Changeset 2fa0237 for tests/io/manipulatorsInput.cfa

Timestamp:

Sep 8, 2023, 12:46:55 AM (9 months ago)

Author:

Michael Brooks <mlbrooks@…>

Branches:

master

Children:

553f032f

Parents:

3ee8853

Message:

Fix cstring input length interpretation issue that had a buffer overflow case.

The cases added to the manipulatorsInput test are runnable against an old libcfa build. In this setup, the test fails with an illustration of the bug.

The testing in this commit drives the following inputs through a length-8 buffer.

• 123456
• 123456789

The obviously-missing cases, like 1234567, will be added later.
They will accompany fixes for further bugs not solved yet.

File:

• tests/io/manipulatorsInput.cfa (modified) (1 diff)

tests/io/manipulatorsInput.cfa

@@ -15 +15 @@
 
 int main() {
+        {
+                // Upfront checks to ensure buffer safety.  Once these pass, the simpler `wdi(sizeof(s),s)`
+                // usage, as in the scanf alignment cases below, is justified.
+                struct {
+                        char buf[8];
+                        char canary;
+                } data;
+                static_assert( sizeof(data.buf) == 8 );
+                static_assert( &data.buf[8] == &data.canary );  // canary comes right after buf
+
+                void rep(const char* casename) {
+                        data.canary = 42;
+                        bool caught = false;
+                        try {
+                                sin | wdi( sizeof(data.buf), data.buf );
+                        } catch (cstring_length*) {
+                                caught = true;
+                        }
+                        printf( "%s \"%s\"", casename, data.buf );
+                        if ( caught ) {
+                                printf(", exception occurred");
+                        }
+                        if ( data.canary == 42 ) {
+                                printf(", canary ok");
+                        } else {
+                                printf(", canary overwritten to %d", data.canary);
+                        }
+                        printf("\n");
+                }
+
+                rep("pre1");
+                rep("pre2a");
+                rep("pre2b");
+                scanf("\n");  // next test does not start with %s so does not tolerate leading whitespace
+        }
         {
                 char s[] = "yyyyyyyyyyyyyyyyyyyy";