From 3d42833d389134b7b05b655c264e4dba5a2179e9 Mon Sep 17 00:00:00 2001 From: Tomas Mraz Date: Thu, 4 Apr 2019 09:48:47 +0200 Subject: [PATCH] Add documentation for the BIO_s_mem pecularities Reviewed-by: Bernd Edlinger Reviewed-by: Matt Caswell (Merged from https://github.com/openssl/openssl/pull/8649) --- doc/man3/BIO_s_mem.pod | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/doc/man3/BIO_s_mem.pod b/doc/man3/BIO_s_mem.pod index bd0824a080..6d9e747b25 100644 --- a/doc/man3/BIO_s_mem.pod +++ b/doc/man3/BIO_s_mem.pod @@ -88,6 +88,22 @@ a buffering BIO to the chain will speed up the process. Calling BIO_set_mem_buf() on a BIO created with BIO_new_secmem() will give undefined results, including perhaps a program crash. +Switching the memory BIO from read write to read only is not supported and +can give undefined results including a program crash. There are two notable +exceptions to the rule. The first one is to assign a static memory buffer +immediately after BIO creation and set the BIO as read only. + +The other supported sequence is to start with read write BIO then temporarily +switch it to read only and call BIO_reset() on the read only BIO immediately +before switching it back to read write. Before the BIO is freed it must be +switched back to the read write mode. + +Calling BIO_get_mem_ptr() on read only BIO will return a BUF_MEM that +contains only the remaining data to be read. If the close status of the +BIO is set to BIO_NOCLOSE, before freeing the BUF_MEM the data pointer +in it must be set to NULL as the data pointer does not point to an +allocated memory. + =head1 BUGS There should be an option to set the maximum size of a memory BIO. -- 2.25.1