/usr/include/dovecot/sieve/ is in dovecot-dev 1:2.2.9-1ubuntu2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/dovecot/sieve/edit-mail.h
/usr/include/dovecot/sieve/pigeonhole-config.h
/usr/include/dovecot/sieve/rfc2822.h
/usr/include/dovecot/sieve/sieve-actions.h
/usr/include/dovecot/sieve/sieve-address-parts.h
/usr/include/dovecot/sieve/sieve-address.h
/usr/include/dovecot/sieve/sieve-ast.h
/usr/include/dovecot/sieve/sieve-binary-dumper.h
/usr/include/dovecot/sieve/sieve-binary-private.h
/usr/include/dovecot/sieve/sieve-binary.h
/usr/include/dovecot/sieve/sieve-code-dumper.h
/usr/include/dovecot/sieve/sieve-code.h
/usr/include/dovecot/sieve/sieve-commands.h
/usr/include/dovecot/sieve/sieve-common.h
/usr/include/dovecot/sieve/sieve-comparators.h
/usr/include/dovecot/sieve/sieve-config.h
/usr/include/dovecot/sieve/sieve-dump.h
/usr/include/dovecot/sieve/sieve-error-private.h
/usr/include/dovecot/sieve/sieve-error.h
/usr/include/dovecot/sieve/sieve-ext-copy.h
/usr/include/dovecot/sieve/sieve-ext-enotify.h
/usr/include/dovecot/sieve/sieve-ext-environment.h
/usr/include/dovecot/sieve/sieve-ext-variables.h
/usr/include/dovecot/sieve/sieve-extensions.h
/usr/include/dovecot/sieve/sieve-generator.h
/usr/include/dovecot/sieve/sieve-interpreter.h
/usr/include/dovecot/sieve/sieve-lexer.h
/usr/include/dovecot/sieve/sieve-limits.h
/usr/include/dovecot/sieve/sieve-match-types.h
/usr/include/dovecot/sieve/sieve-match.h
/usr/include/dovecot/sieve/sieve-message.h
/usr/include/dovecot/sieve/sieve-objects.h
/usr/include/dovecot/sieve/sieve-parser.h
/usr/include/dovecot/sieve/sieve-plugins.h
/usr/include/dovecot/sieve/sieve-result.h
/usr/include/dovecot/sieve/sieve-runtime-trace.h
/usr/include/dovecot/sieve/sieve-runtime.h
/usr/include/dovecot/sieve/sieve-script-file.h
/usr/include/dovecot/sieve/sieve-script-private.h
/usr/include/dovecot/sieve/sieve-script.h
/usr/include/dovecot/sieve/sieve-settings.h
/usr/include/dovecot/sieve/sieve-smtp.h
/usr/include/dovecot/sieve/sieve-stringlist.h
/usr/include/dovecot/sieve/sieve-types.h
/usr/include/dovecot/sieve/sieve-validator.h
/usr/include/dovecot/sieve/sieve.h