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Re: [Qemu-devel] [PATCH 3/5] seccomp: add elevateprivileges argument to
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH 3/5] seccomp: add elevateprivileges argument to command line |
Date: |
Tue, 14 Mar 2017 12:47:10 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0 |
On 14/03/2017 12:32, Eduardo Otubo wrote:
> This patch introduces the new argument [,elevateprivileges=deny] to the
> `-sandbox on'. It avoids Qemu process to elevate its privileges by
> blacklisting all set*uid|gid system calls
>
> Signed-off-by: Eduardo Otubo <address@hidden>
> ---
> include/sysemu/seccomp.h | 1 +
> qemu-options.hx | 8 ++++++--
> qemu-seccomp.c | 28 ++++++++++++++++++++++++++++
> vl.c | 11 +++++++++++
> 4 files changed, 46 insertions(+), 2 deletions(-)
>
> diff --git a/include/sysemu/seccomp.h b/include/sysemu/seccomp.h
> index 7a7bde246b..e6e78d85ce 100644
> --- a/include/sysemu/seccomp.h
> +++ b/include/sysemu/seccomp.h
> @@ -16,6 +16,7 @@
> #define QEMU_SECCOMP_H
>
> #define OBSOLETE 0x0001
> +#define PRIVILEGED 0x0010
>
> #include <seccomp.h>
>
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 1403d0c85f..47018db5aa 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -3732,8 +3732,10 @@ Old param mode (ARM only).
> ETEXI
>
> DEF("sandbox", HAS_ARG, QEMU_OPTION_sandbox, \
> - "-sandbox on[,obsolete=allow] Enable seccomp mode 2 system call filter
> (default 'off').\n" \
> - " obsolete: Allow obsolete system calls",
> + "-sandbox on[,obsolete=allow][,elevateprivileges=deny]\n" \
> + " Enable seccomp mode 2 system call filter
> (default 'off').\n" \
> + " obsolete: Allow obsolete system calls\n"
> \
> + " elevateprivileges: avoids Qemu process
> to elevate its privileges by blacklisting all set*uid|gid system calls",
Why allow these by default?
Paolo
> QEMU_ARCH_ALL)
> STEXI
> @item -sandbox @var{arg}[,address@hidden
> @@ -3743,6 +3745,8 @@ disable it. The default is 'off'.
> @table @option
> @item address@hidden
> Enable Obsolete system calls
> address@hidden address@hidden
> +Disable set*uid|gid systema calls
> @end table
> ETEXI
>
> diff --git a/qemu-seccomp.c b/qemu-seccomp.c
> index 5ef36890da..5aa6590386 100644
> --- a/qemu-seccomp.c
> +++ b/qemu-seccomp.c
> @@ -31,6 +31,19 @@ struct QemuSeccompSyscall {
> uint8_t priority;
> };
>
> +static const struct QemuSeccompSyscall privileged_syscalls[] = {
> + { SCMP_SYS(setuid), 255 },
> + { SCMP_SYS(setgid), 255 },
> + { SCMP_SYS(setpgid), 255 },
> + { SCMP_SYS(setsid), 255 },
> + { SCMP_SYS(setreuid), 255 },
> + { SCMP_SYS(setregid), 255 },
> + { SCMP_SYS(setresuid), 255 },
> + { SCMP_SYS(setresgid), 255 },
> + { SCMP_SYS(setfsuid), 255 },
> + { SCMP_SYS(setfsgid), 255 },
> +};
> +
> static const struct QemuSeccompSyscall obsolete[] = {
> { SCMP_SYS(readdir), 255 },
> { SCMP_SYS(_sysctl), 255 },
> @@ -125,6 +138,21 @@ int seccomp_start(uint8_t seccomp_opts)
> }
> }
>
> + if (seccomp_opts & PRIVILEGED) {
> + for (i = 0; i < ARRAY_SIZE(privileged_syscalls); i++) {
> + rc = seccomp_rule_add(ctx, SCMP_ACT_KILL,
> privileged_syscalls[i].num, 0);
> + if (rc < 0) {
> + goto seccomp_return;
> + }
> + rc = seccomp_syscall_priority(ctx, privileged_syscalls[i].num,
> + privileged_syscalls[i].priority);
> + if (rc < 0) {
> + goto seccomp_return;
> + }
> + }
> + }
> +
> +
> rc = seccomp_load(ctx);
>
> seccomp_return:
> diff --git a/vl.c b/vl.c
> index 7b08b3383b..d071e240b0 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -273,6 +273,10 @@ static QemuOptsList qemu_sandbox_opts = {
> .name = "obsolete",
> .type = QEMU_OPT_STRING,
> },
> + {
> + .name = "elevateprivileges",
> + .type = QEMU_OPT_STRING,
> + },
> { /* end of list */ }
> },
> };
> @@ -1045,6 +1049,13 @@ static int parse_sandbox(void *opaque, QemuOpts *opts,
> Error **errp)
> }
> }
>
> + value = qemu_opt_get(opts,"elevateprivileges");
> + if (value) {
> + if (strcmp(value, "deny") == 0) {
> + seccomp_opts |= PRIVILEGED;
> + }
> + }
> +
> if (seccomp_start(seccomp_opts) < 0) {
> error_report("failed to install seccomp syscall filter "
> "in the kernel");
>
- [Qemu-devel] [PATCH 0/5] seccomp: feature refactoring, Eduardo Otubo, 2017/03/14
- [Qemu-devel] [PATCH 2/5] seccomp: add obsolete argument to command line, Eduardo Otubo, 2017/03/14
- [Qemu-devel] [PATCH 5/5] seccomp: add resourcecontrol argument to command line, Eduardo Otubo, 2017/03/14
- [Qemu-devel] [PATCH 3/5] seccomp: add elevateprivileges argument to command line, Eduardo Otubo, 2017/03/14
- Re: [Qemu-devel] [PATCH 3/5] seccomp: add elevateprivileges argument to command line,
Paolo Bonzini <=
- Re: [Qemu-devel] [PATCH 3/5] seccomp: add elevateprivileges argument to command line, Eduardo Otubo, 2017/03/14
- Re: [Qemu-devel] [PATCH 3/5] seccomp: add elevateprivileges argument to command line, Paolo Bonzini, 2017/03/14
- Re: [Qemu-devel] [PATCH 3/5] seccomp: add elevateprivileges argument to command line, Daniel P. Berrange, 2017/03/14
- Re: [Qemu-devel] [PATCH 3/5] seccomp: add elevateprivileges argument to command line, Paolo Bonzini, 2017/03/14
- Re: [Qemu-devel] [PATCH 3/5] seccomp: add elevateprivileges argument to command line, Daniel P. Berrange, 2017/03/14
[Qemu-devel] [PATCH 1/5] seccomp: changing from whitelist to blacklist, Eduardo Otubo, 2017/03/14