From 334ea87d25fe1e9ca0186c126a420b521c69b15e Mon Sep 17 00:00:00 2001
From: Godzil <godzil@godzil.net>
Date: Fri, 27 May 2022 12:02:15 +0100
Subject: [PATCH] Add missing boundary check when seeking in a file.

---
 includes/miniffs.h       |  1 +
 miniffs.c                | 50 +++++++++++++++++++++++++++++-----------
 test/file_operations.cpp | 46 +++++++++++++++++++++++++++++++++++-
 3 files changed, 82 insertions(+), 15 deletions(-)

diff --git a/includes/miniffs.h b/includes/miniffs.h
index 1c1adba..e255ea4 100644
--- a/includes/miniffs.h
+++ b/includes/miniffs.h
@@ -101,6 +101,7 @@ typedef enum miniffs_error_t
     MINIFFS_INVALID_PARAMS,
     MINIFFS_FILE_NOT_FOUND,
     MINIFFS_ALLOCATION_ERROR,
+    MINIFFS_SEEK_OUT_OF_BOUNDARIES,
     MINIFFS_END_OF_FILE,
     //MINIFFS_,
 } miniffs_error_t;
diff --git a/miniffs.c b/miniffs.c
index 9c1b403..3803cd6 100644
--- a/miniffs.c
+++ b/miniffs.c
@@ -116,23 +116,45 @@ int miniffs_read_blocks(void *ptr, size_t size, size_t nmemb, file_t *file)
 
 int miniffs_seek(file_t *file, size_t offset, int whence)
 {
-    switch(whence)
-    {
-    default:
-        miniffs_seterror(MINIFFS_INVALID_PARAMS);
-        return -1;
+    bool noError = true;
+    switch(whence) {
+        default:
+            miniffs_seterror(MINIFFS_INVALID_PARAMS);
+            return -1;
 
-    case MFFS_SEEK_SET:
-        file->offset = offset;
-        break;
-    case MFFS_SEEK_CUR:
-        file->offset += offset;
-        break;
-    case MFFS_SEEK_END:
-        file->offset = file->fent->size - 1 - offset;
+        case MFFS_SEEK_SET:
+            file->offset = offset;
+            break;
+        case MFFS_SEEK_CUR:
+            file->offset += offset;
+            break;
+        case MFFS_SEEK_END:
+            if (file->fent->size <= offset)
+            {
+                /* Negative boundary check */
+                noError = false;
+                miniffs_seterror(MINIFFS_SEEK_OUT_OF_BOUNDARIES);
+                file->offset = 0;
+            }
+            else
+            {
+                file->offset = file->fent->size - 1 - offset;
+            }
         break;
     }
-    miniffs_seterror(MINIFFS_NOERROR);
+
+    if (file->offset >= file->fent->size)
+    {
+        /* Positive Boundary check */
+        noError = false;
+        miniffs_seterror(MINIFFS_SEEK_OUT_OF_BOUNDARIES);
+        file->offset = file->fent->size - 1;
+    }
+
+    if (noError)
+    {
+        miniffs_seterror(MINIFFS_NOERROR);
+    }
 }
 
 size_t miniffs_tell(file_t *file)
diff --git a/test/file_operations.cpp b/test/file_operations.cpp
index a36ad04..f41efd6 100644
--- a/test/file_operations.cpp
+++ b/test/file_operations.cpp
@@ -97,6 +97,51 @@ TEST(FileOperations, TestingSeek)
     ASSERT_EQ(miniffs_read(fp), '!');
 }
 
+TEST(FileOperations, LargeOutOfBoundarySeeks)
+{
+    miniffs_t *fs = get_fs("simple_test.mffs");
+    file_t *fp = miniffs_open(fs, "HELLO.TXT");
+
+    miniffs_seek(fp, 100, MFFS_SEEK_SET);
+    ASSERT_EQ(miniffs_geterror(), MINIFFS_SEEK_OUT_OF_BOUNDARIES);
+    ASSERT_EQ(miniffs_read(fp), '!');
+    ASSERT_EQ(miniffs_geterror(), MINIFFS_END_OF_FILE);
+
+    miniffs_seek(fp, 100, MFFS_SEEK_END);
+    ASSERT_EQ(miniffs_geterror(), MINIFFS_SEEK_OUT_OF_BOUNDARIES);
+    ASSERT_EQ(miniffs_read(fp), 'H');
+}
+
+TEST(FileOperations, SeekingAroundBoundaries)
+{
+    miniffs_t *fs = get_fs("simple_test.mffs");
+    file_t *fp = miniffs_open(fs, "HELLO.TXT");
+
+    miniffs_seek(fp, 10, MFFS_SEEK_SET);
+    ASSERT_EQ(miniffs_geterror(), MINIFFS_NOERROR);
+    ASSERT_EQ(miniffs_read(fp), 'd');
+
+    miniffs_seek(fp, 11, MFFS_SEEK_SET);
+    ASSERT_EQ(miniffs_geterror(), MINIFFS_NOERROR);
+    ASSERT_EQ(miniffs_read(fp), '!');
+
+    miniffs_seek(fp, 12, MFFS_SEEK_SET);
+    ASSERT_EQ(miniffs_geterror(), MINIFFS_SEEK_OUT_OF_BOUNDARIES);
+    ASSERT_EQ(miniffs_read(fp), '!');
+
+    miniffs_seek(fp, 10, MFFS_SEEK_END);
+    ASSERT_EQ(miniffs_geterror(), MINIFFS_NOERROR);
+    ASSERT_EQ(miniffs_read(fp), 'e');
+
+    miniffs_seek(fp, 11, MFFS_SEEK_END);
+    ASSERT_EQ(miniffs_geterror(), MINIFFS_NOERROR);
+    ASSERT_EQ(miniffs_read(fp), 'H');
+
+    miniffs_seek(fp, 12, MFFS_SEEK_END);
+    ASSERT_EQ(miniffs_geterror(), MINIFFS_SEEK_OUT_OF_BOUNDARIES);
+    ASSERT_EQ(miniffs_read(fp), 'H');
+}
+
 TEST(FileOperations, TestingEndOfFileBoundary)
 {
     miniffs_t *fs = get_fs("simple_test.mffs");
@@ -197,5 +242,4 @@ TEST(FileOperations, ReadTooManyBlocks)
     ASSERT_EQ(buffer[9], 'l');
     ASSERT_EQ(buffer[10], 'd');
     ASSERT_EQ(buffer[11], '!');
-
 }
\ No newline at end of file