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1 #!/usr/bin/env bash
2 # Mkinitramfs creates a basic init ram fs with encryption support.
3 # Copyright (C) 2023 Aaron Ball <nullspoon@oper.io>
4 #
5 # This program is free software: you can redistribute it and/or modify
6 # it under the terms of the GNU General Public License as published by
7 # the Free Software Foundation, either version 3 of the License, or
8 # (at your option) any later version.
9 #
10 # This program is distributed in the hope that it will be useful,
11 # but WITHOUT ANY WARRANTY; without even the implied warranty of
12 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 # GNU General Public License for more details.
14 #
15 # You should have received a copy of the GNU General Public License
16 # along with this program. If not, see <http://www.gnu.org/licenses/>.
17
18
19 # Hash of fully-qualified binaries
20 declare -a fqbins
21
22 #
23 # Searches PATH for all binaries listed as function arguments. Each found
24 # binary is then put into the global "bins" array.
25 #
26 # This function also serves to ensure all specified binaries are present and
27 # in PATH. It will exit code 1 with an error message if any binaries are not
28 # found.
29 #
30 # Note: To use this function, insert "declare -a fqbins" at top of script).
31 #
32 # @param bins All function arguments are the names of binaries to locate.
33 #
34 function resolve_bins {
35 local args=${@}
36
37 for i in ${args[@]}; do
38 local path=$(type -p ${i} 2>/dev/null)
39
40 if [[ $? -gt 0 ]]; then
41 echo "Could not find binary ${i}. Is it installed?"
42 exit 1
43 fi
44
45 echo "Located ${i} at ${path}"
46 fqbins+=("${path}")
47 done
48 }
49
50
51 #
52 # Gets first path locatable in a string
53 #
54 function get_first_path {
55 local str=${1}
56
57 local out=''
58 local cursor=''
59
60 for ((i=0; i<${#str}; i++)); do
61 if [[ ${str:$i:1} == '/' ]]; then
62 cursor=${i}
63 break
64 fi
65 done
66
67 # Exit if no path found
68 [[ ${cursor} == '' ]] && return
69
70 while [[ ${str:$cursor:1} != ' ' ]] && [[ ${cursor} -lt ${#str} ]]; do
71 out="${out}${str:$cursor:1}"
72 cursor=$((${cursor} + 1))
73 done
74
75 echo "${out}"
76 }
77
78
79 function get_deps {
80 local bin=${1}
81
82 for dep in $(ldd ${bin}); do
83 get_first_path "${dep}"
84 done
85 }
86
87
88 #
89 # Creates cpio file for specified initrd cache directory.
90 # Outputs to /boot/initrd-${version}.
91 #
92 # @param cache Path to the uncompressed source directory to be archived
93 # @param version Version of initrd archive
94 #
95 function mkcpio {
96 [[ -z ${1} ]] && echo "Initramfs cache path required." && exit 1
97 [[ -z ${2} ]] && echo "Kernel version required." && exit 1
98
99 local cache=${1}
100 local version=${2}
101
102 cd ${cache}
103 fspath="/boot/initrd-${version}"
104
105 # Notify user of initrd overwriting
106 [[ -f ${fspath} ]] && echo -e "\n\n${fspath} exists. Overwriting.\n"
107
108 # Create the initrd
109 echo "Building initrd to ${fspath}"
110 find . -print0 | cpio --null -o --format=newc | xz -C crc32 -9 -c > ${fspath}
111 }
112
113
114 #
115 # Sets up cache dir for later writing to an archive (via cpio).
116 # Performs simple operations like creating a basic directory structure,
117 #
118 # @param cache Path to the cache directory. Will be created if not exists
119 #
120 function cache_dir_setup {
121 [[ -z ${1} ]] && echo "Please specify a cache dir." && exit 1
122 local cache=${1}
123
124 # Clean the cache so we start fresh
125 rm -rf ${cache} && mkdir ${cache}
126
127 local dirs=(bin dev etc lib lib32 lib64 mnt/root proc root run sbin sys usr)
128
129 # Create the temporary directory structure
130 for i in ${dirs[*]}; do
131 mkdir -p ${cache}/${i}
132 done
133
134 # Copy in terminals database for `l` (linux - stock tty)
135 mkdir -p "${cache}/usr/share/terminfo"
136 cp -r /usr/share/terminfo/l "${cache}/usr/share/terminfo/l"
137 }
138
139
140 #
141 # Checks installed kernel modules for the specified version to see if the
142 # corresponding kernel has encryption support statically compiled in.
143 #
144 # @param version Version of kernel modules to check
145 #
146 function check_crypto_support {
147 [[ -z ${1} ]] && echo "Kernel version required." && exit 1
148 local version=${1}
149 local buf=''
150
151 builtinpath=/lib/modules/${version}/modules.builtin
152
153 mkdir -p ${cache}/lib/modules/
154 cp -vr "/lib/modules/${version}/" "${cache}/lib/modules/${version}"
155
156 # Strip out kernel modules not required for bootstrapping
157 for i in virt sound drivers/{bluetooth,gpu,hid,media,mmc,net,video,virtio}; do
158 buf="${cache}/lib/modules/${version}/kernel/${i}"
159 if [ -d "${buf}" ]; then
160 printf 'Stripping %s from initramfs\n' "${buf}"
161 rm -r "${buf:?}"
162 fi
163 done
164 }
165
166
167 #
168 # Checks to see if kernel modules for the specified version have been
169 # installed.
170 #
171 # @param version Version to check for installation status
172 #
173 function check_kernel_version {
174 [[ -z ${1} ]] && echo "Kernel version required." && exit 1
175 local version=${1}
176
177 modulespath=/lib/modules/${version}
178 if [[ ! -d ${modulespath} ]]; then
179 echo "Error: Could not find ${modulespath}."
180 echo "Has kernel version ${version} been comiled?"
181 exit 1
182 fi
183 }
184
185
186 function main {
187 [[ -z ${1} ]] && echo "Please specify a kernel version" && exit 1
188
189 local version=${1}
190
191 check_kernel_version ${version}
192
193 local cache='/tmp/initrd'
194 local res_path=/usr/share/mkinitramfs/
195
196 # Ensure init script has no syntax errors (linting process)
197 if ! bash -n ${res_path}/init; then
198 printf '\n\nERROR: Syntax errors were found in the init script.\n'
199 printf 'Please resolve the above issues and try again.\n'
200 printf 'Exiting to avoid creating an unbootable initramfs.\n\n'
201 return 1
202 fi
203
204 # List of binaries to exist in the new initramfs
205 # Standard shell binaries
206 resolve_bins bash pidof ps ls grep less switch_root kill
207 # Module management
208 resolve_bins udevadm udevd modprobe rmmod
209 # For encrypted and block device support
210 resolve_bins partprobe dmsetup mount umount cryptsetup
211
212 # For debugging
213 #resolve_bins sleep mkdir chmod chown tr clear cat
214
215 # Set up the archive source dir.
216 cache_dir_setup ${cache}
217
218 # Ensure static crypto support exists in kernel
219 check_crypto_support ${version}
220
221 # Copy in libgcc_s for newer cryptsetup
222 install -v -D /usr/lib/libgcc_s.so "${cache}/usr/lib/libgcc_s.so"
223 install -v -D /usr/lib/libgcc_s.so.1 "${cache}/usr/lib/libgcc_s.so.1"
224
225 # Install udev rules for block devices
226 mkdir -p "${cache}/lib/udev"
227 cp -rv /lib/udev/rules.d "${cache}/lib/udev/rules.d"
228
229 # Copy binary and dependencies to cache dir
230 for bin in ${fqbins[@]}; do
231 # Copy the binary of interest
232 install -v -D "${bin}" "${cache}/${bin}"
233
234 local deps=$(get_deps ${bin})
235 # Copy each of the binary's deps
236 for dep in ${deps[@]}; do
237 install -v -D ${dep} "${cache}/${dep}"
238 done
239 done
240
241 # Copy in message file
242 [ -f "/etc/msg" ] && install -v -D "/etc/msg" "${cache}/etc/msg"
243 # Copy in init script and add execute
244 install -v -D -m 755 "${res_path}/init" "${cache}/init"
245 # Copy in the system shell profile
246 install -v -D "/etc/profile" "${cache}/etc/profile"
247
248 # Create archive image
249 mkcpio ${cache} ${version}
250 }
251
252 main ${@}
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