Merge pull request #93 from kisslinux/ezupdate2

kiss: Reverse permissions model (simpler method)

FossilOrigin-Name: e1af2f19d6887d421c58756cb5f82db1c94cd85c68ce3ae7326321c005ddbc3f

1 files changed, 153 insertions, 43 deletions

diff --git a/kiss b/kiss
index c353568..28b0161 100755
--- a/kiss
+++ b/kiss
@@ -45,6 +45,106 @@ prompt() {
     read -r _
 }
 
+root_cache() {
+    # This function simply mimics a 'su' prompt to then store
+    # the root password for the lifetime of the package manager.
+    #
+    # This function is called once when needed to cache the
+    # password. The password is not accessible to any subprocesses
+    # and should never leave the package manager's process.
+    #
+    # This behavior is needed as there is no POSIX shell method
+    # of running a shell function as a different user. We can't
+    # selectively lower or raise permissions in a seamless way
+    # through "normal" means.
+    #
+    # Root is only needed when installing/removing packages whereas
+    # non-root permissions are needed in countless places throughout.
+    #
+    # This is the only *workable* solution to 1) not run the entire
+    # package manager as root and 2) avoid prompting for password
+    # before, during and after builds numerous times.
+    #
+    # NOTE: Careful consideration has been taken in regards to this
+    #       change and I would have loved an inconspicuous solution
+    #       to this problem... but it doesn't exist.
+    #
+    # This change was needed as the existing behavior was not ideal
+    # in any way and needed to be fixed.
+    printf 'Password: '
+
+    # Disable echoing to the terminal while the password is inputted
+    # by the user. The below commands read from '/dev/tty' to ensure
+    # they work when run from a subshell.
+    #
+    # The variable '$cached' is used to check if we've been here
+    # before. We cannot check whether or not '$pass' is empty as the
+    # '[' command may be external which would result in /proc leakage.
+    stty -F /dev/tty -echo
+    IFS= read -r pass < /dev/tty && cached=1
+    stty -F /dev/tty echo
+
+    printf '\n'
+
+    # Validate the password now with a simple 'true' command as we
+    # don't yet need to elevate permissions.
+    dosu /bin/true
+}
+
+dosu() {
+    [ "$cached" ] || root_cache
+
+    # Declare this as a function to avoid repeating it twice
+    # below. Great naming of functions all around.
+    #
+    # Run a command as root using the cached password. The 'su'
+    # command allows you to input a password via stdin. To hide
+    # the prompt, the command's output is sent to '/dev/tty'
+    # and the output of 'su' is sent to '/dev/null'.
+    dosudo() { su "${drop_to:-root}" -c "$* >/dev/tty" >/dev/null; }
+
+    # The code below uses the most secure method of sending
+    # data over stdin based on what is available in the system.
+    #
+    # The great debate: Use a heredoc or echo+pipe for password
+    # input over stdin? Time to explain.
+    #
+    # 1) 'printf | cmd' is the most secure IF 'printf' is built
+    #    into the shell and NOT an external command. When 'printf'
+    #    is external, the password WILL be leaked over '/proc'.
+    #
+    #    Safe shells here are anything with a builtin 'printf',
+    #    'ash', 'dash', 'bash' and most other shells.
+    #
+    # 2) Using a heredoc is as secure as the above method (when
+    #    builtin) IF and only IF the user's shell implements
+    #    heredocs WITHOUT the use of temporary files (See bash!).
+    #
+    #    When using heredocs and a temporary file the risk is a
+    #    tiny window in which the input is available inside of
+    #    a temporary file.
+    #
+    #    'ash' and 'dash' are safe here, 'bash' is not ('bash'
+    #    falls under (1) however).
+    #
+    # Which is best? (order is best to worst)
+    #
+    # 1) builtin 'printf'.
+    # 2) heredocs with no temporary file.
+    # 3) heredocs with a temporary file.
+    #
+    # This code below follows the above ordering when deciding
+    # which method to use. The '$heredocs' variable is declared
+    # in 'main()' after a check to see if 'printf' is builtin.
+    if [ "$heredocs" ]; then
+        dosudo "$@" <<-EOF
+			$pass
+		EOF
+    else
+        printf '%s\n' "$pass" | dosudo "$@"
+    fi
+}
+
 pkg_lint() {
     # Check that each mandatory file in the package entry exists.
     log "$1" "Checking repository files"
@@ -448,7 +548,15 @@ pkg_build() {
     log "Building: $*"
 
     # Only ask for confirmation if more than one package needs to be built.
-    [ $# -gt 1 ] || [ "$pkg_update" ] && prompt
+    [ $# -gt 1 ] || [ "$pkg_update" ] && {
+        prompt
+
+        # Prompt for password prior to the build if more than one package
+        # will be built and installed. No use in forcing the user to wait
+        # for the first password prompt (before caching) if it may take a
+        # long long while.
+        [ "$cached" ] || root_cache
+    }
 
     log "Checking to see if any dependencies have already been built"
     log "Installing any pre-built dependencies"
@@ -467,7 +575,9 @@ pkg_build() {
             # to 'su' to elevate permissions.
             [ -f "$bin_dir/$pkg#$version-$release.tar.gz" ] && {
                 log "$pkg" "Found pre-built binary, installing"
-                (KISS_FORCE=1 args i "$bin_dir/$pkg#$version-$release.tar.gz")
+
+                (KISS_FORCE=1 \
+                    pkg_install "$bin_dir/$pkg#$version-$release.tar.gz")
 
                 # Remove the now installed package from the build
                 # list. No better way than using 'sed' in POSIX 'sh'.
@@ -554,7 +664,9 @@ pkg_build() {
         contains "$explicit" "$pkg" && [ -z "$pkg_update" ] && continue
 
         log "$pkg" "Needed as a dependency or has an update, installing"
-        (KISS_FORCE=1 args i "$pkg")
+
+        (KISS_FORCE=1 \
+            pkg_install "$bin_dir/$pkg#$version-$release.tar.gz")
     done
 
     # End here as this was a system update and all packages have been installed.
@@ -692,9 +804,9 @@ pkg_remove() {
         [ "${file##/etc/*}" ] || continue
 
         if [ -d "$KISS_ROOT/$file" ]; then
-            rmdir "$KISS_ROOT/$file" 2>/dev/null || continue
+            dosu rmdir "'$KISS_ROOT/$file'" 2>/dev/null || continue
         else
-            rm -f "$KISS_ROOT/$file"
+            dosu rm -f "'$KISS_ROOT/$file'"
         fi
     done < "$sys_db/$1/manifest"
 
@@ -770,9 +882,9 @@ pkg_install() {
 
     # This is repeated multiple times. Better to make it a function.
     pkg_rsync() {
-        rsync --chown=root:root --chmod=Du-s,Dg-s,Do-s \
+        dosu rsync --chown=root:root --chmod=Du-s,Dg-s,Do-s \
               -WhHKa --no-compress "$1" --exclude /etc \
-              "$tar_dir/$pkg_name/" "$KISS_ROOT/"
+              "'$tar_dir/$pkg_name/'" "'$KISS_ROOT/'"
     }
 
     # Install the package by using 'rsync' and overwrite any existing files
@@ -781,8 +893,8 @@ pkg_install() {
 
     # If '/etc/' exists in the package, install it but don't overwrite.
     [ -d "$tar_dir/$pkg_name/etc" ] &&
-        rsync --chown=root:root -WhHKa --no-compress --ignore-existing \
-            "$tar_dir/$pkg_name/etc" "$KISS_ROOT/"
+        dosu rsync --chown=root:root -WhHKa --no-compress --ignore-existing \
+            "'$tar_dir/$pkg_name/etc'" "'$KISS_ROOT/'"
 
     # Remove any leftover files if this is an upgrade.
     [ "$old_manifest" ] && {
@@ -799,18 +911,18 @@ pkg_install() {
 
             # Remove files.
             if [ -f "$file" ] && [ ! -L "$file" ]; then
-                rm -f "$file"
+                dosu rm -f "'$file'"
 
             # Remove file symlinks.
             elif [ -L "$file" ] && [ ! -d "$file" ]; then
-                unlink "$file" ||:
+                dosu unlink "'$file'" ||:
 
             # Skip directory symlinks.
             elif [ -L "$file" ] && [ -d "$file" ]; then :
 
             # Remove directories if empty.
             elif [ -d "$file" ]; then
-                rmdir "$file" 2>/dev/null ||:
+                dosu rmdir "'$file'" 2>/dev/null ||:
             fi
         done ||:
     }
@@ -826,7 +938,7 @@ pkg_install() {
 
     if [ -x "$sys_db/$pkg_name/post-install" ]; then
         log "$pkg_name" "Running post-install script"
-        "$sys_db/$pkg_name/post-install" ||:
+        dosu "'$sys_db/$pkg_name/post-install'" ||:
     fi
 
     log "$pkg_name" "Installed successfully"
@@ -879,18 +991,20 @@ pkg_updates() {
             if [ -w "$PWD" ]; then
                 git fetch
                 git merge
+
             else
                 log "$PWD" "Need root to update"
 
-                if command -v sudo >/dev/null; then
-                    sudo git fetch
-                    sudo git merge
-                elif command -v doas >/dev/null; then
-                    doas git fetch
-                    doas git merge
-                else
-                    su -c 'git fetch && git merge'
-                fi
+                # Find out the owner of the repository and spawn
+                # git as this user below.
+                #
+                # This prevents 'git' from changing the original
+                # ownership of files and directories in the rare
+                # case that the repository is owned by a 3rd user.
+                (drop_to=$(stat -c %U "$PWD")
+
+                dosu git fetch
+                dosu git merge)
             fi
         }
     done
@@ -922,8 +1036,8 @@ pkg_updates() {
 
         prompt
 
-        pkg_build kiss
-        args i kiss
+        pkg_build   kiss
+        pkg_install kiss
 
         log "Updated the package manager"
         log "Re-run 'kiss update' to update your system"
@@ -956,6 +1070,8 @@ pkg_updates() {
 pkg_clean() {
     # Clean up on exit or error. This removes everything related
     # to the build.
+    stty -F /dev/tty echo 2>/dev/null
+
     [ "$KISS_DEBUG" != 1 ] || return
 
     # Block 'Ctrl+C' while cache is being cleaned.
@@ -991,27 +1107,9 @@ args() {
 
     # Parse some arguments earlier to remove the need to duplicate code.
     case $action in
-        c|checksum|s|search)
+        c|checksum|s|search|i|install|r|remove)
             [ "$1" ] || die "'kiss $action' requires an argument"
         ;;
-
-        i|install|r|remove)
-            [ "$1" ] || die "'kiss $action' requires an argument"
-
-            # Rerun the script with 'su' if the user isn't root.
-            # Cheeky but 'su' can't be used on shell functions themselves.
-            [ "$(id -u)" = 0 ] || {
-                if command -v sudo >/dev/null; then
-                    sudo -E KISS_FORCE="$KISS_FORCE" kiss "$action" "$@"
-                elif command -v doas >/dev/null; then
-                    KISS_FORCE="$KISS_FORCE" doas kiss "$action" "$@"
-                else
-                    su -pc "KISS_FORCE=$KISS_FORCE kiss $action $*"
-                fi
-
-                return
-            }
-        ;;
     esac
 
     # Actions can be abbreviated to their first letter. This saves
@@ -1113,6 +1211,18 @@ args() {
 }
 
 main() {
+    # Ensure that debug mode is never enabled to prevent internal
+    # package manager information from leaking to stdout.
+    set +x
+
+    # Prevent the package manager from running as root. The package
+    # manager will elevate permissions where needed.
+    [ "$(id -u)" != 0 ] || die "kiss must be run as a normal user"
+
+    # Use the most secure method of sending data over stdin based on
+    # whether or not the 'printf' command is built into the shell.
+    [ "$(command -v printf)" = printf ] || heredocs=1
+
     # Set the location to the repository and package database.
     pkg_db=var/db/kiss/installed