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ssh: add trust checks before sourcing env vars #1395

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ssh: add trust checks before sourcing env vars #1395

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56d0dc5
ssh: remove persistent socket; use macOS Keychain
slarew Jul 22, 2017
3f8dace
Load :prezto:module:ssh:load identities on macOS
slarew Oct 6, 2017
84ad1f3
ssh: add trust checks before sourcing env vars
slarew Jul 22, 2017
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41 changes: 27 additions & 14 deletions modules/ssh/init.zsh
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Original file line number Diff line number Diff line change
Expand Up @@ -16,26 +16,32 @@ _ssh_dir="$HOME/.ssh"
# Set the path to the environment file if not set by another module.
_ssh_agent_env="${_ssh_agent_env:-${TMPDIR:-/tmp}/ssh-agent.env.$UID}"

# Set the path to the persistent authentication socket.
_ssh_agent_sock="${TMPDIR:-/tmp}/ssh-agent.sock.$UID"
# Due to the predictability of the env file, check the env file exists and is
# owned by current EUID before trusting it.
if [[ -f "$_ssh_agent_env" && ! -O "$_ssh_agent_env" ]]; then
cat 1>&2 <<-EOF
ERROR: Cannot trust the SSH agent environment variables persistence
file because it is owned by another user.
The ssh-agent will not be started.
$_ssh_agent_env
EOF
unset _ssh_{dir,agent_env}
return 1
fi

# Start ssh-agent if not started.
# If a socket exists at SSH_AUTH_SOCK, assume ssh-agent is already running and
# skip starting it.
if [[ ! -S "$SSH_AUTH_SOCK" ]]; then
# Export environment variables.
# Try to grab previously exported environment variables.
source "$_ssh_agent_env" 2> /dev/null

# Start ssh-agent if not started.
if ! ps -U "$LOGNAME" -o pid,ucomm | grep -q -- "${SSH_AGENT_PID:--1} ssh-agent"; then
# Do not start ssh-agent if the PID from the last start of ssh-agent exists and
# corresponds to a running ssh-agent under the current user.
if ! ps -U "$LOGNAME" -o pid,comm | grep -E -q -e "^[[:blank:]]*${SSH_AGENT_PID:--1}[[:blank:]].*ssh-agent$"; then
eval "$(ssh-agent | sed '/^echo /d' | tee "$_ssh_agent_env")"
fi
fi

# Create a persistent SSH authentication socket.
if [[ -S "$SSH_AUTH_SOCK" && "$SSH_AUTH_SOCK" != "$_ssh_agent_sock" ]]; then
ln -sf "$SSH_AUTH_SOCK" "$_ssh_agent_sock"
export SSH_AUTH_SOCK="$_ssh_agent_sock"
fi

# Load identities.
if ssh-add -l 2>&1 | grep -q 'The agent has no identities'; then
zstyle -a ':prezto:module:ssh:load' identities '_ssh_identities'
Expand All @@ -50,11 +56,18 @@ if ssh-add -l 2>&1 | grep -q 'The agent has no identities'; then
# program specified by SSH_ASKPASS and open an X11 window to read the
# passphrase.
if [[ -n "$DISPLAY" && -x "$SSH_ASKPASS" ]]; then
ssh-add ${_ssh_identities:+$_ssh_dir/${^_ssh_identities[@]}} < /dev/null 2> /dev/null
ssh-add "${_ssh_identities:+$_ssh_dir/${^_ssh_identities[@]}}" < /dev/null 2> /dev/null
else
ssh-add ${_ssh_identities:+$_ssh_dir/${^_ssh_identities[@]}} 2> /dev/null
fi

if [[ "$OSTYPE" == darwin* ]]; then
# macOS: `ssh-add -A` will load all identities defined in Keychain.
# Assume `/usr/bin/ssh-add` is Apple customized version that understands
# the `-A` switch.
/usr/bin/ssh-add -A
fi
fi

# Clean up.
unset _ssh_{dir,identities} _ssh_agent_{env,sock}
unset _ssh_{dir,identities,agent_env}