From 68beecef0a2a07649b05cc9723662f11ebdd52f3 Mon Sep 17 00:00:00 2001
From: jfreegman <jfreegman@gmail.com>
Date: Wed, 28 Feb 2024 11:31:19 -0500
Subject: [PATCH] feat: hard cap the size of a session chat log to 100 MiB

This mitigates a potential DOS attack vector.
---
 src/log.c | 24 +++++++++++++++++++++---
 src/log.h | 10 ++++++++--
 2 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/src/log.c b/src/log.c
index 2d4e1a3d8..81f812a87 100644
--- a/src/log.c
+++ b/src/log.c
@@ -124,7 +124,13 @@ static int init_logging_session(const Client_Config *c_config, const char *name,
     return 0;
 }
 
-#define LOG_FLUSH_LIMIT 1  /* limits calls to fflush to a max of one per LOG_FLUSH_LIMIT seconds */
+/* limits calls to fflush to a max of one per LOG_FLUSH_LIMIT seconds */
+#define LOG_FLUSH_LIMIT 1
+
+/* We stop writing to the log after we've written at least this many bytes during the current session.
+ * A new session is started with `log_enable()`, and ended with `log_disable()`.
+ */
+#define LOG_BYTES_THRESHOLD ((1024 << 10) * 100)  // 100 MiB
 
 int write_to_log(struct chatlog *log, const Client_Config *c_config, const char *msg, const char *name,
                  bool is_event, Log_Hint log_hint)
@@ -142,6 +148,11 @@ int write_to_log(struct chatlog *log, const Client_Config *c_config, const char
         return -1;
     }
 
+    if (log->bytes_written >= LOG_BYTES_THRESHOLD) {
+        fprintf(stderr, "Warning: Log file is full (%u bytes written)\n", log->bytes_written);
+        return -1;
+    }
+
     char name_frmt[TOXIC_MAX_NAME_LENGTH + 3];
 
     if (name != NULL) {
@@ -156,10 +167,12 @@ int write_to_log(struct chatlog *log, const Client_Config *c_config, const char
     char s[MAX_STR_SIZE];
     get_time_str(s, sizeof(s), t);
 
+    int bytes_written;
+
     if (name == NULL) {
-        fprintf(log->file, "{%d} %s %s\n", log_hint, s, msg);
+        bytes_written = fprintf(log->file, "{%d} %s %s\n", log_hint, s, msg);
     } else {
-        fprintf(log->file, "{%d} %s %s %s\n", log_hint, s, name_frmt, msg);
+        bytes_written = fprintf(log->file, "{%d} %s %s %s\n", log_hint, s, name_frmt, msg);
     }
 
     if (timed_out(log->lastwrite, LOG_FLUSH_LIMIT)) {
@@ -167,6 +180,10 @@ int write_to_log(struct chatlog *log, const Client_Config *c_config, const char
         log->lastwrite = get_unix_time();
     }
 
+    if (bytes_written > 0) {
+        log->bytes_written += bytes_written;
+    }
+
     return 0;
 }
 
@@ -183,6 +200,7 @@ void log_disable(struct chatlog *log)
 
     log->lastwrite = 0;
     log->log_on = false;
+    log->bytes_written = 0;
 }
 
 int log_enable(struct chatlog *log)
diff --git a/src/log.h b/src/log.h
index ec1557d93..f0c171ebd 100644
--- a/src/log.h
+++ b/src/log.h
@@ -30,6 +30,7 @@ struct chatlog {
     time_t lastwrite;
     char path[MAX_STR_SIZE];
     bool log_on;    /* specific to current chat window */
+    uint32_t bytes_written;
 };
 
 typedef enum Log_Type {
@@ -75,14 +76,19 @@ int log_init(struct chatlog *log, const Client_Config *c_config, const char *nam
 int write_to_log(struct chatlog *log, const Client_Config *c_config, const char *msg, const char *name,
                  bool is_event, Log_Hint log_hint);
 
-/* enables logging for specified log.
+/* Enables logging for specified log.
+ *
+ * Calling this function on a log that's already enabled has no effect.
  *
  * Returns 0 on success.
  * Returns -1 on failure.
  */
 int log_enable(struct chatlog *log);
 
-/* disables logging for specified log and closes file */
+/* Disables logging for specified log and closes file.
+ *
+ * Calling this function on a log that's already disabled has no effect.
+ */
 void log_disable(struct chatlog *log);
 
 /* Loads chat log history and prints it to `self` window.