programs/ssl: Fixes incorrect EOF check in ssl_context_info.c

read_next_b64_code() function, that parses base64 encoded input doesn't recognize the EOF and returns when "Too many bad symbols are detected". This issue got identified when gcc complained for type-limit error during cmake. This patch fixes the issue by changing the variable type to int and removing type-cast of fgetc() output to 'char'. [[email protected]] The context info test stores the result of `fgetc` in a 'char'. On platforms with signed characters, reading a 0xFF byte will result in this character being -1, triggering an early end of file. On platforms with an unsigned char, all characters will be valid, but end of file won't be detected. Fixes Mbed-TLS#3794. Signed-off-by: Nayna Jain <[email protected]> Signed-off-by: David Brown <[email protected]>
d3zd3z · Oct 16, 2020 · 25b1f0a · 25b1f0a
1 parent 8f24a8b
commit 25b1f0a
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diff --git a/ChangeLog.d/bugfix_3794.txt b/ChangeLog.d/bugfix_3794.txt
@@ -0,0 +1,3 @@
+Bugfix
+  * Fix handling of EOF against 0xff bytes and on platforms with
+    unsigned chars. Fixes #3794.
diff --git a/programs/ssl/ssl_context_info.c b/programs/ssl/ssl_context_info.c
@@ -377,13 +377,13 @@ size_t read_next_b64_code( uint8_t **b64, size_t *max_len )
     int valid_balance = 0;  /* balance between valid and invalid characters */
     size_t len = 0;
     char pad = 0;
-    char c = 0;
+    int c = 0;
 
     while( EOF != c )
     {
         char c_valid = 0;
 
-        c = (char) fgetc( b64_file );
+        c = fgetc( b64_file );
 
         if( pad > 0 )
         {