imap/smtp polishing;

include/ilib/curl_imapsmtp.h

@@ -0,0 +1,56 @@
+/*
+ * this is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published
+ * by the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * this is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.";
+ *
+ * (c) Alexander Vdolainen 2007, 2026 <alex@vapaa.xyz>
+ * subrelay: a minimalistic maillist server based on external IMAPs/SMTPs
+ *
+ * curl_imapsmtp.h: IMAPS SMTPs functions using libcurl
+ *
+ */
+#ifndef __MAIL_ENGINE_H__
+#define __MAIL_ENGINE_H__
+
+#include <stddef.h>
+
+#include <ilib/configuration.h>
+
+#define MAX_IMAP_RESPONSE (25u * 1024u * 1024u)
+
+typedef struct mail_message {
+  char *raw_data; /* Full raw RFC 822 byte payload */
+  size_t size; /* Size of raw payload */
+  unsigned long uid; /* IMAP Unique Identifier */
+} mail_message_t;
+
+typedef struct mail_list_results {
+  unsigned long *uids;
+  size_t count;
+} mail_list_results_t;
+
+/* Initialize and cleanup global libcurl environment */
+int mail_engine_global_init(void);
+void mail_engine_global_cleanup(void);
+
+/* IMAP Client API */
+int imap_fetch_unseen_uids(const subrelay_config_t *cfg, mail_list_results_t *results);
+int imap_fetch_message(const subrelay_config_t *cfg, unsigned long uid, mail_message_t *msg);
+int imap_expunge_message(const subrelay_config_t *cfg, unsigned long uid);
+void mail_message_free(mail_message_t *msg);
+void mail_list_results_free(mail_list_results_t *res);
+
+/* SMTP Client API */
+int smtp_send_message(const subrelay_config_t *cfg, const char **recipients,
+                      size_t recipient_count, const char *raw_msg, size_t msg_len);
+
+#endif /* __MAIL_ENGINE_H__ */

include/ilib/mail_engine.h

@@ -1,38 +0,0 @@
-/* mail_engine.h - IMAP fetching & SMTP fan-out engine using libcurl */
-#ifndef __MAIL_ENGINE_H__
-#define __MAIL_ENGINE_H__
-
-#include <stddef.h>
-
-#include <ilib/configuration.h>
-
-typedef struct mail_message {
-  char *raw_data;     /* Full raw RFC 822 byte payload */
-  size_t size;        /* Size of raw payload */
-  unsigned long uid;  /* IMAP Unique Identifier */
-} mail_message_t;
-
-typedef struct mail_list_results {
-  unsigned long *uids;
-  size_t count;
-} mail_list_results_t;
-
-/* Initialize and cleanup global libcurl environment */
-int mail_engine_global_init(void);
-void mail_engine_global_cleanup(void);
-
-/* IMAP Client API */
-int imap_fetch_unseen_uids(const subrelay_config_t *cfg, mail_list_results_t *results);
-int imap_fetch_message(const subrelay_config_t *cfg, unsigned long uid, mail_message_t *msg);
-int imap_expunge_message(const subrelay_config_t *cfg, unsigned long uid);
-void mail_message_free(mail_message_t *msg);
-void mail_list_results_free(mail_list_results_t *res);
-
-/* SMTP Client API */
-int smtp_send_message(const subrelay_config_t *cfg, 
-                      const char **recipients, 
-                      size_t recipient_count, 
-                      const char *raw_msg, 
-                      size_t msg_len);
-
-#endif /* __MAIL_ENGINE_H__ */

include/ilib/mail_processor.h

@@ -24,7 +24,7 @@
 #include <ilib/configuration.h>
 #include <ilib/subscribers.h>
 #include <ilib/pending.h>
-#include <ilib/mail_engine.h>
+#include <ilib/curl_imapsmtp.h>
 
 typedef struct mail_processor {
   subrelay_config_t *cfg;

src/Makefile.am

@@ -3,7 +3,7 @@ bin_PROGRAMS = subrelayd sbrlctrl
 noinst_HEADERS = \
     $(top_srcdir)/include/ilib/configuration.h \
     $(top_srcdir)/include/ilib/local.h \
-    $(top_srcdir)/include/ilib/mail_engine.h \
+    $(top_srcdir)/include/ilib/curl_imapsmtp.h \
     $(top_srcdir)/include/ilib/mail_processor.h \
     $(top_srcdir)/include/ilib/pending.h \
     $(top_srcdir)/include/ilib/splay.h \
@@ -20,7 +20,7 @@ subrelayd_SOURCES = \
     pending.c \
     configuration.c \
     template.c \
-    mail_engine.c \
+    curl_imapsmtp.c \
     mail_processor.c \
     local.c
 

src/curl_imapsmtp.c

@@ -1,11 +1,33 @@
-/* mail_engine.c - libcurl IMAP and SMTP implementation */
+/*
+ * this is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published
+ * by the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * this is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.";
+ *
+ * (c) Alexander Vdolainen 2007, 2026 <alex@vapaa.xyz>
+ * subrelay: a minimalistic maillist server based on external IMAPs/SMTPs
+ *
+ * curl_imapsmtp.c: IMAPS SMTPs functions using libcurl
+ *
+ */
+
+
 #include <stdio.h>
 #include <stdlib.h>
+#include <stdint.h>
 #include <string.h>
 #include <errno.h>
 #include <curl/curl.h>
 
-#include <ilib/mail_engine.h>
+#include <ilib/curl_imapsmtp.h>
 
 typedef struct memory_buffer {
   char *data;
@@ -20,24 +42,28 @@ typedef struct upload_buffer {
 /* Callback for libcurl to append fetched HTTP/IMAP bytes into memory */
 static size_t write_memory_callback(void *contents, size_t size, size_t nmemb, void *userp)
 {
-  size_t real_size = size * nmemb;
+  memory_buffer_t *mem = userp;
-  memory_buffer_t *mem = (memory_buffer_t *)userp;
 
-  char *ptr = realloc(mem->data, mem->size + real_size + 1);
+  if (size != 0 && nmemb > SIZE_MAX / size)    return 0;
-  if (!ptr) return 0; /* Out of memory */
+  size_t n = size * nmemb;
+  if (n > MAX_IMAP_RESPONSE - mem->size)    return 0;
+
+  char *ptr = realloc(mem->data, mem->size + n + 1);
+  if (!ptr)    return 0;
 
   mem->data = ptr;
-  memcpy(&(mem->data[mem->size]), contents, real_size);
+  memcpy(mem->data + mem->size, contents, n);
-  mem->size += real_size;
+  mem->size += n;
-  mem->data[mem->size] = 0;
+  mem->data[mem->size] = '\0';
 
-  return real_size;
+  return n;
 }
 
 /* Callback for libcurl to read bytes when sending outbound mail via SMTP */
 static size_t read_payload_callback(char *buffer, size_t size, size_t nitems, void *userp)
 {
   upload_buffer_t *upload = (upload_buffer_t *)userp;
+  if (size != 0 && nitems > SIZE_MAX / size)    return CURL_READFUNC_ABORT;
   size_t max_bytes = size * nitems;
 
   if (upload->bytes_remaining == 0) return 0; /* EOF */
@@ -61,9 +87,7 @@ void mail_engine_global_cleanup(void)
   curl_global_cleanup();
 }
 
-/* -------------------------------------------------------------------------- */
+/* IMAPs */
-/* IMAP Operations                                                            */
-/* -------------------------------------------------------------------------- */
 
 int imap_fetch_unseen_uids(const subrelay_config_t *cfg, mail_list_results_t *results)
 {
@@ -77,6 +101,7 @@ int imap_fetch_unseen_uids(const subrelay_config_t *cfg, mail_list_results_t *re
   snprintf(url, sizeof(url), "imaps://%s:%d/INBOX", cfg->imap_host, cfg->imap_port);
 
   memory_buffer_t buf = { calloc(1, 1), 0 };
+  if(!buf.data) return -ENOMEM;
 
   curl_easy_setopt(curl, CURLOPT_URL, url);
   curl_easy_setopt(curl, CURLOPT_USERNAME, cfg->maillist_addr);
@@ -97,12 +122,18 @@ int imap_fetch_unseen_uids(const subrelay_config_t *cfg, mail_list_results_t *re
   /* Parse IMAP response string (e.g., "* SEARCH 101 102 103\r\n") */
   char *search_str = strstr(buf.data, "* SEARCH");
   if (search_str) {
-    search_str += 8; /* Skip "* SEARCH" */
+    search_str += 8; /* skip "* SEARCH" */
     char *token = strtok(search_str, " \r\n");
     while (token) {
       unsigned long uid = strtoul(token, NULL, 10);
       if (uid > 0) {
-        results->uids = realloc(results->uids, sizeof(unsigned long) * (results->count + 1));
+        unsigned long *tmp = realloc(results->uids, sizeof(unsigned long) * (results->count + 1));
+        if(!tmp) {
+          free(buf.data);
+          mail_list_results_free(results);
+          return -ENOMEM;
+        }
+        results->uids = tmp;
         results->uids[results->count++] = uid;
       }
       token = strtok(NULL, " \r\n");
@@ -125,6 +156,7 @@ int imap_fetch_message(const subrelay_config_t *cfg, unsigned long uid, mail_mes
   snprintf(url, sizeof(url), "imaps://%s:%d/INBOX;UID=%lu", cfg->imap_host, cfg->imap_port, uid);
 
   memory_buffer_t buf = { calloc(1, 1), 0 };
+  if(!buf.data) return -ENOMEM;
 
   curl_easy_setopt(curl, CURLOPT_URL, url);
   curl_easy_setopt(curl, CURLOPT_USERNAME, cfg->maillist_addr);
@@ -179,15 +211,10 @@ int imap_expunge_message(const subrelay_config_t *cfg, unsigned long uid)
   return (res == CURLE_OK) ? 0 : -EIO;
 }
 
-/* -------------------------------------------------------------------------- */
+/* SMTPS */
-/* SMTP Operations                                                            */
-/* -------------------------------------------------------------------------- */
 
-int smtp_send_message(const subrelay_config_t *cfg, 
+int smtp_send_message(const subrelay_config_t *cfg, const char **recipients, size_t recipient_count,
-                      const char **recipients, 
+                      const char *raw_msg, size_t msg_len)
-                      size_t recipient_count, 
-                      const char *raw_msg, 
-                      size_t msg_len)
 {
   if (!cfg || !recipients || recipient_count == 0 || !raw_msg) return -EINVAL;
 

src/subrelayd.c

@@ -33,7 +33,7 @@
 #include <ilib/configuration.h>
 #include <ilib/subscribers.h>
 #include <ilib/pending.h>
-#include <ilib/mail_engine.h>
+#include <ilib/curl_imapsmtp.h>
 #include <ilib/mail_processor.h>
 #include <ilib/local.h>