filter: reduce memory usage, fix OOM crashes

* check return values of memory allocation and abort gracefully
  in out-of-memory situations

* use sblist (linear dynamic array) instead of linked list
  - this removes one pointer per filter rule
  - removes need to manually allocate/free every single list item
    (instead block allocation is used)
  - simplifies code

* remove storage of (unused) input rule
  - removes one char* pointer per filter rule
  - removes storage of the raw bytes of each filter rule

* add line number to display on out-of-memory/invalid regex situation

* replace duplicate filter_domain()/filter_host() code with a single
  function filter_run()
  - reduces code size and management effort

with these improvements, >1 million regex rules can be loaded with
4 GB of RAM, whereas previously it crashed with about 950K.

the list for testing was assembled from
http://www.shallalist.de/Downloads/shallalist.tar.gz

closes #20

3 files changed, 35 insertions, 65 deletions

diff --git a/src/filter.c b/src/filter.c
index 206bf31..8a0b085 100644
--- a/src/filter.c
+++ b/src/filter.c
@@ -29,18 +29,17 @@
 #include "log.h"
 #include "reqs.h"
 #include "conf.h"
+#include "sblist.h"
 
 #define FILTER_BUFFER_LEN (512)
 
 static int err;
 
 struct filter_list {
-        struct filter_list *next;
-        char *pat;
-        regex_t *cpat;
+        regex_t cpatb;
 };
 
-static struct filter_list *fl = NULL;
+static sblist *fl = NULL;
 static int already_init = 0;
 static filter_policy_t default_policy = FILTER_DEFAULT_ALLOW;
 
@@ -50,10 +49,10 @@ static filter_policy_t default_policy = FILTER_DEFAULT_ALLOW;
 void filter_init (void)
 {
         FILE *fd;
-        struct filter_list *p;
+        struct filter_list fe;
         char buf[FILTER_BUFFER_LEN];
         char *s, *start;
-        int cflags;
+        int cflags, lineno = 0;
 
         if (fl || already_init) {
                 return;
@@ -64,8 +63,6 @@ void filter_init (void)
                 return;
         }
 
-        p = NULL;
-
         cflags = REG_NEWLINE | REG_NOSUB;
         if (config->filter_extended)
                 cflags |= REG_EXTENDED;
@@ -73,6 +70,7 @@ void filter_init (void)
                 cflags |= REG_ICASE;
 
         while (fgets (buf, FILTER_BUFFER_LEN, fd)) {
+                ++lineno;
                 /* skip leading whitespace */
                 s = buf;
                 while (*s && isspace ((unsigned char) *s))
@@ -104,24 +102,22 @@ void filter_init (void)
                 if (*s == '\0')
                         continue;
 
-                if (!p) /* head of list */
-                        fl = p =
-                            (struct filter_list *)
-                            safecalloc (1, sizeof (struct filter_list));
-                else {  /* next entry */
-                        p->next =
-                            (struct filter_list *)
-                            safecalloc (1, sizeof (struct filter_list));
-                        p = p->next;
-                }
+                if (!fl) fl = sblist_new(sizeof(struct filter_list),
+                                         4096/sizeof(struct filter_list));
 
-                p->pat = safestrdup (s);
-                p->cpat = (regex_t *) safemalloc (sizeof (regex_t));
-                err = regcomp (p->cpat, p->pat, cflags);
+                err = regcomp (&fe.cpatb, s, cflags);
                 if (err != 0) {
+                        if (err == REG_ESPACE) goto oom;
+                        fprintf (stderr,
+                                 "Bad regex in %s: line %d - %s\n",
+                                 config->filter, lineno, s);
+                        exit (EX_DATAERR);
+                }
+                if (!sblist_add(fl, &fe)) {
+                oom:;
                         fprintf (stderr,
-                                 "Bad regex in %s: %s\n",
-                                 config->filter, p->pat);
+                                 "out of memory parsing filter file %s: line %d\n",
+                                 config->filter, lineno);
                         exit (EX_DATAERR);
                 }
         }
@@ -137,15 +133,16 @@ void filter_init (void)
 /* unlink the list */
 void filter_destroy (void)
 {
-        struct filter_list *p, *q;
+        struct filter_list *p;
+        size_t i;
 
         if (already_init) {
-                for (p = q = fl; p; p = q) {
-                        regfree (p->cpat);
-                        safefree (p->cpat);
-                        safefree (p->pat);
-                        q = p->next;
-                        safefree (p);
+                if (fl) {
+                        for (i = 0; i < sblist_getsize(fl); ++i) {
+                                p = sblist_get(fl, i);
+                                regfree (&p->cpatb);
+                        }
+                        sblist_free(fl);
                 }
                 fl = NULL;
                 already_init = 0;
@@ -165,45 +162,19 @@ void filter_reload (void)
 }
 
 /* Return 0 to allow, non-zero to block */
-int filter_domain (const char *host)
-{
-        struct filter_list *p;
-        int result;
-
-        if (!fl || !already_init)
-                goto COMMON_EXIT;
-
-        for (p = fl; p; p = p->next) {
-                result =
-                    regexec (p->cpat, host, (size_t) 0, (regmatch_t *) 0, 0);
-
-                if (result == 0) {
-                        if (default_policy == FILTER_DEFAULT_ALLOW)
-                                return 1;
-                        else
-                                return 0;
-                }
-        }
-
-COMMON_EXIT:
-        if (default_policy == FILTER_DEFAULT_ALLOW)
-                return 0;
-        else
-                return 1;
-}
-
-/* returns 0 to allow, non-zero to block */
-int filter_url (const char *url)
+int filter_run (const char *str)
 {
         struct filter_list *p;
+        size_t i;
         int result;
 
         if (!fl || !already_init)
                 goto COMMON_EXIT;
 
-        for (p = fl; p; p = p->next) {
+        for (i = 0; i < sblist_getsize(fl); ++i) {
+                p = sblist_get(fl, i);
                 result =
-                    regexec (p->cpat, url, (size_t) 0, (regmatch_t *) 0, 0);
+                    regexec (&p->cpatb, str, (size_t) 0, (regmatch_t *) 0, 0);
 
                 if (result == 0) {
                         if (default_policy == FILTER_DEFAULT_ALLOW)
diff --git a/src/filter.h b/src/filter.h
index 8c6f270..8a7575b 100644
--- a/src/filter.h
+++ b/src/filter.h
@@ -29,8 +29,7 @@ typedef enum {
 extern void filter_init (void);
 extern void filter_destroy (void);
 extern void filter_reload (void);
-extern int filter_domain (const char *host);
-extern int filter_url (const char *url);
+extern int filter_run (const char *str);
 
 extern void filter_set_default_policy (filter_policy_t policy);
 
diff --git a/src/reqs.c b/src/reqs.c
index 859ac6b..c58bbed 100644
--- a/src/reqs.c
+++ b/src/reqs.c
@@ -457,9 +457,9 @@ BAD_REQUEST_ERROR:
          */
         if (config->filter) {
                 if (config->filter_url)
-                        ret = filter_url (url);
+                        ret = filter_run (url);
                 else
-                        ret = filter_domain (request->host);
+                        ret = filter_run (request->host);
 
                 if (ret) {
                         update_stats (STAT_DENIED);