1 SSH-AGENT(1) General Commands Manual SSH-AGENT(1) 2 3 NAME 4 ssh-agent M-bM-^@M-^S authentication agent 5 6 SYNOPSIS 7 ssh-agent [-c | -s] [-Dd] [-a bind_address] [-E fingerprint_hash] 8 [-P pkcs11_whitelist] [-t life] [command [arg ...]] 9 ssh-agent [-c | -s] -k 10 11 DESCRIPTION 12 ssh-agent is a program to hold private keys used for public key 13 authentication (RSA, DSA, ECDSA, Ed25519). ssh-agent is usually started 14 in the beginning of an X-session or a login session, and all other 15 windows or programs are started as clients to the ssh-agent program. 16 Through use of environment variables the agent can be located and 17 automatically used for authentication when logging in to other machines 18 using ssh(1). 19 20 The agent initially does not have any private keys. Keys are added using 21 ssh(1) (see AddKeysToAgent in ssh_config(5) for details) or ssh-add(1). 22 Multiple identities may be stored in ssh-agent concurrently and ssh(1) 23 will automatically use them if present. ssh-add(1) is also used to 24 remove keys from ssh-agent and to query the keys that are held in one. 25 26 The options are as follows: 27 28 -a bind_address 29 Bind the agent to the UNIX-domain socket bind_address. The 30 default is $TMPDIR/ssh-XXXXXXXXXX/agent.<ppid>. 31 32 -c Generate C-shell commands on stdout. This is the default if 33 SHELL looks like it's a csh style of shell. 34 35 -D Foreground mode. When this option is specified ssh-agent will 36 not fork. 37 38 -d Debug mode. When this option is specified ssh-agent will not 39 fork and will write debug information to standard error. 40 41 -E fingerprint_hash 42 Specifies the hash algorithm used when displaying key 43 fingerprints. Valid options are: M-bM-^@M-^\md5M-bM-^@M-^] and M-bM-^@M-^\sha256M-bM-^@M-^]. The 44 default is M-bM-^@M-^\sha256M-bM-^@M-^]. 45 46 -k Kill the current agent (given by the SSH_AGENT_PID environment 47 variable). 48 49 -P pkcs11_whitelist 50 Specify a pattern-list of acceptable paths for PKCS#11 shared 51 libraries that may be added using the -s option to ssh-add(1). 52 The default is to allow loading PKCS#11 libraries from 53 M-bM-^@M-^\/usr/lib/*,/usr/local/lib/*M-bM-^@M-^]. PKCS#11 libraries that do not 54 match the whitelist will be refused. See PATTERNS in 55 ssh_config(5) for a description of pattern-list syntax. 56 57 -s Generate Bourne shell commands on stdout. This is the default if 58 SHELL does not look like it's a csh style of shell. 59 60 -t life 61 Set a default value for the maximum lifetime of identities added 62 to the agent. The lifetime may be specified in seconds or in a 63 time format specified in sshd_config(5). A lifetime specified 64 for an identity with ssh-add(1) overrides this value. Without 65 this option the default maximum lifetime is forever. 66 67 If a command line is given, this is executed as a subprocess of the 68 agent. When the command dies, so does the agent. 69 70 The idea is that the agent is run in the user's local PC, laptop, or 71 terminal. Authentication data need not be stored on any other machine, 72 and authentication passphrases never go over the network. However, the 73 connection to the agent is forwarded over SSH remote logins, and the user 74 can thus use the privileges given by the identities anywhere in the 75 network in a secure way. 76 77 There are two main ways to get an agent set up: The first is that the 78 agent starts a new subcommand into which some environment variables are 79 exported, eg ssh-agent xterm &. The second is that the agent prints the 80 needed shell commands (either sh(1) or csh(1) syntax can be generated) 81 which can be evaluated in the calling shell, eg eval `ssh-agent -s` for 82 Bourne-type shells such as sh(1) or ksh(1) and eval `ssh-agent -c` for 83 csh(1) and derivatives. 84 85 Later ssh(1) looks at these variables and uses them to establish a 86 connection to the agent. 87 88 The agent will never send a private key over its request channel. 89 Instead, operations that require a private key will be performed by the 90 agent, and the result will be returned to the requester. This way, 91 private keys are not exposed to clients using the agent. 92 93 A UNIX-domain socket is created and the name of this socket is stored in 94 the SSH_AUTH_SOCK environment variable. The socket is made accessible 95 only to the current user. This method is easily abused by root or 96 another instance of the same user. 97 98 The SSH_AGENT_PID environment variable holds the agent's process ID. 99 100 The agent exits automatically when the command given on the command line 101 terminates. 102 103 FILES 104 $TMPDIR/ssh-XXXXXXXXXX/agent.<ppid> 105 UNIX-domain sockets used to contain the connection to the 106 authentication agent. These sockets should only be readable by 107 the owner. The sockets should get automatically removed when the 108 agent exits. 109 110 SEE ALSO 111 ssh(1), ssh-add(1), ssh-keygen(1), sshd(8) 112 113 AUTHORS 114 OpenSSH is a derivative of the original and free ssh 1.2.12 release by 115 Tatu Ylonen. Aaron Campbell, Bob Beck, Markus Friedl, Niels Provos, Theo 116 de Raadt and Dug Song removed many bugs, re-added newer features and 117 created OpenSSH. Markus Friedl contributed the support for SSH protocol 118 versions 1.5 and 2.0. 119 120 OpenBSD 6.0 November 30, 2016 OpenBSD 6.0 121
