Merge pull request #2602 from edsiper/crt-symlink

x509_crt: handle properly broken links when looking for certificates

ChangeLog.d/x509-broken-symlink-handling.txt

@@ -0,0 +1,5 @@
+Bugfix
+   * Fix handling of broken symlinks when loading certificates using
+     mbedtls_x509_crt_parse_path(). Instead of returning an error as soon as a
+     broken link is encountered, skip the broken link and continue parsing
+     other certificate files. Contributed by Eduardo Silva in #2602.

library/x509_crt.c

@@ -82,6 +82,7 @@
 #else
 #include <dirent.h>
 #endif /* __MBED__ */
+#include <errno.h>
 #endif /* !_WIN32 || EFIX64 || EFI32 */
 #endif
 
@@ -1658,8 +1659,22 @@ int mbedtls_x509_crt_parse_path( mbedtls_x509_crt *chain, const char *path )
         }
         else if( stat( entry_name, &sb ) == -1 )
         {
-            ret = MBEDTLS_ERR_X509_FILE_IO_ERROR;
-            goto cleanup;
+            if( errno == ENOENT )
+            {
+                /* Broken symbolic link - ignore this entry.
+                    stat(2) will return this error for either (a) a dangling
+                    symlink or (b) a missing file.
+                    Given that we have just obtained the filename from readdir,
+                    assume that it does exist and therefore treat this as a
+                    dangling symlink. */
+                continue;
+            }
+            else
+            {
+                /* Some other file error; report the error. */
+                ret = MBEDTLS_ERR_X509_FILE_IO_ERROR;
+                goto cleanup;
+            }
         }
 
         if( !S_ISREG( sb.st_mode ) )