Fix undocumented free() in x509_string_to_names()
Now programs/x509/cert_write san="DN:CN=#0000;DN:CN=#0000" is no longer
crashing with use-after-free, instead it's now failing cleanly:
failed
! mbedtls_x509_string_to_names returned -0x2800 - X509 - Input invalid
That's better of course but still not great, will be fixed by future
commits.
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/ChangeLog.d/fix-string-to-names-memory-management.txt b/ChangeLog.d/fix-string-to-names-memory-management.txt
new file mode 100644
index 0000000..1b21982
--- /dev/null
+++ b/ChangeLog.d/fix-string-to-names-memory-management.txt
@@ -0,0 +1,18 @@
+Security
+ * Fix possible use-after-free or double-free in code calling
+ mbedtls_x509_string_to_names(). This was caused by the function calling
+ mbedtls_asn1_free_named_data_list() on its head argument, while the
+ documentation did no suggest it did, making it likely for callers relying
+ on the documented behaviour to still hold pointers to memory blocks after
+ they were free()d, resulting in high risk of use-after-free or double-free,
+ with consequences ranging up to arbitrary code execution.
+ In particular, the two sample programs x509/cert_write and x509/cert_req
+ were affected (use-after-free if the san string contains more than one DN).
+ Code that does not call mbedtls_string_to_names() directly is not affected.
+ Found by Linh Le and Ngan Nguyen from Calif.
+
+Changes
+ * The function mbedtls_x509_string_to_names() now requires its head argument
+ to point to NULL on entry. This make it likely that existing risky uses of
+ this function (see the entry in the Security section) will be detected and
+ fixed.