Merge pull request #127 from kerl/check_paths

Be more careful about paths before install and delete operations

2 files changed, 182 insertions, 31 deletions

diff --git a/README.md b/README.md
index 02a809e..8b4c699 100644
--- a/README.md
+++ b/README.md
@@ -285,9 +285,21 @@ Installs a named build to the specified filesystem location.
 
     $ kerl install r14b02 /srv/otp/r14b02
 
-If path is omitted the current working directory will be used. However, if `KERL_DEFAULT_INSTALL_DIR` is defined in ~/.kerlrc, `KERL_DEFAULT_INSTALL_DIR/<build-name>` will be used instead.
+If path is omitted the current working directory will be used. However, if
+`KERL_DEFAULT_INSTALL_DIR` is defined in ~/.kerlrc,
+`KERL_DEFAULT_INSTALL_DIR/<build-name>` will be used instead.
 
-*Note*: kerl assumes the specified directory is for its sole use. If you later delete it with the kerl delete command, the whole directory will be deleted, along with anything you may have added to it!
+#### Install location restrictions
+
+**WARNING**: kerl assumes the given installation directory is for its sole use.
+If you later delete it with the `kerl delete` command, the whole directory will
+be deleted, along with anything you may have added to it!
+
+So please only install kerl in an empty (or non-existant) directory.  
+
+If you attempt to install kerl in `$HOME` or `.erlang` or `$KERL_BASE_DIR`,
+then kerl will give you an error and refuse to proceed. If you try to install
+kerl in a directory that exists and is not empty, kerl will give you an error.
 
 #### Tuning
 
diff --git a/kerl b/kerl
index 1af46b4..0329f7d 100755
--- a/kerl
+++ b/kerl
@@ -72,7 +72,7 @@ KERL_INSTALL_MANPAGES=
 KERL_BUILD_PLT=
 KERL_BUILD_DOCS=
 
-# ensure the base dir exsists
+# ensure the base dir exists
 mkdir -p "$KERL_BASE_DIR" || exit 1
 
 # source the config file if available
@@ -276,8 +276,16 @@ get_newest_valid_release()
 
 is_valid_installation()
 {
-    if [ -f "$1"/activate ]; then
-        return 0
+    if [ -f "$KERL_BASE_DIR"/otp_installations ]; then
+        while read -r l; do
+            name=$(echo "$l" | cut -d " " -f 1)
+            path=$(echo "$l" | cut -d " " -f 2)
+            if [ "$name" = "$1" -o "$path" = "$1" ]; then
+                if [ -f "$1"/activate ]; then
+                    return 0
+                fi
+            fi
+        done < "$KERL_BASE_DIR"/otp_installations
     fi
     return 1
 }
@@ -309,7 +317,7 @@ do_git_build()
     assert_build_name_unused "$3"
 
     GIT=$(echo -n "$1" | $MD5SUM | cut -d ' ' -f $MD5SUM_FIELD)
-    mkdir -p "$KERL_GIT_DIR"
+    mkdir -p "$KERL_GIT_DIR" || exit 1
     cd "$KERL_GIT_DIR" || exit 1
     echo "Checking Erlang/OTP git repository from $1..."
     if [ ! -d "$GIT" ]; then
@@ -327,7 +335,7 @@ do_git_build()
     fi
 
     rm -Rf "${KERL_BUILD_DIR:?}/$3"
-    mkdir -p "$KERL_BUILD_DIR/$3"
+    mkdir -p "$KERL_BUILD_DIR/$3" || exit 1
     cd "$KERL_BUILD_DIR/$3" || exit 1
     git clone -l "$KERL_GIT_DIR/$GIT" otp_src_git > /dev/null 2>&1
     if [ $? -ne 0 ]; then
@@ -377,12 +385,12 @@ do_normal_build()
     assert_build_name_unused "$2"
     FILENAME=""
     download $1
-    mkdir -p "$KERL_BUILD_DIR/$2"
+    mkdir -p "$KERL_BUILD_DIR/$2" || exit 1
     if [ ! -d "$KERL_BUILD_DIR/$2/$FILENAME" ]; then
         echo "Extracting source code"
         UNTARDIRNAME="$KERL_BUILD_DIR/$2/$FILENAME-kerluntar-$$"
         rm -rf "$UNTARDIRNAME"
-        mkdir -p "$UNTARDIRNAME"
+        mkdir -p "$UNTARDIRNAME" || exit 1
         # github tarballs have a directory in the form of "otp-TAGNAME"
         # Ericsson tarballs have the classic otp_src_RELEASE pattern
         # Standardize on Ericsson format because that's what the rest of the script expects
@@ -518,11 +526,10 @@ do_install()
         echo "No build named $1"
         exit 1
     fi
-    mkdir -p "$2"
-    if [ ! -d "$2" ]; then
-        echo "Destination is not a directory"
+    if ! is_valid_install_path "$2"; then
         exit 1
     fi
+    mkdir -p "$2" || exit 1
     absdir=$(cd "$2" && pwd)
     echo "Installing Erlang/OTP $rel ($1) in $absdir..."
     ERL_TOP="$KERL_BUILD_DIR/$1/otp_src_$rel"
@@ -597,7 +604,7 @@ ACTIVATE
         DOC_DIR="$KERL_BUILD_DIR/$1/release_$rel/lib/erlang"
         if [ -d "$DOC_DIR" ]; then
             echo "Installing docs..."
-            mkdir -p "$absdir/lib/erlang"
+            mkdir -p "$absdir/lib/erlang" || exit 1
             cp $CP_OPT "$DOC_DIR/" "$absdir/lib/erlang"
             ln -s "$absdir/lib/erlang/man" "$absdir/man"
             ln -s "$absdir/lib/erlang/doc" "$absdir/html"
@@ -617,7 +624,7 @@ ACTIVATE
             fi
         fi
     fi
-    
+
     if [ -n "$KERL_BUILD_PLT" ]; then
         echo "Building Dialyzer PLT..."
         build_plt "$absdir"
@@ -649,7 +656,7 @@ download_htmldocs()
 build_plt()
 {
     dialyzerd=$1/dialyzer
-    mkdir -p $dialyzerd
+    mkdir -p $dialyzerd || exit 1
     plt=$dialyzerd/plt
     build_log=$dialyzerd/build.log
     dialyzer=$1/bin/dialyzer
@@ -693,6 +700,9 @@ do_deploy()
     host="$1"
 
     assert_valid_installation "$2"
+    if ! is_valid_install_path "$2"; then
+        exit 1
+    fi
     rel="$(get_name_from_install_path "$2")"
     path="$2"
     remotepath="$path"
@@ -733,6 +743,145 @@ do_deploy()
     echo "kerl_deactivate"
 }
 
+
+# Quoted from https://github.com/mkropat/sh-realpath
+# LICENSE: MIT
+
+realpath() {
+    canonicalize_path "$(resolve_symlinks "$1")"
+}
+
+resolve_symlinks() {
+    _resolve_symlinks "$1"
+}
+
+_resolve_symlinks() {
+    _assert_no_path_cycles "$@" || return
+
+    local dir_context path
+    path=$(readlink -- "$1")
+    if [ $? -eq 0 ]; then
+        dir_context=$(dirname -- "$1")
+        _resolve_symlinks "$(_prepend_dir_context_if_necessary "$dir_context" "$path")" "$@"
+    else
+        printf '%s\n' "$1"
+    fi
+}
+
+_prepend_dir_context_if_necessary() {
+    if [ "$1" = . ]; then
+        printf '%s\n' "$2"
+    else
+        _prepend_path_if_relative "$1" "$2"
+    fi
+}
+
+_prepend_path_if_relative() {
+    case "$2" in
+        /* ) printf '%s\n' "$2" ;;
+         * ) printf '%s\n' "$1/$2" ;;
+    esac
+}
+
+_assert_no_path_cycles() {
+    local target path
+
+    target=$1
+    shift
+
+    for path in "$@"; do
+        if [ "$path" = "$target" ]; then
+            return 1
+        fi
+    done
+}
+
+canonicalize_path() {
+    if [ -d "$1" ]; then
+        _canonicalize_dir_path "$1"
+    else
+        _canonicalize_file_path "$1"
+    fi
+}
+
+_canonicalize_dir_path() {
+    (cd "$1" 2>/dev/null && pwd -P)
+}
+
+_canonicalize_file_path() {
+    local dir file
+    dir=$(dirname -- "$1")
+    file=$(basename -- "$1")
+    (cd "$dir" 2>/dev/null && printf '%s/%s\n' "$(pwd -P)" "$file")
+}
+
+# END QUOTE
+
+is_valid_install_path()
+{
+
+    # don't allow installs into .erlang because
+    # it's a special configuration file location
+    # for OTP
+    if [ $(basename -- "$1") = ".erlang" ]; then
+        echo "ERROR: You cannot install a build into '.erlang'. (It's a special configuration file location for OTP.)"
+        return 1
+    fi
+
+    candidate=$(realpath "$1")
+    canonical_home=$(realpath "$HOME")
+    canonical_base_dir=$(realpath "$KERL_BASE_DIR")
+
+    # don't allow installs into home directory
+    if [ "$candidate" = "$canonical_home" ]; then
+        echo "ERROR: You cannot install a build into $HOME. It's a really bad idea."
+        return 1
+    fi
+
+    # don't install into our base directory either.
+    if [ "$candidate" = "$canonical_base_dir" ]; then
+        echo "ERROR: You cannot install a build into $KERL_BASE_DIR."
+        return 1
+    fi
+
+    # if the install directory exists,
+    # do not allow installs into a directory
+    # that is not empty
+    if [ -e "$1" ]; then
+	if [ -d "$1" ]; then
+	    count=$(ls -la "$1" | wc -l)
+	    if [ $count -ne 3 ]; then
+		echo "ERROR: $1 does not appear to be an empty directory."
+		return 1
+	    fi
+	else
+	    echo "ERROR: $1 is not a directory."
+	    return 1
+	fi
+    fi
+
+    return 0
+}
+
+maybe_remove()
+{
+    candidate=$(realpath "$1")
+    canonical_home=$(realpath "$HOME")
+
+    if [ "$candidate" = "$canonical_home" ]; then
+        echo "WARNING: You cannot remove an install from $HOME; it's your home directory."
+        return 0
+    fi
+
+    ACTIVE_PATH="$(get_active_path)"
+    if [ "$candidate" = "$ACTIVE_PATH" ]; then
+	echo "ERROR: You cannot delete the active installation. Deactivate it first."
+	exit 1
+    fi
+
+    rm -Rf "$1"
+}
+
 list_print()
 {
     if [ -f "$KERL_BASE_DIR/otp_$1" ]; then
@@ -828,7 +977,7 @@ do_active()
 
 download()
 {
-    mkdir -p "$KERL_DOWNLOAD_DIR"
+    mkdir -p "$KERL_DOWNLOAD_DIR" || exit 1
     if [ "$KERL_BUILD_BACKEND" = "git" ]; then
         FILENAME="OTP-$1"
         github_download "$FILENAME.tar.gz"
@@ -885,20 +1034,10 @@ case "$1" in
             exit 1
         fi
         if [ $# -eq 3 ]; then
-            if [ "$3" = "$HOME" ]; then
-                echo "Refusing to install in $HOME, this is a bad idea."
-                exit 1
-            else
-                do_install "$2" "$3"
-            fi
+            do_install "$2" "$3"
         else
             if [ -z "$KERL_DEFAULT_INSTALL_DIR" ]; then
-                if [ "$PWD" = "$HOME" ]; then
-                    echo "Refusing to install in $HOME, this is a bad idea."
-                    exit 1
-                else
-                    do_install "$2" .
-                fi
+                do_install "$2" "$PWD"
             else
                 do_install "$2" "$KERL_DEFAULT_INSTALL_DIR/$2"
             fi
@@ -970,7 +1109,7 @@ case "$1" in
             build)
                 rel="$(get_release_from_name "$3")"
                 if [ -d "${KERL_BUILD_DIR:?}/$3" ]; then
-                    rm -Rf "${KERL_BUILD_DIR:?}/$3"
+                    maybe_remove "${KERL_BUILD_DIR:?}/$3"
                 else
                     if [ -z "$rel" ]; then
                       echo "No build named $3"
@@ -982,7 +1121,7 @@ case "$1" in
                 ;;
             installation)
                 assert_valid_installation "$3"
-                rm -Rf "$3"
+                maybe_remove "$3"
                 escaped="$(echo "$3" | sed $SED_OPT -e 's#/$##' -e 's#\/#\\\/#g')"
                 list_remove "$2"s "$escaped"
                 echo "The installation in $3 has been deleted"
@@ -1049,7 +1188,7 @@ case "$1" in
             *)
                 echo "Cleaning up compilation products for $3"
                 rm -rf "${KERL_BUILD_DIR:?}/$3"
-                echo "Cleaned up all compilation products under $KERL_BUILD_DIR"
+                echo "Cleaned up compilation products for $3 under $KERL_BUILD_DIR"
                 ;;
         esac
         ;;