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Marco Cetica 2024-04-03 08:55:06 +02:00
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82
README.md
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@ -1,14 +1,9 @@
# backup.sh ![](https://github.com/ceticamarco/backup.sh/actions/workflows/backup.sh.yml/badge.svg)
`backup.sh` is a POSIX compliant, modular and lightweight backup utility to save and encrypt your files.
This tool is intended to be used on small scale UNIX environments such as VPS, personal servers and
workstations. `backup.sh` uses [rsync](https://linux.die.net/man/1/rsync), [tar](https://linux.die.net/man/1/tar)
and [gpg](https://linux.die.net/man/1/gpg) to copy, compress and encrypt the backup.
`backup.sh` works under the following operating systems:
- GNU/Linux;
- OpenBSD
- FreeBSD;
- Apple MacOS.
workstations. `backup.sh` uses [rsync](https://linux.die.net/man/1/rsync), [tar](https://linux.die.net/man/1/tar),
[gpg](https://linux.die.net/man/1/gpg) and [sha256sum](https://linux.die.net/man/1/sha256sum)
to copy, compress, encrypt the backup and verify the backup.
## Installation
`backup.sh` consists in a single source file, to install it you can copy the script wherever you want.
@ -30,18 +25,23 @@ To show the available options, you can run `backup.sh --help`, which will print
```text
backup.sh - POSIX compliant, modular and lightweight backup utility.
Syntax: ./backup.sh [-b|-e|-h]
Syntax: ./backup.sh [-b|-c|-e|-h]
options:
-b|--backup SOURCES DEST PASS Backup folders from SOURCES file.
-c|--checksum Generate/check SHA256 of a backup.
-e|--extract ARCHIVE PASS Extract ARCHIVE using PASS.
-h|--help Show this helper.
General help with the software: https://github.com/ceticamarco/backup.sh
Report bugs to: Marco Cetica(<email@marcocetica.com>)
```
As you can see, `backup.sh` supports two options: **backup creation** and **backup extraction**, the former requires
root permissions, while the latter does not. Let us see them in details.
As you can see, `backup.sh` supports three options: **backup creation**, **backup extraction** and **checksum** to verify the
integrity of a backup. The first option requires
root permissions, while the second one does not. The checksum option must be used in combination of one of the previous options.
### Backup creation
To specify the directories to backup, `backup.sh` uses an associative array
To specify the directories to back up, `backup.sh` uses an associative array
defined in a text file(called _sources file_) with the following syntax:
```text
@ -68,7 +68,7 @@ backup-ssh-<YYYYMMDD>
```
You can add as many entries as you want, just be sure to use the proper syntax. In particular,
the _sources file_, **should not** includes:
the _sources file_, **should not** include:
- Spaces between the label and the equal sign;
- Empty lines;
- Comments.
@ -88,19 +88,26 @@ In the previous example, this would be:
$> sudo ./backup.sh --backup sources.bk /home/john badpw1234
```
You can also tell `backup.sh` to generate a SHA256 file containing the hash of each file using the `-c` option.
In the previous example, this would be:
```sh
$> sudo ./backup.sh --checksum --backup sources.bk /home/john badpw1234
```
The backup utility will begin to copy the files defined in the _sources file_:
```text
Copying nginx(1/2)
Copying ssh(2/2)
Compressing backup...
Encrypting backup...
File name: /home/marco/backup-<HOSTNAME>-<YYYYMMDD>.tar.gz.enc
File name: /home/john/backup-<HOSTNAME>-<YYYYMMDD>.tar.gz.enc
Checksum file: /home/john/backup-<HOSTNAME>-<YYYYMMDD>.sha256
File size: 7336400696(6.9G)
File hash: 0e75ca393117f389d9e8edfea7106d98
Elapsed time: 259 seconds.
```
After that, you will find the final backup archive in `/home/john/backup-<HOSTNAME>-<YYYYMMDD>.tar.gz.enc`.
After that, you will find the backup archive and the checksum file in
`/home/john/backup-<HOSTNAME>-<YYYYMMDD>.tar.gz.enc` and `/home/john/backup-<HOSTNAME>-<YYYYMMDD>.sha256`, respectively.
You can also use `backup.sh` from a crontab rule:
```sh
@ -114,7 +121,8 @@ key is stored in a local file(with fixed permissions) to avoid password leaking
adopt this practice while using the `--extract` option to avoid password leaking in shell history.
### Backup extraction
`backup.sh` can also extract the encrypted backup archive using the following syntax:
`backup.sh` can also be used to extract the encrypted backup as well to verify the integrity
of the backup data. To do so, use the following commands:
```sh
$> ./backup.sh --extract <ENCRYPTED_ARCHIVE> <ARCHIVE_PASSWORD>
@ -128,16 +136,31 @@ For instance:
$> ./backup.sh --extract backup-<hostname>-<YYYYMMDD>.tar.gz.enc badpw1234
```
This will create a new folder called `backup.sh.tmp` in your local directory. Be sure to rename any directory
with that name to avoid collisions. From the previous example, you should have the following directories:
This will create a new folder called `backup.sh.tmp` in your local directory with the following content:
```text
backup-nginx-<YYYYMMDD>
backup-ssh-<YYYYMMDD>
```
**note:**: be sure to rename any directory with that name to avoid collisions.
Instead, if you also want to verify the integrity of the backup data, use the following commands:
```sh
$> ./backup.sh --checksum --extract <ENCRYPTED_ARCHIVE> <ARCHIVE_PASSWORD> <CHECKSUM_ABSOLUTE_PATH>
```
For instance:
```sh
$> ./backup.sh --checksum --extract backup-<hostname>-<YYYYMMDD>.tar.gz.enc badpw1234 $PWD/backup-<hostname>-<YYYYMMDD>.sha256
```
**note:** be sure to provide the ABSOLUTE PATH of the checksum file.
## How does backup.sh work?
**backup.sh** uses _rsync_ to copy the files, _tar_ to compress the backup and _gpg_ to encrypt it.
**backup.sh** uses _rsync_ to copy the files, _tar_ to compress the backup, _gpg_ to encrypt it and
_sha256sum_ to verify it.
By default, rsync is being used with the following parameters:
```
@ -153,10 +176,15 @@ That is:
- q: quiet mode: reduces the amount of information rsync produces;
- delete: delete mode: forces rsync to delete any extraneous files at the destination dir.
If specified(`--checksum` option), `backup.sh` can also generate the checksum of each file of the backup.
To do so, it uses `sha256sum(1)` to compute the hash of every single file using the SHA256 hashing algorithm.
The checksum file contains nothing but the checksums of the files, no other information about the files stored
on the backup archive is exposed on the unencrypted checksum file. This may be an issue if you want plausible
deniability(see privacy section for more information).
After that the backup folder is being encrypted using gpg. By default, it is used with the following parameters:
```
$> gpg -a \
--symmetric \
@ -177,6 +205,18 @@ This command encrypts the backup using the AES-256 symmetric encryption algorith
- `--output`: Specify output file;
- `$INPUT`: Specify input file.
## Plausible Deniability
While `backup.sh` provide some pretty strong security against bruteforce attack(assuming a strong passphrase is being used)
it should by no means considered a viable tool against a cryptanalysis investigation. Many of the copying, compressing and
encrypting operations made by `backup.sh` during the backup process can be used to invalidate plausible deniability.
In particular, you should pay attention to the following details:
1. The `--checksum` option generates an **UNENCRYPTED** checksum file containing the _digests_ of **EVERY**
file in your backup archive. If your files are known to your adversary(e.g., a banned book), they may use a rainbow table attack to
determine whether you own a given file, voiding your plausible deniability;
2. Since `backup.sh` is essentially a set of shell commands, an eavesdropper could monitor the whole backup process to extract
the name of the files or the encryption password.
## Unit tests
`backup.sh` provides some unit tests inside the `tests.sh` script. This script generates some dummy files inside the following
directories:

99
backup.sh
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@ -13,19 +13,23 @@
# logs=/var/log/
#
# After that you can launch the script with(sample usage):
# sudo ./backup.sh --backup sources.bk /home/john badpw1234
# sudo ./backup.sh --checksum --backup sources.bk /home/john badpw1234
#
# This will create an encrypted tar archive(password: 'badpw1234')
# in '/home/john/backup-<hostname>-<YYYMMDD>.tar.gz.enc' containing
# in '/home/john/backup-<hostname>-<YYYYMMDD>.tar.gz.enc' containing
# the following three directories:
# backup-nginx-<YYYYMMDD>
# backup-ssh-<YYYYMMDD>
# backup-logs-<YYYYMMDD>
#
# You can then decrypt it using:
# ./backup.sh --extract backup-<hostname>-<YYYMMDD>.tar.gz.enc badpw1234
# as well as a SHA256 file('/home/john/backup-<hostname>-<YYYYMMDD>.sha256')
# containing the file hashes of the backup.
#
# You can read the full guide on https://github.com/ice-bit/backup.sh
# You can then decrypt it using:
# ./backup.sh --checksum --extract backup-<hostname>-<YYYYMMDD>.tar.gz.enc badpw1234 $PWD/backup-<hostname>-<YYYYMMDD>.sha256
# which will also check the integrity of the backup(optional feature).
#
# You can read the full guide on https://github.com/ceticamarco/backup.sh
# or on the manual page.
# Copyright (c) 2018,2023,2024 Marco Cetica <email@marcocetica.com>
#
@ -47,29 +51,23 @@ checkdeps() {
fi
}
checksum() {
BACKUP_SH_FILENAME="$1"
BACKUP_SH_OS="$(uname | tr '[:lower:]' '[:upper:]')"
if [ "$BACKUP_SH_OS" = "LINUX" ]; then
RES="$(md5sum "$BACKUP_SH_FILENAME" | awk '{print $1}')"
else
RES="$(md5 -q "$BACKUP_SH_FILENAME")"
fi
echo "$RES"
}
# $1: sources.bk file
# $2: output path
# $3: password
# $4: compute sha256(0,1)
make_backup() {
BACKUP_SH_SOURCES_PATH="$1"
BACKUP_SH_OUTPATH="$2"
BACKUP_SH_PASS="$3"
BACKUP_SH_SHA256="$4"
BACKUP_SH_COMMAND="rsync -aPhrq --delete"
BACKUP_SH_DATE="$(date +'%Y%m%d')"
BACKUP_SH_FOLDER="backup.sh.tmp"
BACKUP_SH_OUTPUT="$BACKUP_SH_OUTPATH/$BACKUP_SH_FOLDER"
BACKUP_SH_START_TIME="$(date +%s)"
BACKUP_SH_FILENAME="$BACKUP_SH_OUTPATH/backup-$(uname -n)-$BACKUP_SH_DATE.tar.gz.enc"
BACKUP_SH_CHECKSUM_FILE="$BACKUP_SH_OUTPATH/backup-$(uname -n)-$BACKUP_SH_DATE.sha256"
# Check for root permissions
if [ "$(id -u)" -ne 0 ]; then
@ -96,6 +94,13 @@ make_backup() {
mkdir -p "$BACKUP_SH_SUBDIR"
printf "Copying %s(%s/%s)\n" "$label" "$BACKUP_SH_PROGRESS" "$BACKUP_SH_TOTAL"
# Compute SHA256 of all files of the current directory
if [ "$BACKUP_SH_SHA256" -eq 1 ]; then
find "$path" -type f -exec sha256sum {} + | sort -k 2 | awk '{print $1}' >> "$BACKUP_SH_CHECKSUM_FILE"
fi
# Copy files
$BACKUP_SH_COMMAND "$path" "$BACKUP_SH_SUBDIR"
BACKUP_SH_PROGRESS=$((BACKUP_SH_PROGRESS+1))
done < "$BACKUP_SH_SOURCES_PATH"
@ -124,20 +129,24 @@ make_backup() {
BACKUP_SH_END_TIME="$(date +%s)"
BACKUP_SH_FILE_SIZE="$(find "$BACKUP_SH_FILENAME" -exec ls -l {} \; | awk '{print $5}')"
BACKUP_SH_FILE_SIZE_H="$(find "$BACKUP_SH_FILENAME" -exec ls -lh {} \; | awk '{print $5}')"
BACKUP_SH_HASH="$(checksum "$BACKUP_SH_FILENAME")"
echo "File name: $BACKUP_SH_FILENAME"
[ "$BACKUP_SH_SHA256" -eq 1 ] && { echo "Checksum file: $BACKUP_SH_CHECKSUM_FILE"; }
echo "File size: $BACKUP_SH_FILE_SIZE($BACKUP_SH_FILE_SIZE_H)"
echo "File hash: $BACKUP_SH_HASH"
printf "Elapsed time: %s seconds.\n" "$((BACKUP_SH_END_TIME - BACKUP_SH_START_TIME))"
}
# $1: archive file
# $2: archive password
# $3: sha256 file(optional)
extract_backup() {
BACKUP_SH_ARCHIVE_PATH="$1"
BACKUP_SH_ARCHIVE_PW="$2"
BACKUP_SH_SHA256_FILE="$3"
# Decrypt the archive
gpg -a \
--quiet \
--decrypt \
--no-symkey-cache \
--pinentry-mode=loopback \
@ -148,7 +157,20 @@ extract_backup() {
# Extract archive
tar -xzf backup.sh.tar.gz 1> /dev/null 2>&1
# Remove temporary files
# If specified, use SHA256 file to compute checksum of files
if [ -n "$BACKUP_SH_SHA256_FILE" ]; then
for file in $(find "backup.sh.tmp" -type f | sort -k 2); do
# Compute sha256 for current file
sha256="$(sha256sum "$file" | awk '{print $1}')"
# Check if checksum file contains hash
if ! grep -wq "$sha256" "$BACKUP_SH_SHA256_FILE"; then
printf "[FATAL] - integrity error for '%s'.\n" "$file"
rm -rf backup.sh.tar.gz backup.sh.tmp
exit 1
fi
done
fi
rm -rf backup.sh.tar.gz
}
@ -158,13 +180,14 @@ helper() {
cat <<EOF
backup.sh - POSIX compliant, modular and lightweight backup utility.
Syntax: $CLI_NAME [-b|-e|-h]
Syntax: $CLI_NAME [-b|-c|-e|-h]
options:
-b|--backup SOURCES DEST PASS Backup folders from SOURCES file.
-c|--checksum Generate/check SHA256 of a backup.
-e|--extract ARCHIVE PASS Extract ARCHIVE using PASS.
-h|--help Show this helper.
General help with the software: https://github.com/ice-bit/backup.sh
General help with the software: https://github.com/ceticamarco/backup.sh
Report bugs to: Marco Cetica(<email@marcocetica.com>)
EOF
}
@ -179,6 +202,7 @@ main() {
exit 1
fi
CHECKSUM_FLAG=0
# Parse CLI arguments
while [ $# -gt 0 ]; do
case $1 in
@ -192,19 +216,46 @@ main() {
echo "For more informatio, try --help"
exit 1
fi
make_backup "$BACKUP_SH_SOURCES_PATH" "$BACKUP_SH_OUTPATH" "$BACKUP_SH_PASSWORD"
if [ "$CHECKSUM_FLAG" -eq 1 ]; then
make_backup "$BACKUP_SH_SOURCES_PATH" "$BACKUP_SH_OUTPATH" "$BACKUP_SH_PASSWORD" 1
else
make_backup "$BACKUP_SH_SOURCES_PATH" "$BACKUP_SH_OUTPATH" "$BACKUP_SH_PASSWORD" 0
fi
exit 0
;;
-c|--checksum)
[ $# -eq 1 ] && { echo "Use this option with '--backup' or '--extract'"; exit 1; }
CHECKSUM_FLAG=1
shift 1
;;
-e|--extract)
BACKUP_SH_ARCHIVE_PATH="$2"
BACKUP_SH_ARCHIVE_PW="$3"
BACKUP_SH_SHA256_FILE="$4"
if [ "$CHECKSUM_FLAG" -eq 1 ]; then
if [ -z "$BACKUP_SH_ARCHIVE_PATH" ] || [ -z "$BACKUP_SH_ARCHIVE_PW" ] || [ -z "$BACKUP_SH_SHA256_FILE" ]; then
echo "Please, specify an encrypted archive, a password and a SHA256 file."
echo "For more informatio, try --help"
exit 1
fi
else
if [ -z "$BACKUP_SH_ARCHIVE_PATH" ] || [ -z "$BACKUP_SH_ARCHIVE_PW" ]; then
echo "Please, specify an encrypted archive and a password."
echo "For more informatio, try --help"
exit 1
fi
fi
if [ "$CHECKSUM_FLAG" -eq 1 ]; then
[ -e "$BACKUP_SH_SHA256_FILE" ] || { echo "Checksum file does not exist"; exit 1; }
extract_backup "$BACKUP_SH_ARCHIVE_PATH" "$BACKUP_SH_ARCHIVE_PW" "$BACKUP_SH_SHA256_FILE"
else
extract_backup "$BACKUP_SH_ARCHIVE_PATH" "$BACKUP_SH_ARCHIVE_PW"
fi
exit 0
;;
-h|--help)

357
backup.sh.1
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@ -1,265 +1,406 @@
.\" Automatically generated by Pandoc 3.1.8
.\" Automatically generated by Pandoc 2.17.1.1
.\"
.TH "backup.sh" "1" "February 27, 2024" "Marco Cetica" "General Commands Manual"
.\" Define V font for inline verbatim, using C font in formats
.\" that render this, and otherwise B font.
.ie "\f[CB]x\f[]"x" \{\
. ftr V B
. ftr VI BI
. ftr VB B
. ftr VBI BI
.\}
.el \{\
. ftr V CR
. ftr VI CI
. ftr VB CB
. ftr VBI CBI
.\}
.TH "backup.sh" "1" "April 3, 2024" "Marco Cetica" "General Commands Manual"
.hy
.SH NAME
.PP
\f[B]backup.sh\f[R] - POSIX compliant, modular and lightweight backup
utility to save and encrypt your files.
.SH SYNOPSIS
.IP
.EX
Syntax: backup.sh [-b|-e|-h]
.nf
\f[C]
Syntax: ./backup.sh [-b|-c|-e|-h]
options:
-b|--backup SOURCES DEST PASS Backup folders from SOURCES file.
-c|--checksum Generate/check SHA256 of a backup.
-e|--extract ARCHIVE PASS Extract ARCHIVE using PASS.
-h|--help Show this helper.
.EE
\f[R]
.fi
.SH DESCRIPTION
.PP
\f[B]backup.sh\f[R] is a POSIX compliant, modular and lightweight backup
utility to save and encrypt your files.
This tool is intended to be used on small scale UNIX environment such as
VPS, small servers and workstations.
\f[B]backup.sh\f[R] uses \f[I]rsync\f[R], \f[I]tar\f[R] and
\f[I]gpg\f[R] to copy, compress and encrypt the backup.
\f[B]backup.sh\f[R] uses \f[I]rsync\f[R], \f[I]tar\f[R],
\f[I]sha256sum\f[R] and \f[I]gpg\f[R] to copy, compress, verify and
encrypt the backup.
.SH OPTIONS
\f[B]backup.sh\f[R] supports two options: \f[I]backup creation\f[R] and
\f[I]backup extraction\f[R].
The former requires root permissions, while the latter does not.
Let us see them in details:
.PP
\f[B]backup.sh\f[R] supports three options: \f[B]backup creation\f[R],
\f[B]backup extraction\f[R] and \f[B]checksum\f[R] to verify the
integrity of a backup.
The first option requires root permissions, while the second one does
not.
The checksum option must be used in combination of one of the previous
options.
.SS Backup creation
To specify the directories to backup, \f[B]backup.sh\f[R] uses an
associative array defined in a text file(called sources file) with the
following syntax:
.IP
.EX
<LABEL>=<PATH>
.EE
.PP
Where \f[CR]<LABEL>\f[R] is the name of the backup and \f[CR]<PATH>\f[R]
is its path.
For example, if you want to back up \f[I]/etc/nginx\f[R] and
\f[I]/etc/ssh\f[R], add the following entries to the sources file:
.IP
.EX
nginx=/etc/nginx/
ssh=/etc/ssh/
.EE
.PP
\f[B]backup.sh\f[R] will create two folders inside the backup archive
To specify the directories to back up, \f[V]backup.sh\f[R] uses an
associative array defined in a text file(called \f[I]sources file\f[R])
with the following syntax:
.IP
.EX
.nf
\f[C]
<LABEL>=<PATH>
\f[R]
.fi
.PP
Where \f[V]<LABEL>\f[R] is the name of the backup and \f[V]<PATH>\f[R]
is its path.
For example, if you want to back up \f[V]/etc/nginx\f[R] and
\f[V]/etc/ssh\f[R], add the following entries to the \f[I]sources
file\f[R]:
.IP
.nf
\f[C]
nginx=/etc/nginx/
ssh=/etc/ssh/
\f[R]
.fi
.PP
\f[V]backup.sh\f[R] will create two folders inside the backup archive
with the following syntax:
.IP
.nf
\f[C]
backup-<LABEL>-<YYYYMMDD>
.EE
\f[R]
.fi
.PP
In the previous example, this would be:
.IP
.EX
.nf
\f[C]
backup-nginx-<YYYYMMDD>
backup-ssh-<YYYYMMDD>
.EE
\f[R]
.fi
.PP
You can add as many entries as you want, just be sure to use the proper
syntax.
In particular, the sources file, \f[I]should not\f[R] includes:
.IP
.EX
In particular, the \f[I]sources file\f[R], \f[B]should not\f[R] include:
- Spaces between the label and the equal sign;
.PD 0
.P
.PD
- Empty lines;
.PD 0
.P
.PD
- Comments.
.EE
.PP
You can find a sample sources file at \f[CR]sources.bk\f[R](or at
\f[CR]/usr/local/etc/sources.bk\f[R]).
You can find a sample \f[I]sources file\f[R] at \f[V]sources.bk\f[R](or
at \f[V]/usr/local/etc/sources.bk\f[R]).
.PP
After having defined the sources file, you can invoke
\f[B]backup.sh\f[R] using the following syntax:
After having defined the \f[I]sources file\f[R], you can invoke
\f[V]backup.sh\f[R] using the following syntax:
.IP
.EX
.nf
\f[C]
$> sudo ./backup.sh --backup <SOURCES_FILE> <DEST> <ENCRYPTION_PASSWORD>
.EE
\f[R]
.fi
.PP
Where \f[CR]<SOURCES_FILE>\f[R] is the \f[I]sources file\f[R],
\f[CR]<DEST>\f[R] is the absolute path of the output of the backup
\f[I]without trailing slashes\f[R] and \f[CR]<ENCRYPTION_PASSWORD>\f[R]
Where \f[V]<SOURCES_FILE>\f[R] is the \f[I]sources file\f[R],
\f[V]<DEST>\f[R] is the absolute path of the output of the backup
\f[B]without trailing slashes\f[R] and \f[V]<ENCRYPTION_PASSWORD>\f[R]
is the password to encrypt the compressed archive.
.PP
In the previous example, this would be:
.IP
.EX
.nf
\f[C]
$> sudo ./backup.sh --backup sources.bk /home/john badpw1234
.EE
\f[R]
.fi
.PP
The backup utility will begin to copy the files defined in the sources
file:
You can also tell \f[V]backup.sh\f[R] to generate a SHA256 file
containing the hash of each file using the \f[V]-c\f[R] option.
In the previous example, this would be:
.IP
.EX
.nf
\f[C]
$> sudo ./backup.sh --checksum --backup sources.bk /home/john badpw1234
\f[R]
.fi
.PP
The backup utility will begin to copy the files defined in the
\f[I]sources file\f[R]:
.IP
.nf
\f[C]
Copying nginx(1/2)
Copying ssh(2/2)
Compressing backup...
Encrypting backup...
File name: /home/marco/backup-<HOSTNAME>-<YYYYMMDD>.tar.gz.enc
File name: /home/john/backup-<HOSTNAME>-<YYYYMMDD>.tar.gz.enc
Checksum file: /home/john/backup-<HOSTNAME>-<YYYYMMDD>.sha256
File size: 7336400696(6.9G)
File hash: 0e75ca393117f389d9e8edfea7106d98
Elapsed time: 259 seconds.
.EE
\f[R]
.fi
.PP
After that, you will find the final backup archive in
\f[CR]/home/john/backup-<HOSTNAME>-<YYYYMMDD>.tar.gz.enc\f[R].
After that, you will find the backup archive and the checksum file in
\f[V]/home/john/backup-<HOSTNAME>-<YYYYMMDD>.tar.gz.enc\f[R] and
\f[V]/home/john/backup-<HOSTNAME>-<YYYYMMDD>.sha256\f[R], respectively.
.PP
You can also use \f[B]backup.sh\f[R] from a crontab rule:
You can also use \f[V]backup.sh\f[R] from a crontab rule:
.IP
.EX
.nf
\f[C]
$> sudo crontab -e
30 03 * * 6 EKEY=$(cat /home/john/.ekey) sh -c \[aq]/usr/local/bin/backup.sh -b /usr/local/etc/sources.bk /home/john $EKEY\[aq] > /dev/null 2>&1
.EE
\f[R]
.fi
.PP
This will automatically run \f[B]backup.sh\f[R] every Saturday morning
This will automatically run \f[V]backup.sh\f[R] every Saturday morning
at 03:30 AM.
In the example above, the encryption key is stored in a local file(with
fixed permissions) to avoid password leaking in crontab logs.
You can also adopt this practice while using the \f[CR]--extract\f[R]
You can also adopt this practice while using the \f[V]--extract\f[R]
option to avoid password leaking in shell history.
.SS Backup extraction
\f[B]backup.sh\f[R] can also extract the encrypted backup archive using
the following syntax:
.IP
.EX
$> ./backup.sh --extract <ENCRYPTED_ARCHIVE> <ARCHIVE_PASSWORD>
.EE
.PP
Where \f[CR]<ENCRYPTED_ARCHIVE>\f[R] is the encrypted backup and
\f[CR]<ARCHIVE_PASSWORD>\f[R] is the backup password.
\f[B]backup.sh\f[R] can also be used to extract the encrypted backup as
well to verify the integrity of the backup data.
To do so, use the following commands:
.IP
.nf
\f[C]
$> ./backup.sh --extract <ENCRYPTED_ARCHIVE> <ARCHIVE_PASSWORD>
\f[R]
.fi
.PP
Where \f[V]<ENCRYPTED_ARCHIVE>\f[R] is the encrypted backup and
\f[V]<ARCHIVE_PASSWORD>\f[R] is the backup password.
.PP
For instance:
.IP
.EX
.nf
\f[C]
$> ./backup.sh --extract backup-<hostname>-<YYYYMMDD>.tar.gz.enc badpw1234
.EE
\f[R]
.fi
.PP
This will create a new folder called \f[CR]backup.sh.tmp\f[R] in your
local directory.
Be sure to rename any directory with that name to avoid collisions.
From the previous example, you should have the following directories:
This will create a new folder called \f[V]backup.sh.tmp\f[R] in your
local directory with the following content:
.IP
.EX
.nf
\f[C]
backup-nginx-<YYYYMMDD>
backup-ssh-<YYYYMMDD>
.EE
\f[R]
.fi
.PP
\f[B]note:\f[R]: be sure to rename any directory with that name to avoid
collisions.
.PP
Instead, if you also want to verify the integrity of the backup data,
use the following commands:
.IP
.nf
\f[C]
$> ./backup.sh --checksum --extract <ENCRYPTED_ARCHIVE> <ARCHIVE_PASSWORD> <CHECKSUM_ABSOLUTE_PATH>
\f[R]
.fi
.PP
For instance:
.IP
.nf
\f[C]
$> ./backup.sh --checksum --extract backup-<hostname>-<YYYYMMDD>.tar.gz.enc badpw1234 $PWD/backup-<hostname>-<YYYYMMDD>.sha256
\f[R]
.fi
.PP
\f[B]note:\f[R] be sure to provide the ABSOLUTE PATH of the checksum
file.
.SS How does backup.sh work?
.PP
\f[B]backup.sh\f[R] uses \f[I]rsync\f[R] to copy the files,
\f[I]tar\f[R] to compress the backup and \f[I]gpg\f[R] to encrypt it.
\f[I]tar\f[R] to compress the backup, \f[I]gpg\f[R] to encrypt it and
\f[I]sha256sum\f[R] to verify it.
By default, rsync is being used with the following parameters:
.IP
.EX
.nf
\f[C]
$> rsync -aPhrq --delete
.EE
\f[R]
.fi
.PP
That is:
.IP
.EX
.nf
\f[C]
- a: archive mode: rsync copies files recursively while preserving as much metadata as possible;
- P: progress/partial: allows rsync to resume interrupted transfers and to shows progress information;
- h: human readable output, rsync shows output numbers in a more readable way;
- r: recursive mode: forces rsync to copy directories and their content;
- q: quiet mode: reduces the amount of information rsync produces;
- delete: delete mode: forces rsync to delete any extraneous files at the destination dir.
.EE
\f[R]
.fi
.PP
If specified(\f[V]--checksum\f[R] option), \f[V]backup.sh\f[R] can also
generate the checksum of each file of the backup.
To do so, it uses \f[V]sha256sum(1)\f[R] to compute the hash of every
single file using the SHA256 hashing algorithm.
The checksum file contains nothing but the checksums of the files, no
other information about the files stored on the backup archive is
exposed on the unencrypted checksum file.
This may be an issue if you want plausible deniability(see privacy
section for more information).
.PP
After that the backup folder is being encrypted using gpg.
By default, it is used with the following parameters:
.IP
.EX
.nf
\f[C]
$> gpg -a \[rs]
--symmetric \[rs]
--cipher-algo=AES256 \[rs]
--no-symkey-cache \[rs]
--pinentry-mode=loopback \[rs]
--batch --passphrase-fd \[dq]$PASSWORD\[dq] \[rs]
--batch --passphrase \[dq]$PASSWORD\[dq] \[rs]
--output \[dq]$OUTPUT\[dq] \[rs]
\[dq]$INPUT\[dq]
.EE
\f[R]
.fi
.PP
This command encrypts the backup using the AES-256 symmetric encryption
algorithm with a 256bit key.
Here is what each flag do: - \f[CR]--symmetric\f[R]: Use symmetric
Here is what each flag do: - \f[V]--symmetric\f[R]: Use symmetric
encryption;
.PD 0
.P
.PD
- \f[CR]--cipher-algo=AES256\f[R]: Use AES256 algorithm;
- \f[V]--cipher-algo=AES256\f[R]: Use AES256 algorithm;
.PD 0
.P
.PD
- \f[CR]--no-symkey-cache\f[R]: Do not save password on GPG\[cq]s cache;
- \f[V]--no-symkey-cache\f[R]: Do not save password on GPG\[cq]s cache;
.PD 0
.P
.PD
- \f[CR]--pinentry-mode=loopback --batch\f[R]: Do not prompt the user;
- \f[V]--pinentry-mode=loopback --batch\f[R]: Do not prompt the user;
.PD 0
.P
.PD
- \f[CR]--passphrase-fd 3 3<< \[dq]$PASSWORD\[dq]\f[R]: Read password
without revealing it on \f[CR]ps\f[R];
- \f[V]--passphrase-fd 3 3<< \[dq]$PASSWORD\[dq]\f[R]: Read password
without revealing it on \f[V]ps\f[R];
.PD 0
.P
.PD
- \f[CR]--output\f[R]: Specify output file;
- \f[V]--output\f[R]: Specify output file;
.PD 0
.P
.PD
- \f[CR]$INPUT\f[R]: Specify input file.
- \f[V]$INPUT\f[R]: Specify input file.
.SS Plausible Deniability
.PP
While \f[V]backup.sh\f[R] provide some pretty strong security against
bruteforce attack(assuming a strong passphrase is being used) it should
by no means considered a viable tool against a cryptanalysis
investigation.
Many of the copying, compressing and encrypting operations made by
\f[V]backup.sh\f[R] during the backup process can be used to invalidate
plausible deniability.
In particular, you should pay attention to the following details:
.IP "1." 3
The \f[V]--checksum\f[R] option generates an \f[B]UNENCRYPTED\f[R]
checksum file containing the \f[I]digests\f[R] of \f[B]EVERY\f[R] file
in your backup archive.
If your files are known to your adversary(e.g., a banned book), they may
use a rainbow table attack to determine whether you own a given file,
voiding your plausible deniability;
.PD 0
.P
.PD
.IP "2." 3
Since \f[V]backup.sh\f[R] is essentially a set of shell commands, an
eavesdropper could monitor the whole backup process to extract the name
of the files or the encryption password.
.SH EXAMPLES
.PP
Below there are some examples that demonstrate \f[B]backup.sh\f[R]\[cq]s
usage.
.IP "1." 3
Create a backup of \f[CR]/etc/ssh\f[R], \f[CR]/var/www\f[R] and
\f[CR]/var/log\f[R] inside the \f[CR]/tmp\f[R] directory using a
password stored in \f[CR]/home/op1/.backup_pw\f[R]
Create a backup of \f[V]/etc/ssh\f[R], \f[V]/var/www\f[R] and
\f[V]/var/log\f[R] inside the \f[V]/tmp\f[R] directory using a password
stored in \f[V]/home/op1/.backup_pw\f[R]
.PP
The first thing to do is to define the source paths inside a
\f[I]sources file\f[R]:
.IP
.EX
.nf
\f[C]
$> cat sources.bk
ssh=/etc/ssh
web_root=/var/www
logs=/var/log
.EE
\f[R]
.fi
.PP
After that we can load our encryption key from the specified file inside
a environment variable:
an environment variable:
.IP
.EX
.nf
\f[C]
$> ENC_KEY=$(cat /home/op1/.backup_pw)
.EE
\f[R]
.fi
.PP
Finally, we can start the backup process with:
.IP
.EX
.nf
\f[C]
$> sudo backup.sh --backup sources.bk /tmp $ENC_KEY
.EE
\f[R]
.fi
.IP "2." 3
Extract the content of a backup made on 2023-03-14 with the password
`Ax98f!'
.PP
To do this, we can simply issue the following command:
.IP
.EX
.nf
\f[C]
$> backup.sh --extract backup-af9a8e6bfe15-20230314.tar.gz.enc \[dq]Ax98f!\[dq]
.EE
\f[R]
.fi
.IP "3." 3
Extract the content of a backup made on 2018-04-25 using the password in
\f[CR]/home/john/.pw\f[R]
\f[V]/home/john/.pw\f[R]
.PP
This example is very similar to the previous one, we just need to read
the password from the text file:
.IP
.EX
.nf
\f[C]
$> backup.sh --extract backup-af9a8e6bfe15-20180425.tar.gz.enc \[dq]$(cat /home/john/.pw)\[dq]
.EE
\f[R]
.fi
.SH AUTHORS
.PP
\f[B]backup.sh\f[R] was written by Marco Cetica on late 2018.
.SH BUGS
.PP
Submit bug reports online at: <email@marcocetica.com> or open an issue
on the issue tracker of the GitHub page of this project:
https://github.com/ice-bit/backup.sh

120
man.md
View File

@ -3,7 +3,7 @@ title: backup.sh
section: 1
header: General Commands Manual
footer: Marco Cetica
date: February 27, 2024
date: April 3, 2024
---
# NAME
@ -11,9 +11,10 @@ date: February 27, 2024
# SYNOPSIS
```
Syntax: backup.sh [-b|-e|-h]
Syntax: ./backup.sh [-b|-c|-e|-h]
options:
-b|--backup SOURCES DEST PASS Backup folders from SOURCES file.
-c|--checksum Generate/check SHA256 of a backup.
-e|--extract ARCHIVE PASS Extract ARCHIVE using PASS.
-h|--help Show this helper.
```
@ -21,92 +22,96 @@ options:
# DESCRIPTION
**backup.sh** is a POSIX compliant, modular and lightweight backup utility to save and encrypt your files.
This tool is intended to be used on small scale UNIX environment such as VPS, small servers and workstations.
**backup.sh** uses _rsync_, _tar_ and _gpg_ to copy, compress and encrypt the backup.
**backup.sh** uses _rsync_, _tar_, _sha256sum_ and _gpg_ to copy, compress, verify and encrypt the backup.
# OPTIONS
**backup.sh** supports two options: _backup creation_ and _backup extraction_.
The former requires root permissions, while the latter does not. Let us see them in details:
**backup.sh** supports three options: **backup creation**, **backup extraction** and **checksum** to verify the
integrity of a backup. The first option requires
root permissions, while the second one does not. The checksum option must be used in combination of one of the previous options.
## Backup creation
To specify the directories to backup, **backup.sh** uses an associative array defined in a text file(called sources file)
with the following syntax:
To specify the directories to back up, `backup.sh` uses an associative array
defined in a text file(called _sources file_) with the following syntax:
```
<LABEL>=<PATH>
```
Where `<LABEL>` is the name of the backup and `<PATH>` is its path.
For example, if you want to back up _/etc/nginx_ and _/etc/ssh_, add the following entries to the sources file:
Where `<LABEL>` is the name of the backup and `<PATH>` is its path. For example,
if you want to back up `/etc/nginx` and `/etc/ssh`, add the following entries to the _sources file_:
```
nginx=/etc/nginx/
ssh=/etc/ssh/
```
**backup.sh** will create two folders inside the backup archive with the following syntax:
`backup.sh` will create two folders inside the backup archive with the following syntax:
```
backup-<LABEL>-<YYYYMMDD>
```
In the previous example, this would be:
```
backup-nginx-<YYYYMMDD>
backup-ssh-<YYYYMMDD>
```
You can add as many entries as you want, just be sure to use the proper syntax.
In particular, the sources file, _should not_ includes:
You can add as many entries as you want, just be sure to use the proper syntax. In particular,
the _sources file_, **should not** include:
- Spaces between the label and the equal sign;
- Empty lines;
- Comments.
- Spaces between the label and the equal sign;
- Empty lines;
- Comments.
You can find a sample _sources file_ at `sources.bk`(or at `/usr/local/etc/sources.bk`).
You can find a sample sources file at `sources.bk`(or at `/usr/local/etc/sources.bk`).
After having defined the sources file, you can invoke **backup.sh** using the following syntax:
After having defined the _sources file_, you can invoke `backup.sh` using the following syntax:
```
$> sudo ./backup.sh --backup <SOURCES_FILE> <DEST> <ENCRYPTION_PASSWORD>
```
Where `<SOURCES_FILE>` is the _sources file_, `<DEST>` is the absolute path of the output of the backup _without trailing slashes_
and `<ENCRYPTION_PASSWORD>` is the password to encrypt the compressed archive.
Where `<SOURCES_FILE>` is the _sources file_, `<DEST>` is the absolute path of the output of the backup
**without trailing slashes** and `<ENCRYPTION_PASSWORD>` is the password to encrypt the compressed archive.
In the previous example, this would be:
```
$> sudo ./backup.sh --backup sources.bk /home/john badpw1234
```
The backup utility will begin to copy the files defined in the sources file:
You can also tell `backup.sh` to generate a SHA256 file containing the hash of each file using the `-c` option.
In the previous example, this would be:
```
$> sudo ./backup.sh --checksum --backup sources.bk /home/john badpw1234
```
The backup utility will begin to copy the files defined in the _sources file_:
```
Copying nginx(1/2)
Copying ssh(2/2)
Compressing backup...
Encrypting backup...
File name: /home/marco/backup-<HOSTNAME>-<YYYYMMDD>.tar.gz.enc
File name: /home/john/backup-<HOSTNAME>-<YYYYMMDD>.tar.gz.enc
Checksum file: /home/john/backup-<HOSTNAME>-<YYYYMMDD>.sha256
File size: 7336400696(6.9G)
File hash: 0e75ca393117f389d9e8edfea7106d98
Elapsed time: 259 seconds.
```
After that, you will find the final backup archive in `/home/john/backup-<HOSTNAME>-<YYYYMMDD>.tar.gz.enc`.
You can also use **backup.sh** from a crontab rule:
After that, you will find the backup archive and the checksum file in
`/home/john/backup-<HOSTNAME>-<YYYYMMDD>.tar.gz.enc` and `/home/john/backup-<HOSTNAME>-<YYYYMMDD>.sha256`, respectively.
You can also use `backup.sh` from a crontab rule:
```
$> sudo crontab -e
30 03 * * 6 EKEY=$(cat /home/john/.ekey) sh -c '/usr/local/bin/backup.sh -b /usr/local/etc/sources.bk /home/john $EKEY' > /dev/null 2>&1
```
This will automatically run **backup.sh** every Saturday morning at 03:30 AM.
In the example above, the encryption key is stored in a local file(with fixed permissions) to avoid password leaking in crontab logs.
You can also adopt this practice while using the `--extract` option to avoid password leaking in shell history.
This will automatically run `backup.sh` every Saturday morning at 03:30 AM. In the example above, the encryption
key is stored in a local file(with fixed permissions) to avoid password leaking in crontab logs. You can also
adopt this practice while using the `--extract` option to avoid password leaking in shell history.
## Backup extraction
**backup.sh** can also extract the encrypted backup archive using the following syntax:
**backup.sh** can also be used to extract the encrypted backup as well to verify the integrity
of the backup data. To do so, use the following commands:
```
$> ./backup.sh --extract <ENCRYPTED_ARCHIVE> <ARCHIVE_PASSWORD>
@ -115,20 +120,36 @@ $> ./backup.sh --extract <ENCRYPTED_ARCHIVE> <ARCHIVE_PASSWORD>
Where `<ENCRYPTED_ARCHIVE>` is the encrypted backup and `<ARCHIVE_PASSWORD>` is the backup password.
For instance:
```
$> ./backup.sh --extract backup-<hostname>-<YYYYMMDD>.tar.gz.enc badpw1234
```
This will create a new folder called `backup.sh.tmp` in your local directory.
Be sure to rename any directory with that name to avoid collisions. From the previous example, you should have the following directories:
This will create a new folder called `backup.sh.tmp` in your local directory with the following content:
```
backup-nginx-<YYYYMMDD>
backup-ssh-<YYYYMMDD>
```
**note:**: be sure to rename any directory with that name to avoid collisions.
Instead, if you also want to verify the integrity of the backup data, use the following commands:
```
$> ./backup.sh --checksum --extract <ENCRYPTED_ARCHIVE> <ARCHIVE_PASSWORD> <CHECKSUM_ABSOLUTE_PATH>
```
For instance:
```
$> ./backup.sh --checksum --extract backup-<hostname>-<YYYYMMDD>.tar.gz.enc badpw1234 $PWD/backup-<hostname>-<YYYYMMDD>.sha256
```
**note:** be sure to provide the ABSOLUTE PATH of the checksum file.
## How does backup.sh work?
**backup.sh** uses _rsync_ to copy the files, _tar_ to compress the backup and _gpg_ to encrypt it.
**backup.sh** uses _rsync_ to copy the files, _tar_ to compress the backup, _gpg_ to encrypt it and
_sha256sum_ to verify it.
By default, rsync is being used with the following parameters:
```
@ -144,17 +165,22 @@ That is:
- q: quiet mode: reduces the amount of information rsync produces;
- delete: delete mode: forces rsync to delete any extraneous files at the destination dir.
If specified(`--checksum` option), `backup.sh` can also generate the checksum of each file of the backup.
To do so, it uses `sha256sum(1)` to compute the hash of every single file using the SHA256 hashing algorithm.
The checksum file contains nothing but the checksums of the files, no other information about the files stored
on the backup archive is exposed on the unencrypted checksum file. This may be an issue if you want plausible
deniability(see privacy section for more information).
After that the backup folder is being encrypted using gpg. By default, it is used with the following parameters:
```
$> gpg -a \
--symmetric \
--cipher-algo=AES256 \
--no-symkey-cache \
--pinentry-mode=loopback \
--batch --passphrase-fd "$PASSWORD" \
--batch --passphrase "$PASSWORD" \
--output "$OUTPUT" \
"$INPUT"
```
@ -168,6 +194,19 @@ This command encrypts the backup using the AES-256 symmetric encryption algorith
- `--output`: Specify output file;
- `$INPUT`: Specify input file.
## Plausible Deniability
While `backup.sh` provide some pretty strong security against bruteforce attack(assuming a strong passphrase is being used)
it should by no means considered a viable tool against a cryptanalysis investigation. Many of the copying, compressing and
encrypting operations made by `backup.sh` during the backup process can be used to invalidate plausible deniability.
In particular, you should pay attention to the following details:
1. The `--checksum` option generates an **UNENCRYPTED** checksum file containing the _digests_ of **EVERY**
file in your backup archive. If your files are known to your adversary(e.g., a banned book), they may use a rainbow table attack to
determine whether you own a given file, voiding your plausible deniability;
2. Since `backup.sh` is essentially a set of shell commands, an eavesdropper could monitor the whole backup process to extract
the name of the files or the encryption password.
# EXAMPLES
Below there are some examples that demonstrate **backup.sh**'s usage.
@ -183,7 +222,7 @@ web_root=/var/www
logs=/var/log
```
After that we can load our encryption key from the specified file inside a environment variable:
After that we can load our encryption key from the specified file inside an environment variable:
```
$> ENC_KEY=$(cat /home/op1/.backup_pw)
@ -196,7 +235,6 @@ $> sudo backup.sh --backup sources.bk /tmp $ENC_KEY
```
2. Extract the content of a backup made on 2023-03-14 with the password 'Ax98f!'
To do this, we can simply issue the following command:

8
tests.sh
View File

@ -5,6 +5,8 @@
# By Marco Cetica 2023 (<email@marcocetica.com>)
#
set -e
helper() {
cat <<EOF
backup.sh unit testing suite.
@ -49,11 +51,13 @@ create_files() {
}
execute_backup() {
./backup.sh -b sources.bk "$PWD" badpw
./backup.sh -c -b sources.bk "$PWD" badpw
}
extract_backup() {
./backup.sh -e "$PWD"/backup-*-*.tar.gz.enc badpw
host="$(uname -n)"
date="$(date +'%Y%m%d')"
./backup.sh -c -e "$PWD"/backup-"$host"-"$date".tar.gz.enc badpw "$PWD"/backup-"$host"-"$date".sha256
}
test_backup() {