X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/e5a9dba621b4301bfbe2bc05576ddc5ec752b1b5..870f6ba8a2945754a7f2f66097e3a64465fe1a04:/src/src/acl.c diff --git a/src/src/acl.c b/src/src/acl.c index b91d9d041..8125e38c9 100644 --- a/src/src/acl.c +++ b/src/src/acl.c @@ -1,4 +1,4 @@ -/* $Cambridge: exim/src/src/acl.c,v 1.29 2005/05/10 10:19:11 ph10 Exp $ */ +/* $Cambridge: exim/src/src/acl.c,v 1.34 2005/05/23 16:58:56 fanf2 Exp $ */ /************************************************* * Exim - an Internet mail transport agent * @@ -63,6 +63,7 @@ ACLC_CONDITION, ACLC_CONTROL, #ifdef WITH_CONTENT_SCAN ACLC_MIME_REGEX, #endif + ACLC_RATELIMIT, ACLC_RECIPIENTS, #ifdef WITH_CONTENT_SCAN ACLC_REGEX, @@ -110,6 +111,7 @@ static uschar *conditions[] = { US"acl", US"authenticated", #ifdef WITH_CONTENT_SCAN US"mime_regex", #endif + US"ratelimit", US"recipients", #ifdef WITH_CONTENT_SCAN US"regex", @@ -171,6 +173,7 @@ static uschar cond_expand_at_top[] = { #ifdef WITH_CONTENT_SCAN TRUE, /* mime_regex */ #endif + TRUE, /* ratelimit */ FALSE, /* recipients */ #ifdef WITH_CONTENT_SCAN TRUE, /* regex */ @@ -227,6 +230,7 @@ static uschar cond_modifiers[] = { #ifdef WITH_CONTENT_SCAN FALSE, /* mime_regex */ #endif + FALSE, /* ratelimit */ FALSE, /* recipients */ #ifdef WITH_CONTENT_SCAN FALSE, /* regex */ @@ -363,6 +367,8 @@ static unsigned int cond_forbids[] = { ~(1<message); - /* Search previously logged warnings. They are kept in malloc store so they - can be freed at the start of a new message. */ + /* Search previously logged warnings. They are kept in malloc + store so they can be freed at the start of a new message. */ for (logged = acl_warn_logged; logged != NULL; logged = logged->next) if (Ustrcmp(logged->text, text) == 0) break; @@ -1877,6 +1889,283 @@ return d->value; +/************************************************* +* Handle rate limiting * +*************************************************/ + +/* Called by acl_check_condition() below to calculate the result +of the ACL ratelimit condition. + +Note that the return value might be slightly unexpected: if the +sender's rate is above the limit then the result is OK. This is +similar to the dnslists condition, and is so that you can write +ACL clauses like: defer ratelimit = 15 / 1h + +Arguments: + arg the option string for ratelimit= + log_msgptr for error messages + +Returns: OK - Sender's rate is above limit + FAIL - Sender's rate is below limit + DEFER - Problem opening ratelimit database + ERROR - Syntax error in options. +*/ + +static int +acl_ratelimit(uschar *arg, uschar **log_msgptr) +{ +double limit, period; +uschar *ss, *key = arg; +int sep = '/'; +BOOL have_key = FALSE, leaky = FALSE, strict = FALSE; +BOOL per_byte = FALSE, per_cmd = FALSE, per_conn = FALSE, per_mail = FALSE; +int old_pool, rc; +tree_node **anchor, *t; +open_db dbblock, *dbm; +dbdata_ratelimit *dbd; +struct timeval tv; + +/* Parse the first two options and record their values in expansion +variables. These variables allow the configuration to have informative +error messages based on rate limits obtained from a table lookup. */ + +/* First is the maximum number of messages per period and maximum burst +size, which must be greater than or equal to zero. Zero is useful for +rate measurement as opposed to rate limiting. */ + +sender_rate_limit = string_nextinlist(&arg, &sep, NULL, 0); +if (sender_rate_limit == NULL) + limit = -1.0; +else + { + limit = Ustrtod(sender_rate_limit, &ss); + if (tolower(*ss) == 'k') { limit *= 1024.0; ss++; } + else if (tolower(*ss) == 'm') { limit *= 1024.0*1024.0; ss++; } + else if (tolower(*ss) == 'g') { limit *= 1024.0*1024.0*1024.0; ss++; } + } +if (limit < 0.0 || *ss != 0) + { + *log_msgptr = string_sprintf("syntax error in argument for " + "\"ratelimit\" condition: \"%s\" is not a positive number", + sender_rate_limit); + return ERROR; + } + +/* Second is the rate measurement period and exponential smoothing time +constant. This must be strictly greater than zero, because zero leads to +run-time division errors. */ + +sender_rate_period = string_nextinlist(&arg, &sep, NULL, 0); +if (sender_rate_period == NULL) period = -1.0; +else period = readconf_readtime(sender_rate_period, 0, FALSE); +if (period <= 0.0) + { + *log_msgptr = string_sprintf("syntax error in argument for " + "\"ratelimit\" condition: \"%s\" is not a time value", + sender_rate_period); + return ERROR; + } + +/* Parse the other options. Should we check if the per_* options are being +used in ACLs where they don't make sense, e.g. per_mail in the connect ACL? */ + +while ((ss = string_nextinlist(&arg, &sep, big_buffer, big_buffer_size)) + != NULL) + { + if (strcmpic(ss, US"leaky") == 0) leaky = TRUE; + else if (strcmpic(ss, US"strict") == 0) strict = TRUE; + else if (strcmpic(ss, US"per_byte") == 0) per_byte = TRUE; + else if (strcmpic(ss, US"per_cmd") == 0) per_cmd = TRUE; + else if (strcmpic(ss, US"per_conn") == 0) per_conn = TRUE; + else if (strcmpic(ss, US"per_mail") == 0) per_mail = TRUE; + else if (strcmpic(ss, US"per_rcpt") == 0) per_cmd = TRUE; /* alias */ + else have_key = TRUE; + } +if (leaky + strict > 1 || per_byte + per_cmd + per_conn + per_mail > 1) + { + *log_msgptr = US"conflicting options for \"ratelimit\" condition"; + return ERROR; + } + +/* Default option values */ +if (!strict) leaky = TRUE; +if (!per_byte && !per_cmd && !per_conn) per_mail = TRUE; + +/* We use the whole of the argument list as the lookup key, because it doesn't +make sense to use the same stored data if any of the arguments are different. +If there is no explicit key, use the sender_host_address. If there is no +sender_host_address (e.g. -bs or acl_not_smtp) then we simply omit it. */ + +if (!have_key && sender_host_address != NULL) + key = string_sprintf("%s / %s", key, sender_host_address); + +HDEBUG(D_acl) debug_printf("ratelimit condition limit=%.0f period=%.0f key=%s\n", + limit, period, key); + +/* If we are dealing with rate limits per connection, per message, or per byte, +see if we have already computed the rate by looking in the relevant tree. For +per-connection rate limiting, store tree nodes and dbdata in the permanent pool +so that they survive across resets. */ + +anchor = NULL; +old_pool = store_pool; + +if (per_conn) + { + anchor = &ratelimiters_conn; + store_pool = POOL_PERM; + } +if (per_mail || per_byte) + anchor = &ratelimiters_mail; + +if (anchor != NULL && (t = tree_search(*anchor, key)) != NULL) + { + dbd = t->data.ptr; + /* The following few lines duplicate some of the code below. */ + if (dbd->rate > limit) rc = OK; + else rc = FAIL; + store_pool = old_pool; + sender_rate = string_sprintf("%.1f", dbd->rate); + HDEBUG(D_acl) + debug_printf("ratelimit found pre-computed rate %s\n", sender_rate); + return rc; + } + +/* We aren't using a pre-computed rate, so get a previously recorded +rate from the database, update it, and write it back. If there's no +previous rate for this key, create one. */ + +dbm = dbfn_open(US"ratelimit", O_RDWR, &dbblock, TRUE); +if (dbm == NULL) + { + store_pool = old_pool; + sender_rate = NULL; + HDEBUG(D_acl) debug_printf("ratelimit database not available\n"); + *log_msgptr = US"ratelimit database not available"; + return DEFER; + } +dbd = dbfn_read(dbm, key); + +gettimeofday(&tv, NULL); + +if (dbd == NULL) + { + HDEBUG(D_acl) debug_printf("ratelimit initializing new key's data\n"); + dbd = store_get(sizeof(dbdata_ratelimit)); + dbd->time_stamp = tv.tv_sec; + dbd->time_usec = tv.tv_usec; + dbd->rate = 0.0; + } +else + { + /* The smoothed rate is computed using an exponentially weighted moving + average adjusted for variable sampling intervals. The standard EWMA for + a fixed sampling interval is: f'(t) = (1 - a) * f(t) + a * f'(t - 1) + where f() is the measured value and f'() is the smoothed value. + + Old data decays out of the smoothed value exponentially, such that data n + samples old is multiplied by a^n. The exponential decay time constant p + is defined such that data p samples old is multiplied by 1/e, which means + that a = exp(-1/p). We can maintain the same time constant for a variable + sampling interval i by using a = exp(-i/p). + + The rate we are measuring is messages per period, suitable for directly + comparing with the limit. The average rate between now and the previous + message is period / interval, which we feed into the EWMA as the sample. + + It turns out that the number of messages required for the smoothed rate + to reach the limit when they are sent in a burst is equal to the limit. + This can be seen by analysing the value of the smoothed rate after N + messages sent at even intervals. Let k = (1 - a) * p/i + + rate_1 = (1 - a) * p/i + a * rate_0 + = k + a * rate_0 + rate_2 = k + a * rate_1 + = k + a * k + a^2 * rate_0 + rate_3 = k + a * k + a^2 * k + a^3 * rate_0 + rate_N = rate_0 * a^N + k * SUM(x=0..N-1)(a^x) + = rate_0 * a^N + k * (1 - a^N) / (1 - a) + = rate_0 * a^N + p/i * (1 - a^N) + + When N is large, a^N -> 0 so rate_N -> p/i as desired. + + rate_N = p/i + (rate_0 - p/i) * a^N + a^N = (rate_N - p/i) / (rate_0 - p/i) + N * -i/p = log((rate_N - p/i) / (rate_0 - p/i)) + N = p/i * log((rate_0 - p/i) / (rate_N - p/i)) + + Numerical analysis of the above equation, setting the computed rate to + increase from rate_0 = 0 to rate_N = limit, shows that for large sending + rates, p/i, the number of messages N = limit. So limit serves as both the + maximum rate measured in messages per period, and the maximum number of + messages that can be sent in a fast burst. */ + + double this_time = (double)tv.tv_sec + + (double)tv.tv_usec / 1000000.0; + double prev_time = (double)dbd->time_stamp + + (double)dbd->time_usec / 1000000.0; + double interval = this_time - prev_time; + + double i_over_p = interval / period; + double a = exp(-i_over_p); + + /* We must avoid division by zero, and deal gracefully with the clock going + backwards. If we blunder ahead when time is in reverse then the computed + rate will become bogusly huge. Clamp i/p to a very small number instead. */ + + if (i_over_p <= 0.0) i_over_p = 1e-9; + + dbd->time_stamp = tv.tv_sec; + dbd->time_usec = tv.tv_usec; + + /* If we are measuring the rate in bytes per period, multiply the + measured rate by the message size. If we don't know the message size + then it's safe to just use a value of zero and let the recorded rate + decay as if nothing happened. */ + + if (per_byte) + dbd->rate = (message_size < 0 ? 0.0 : (double)message_size) + * (1 - a) / i_over_p + a * dbd->rate; + else + dbd->rate = (1 - a) / i_over_p + a * dbd->rate; + } + +if (dbd->rate > limit) rc = OK; + else rc = FAIL; + +/* Update the state if the rate is low or if we are being strict. If we +are in leaky mode and the sender's rate is too high, we do not update +the recorded rate in order to avoid an over-aggressive sender's retry +rate preventing them from getting any email through. */ + +if (rc == FAIL || !leaky) + dbfn_write(dbm, key, dbd, sizeof(dbdata_ratelimit)); +dbfn_close(dbm); + +/* Store the result in the tree for future reference, if necessary. */ + +if (anchor != NULL) + { + t = store_get(sizeof(tree_node) + Ustrlen(key)); + t->data.ptr = dbd; + Ustrcpy(t->name, key); + (void)tree_insertnode(anchor, t); + } + +/* We create the formatted version of the sender's rate very late in +order to ensure that it is done using the correct storage pool. */ + +store_pool = old_pool; +sender_rate = string_sprintf("%.1f", dbd->rate); + +HDEBUG(D_acl) + debug_printf("ratelimit computed rate %s\n", sender_rate); + +return rc; +} + + + /************************************************* * Handle conditions/modifiers on an ACL item * *************************************************/ @@ -2101,19 +2390,20 @@ for (; cb != NULL; cb = cb->next) no_multiline_responses = TRUE; break; + case CONTROL_FAKEDEFER: case CONTROL_FAKEREJECT: - fake_reject = TRUE; + fake_response = (control_type == CONTROL_FAKEDEFER) ? DEFER : FAIL; if (*p == '/') { uschar *pp = p + 1; while (*pp != 0) pp++; - fake_reject_text = expand_string(string_copyn(p+1, pp-p)); + fake_response_text = expand_string(string_copyn(p+1, pp-p-1)); p = pp; } else { /* Explicitly reset to default string */ - fake_reject_text = US"Your message has been rejected but is being kept for evaluation.\nIf it was a legitimate message, it may still be delivered to the target recipient(s)."; + fake_response_text = US"Your message has been rejected but is being kept for evaluation.\nIf it was a legitimate message, it may still be delivered to the target recipient(s)."; } break; @@ -2127,6 +2417,7 @@ for (; cb != NULL; cb = cb->next) break; case CONTROL_SUBMISSION: + originator_name = US""; submission_mode = TRUE; while (*p == '/') { @@ -2140,7 +2431,15 @@ for (; cb != NULL; cb = cb->next) { uschar *pp = p + 8; while (*pp != 0 && *pp != '/') pp++; - submission_domain = string_copyn(p+8, pp-p); + submission_domain = string_copyn(p+8, pp-p-8); + p = pp; + } + else if (Ustrncmp(p, "/name=", 6) == 0) + { + uschar *pp = p + 6; + while (*pp != 0 && *pp != '/') pp++; + originator_name = string_copy(parse_fix_phrase(p+6, pp-p-6, + big_buffer, big_buffer_size)); p = pp; } else break; @@ -2178,6 +2477,22 @@ for (; cb != NULL; cb = cb->next) HDEBUG(D_acl) debug_printf("delay skipped in -bh checking mode\n"); } + + /* It appears to be impossible to detect that a TCP/IP connection has + gone away without reading from it. This means that we cannot shorten + the delay below if the client goes away, because we cannot discover + that the client has closed its end of the connection. (The connection + is actually in a half-closed state, waiting for the server to close its + end.) It would be nice to be able to detect this state, so that the + Exim process is not held up unnecessarily. However, it seems that we + can't. The poll() function does not do the right thing, and in any case + it is not always available. + + NOTE: If ever this state of affairs changes, remember that we may be + dealing with stdin/stdout here, in addition to TCP/IP connections. + Whatever is done must work in both cases. To detected the stdin/stdout + case, check for smtp_in or smtp_out being NULL. */ + else { while (delay > 0) delay = sleep(delay); @@ -2383,6 +2698,10 @@ for (; cb != NULL; cb = cb->next) break; #endif + case ACLC_RATELIMIT: + rc = acl_ratelimit(arg, log_msgptr); + break; + case ACLC_RECIPIENTS: rc = match_address_list(addr->address, TRUE, TRUE, &arg, NULL, -1, 0, &recipient_data); @@ -2934,9 +3253,10 @@ while (acl != NULL) if (cond == OK) acl_warn(where, *user_msgptr, *log_msgptr); else if (cond == DEFER) - acl_warn(where, NULL, string_sprintf("ACL \"warn\" statement skipped: " - "condition test deferred: %s", - (*log_msgptr == NULL)? US"" : *log_msgptr)); + log_write(0, LOG_MAIN, "%s Warning: ACL \"warn\" statement skipped: " + "condition test deferred%s%s", host_and_ident(TRUE), + (*log_msgptr == NULL)? US"" : US": ", + (*log_msgptr == NULL)? US"" : *log_msgptr); *log_msgptr = *user_msgptr = NULL; /* In case implicit DENY follows */ break;