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diff --git a/doc/spec/rootless-builds.txt b/doc/spec/rootless-builds.txt new file mode 100644 index 0000000..5a5af83 --- /dev/null +++ b/doc/spec/rootless-builds.txt @@ -0,0 +1,177 @@ +Supporting rootless builds +========================== + +Status: recommendation, stable +Version: 1.0 + +Background +---------- + +Traditionally, Debian packages have required (fake)root privileges for some +of the "debian/rules" targets. This has required also a split between build +and binary targets; making the builds slower, due to the increased amount +of invocations of "debian/rules" and the overhead of using fakeroot(1) or +equivalent fake environments, or less secure due to the increased dangers +of running under real root via sudo or equivalent. + +On this document when talking about "(fake)root" privileges, it will refer +to any mechanism, supported by the dpkg-buildpackage "-r/--root-command" +option, that can provide either a real or faked root user environment. + +Specification +------------- + +We add a new field to the "Source" stanza of debian/control: + + Rules-Requires-Root: no | binary-targets | <implementations-keywords> + +The case sensitive values are defined as: + + * If "no", then "debian/rules binary" will not require root at all (not even + fakeroot). This is the default in dpkg-build-api level >= 1. + - If the "no" keyword is used, it MUST be the only keyword in that field + and MUST appear exactly once. + + * If "binary-targets", then "debian/rules binary" (etc.) must always be run + under (fake)root. This is the status quo, default in dpkg-build-api level 0. + + * <implementations-keywords> will be a space separated list of keywords which + define when root is required. + + - Keywords consists of <namespace>/<cases>. The "namespace" part cannot + contain "/" or whitespace. The "cases" part cannot contain whitespace. + Furthermore, both parts MUST consist entirely of printable ASCII + characters. + + - Each tool/package will define a namespace named after itself and provide + a number of cases where (fake)root is required. + (See also "Implementation provided keywords".) + + - When "Rules-Requires-Root" is set to <implementations-keywords>, the + builder (i.e. whatever is executing debian/rules) will expose an + interface that is used to run a command under (fake)root via the + "Gain Root API". If the builder cannot provide such a command, it + MUST behave like "Rules-Requires-Root" was set to "binary-targets", + i.e. run "debian/rules binary" under (fake)root. + +When the builder supports this specification, it MUST notify this fact to +the rules file via the "DEB_RULES_REQUIRES_ROOT" environment variable, with +the value it has obtained from the Rules-Requires-Root field or some builder +specific override mechanism, which will denote the level of support the +builder has chosen to commit to take effect during the build. When set, +it MUST be a valid value for the Rules-Requires-Root field. If unset, +the build system SHOULD assume that the builder does not recognize the +Rules-Requires-Root field at all. + +It is always permissible for a builder to ignore this field and fall back to +running the binary targets under (fake)root. This is to ensure backwards +compatibility when builds are performed by legacy builders or older versions +of the tooling. + +Tools called from the rules file MUST cope gracefully with being called under +(fake)root even when Rules-Requires-Root is set to a value that implies they +should not be (e.g. "no"). However, they MUST NOT attempt to run processes +under (fake)root when run as a regular user when Rules-Requires-Root does +not list any keywords they respond to. + +Tools MUST gracefully ignore valid unknown keywords outside their namespace. +They MAY warn about unknown keywords inside their namespace. + +The value of this field MUST NOT change the content of the package in any +way. Notably, packages that are bit-for-bit reproducible MUST still provide +bit-for-bit identical results even when the field is ignored. + +Implementation provided keywords +-------------------------------- + +Keywords provided by various implementations: + + * dpkg/target-subcommand: When the package needs to run a given command + under (fake)root within the "debian/rules" files directly, this MUST be + declared via this keyword. + + * dpkg/target/<target-name>: When a specific "debian/rules" unofficial + target (none of the root-requiring "binary-indep", "binary-arch", "binary", + "clean", nor the non-root-requiring "build-indep", "build-arch", "build") + needs to be run under (fake)root, this MUST be declared via this dynamic + keyword, where <target-name> is the name of the "debian/rules" target. + + * debhelper/upstream-make-install: The dh_auto_install command will run + the "install" target from the upstream's Makefile under (fake)root (for + the "makefile" build system or one derived from it). + +Gain Root API +------------- + +The builder will provide a command to promote a given command to (fake)root +by exposing it in the environment variable "DEB_GAIN_ROOT_CMD". Tools that +need this promotion will then use it like the following: + + $DEB_GAIN_ROOT_CMD cmd-that-needs-root ... + +This command is subject to the same requirements as the "gain-root-command" +that dpkg-buildpackage accepts via its "-r/--root-command" option, which +means that it can contain space-separated parameters. If dpkg-buildpackage is +called with "-r/--root-command", then dpkg-buildpackage shall use that value +as the value for "DEB_GAIN_ROOT_CMD". The command SHOULD preserve all the +environment variables, unmodified. + +The variable SHOULD only be provided when there is a need for it. Notably +when "Rules-Requires-Root" is either "no" or "binary-targets" the variable +SHOULD NOT be defined. + +(The "DEB_GAIN_ROOT_CMD" variable used to be named "DPKG_GAIN_ROOT_CMD" +starting with dpkg 1.19.0 and before dpkg 1.19.1 when this specification +got released as stable. The old name MUST not be used.) + +Common cases +------------ + + * Upstream installation insists on "sudo make install"-like behavior. + => Use dpkg/target-subcommand or debhelper/upstream-make-install. + + * Files shipped in the package must be owned by another user than root. + => Not covered; use "binary-targets" for now until dpkg+debhelper + provides the required interface. + +Prototyping/preparation +======================= + +dpkg side +--------- + +dpkg-deb --build provides the --root-owner-group option so that dh_builddeb +or direct calls can control the owner/group file values w/o requiring +(fake)root. + +dpkg-buildpackage must export DEB_GAIN_ROOT_CMD when necessary (for +prototyping, doing this unconditionally would be fine). + + +debhelper side +-------------- + +When the field is present: + + * dh_testroot will behave as usual when Rules-Requires-Root is not present + or set to "binary-targets". + + * dh_testroot will be a no-op when Rules-Requires-Root is set to "no". + + * Otherwise, dh_testroot will either verify that it is run under (fake)root + (as usual) OR assert that DEB_GAIN_ROOT_CMD is defined. + + * debhelper build systems will be patched to check for the + "debhelper/upstream-make-install" keyword and use the "Gain Root API" + accordingly. + + * All other (src:)debhelper commands will skip their calls to chown + (currently they just reset them to "0:0" anyway). + +With the above, a default "dh $@" will no longer require (fake)root when +built (and Rules-Requires-Root is "no"). + +Prototyping: + + * During prototyping, dh_builddeb can wrap the dpkg-deb --build call with + fakeroot (when not already root). |