---
name: "libssh2_userauth_publickey_frommemory"
section: "3"
platform: "linux"
package: "libssh2"
version: "1.11.1-7"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/libssh2_userauth_publickey_frommemory"
---

# libssh2\_userauth\_publickey\_frommemory(3)

authenticate a session with a public key, read from memory

## NAME

libssh2\_userauth\_publickey\_frommemory - authenticate a session with a public key, read from memory

## SYNOPSIS

```
#include <libssh2.h>
int
libssh2_userauth_publickey_frommemory(LIBSSH2_SESSION *session,
                                      const char *username,
                                      size_t username_len,
                                      const char *publickeydata,
                                      size_t publickeydata_len,
                                      const char *privatekeydata,
                                      size_t privatekeydata_len,
                                      const char *passphrase);
```

## DESCRIPTION

*session* - Session instance as returned by **[libssh2\_session\_init\_ex(3)](/libssh2_session_init_ex/3.md)**

*username* - Remote user name to authenticate as.

*username\_len* - Length of username.

*publickeydata* - Buffer containing the contents of a public key file.

*publickeydata\_len* - Length of public key data.

*privatekeydata* - Buffer containing the contents of a private key file.

*privatekeydata\_len* - Length of private key data.

*passphrase* - Passphrase to use when decoding private key file.

Attempt public key authentication using either a public key file or a PEM encoded private key file stored in memory. When providing a private key, the public key is automatically extracted from it. When providing both, the passed public key takes precedence.

## RETURN VALUE

Return 0 on success or negative on failure. It returns LIBSSH2\_ERROR\_EAGAIN when it would otherwise block. While LIBSSH2\_ERROR\_EAGAIN is a negative number, it is not really a failure per se.

## ERRORS

*LIBSSH2\_ERROR\_ALLOC* - An internal memory allocation call failed.

*LIBSSH2\_ERROR\_SOCKET\_SEND* - Unable to send data on socket.

*LIBSSH2\_ERROR\_SOCKET\_TIMEOUT* -

*LIBSSH2\_ERROR\_PUBLICKEY\_UNVERIFIED* - The username/public key combination was invalid.

*LIBSSH2\_ERROR\_AUTHENTICATION\_FAILED* - Authentication using the supplied public key was not accepted.

## AVAILABILITY

libssh2\_userauth\_publickey\_frommemory was added in libssh2 1.6.0 Supported with OpenSSL, WinCNG, mbedTLS, OS/400 crypto backends.

## SEE ALSO

**[libssh2\_session\_init\_ex(3)](/libssh2_session_init_ex/3.md)**