---
name: "CMS_uncompress"
section: "3ssl"
platform: "linux"
package: "openssl"
version: "3.6.5-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/CMS_uncompress"
---

# CMS\_uncompress(3ssl)

uncompress a CMS CompressedData structure

## NAME

CMS\_uncompress - uncompress a CMS CompressedData structure

## SYNOPSIS

```
 #include <openssl/cms.h>
 int CMS_uncompress(CMS_ContentInfo *cms, BIO *dcont, BIO *out, unsigned int flags);
```

## DESCRIPTION

**CMS\_uncompress()** extracts and uncompresses the content from a CMS CompressedData structure **cms**. **data** is a BIO to write the content to and **flags** is an optional set of flags.

The **dcont** parameter is used in the rare case where the compressed content is detached. It will normally be set to NULL.

## NOTES

The only currently supported compression algorithm is zlib: if the structure indicates the use of any other algorithm an error is returned.

If zlib support is not compiled into OpenSSL then **CMS\_uncompress()** will always return an error.

The following flags can be passed in the **flags** parameter.

If the **CMS\_TEXT** flag is set MIME headers for type **text/plain** are deleted from the content. If the content is not of type **text/plain** then an error is returned.

## RETURN VALUES

**CMS\_uncompress()** returns either 1 for success or 0 for failure. The error can be obtained from **ERR\_get\_error**(3)

## BUGS

The lack of single pass processing and the need to hold all data in memory as mentioned in **CMS\_verify()** also applies to **CMS\_decompress()**.

## SEE ALSO

**ERR\_get\_error**(3), **CMS\_compress**(3)

## COPYRIGHT

Copyright 2008-2016 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the "License").  You may not use this file except in compliance with the License.  You can obtain a copy in the file LICENSE in the source distribution or at \<https://www.openssl.org/source/license.html\>.