Add a best-effort sudo safety check

As motivation for this; we have had two breakouts of dib in recent
memory.  One was a failure to unmount through symlinks in the core
code (I335316019ef948758392b03e91f9869102a472b9) and the other was
removing host keys on the build-system
(Ib01d71ff9415a0ae04d963f6e380aab9ac2260ce).

For the most part, dib runs unprivileged.  Bits of the core code are
hopefully well tested (modulo bugs like the first one!).  We give free
reign inside the chroot (although there is still some potential there
for adverse external affects via bind mounts).  Where we could be a
bit safer (and could have prevented at least the second of these
breakouts) is with some better checking that the "sudo" calls
*outside* the chroot at least looked sane.

This adds a basic check that we're using chroot or image paths when
calling sudo in those parts of elements that run *outside* the chroot.
Various files are updated to accomodate this check; mostly by just
ignoring it for existing code (I have not audited these calls).

Nobody is pretending this type of checking makes dib magically safe,
or removes the issues with it needing to do things as root during the
build.  But this can help find egregious errors like the key removal.

Change-Id: I161a5aea1d29dcdc7236f70d372c53246ec73749

bin/dib-lint

@@ -54,7 +54,7 @@ excluded() {
 }
 
 error() {
-    echo "ERROR: $1"
+    echo -e "ERROR: $1"
     rc=1
 }
 
@@ -146,6 +146,32 @@ for i in $(find elements -type f   \
             fi
         fi
     fi
+
+
+    # check that sudo calls in phases run outside the chroot look
+    # "safe"; meaning that they seem to operate within the chroot
+    # somehow.  This is not fool-proof, but catches egregious errors,
+    # and makes you think about it if you're doing something outside
+    # the box.
+    if ! excluded safe_sudo; then
+        if [[ $(dirname $i) =~ (root.d|extra-data.d|block-device.d|finalise.d|cleanup.d) ]]; then
+            while read LINE
+            do
+                if [[ $LINE =~ "sudo " ]]; then
+                    # messy regex ahead!  Don't match:
+                    #  - explicitly ignored
+                    #  - basic comments
+                    #  - install-packages ... sudo ...
+                    #  - any of the paths passed into the out-of-chroot elements
+                    if [[ $LINE =~ (dib-lint: safe_sudo|^#|install-packages|TARGET_ROOT|IMAGE_BLOCK_DEVICE|TMP_MOUNT_PATH|TMP_IMAGE_PATH) ]]; then
+                        continue
+                    fi
+                    error "$i : potentially unsafe sudo\n -- $LINE"
+                fi
+            done < $i
+        fi
+    fi
+
 done
 
 for i in $(find elements -type f -and -name '*.rst' -or -type f -executable); do

doc/source/developer/developing_elements.rst

@@ -425,3 +425,30 @@ example if one were building tripleo-images, the variable would be set like:
 
       export ELEMENTS_PATH=tripleo-image-elements/elements
       disk-image-create rhel7 cinder-api
+
+Linting
+-------
+
+You should always run ``bin/dib-lint`` over your elements.  It will
+warn you of common issues.
+
+sudo
+""""
+
+Using ``sudo`` outside the chroot environment can cause breakout
+issues where you accidentally modify parts of the host
+system. ``dib-lint`` will warn if it sees ``sudo`` calls that do not
+use the path arguments given to elements running outside the chroot.
+
+To disable the error for a call you know is safe, add
+
+::
+
+   # dib-lint: safe_sudo
+
+to the end of the ``sudo`` command line.  To disable the check for an
+entire file, add
+
+::
+
+   # dib-lint: disable=safe_sudo

elements/apt-sources/extra-data.d/99-override-default-apt-sources

@@ -21,5 +21,5 @@ DIB_APT_SOURCES=`readlink -f $DIB_APT_SOURCES`
 
 # copy the sources.list to cloudimg
 pushd $TMP_MOUNT_PATH/etc/apt/
-sudo cp -f $DIB_APT_SOURCES sources.list
+sudo cp -f $DIB_APT_SOURCES sources.list # dib-lint: safe_sudo
 popd

elements/baremetal/cleanup.d/99-extract-kernel-and-ramdisk

@@ -14,6 +14,8 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+# dib-lint: disable=safe_sudo
+
 if [ ${DIB_DEBUG_TRACE:-0} -gt 0 ]; then
     set -x
 fi

elements/bootloader/cleanup.d/51-bootloader

@@ -15,6 +15,8 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+# dib-lint: disable=safe_sudo
+
 if [ ${DIB_DEBUG_TRACE:-1} -gt 0 ]; then
     set -x
 fi

elements/dpkg/extra-data.d/01-copy-apt-keys

@@ -31,9 +31,9 @@ if [ -e ${DIR} ]; then
     echo "${DIR} already exists!"
     exit 1
 fi
-sudo mkdir -p ${DIR}
+sudo mkdir -p ${DIR} # dib-lint: safe_sudo
 
 # Copy to DIR
 for KEY in $(find ${DIB_ADD_APT_KEYS} -type f); do
-    sudo cp -L ${KEY} ${DIR}
+    sudo cp -L ${KEY} ${DIR} # dib-lint: safe_sudo
 done

elements/ironic-agent/cleanup.d/99-ramdisk-create

@@ -1,5 +1,7 @@
 #!/bin/bash
 
+# dib-lint: disable=safe_sudo
+
 if [ "${DIB_DEBUG_TRACE:-0}" -gt 0 ]; then
     set -x
 fi

elements/iso/cleanup.d/100-build-iso

@@ -14,6 +14,8 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+# dib-lint: disable=safe_sudo
+
 if [ ${DIB_DEBUG_TRACE:-1} -gt 0 ]; then
     set -x
 fi

elements/partitioning-sfdisk/block-device.d/10-partitioning-sfdisk

@@ -1,5 +1,7 @@
 #!/bin/bash
 
+# dib-lint: disable=safe_sudo
+
 if [ ${DIB_DEBUG_TRACE:-0} -gt 0 ]; then
     set -x
 fi

elements/pypi/extra-data.d/00-mount-pypi-mirror

@@ -10,6 +10,6 @@ MIRROR_SOURCE=$DIB_IMAGE_CACHE/pypi/mirror/
 if [ -d "$MIRROR_SOURCE" ]; then
     MIRROR_TARGET=$TMP_MOUNT_PATH/tmp/pypi
 
-    sudo mkdir -p $MIRROR_SOURCE $MIRROR_TARGET
+    sudo mkdir -p $MIRROR_SOURCE $MIRROR_TARGET # dib-lint: safe_sudo
-    sudo mount --bind $MIRROR_SOURCE $MIRROR_TARGET
+    sudo mount --bind $MIRROR_SOURCE $MIRROR_TARGET # dib-lint: safe_sudo
 fi

elements/rhel/root.d/10-rhel-cloud-image

@@ -1,5 +1,7 @@
 #!/bin/bash
 
+# dib-lint: disable=safe_sudo
+
 if [ ${DIB_DEBUG_TRACE:-0} -gt 0 ]; then
     set -x
 fi

elements/source-repositories/extra-data.d/98-source-repositories

@@ -1,5 +1,6 @@
 #!/bin/bash
 
+# dib-lint: disable=safe_sudo
 if [ ${DIB_DEBUG_TRACE:-0} -gt 1 ]; then
     set -x
 fi

elements/ubuntu-core/root.d/10-cache-ubuntu-image

@@ -1,6 +1,8 @@
 #!/bin/bash
 # These are useful, or at worst not harmful, for all images we build.
 
+# dib-lint: disable=safe_sudo
+
 if [ ${DIB_DEBUG_TRACE:-0} -gt 0 ]; then
     set -x
 fi

elements/vm/block-device.d/10-partition

@@ -1,5 +1,7 @@
 #!/bin/bash
 
+# dib-lint: disable=safe_sudo
+
 if [ ${DIB_DEBUG_TRACE:-0} -gt 0 ]; then
     set -x
 fi

elements/yum-minimal/root.d/08-yum-chroot

@@ -14,6 +14,9 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 #
+
+# dib-lint: disable=safe_sudo
+
 if [ "${DIB_DEBUG_TRACE:-0}" -gt 0 ]; then
     set -x
 fi