| 1 | .de hP |
| 2 | .IP |
| 3 | \h'-\w'\fB\\$1\ \fP'u'\fB\\$1\ \fP\c |
| 4 | .. |
| 5 | .ie t .ds o \(bu |
| 6 | .el .ds o o |
| 7 | . |
| 8 | .TH sshsvc-mkauthkeys 1 "23 April 2015" "distorted.org.uk" "Utilities" |
| 9 | .SH NAME |
| 10 | sshsvc-mkauthkeys \- build authorized_keys files for SSH services |
| 11 | .SH SYNOPSIS |
| 12 | .B sshsvc-mkauthkeys |
| 13 | .RB [ \-c |
| 14 | .IR config ] |
| 15 | .RB [ \-k |
| 16 | .IR keysdir ] |
| 17 | .RB [ \-o |
| 18 | .IR output ] |
| 19 | .br |
| 20 | \&\h'8n' |
| 21 | .RB [ \-H |
| 22 | .IR head ] |
| 23 | .RB [ \-T |
| 24 | .IR tail ] |
| 25 | .SH DESCRIPTION |
| 26 | The |
| 27 | .B sshsvc-mkauthkeys |
| 28 | script constructs an OpenSSH |
| 29 | .B authorized_keys |
| 30 | file |
| 31 | from a collection of SSH public keys |
| 32 | and some configuration in the form of shell variable and function |
| 33 | definitions. |
| 34 | The script expects to be run from a makefile |
| 35 | within a |
| 36 | .B .ssh/ |
| 37 | directory |
| 38 | and reads and writes files with fixed relative pathnames by default. |
| 39 | These can be overridden using command-line options. |
| 40 | .SS "Command line options" |
| 41 | .TP |
| 42 | .BI \-c " config" |
| 43 | Source configuration from |
| 44 | .I config |
| 45 | instead of the default |
| 46 | .BR sshsvc.conf . |
| 47 | .TP |
| 48 | .BI \-k " keysdir" |
| 49 | Collect user keys from |
| 50 | .I keysdir |
| 51 | instead of the default |
| 52 | .BR keys/ . |
| 53 | .TP |
| 54 | .BI \-o " output" |
| 55 | Write the output to |
| 56 | .I output |
| 57 | instead of the default |
| 58 | .BR authorized_keys . |
| 59 | .TP |
| 60 | .BI \-H " head" |
| 61 | Read initial raw entries from |
| 62 | .I head |
| 63 | (if it exists) |
| 64 | instead of the default |
| 65 | .BR sshsvc-authkeys.head . |
| 66 | .TP |
| 67 | .BI \-T " tail" |
| 68 | Read final raw entries from |
| 69 | .I tail |
| 70 | (if it exists) |
| 71 | instead of the default |
| 72 | .BR sshsvc-authkeys.tail . |
| 73 | .SS "Overall operation" |
| 74 | The |
| 75 | .I output |
| 76 | file |
| 77 | .RB ( authorized_keys |
| 78 | by default) |
| 79 | is constructed as follows. |
| 80 | .hP 0. |
| 81 | A comment is written to |
| 82 | the very top of |
| 83 | the output file |
| 84 | explaining that it was generated by |
| 85 | .BR sshsvc-mkauthkeys . |
| 86 | .hP 1. |
| 87 | If the |
| 88 | .I head |
| 89 | file |
| 90 | .RB ( sshsvc-authkeys.head |
| 91 | by default) |
| 92 | exists then its contents are written unchanged to the output. |
| 93 | .hP 2. |
| 94 | Each of the files |
| 95 | .IB keysdir / user\fR[ ! label\fR] .pub |
| 96 | is processed in turn |
| 97 | (see below) |
| 98 | in ascending lexicographic order |
| 99 | to make a single-line entry |
| 100 | in the output file. |
| 101 | The default |
| 102 | .I keysdir |
| 103 | is |
| 104 | .BR keys/ . |
| 105 | .hP 3. |
| 106 | If the |
| 107 | .I tail |
| 108 | file |
| 109 | .RB ( sshsvc-authkeys.tail |
| 110 | by default) |
| 111 | exists then its contents are written unchanged to the output. |
| 112 | .hP 4. |
| 113 | A commend is written to |
| 114 | the very bottom of |
| 115 | the output file |
| 116 | explaining that it was generated by |
| 117 | .BR sshsvc-mkauthkeys . |
| 118 | .SS "Configuration" |
| 119 | The configuration |
| 120 | for a particular SSH service |
| 121 | is read from |
| 122 | .BR sshsvc.conf . |
| 123 | This file must exist |
| 124 | in the current working directory, |
| 125 | though it needn't have any content |
| 126 | since all configurable parameters have sensible |
| 127 | (though not necessarily useful) |
| 128 | defaults. |
| 129 | .SS "The make_full_key_line function" |
| 130 | The most general configuration hook |
| 131 | (and therefore the one requiring most effort from the user) |
| 132 | is the |
| 133 | .B make_full_key_line |
| 134 | function. |
| 135 | It is given the key file's |
| 136 | .I user |
| 137 | name as an argument and |
| 138 | expected to write |
| 139 | the |
| 140 | .I options |
| 141 | portion of an |
| 142 | .B authorized_keys |
| 143 | entry to standard output. |
| 144 | .PP |
| 145 | The default implementation is likely to be suitable |
| 146 | for almost all services. It calls |
| 147 | .B make_key_line |
| 148 | (see below) |
| 149 | to construct |
| 150 | environment variable settings |
| 151 | and other per-user configuration settings, |
| 152 | and attaches general policy settings. |
| 153 | .PP |
| 154 | It uses the following variables. |
| 155 | .TP |
| 156 | .B allow_port_forwarding |
| 157 | If not |
| 158 | .B yes |
| 159 | then forbid port forwarding |
| 160 | (include |
| 161 | .B no-port-forwarding |
| 162 | in the line). |
| 163 | The default is |
| 164 | .BR no . |
| 165 | .TP |
| 166 | .B allow_x11_forwarding |
| 167 | If not |
| 168 | .B yes |
| 169 | then forbid X11 connection forwarding |
| 170 | (include |
| 171 | .B no-X11-forwarding |
| 172 | in the line). |
| 173 | The default is |
| 174 | .BR no . |
| 175 | .TP |
| 176 | .B allow_agent_forwarding |
| 177 | If not |
| 178 | .B yes |
| 179 | then forbid SSH agent forwarding |
| 180 | (include |
| 181 | .B no-agent-forwarding |
| 182 | in the line). |
| 183 | The default is |
| 184 | .BR no . |
| 185 | It's probably not a good idea to enable this. |
| 186 | .TP |
| 187 | .B allow_pty |
| 188 | If not |
| 189 | .B yes |
| 190 | then forbid pty allocation |
| 191 | (include |
| 192 | .B no-pty |
| 193 | in the line). |
| 194 | The default is |
| 195 | .BR no . |
| 196 | This is usually what you want |
| 197 | unless your service needs an interactive terminal |
| 198 | (e.g., a console for a virtual machine). |
| 199 | .TP |
| 200 | .B cmd |
| 201 | If set to any value |
| 202 | and the line from |
| 203 | .B make_key_line |
| 204 | doesn't already contain a |
| 205 | .RB ` command= ...' |
| 206 | option, |
| 207 | then always run |
| 208 | .I cmd |
| 209 | (with the service user's shell) |
| 210 | rather than using the client's requested command line, |
| 211 | which is left in |
| 212 | .B SSH_ORIGINAL_COMMAND |
| 213 | (include |
| 214 | .BI command="" cmd "" |
| 215 | in the line). |
| 216 | The default is |
| 217 | .BR bin/sshsvc . |
| 218 | .SS "The make_key_line function" |
| 219 | The |
| 220 | .B make_key_line |
| 221 | function is called with |
| 222 | the key file's |
| 223 | .I user |
| 224 | name as its only argument, |
| 225 | and is expected to write any per-user |
| 226 | (and unusual) |
| 227 | options to standard output. |
| 228 | Mostly it will be sufficient to generate an |
| 229 | .RB ` environment= ...' |
| 230 | option |
| 231 | and leave the rest to |
| 232 | .BR make_full_key_line . |
| 233 | .PP |
| 234 | The default |
| 235 | .B make_key_line |
| 236 | function is suitable for simple cases. |
| 237 | It examines the |
| 238 | .B env |
| 239 | variable, |
| 240 | replacing |
| 241 | .B @user |
| 242 | placeholders with the key's |
| 243 | .I user |
| 244 | name, |
| 245 | and emits the line |
| 246 | .BI environment= env\fR. |
| 247 | The default value of |
| 248 | .B env |
| 249 | is |
| 250 | .B SSHSVC_USER=@user |
| 251 | which may be good enough for services |
| 252 | explicitly written to work with it. |
| 253 | .SH FILES |
| 254 | .TP |
| 255 | .BR sshsvc.conf |
| 256 | Read for configuration |
| 257 | (shell variable and function definitions). |
| 258 | .TP |
| 259 | .BI keys/ user\fR[ ! label\fR] .pub |
| 260 | Input public keys to process. |
| 261 | .TP |
| 262 | .B sshsvc-authkeys.head |
| 263 | Pre-cooked |
| 264 | .B authorized_keys |
| 265 | entries to write at the top of the output. |
| 266 | .TP |
| 267 | .B sshsvc-authkeys.tail |
| 268 | Pre-cooked |
| 269 | .B authorized_keys |
| 270 | entries to write at the bottom of the output. |
| 271 | .TP |
| 272 | .B authorized_keys |
| 273 | Output file. |
| 274 | .SH BUGS |
| 275 | Perfection guaranteed. |
| 276 | Satisfaction, or your money back. |
| 277 | .SH "SEE ALSO" |
| 278 | .BR ssh (1), |
| 279 | .BR sshd (8). |
| 280 | .SH AUTHOR |
| 281 | Mark Wooding, <mdw@distorted.org.uk> |