Public bug reported:
As it stands today, all exec transitions triggered by a change_profile
rule cause the AT_SECURE flag in the auxiliary vector to be set due to
the kernel function apparmor_bprm_secureexec() returning 1 while setting
up the execution environment. This causes libc to always scrub the
environment variables during such an exec transition.
There should be a way to indicate, in the policy language, that
AT_SECURE should not be triggered. This would be equivalent to the file
rule type having the Px permission to trigger AT_SECURE and the px
permission to not trigger it. The file rule type even has an 'unsafe'
modifier keyword that could be reused as the change_profile modifier
keyword.
Steps to show that AT_SECURE is being set:
# Build a test program to dump the AT_SECURE flag
$ cat <<EOF > print_at_secure.c
> #include <stdio.h>
> #include <sys/auxv.h>
>
> int main(void)
> {
> printf("AT_SECURE = %lu\n", getauxval(AT_SECURE));
> return 0;
> }
> EOF
$ gcc -o print_at_secure print_at_secure.c
# Load the test profile that allows all file accesses and any change_profile
operations
$ echo "profile test { file, change_profile, }" | sudo apparmor_parser -qr
# Run bash under the test profile
$ aa-exec -p test -- bash
# Show the AT_SECURE is not set on exec
$ ./print_at_secure
AT_SECURE = 0
# Set up an exec transition (change_profile from the test profile back to the
test profile)
$ echo "exec test" > /proc/self/attr/exec
# See that AT_SECURE is now set on exec
$ ./print_at_secure
AT_SECURE = 1
** Affects: apparmor (Ubuntu)
Importance: High
Assignee: Tyler Hicks (tyhicks)
Status: In Progress
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https://bugs.launchpad.net/bugs/1584069
Title:
change_profile rules need a modifier to allow non-secureexec
transitions
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