space of identifiers is completely unique * from the old space. (Since the first four unencoded bytes always differ.) + * + * Note: previous implementations used 32-bits of IP address plus pid + * in place of the PRNG output in the "root" field. This was + * insufficient for IPv6-only hosts, required working DNS to determine + * a unique IP address (fragile), and needed a [0, 1) second sleep + * call at startup to avoid pid reuse. Use of the PRNG avoids all + * these issues. */ + /* * Sun Jun 7 05:43:49 CEST 1998 -- Alvaro * More comments: * 1) The UUencoding prodecure is now done in a general way, avoiding the problems * with sizes and paddings that can arise depending on the architecture. Now the * offsets and sizes of the elements of the unique_id_rec structure are calculated * in unique_id_global_init; and then used to duplicate the structure without the * paddings that might exist. The multithreaded server fix should be now very easy: * just add a new "tid" field to the unique_id_rec structure, and increase by one * UNIQUE_ID_REC_MAX. * 2) unique_id_rec.stamp has been changed from "time_t" to "unsigned int", because * its size is 64bits on some platforms (linux/alpha), and this caused problems with * htonl/ntohl. Well, this shouldn't be a problem till year 2106. */ -static unsigned global_in_addr; - /* * XXX: We should have a per-thread counter and not use cur_unique_id.counter * XXX: in all threads, because this is bad for performance on multi-processor * XXX: systems: Writing to the same address from several CPUs causes cache * XXX: thrashing. */ static unique_id_rec cur_unique_id; /* * Number of elements in the structure unique_id_rec. */ -#define UNIQUE_ID_REC_MAX 5 +#define UNIQUE_ID_REC_MAX 4 static unsigned short unique_id_rec_offset[UNIQUE_ID_REC_MAX], unique_id_rec_size[UNIQUE_ID_REC_MAX], unique_id_rec_total_size, unique_id_rec_size_uu; static int unique_id_global_init(apr_pool_t *p, apr_pool_t *plog, apr_pool_t *ptemp, server_rec *main_server) { - char str[APRMAXHOSTLEN + 1]; - apr_status_t rv; - char *ipaddrstr; - apr_sockaddr_t *sockaddr; - /* * Calculate the sizes and offsets in cur_unique_id. */ unique_id_rec_offset[0] = APR_OFFSETOF(unique_id_rec, stamp); unique_id_rec_size[0] = sizeof(cur_unique_id.stamp); - unique_id_rec_offset[1] = APR_OFFSETOF(unique_id_rec, in_addr); - unique_id_rec_size[1] = sizeof(cur_unique_id.in_addr); - unique_id_rec_offset[2] = APR_OFFSETOF(unique_id_rec, pid); - unique_id_rec_size[2] = sizeof(cur_unique_id.pid); - unique_id_rec_offset[3] = APR_OFFSETOF(unique_id_rec, counter); - unique_id_rec_size[3] = sizeof(cur_unique_id.counter); - unique_id_rec_offset[4] = APR_OFFSETOF(unique_id_rec, thread_index); - unique_id_rec_size[4] = sizeof(cur_unique_id.thread_index); + unique_id_rec_offset[1] = APR_OFFSETOF(unique_id_rec, root); + unique_id_rec_size[1] = sizeof(cur_unique_id.root); + unique_id_rec_offset[2] = APR_OFFSETOF(unique_id_rec, counter); + unique_id_rec_size[2] = sizeof(cur_unique_id.counter); + unique_id_rec_offset[3] = APR_OFFSETOF(unique_id_rec, thread_index); + unique_id_rec_size[3] = sizeof(cur_unique_id.thread_index); unique_id_rec_total_size = unique_id_rec_size[0] + unique_id_rec_size[1] + - unique_id_rec_size[2] + unique_id_rec_size[3] + - unique_id_rec_size[4]; + unique_id_rec_size[2] + unique_id_rec_size[3]; /* * Calculate the size of the structure when encoded. */ unique_id_rec_size_uu = (unique_id_rec_total_size*8+5)/6; - /* - * Now get the global in_addr. Note that it is not sufficient to use one - * of the addresses from the main_server, since those aren't as likely to - * be unique as the physical address of the machine - */ - if ((rv = apr_gethostname(str, sizeof(str) - 1, p)) != APR_SUCCESS) { - ap_log_error(APLOG_MARK, APLOG_ALERT, rv, main_server, APLOGNO(01563) - "unable to find hostname of the server"); - return HTTP_INTERNAL_SERVER_ERROR; - } - - if ((rv = apr_sockaddr_info_get(&sockaddr, str, AF_INET, 0, 0, p)) == APR_SUCCESS) { - global_in_addr = sockaddr->sa.sin.sin_addr.s_addr; - } - else { - ap_log_error(APLOG_MARK, APLOG_ALERT, rv, main_server, APLOGNO(01564) - "unable to find IPv4 address of \"%s\"", str); -#if APR_HAVE_IPV6 - if ((rv = apr_sockaddr_info_get(&sockaddr, str, AF_INET6, 0, 0, p)) == APR_SUCCESS) { - memcpy(&global_in_addr, - (char *)sockaddr->ipaddr_ptr + sockaddr->ipaddr_len - sizeof(global_in_addr), - sizeof(global_in_addr)); - ap_log_error(APLOG_MARK, APLOG_ALERT, rv, main_server, APLOGNO(01565) - "using low-order bits of IPv6 address " - "as if they were unique"); - } - else -#endif - return HTTP_INTERNAL_SERVER_ERROR; - } - - apr_sockaddr_ip_get(&ipaddrstr, sockaddr); - ap_log_error(APLOG_MARK, APLOG_INFO, 0, main_server, APLOGNO(01566) "using ip addr %s", - ipaddrstr); - - /* - * If the server is pummelled with restart requests we could possibly end - * up in a situation where we're starting again during the same second - * that has been used in previous identifiers. Avoid that situation. - * - * In truth, for this to actually happen not only would it have to restart - * in the same second, but it would have to somehow get the same pids as - * one of the other servers that was running in that second. Which would - * mean a 64k wraparound on pids ... not very likely at all. - * - * But protecting against it is relatively cheap. We just sleep into the - * next second. - */ - apr_sleep(apr_time_from_sec(1) - apr_time_usec(apr_time_now())); return OK; } static void unique_id_child_init(apr_pool_t *p, server_rec *s) { - pid_t pid; - - /* - * Note that we use the pid because it's possible that on the same - * physical machine there are multiple servers (i.e. using Listen). But - * it's guaranteed that none of them will share the same pids between - * children. - * - * XXX: for multithread this needs to use a pid/tid combo and probably - * needs to be expanded to 32 bits - */ - pid = getpid(); - cur_unique_id.pid = pid; - - /* - * Test our assumption that the pid is 32-bits. It's possible that - * 64-bit machines will declare pid_t to be 64 bits but only use 32 - * of them. It would have been really nice to test this during - * global_init ... but oh well. - */ - if ((pid_t)cur_unique_id.pid != pid) { - ap_log_error(APLOG_MARK, APLOG_CRIT, 0, s, APLOGNO(01567) - "oh no! pids are greater than 32-bits! I'm broken!"); - } - - cur_unique_id.in_addr = global_in_addr; + ap_random_insecure_bytes(&cur_unique_id.root, + sizeof(cur_unique_id.root)); /* * If we use 0 as the initial counter we have a little less protection * against restart problems, and a little less protection against a clock * going backwards in time. */ ap_random_insecure_bytes(&cur_unique_id.counter, sizeof(cur_unique_id.counter)); - - /* - * We must always use network ordering for these bytes, so that - * identifiers are comparable between machines of different byte - * orderings. Note in_addr is already in network order. - */ - cur_unique_id.pid = htonl(cur_unique_id.pid); } /* NOTE: This is *NOT* the same encoding used by base64encode ... the last two * characters should be + and /. But those two characters have very special * meanings in URLs, and we want to make it easy to use identifiers in * URLs. So we replace them with @ and -. */ static const char uuencoder[64] = { 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '@', '-', }; static const char *gen_unique_id(const request_rec *r) { char *str; /* * Buffer padded with two final bytes, used to copy the unique_id_red * structure without the internal paddings that it could have. */ unique_id_rec new_unique_id; struct { unique_id_rec foo; unsigned char pad[2]; } paddedbuf; unsigned char *x,*y; unsigned short counter; int i,j,k; - new_unique_id.in_addr = cur_unique_id.in_addr; - new_unique_id.pid = cur_unique_id.pid; + memcpy(&new_unique_id.root, &cur_unique_id.root, ROOT_SIZE); new_unique_id.counter = cur_unique_id.counter; - new_unique_id.stamp = htonl((unsigned int)apr_time_sec(r->request_time)); new_unique_id.thread_index = htonl((unsigned int)r->connection->id); /* we'll use a temporal buffer to avoid uuencoding the possible internal * paddings of the original structure */ x = (unsigned char *) &paddedbuf; k = 0; for (i = 0; i < UNIQUE_ID_REC_MAX; i++) { y = ((unsigned char *) &new_unique_id) + unique_id_rec_offset[i]; for (j = 0; j < unique_id_rec_size[i]; j++, k++) { x[k] = y[j]; } } /* * We reset two more bytes just in case padding is needed for the uuencoding. */ x[k++] = '\0'; x[k++] = '\0'; /* alloc str and do the uuencoding */