Allow pppd to start as non-root. #98
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This patch adds #ifndef macros in 2 spots in order to allow pppd to be
spawned as a non-root user with only runtime capabilities (e.g.
CAP_NET_{RAW/ADMIN}) instead of giving pppd full root privileges. This
is helpful if pppd is itself spawned by a non-root user and the use of
file permissions (e.g. setuid-root) on the pppd binary is not a
desirable solution.
Collaborator
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The basic idea seems fine, and the commit message is OK, though lacking a signed-off-by line. With the ifndef in pppd/main.c, I'd prefer to see an explicit check that we have the capabilities we need if we're not running with euid=0, rather than simply not checking. The ifndef in pppd/options.c doesn't look to be necessary. That code is about preventing a non-root user from overriding options set by the system administrator, it has basically nothing to do with the euid. |
Author
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Any idea regarding the set of runtime capabilities that pppd uses (and hence which capabilities we should check for in pppd/main.c)? The only capability I know for sure pppd needs is CAP_NET_ADMIN, but we are currently giving it CAP_NET_RAW and CAP_NET_BIND_SERVICE as well as part of a tree of processes. Then again I'm not familiar with the different functionalities of pppd to know if there are any other capabilities it may need in other use cases that I haven't mentioned here. |
Member
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@micah-morton: Have you looked the PR from @a-andreyev? What do you think? @paulusmack: Can you look the update from today too? |
a-andreyev
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Dec 14, 2025
…root Add optional libcap support (--with-libcap) for fine-grained privilege management. When enabled, pppd checks for CAP_NET_ADMIN capability instead of requiring euid 0, allowing it to run with reduced privileges. This addresses issue ppp-project#98 by allowing pppd to run without full root access when given appropriate capabilities via setcap(8). Details: - Add configure option --with-libcap to enable capability checking (Linux only) - Check for CAP_NET_ADMIN (required to open /dev/ppp) instead of CAP_NET_RAW - Add net_capable() function in sys-linux.c and sys-solaris.c - Fallback to geteuid()==0 check when libcap is not available or not built - Add m4/ax_check_cap.m4 macro for autotools detection The feature is disabled by default to maintain backward compatibility. Distributions can enable it with --with-libcap during build. Signed-off-by: Alexey Andreev <[email protected]>
a-andreyev
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Dec 14, 2025
…root Add optional libcap support (--with-libcap) for fine-grained privilege management. When enabled, pppd checks for CAP_NET_ADMIN capability instead of requiring euid 0, allowing it to run with reduced privileges. This addresses issue ppp-project#98 by allowing pppd to run without full root access when given appropriate capabilities via setcap(8). Details: - Add configure option --with-libcap to enable capability checking (Linux only) - Check for CAP_NET_ADMIN (required to open /dev/ppp) instead of CAP_NET_RAW - Add net_capable() function in sys-linux.c and sys-solaris.c - Fallback to geteuid()==0 check when libcap is not available or not built - Add m4/ax_check_cap.m4 macro for autotools detection The feature is disabled by default to maintain backward compatibility. Distributions can enable it with --with-libcap during build. Signed-off-by: Alexey Andreev <[email protected]>
a-andreyev
added a commit
to a-andreyev/ppp
that referenced
this pull request
Dec 14, 2025
…root Add optional libcap support (--with-libcap) for fine-grained privilege management. When enabled, pppd checks for CAP_NET_ADMIN capability instead of requiring euid 0, allowing it to run with reduced privileges. This addresses issue ppp-project#98 by allowing pppd to run without full root access when given appropriate capabilities via setcap(8). Details: - Add configure option --with-libcap to enable capability checking (Linux only) - Check for CAP_NET_ADMIN (required to open /dev/ppp) instead of CAP_NET_RAW - Add net_capable() function in sys-linux.c and sys-solaris.c - Fallback to geteuid()==0 check when libcap is not available or not built - Add m4/ax_check_cap.m4 macro for autotools detection The feature is disabled by default to maintain backward compatibility. Distributions can enable it with --with-libcap during build. Signed-off-by: Alexey Andreyev <[email protected]>
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This patch adds #ifndef macros in 2 spots in order to allow pppd to be
spawned as a non-root user with only runtime capabilities (e.g.
CAP_NET_{RAW/ADMIN}) instead of giving pppd full root privileges. This
is helpful if pppd is itself spawned by a non-root user and the use of
file permissions (e.g. setuid-root) on the pppd binary is not a
desirable solution.