bpf: fix file parsing memory handling

Fix improper fread string handling. Improve error handling.

Skip trailing spaces for slightly more pretty printing.

Coverity CID 400763.

Thanks to Steve Grubb for helping address this issue.

src/suricata.c

@@ -484,11 +484,15 @@ static void SetBpfStringFromFile(char *filename)
     }
     memset(bpf_filter, 0x00, bpf_len);
 
-    nm = fread(bpf_filter, bpf_len - 1, 1, fp);
-    if((ferror(fp) != 0)||( nm != 1)) {
-        *bpf_filter='\0';
+    nm = fread(bpf_filter, 1, bpf_len - 1, fp);
+    if ((ferror(fp) != 0) || (nm != (bpf_len - 1))) {
+        SCLogError(SC_ERR_BPF, "Failed to read complete BPF file %s", filename);
+        SCFree(bpf_filter);
+        fclose(fp);
+        exit(EXIT_FAILURE);
     }
     fclose(fp);
+    bpf_filter[nm] = '\0';
 
     if(strlen(bpf_filter) > 0) {
         /*replace comments with space*/
@@ -508,10 +512,18 @@ static void SetBpfStringFromFile(char *filename)
         while((bpf_comment_tmp = strchr(bpf_filter, '\n')) != NULL) {
             *bpf_comment_tmp = ' ';
         }
-        if(ConfSetFinal("bpf-filter", bpf_filter) != 1) {
-            SCLogError(SC_ERR_FOPEN, "ERROR: Failed to set bpf filter!");
-            SCFree(bpf_filter);
-            exit(EXIT_FAILURE);
+        /* cut trailing spaces */
+        while (strlen(bpf_filter) > 0 &&
+                bpf_filter[strlen(bpf_filter)-1] == ' ')
+        {
+            bpf_filter[strlen(bpf_filter)-1] = '\0';
+        }
+        if (strlen(bpf_filter) > 0) {
+            if(ConfSetFinal("bpf-filter", bpf_filter) != 1) {
+                SCLogError(SC_ERR_FOPEN, "ERROR: Failed to set bpf filter!");
+                SCFree(bpf_filter);
+                exit(EXIT_FAILURE);
+            }
         }
     }
     SCFree(bpf_filter);