| Message ID | 2b1ac6822d852ea70dd2dcdf41065076d9ee8028.1722570749.git.fahimitahera@gmail.com (mailing list archive) |
|---|---|
| State | Handled Elsewhere |
| Headers | show |
| Series | Landlock: Add abstract unix socket connect | expand |
On Thu, Aug 01, 2024 at 10:02:35PM -0600, Tahera Fahimi wrote: > A sandboxer can receive the character "a" as input from the environment > variable LL_SCOPE to restrict the abstract unix sockets from connecting > to a process outside its scoped domain. > > Example > ======= > Create an abstract unix socket to listen with socat(1): > socat abstract-listen:mysocket - > Create a sandboxed shell and pass the character "a" to LL_SCOPED: > LL_FS_RO=/ LL_FS_RW=. LL_SCOPED="a" ./sandboxer /bin/bash > If the sandboxed process tries to connect to the listening socket > with command "socat - abstract-connect:mysocket", the connection > will fail. > > Signed-off-by: Tahera Fahimi <fahimitahera@gmail.com> > > --- > v8: > - Adding check_ruleset_scope function to parse the scope environment > variable and update the landlock attribute based on the restriction > provided by the user. > - Adding Mickaël Salaün reviews on version 7. > > v7: > - Adding IPC scoping to the sandbox demo by defining a new "LL_SCOPED" > environment variable. "LL_SCOPED" gets value "a" to restrict abstract > unix sockets. > - Change LANDLOCK_ABI_LAST to 6. > --- > samples/landlock/sandboxer.c | 56 +++++++++++++++++++++++++++++++++--- > 1 file changed, 52 insertions(+), 4 deletions(-) > > diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c > index e8223c3e781a..98132fd823ad 100644 > --- a/samples/landlock/sandboxer.c > +++ b/samples/landlock/sandboxer.c > @@ -14,6 +14,7 @@ > #include <fcntl.h> > #include <linux/landlock.h> > #include <linux/prctl.h> > +#include <linux/socket.h> > #include <stddef.h> > #include <stdio.h> > #include <stdlib.h> > @@ -22,6 +23,7 @@ > #include <sys/stat.h> > #include <sys/syscall.h> > #include <unistd.h> > +#include <stdbool.h> > > #ifndef landlock_create_ruleset > static inline int > @@ -55,6 +57,7 @@ static inline int landlock_restrict_self(const int ruleset_fd, > #define ENV_FS_RW_NAME "LL_FS_RW" > #define ENV_TCP_BIND_NAME "LL_TCP_BIND" > #define ENV_TCP_CONNECT_NAME "LL_TCP_CONNECT" > +#define ENV_SCOPED_NAME "LL_SCOPED" > #define ENV_DELIMITER ":" > > static int parse_path(char *env_path, const char ***const path_list) > @@ -184,6 +187,38 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd, > return ret; > } > > +static bool check_ruleset_scope(const char *const env_var, > + struct landlock_ruleset_attr *ruleset_attr) > +{ > + bool ret = true; > + char *env_type_scope, *env_type_scope_next, *ipc_scoping_name; > + > + ruleset_attr->scoped &= ~LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET; Why always removing the suported scope? What happen if ABI < 6 ? > + env_type_scope = getenv(env_var); > + /* scoping is not supported by the user */ > + if (!env_type_scope) > + return true; > + env_type_scope = strdup(env_type_scope); > + unsetenv(env_var); > + > + env_type_scope_next = env_type_scope; > + while ((ipc_scoping_name = > + strsep(&env_type_scope_next, ENV_DELIMITER))) { > + if (strcmp("a", ipc_scoping_name) == 0) { > + ruleset_attr->scoped |= > + LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET; There are two issues here: 1. this would not work for ABI < 6 2. "a" can be repeated several times, which should probably not be allowed because we don't want to support this unspecified/undocumented behavior. > + } else { > + fprintf(stderr, "Unsupported scoping \"%s\"\n", > + ipc_scoping_name); > + ret = false; > + goto out_free_name; > + } > + } > +out_free_name: > + free(env_type_scope); > + return ret; > +} > + > /* clang-format off */ > > #define ACCESS_FS_ROUGHLY_READ ( \ > @@ -208,7 +243,7 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd, > > /* clang-format on */ > > -#define LANDLOCK_ABI_LAST 5 > +#define LANDLOCK_ABI_LAST 6 > > int main(const int argc, char *const argv[], char *const *const envp) > { > @@ -223,14 +258,15 @@ int main(const int argc, char *const argv[], char *const *const envp) > .handled_access_fs = access_fs_rw, > .handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP | > LANDLOCK_ACCESS_NET_CONNECT_TCP, > + .scoped = LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET, > }; > > if (argc < 2) { > fprintf(stderr, > - "usage: %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\"%s " > + "usage: %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\" %s " > "<cmd> [args]...\n\n", > ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME, > - ENV_TCP_CONNECT_NAME, argv[0]); > + ENV_TCP_CONNECT_NAME, ENV_SCOPED_NAME, argv[0]); > fprintf(stderr, > "Execute a command in a restricted environment.\n\n"); > fprintf(stderr, > @@ -251,15 +287,18 @@ int main(const int argc, char *const argv[], char *const *const envp) > fprintf(stderr, > "* %s: list of ports allowed to connect (client).\n", > ENV_TCP_CONNECT_NAME); > + fprintf(stderr, "* %s: list of restrictions on IPCs.\n", > + ENV_SCOPED_NAME); > fprintf(stderr, > "\nexample:\n" > "%s=\"${PATH}:/lib:/usr:/proc:/etc:/dev/urandom\" " > "%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" " > "%s=\"9418\" " > "%s=\"80:443\" " > + "%s=\"a\" " > "%s bash -i\n\n", > ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME, > - ENV_TCP_CONNECT_NAME, argv[0]); > + ENV_TCP_CONNECT_NAME, ENV_SCOPED_NAME, argv[0]); > fprintf(stderr, > "This sandboxer can use Landlock features " > "up to ABI version %d.\n", > @@ -327,6 +366,10 @@ int main(const int argc, char *const argv[], char *const *const envp) > /* Removes LANDLOCK_ACCESS_FS_IOCTL_DEV for ABI < 5 */ > ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_IOCTL_DEV; > > + __attribute__((fallthrough)); > + case 5: > + /* Removes LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET for ABI < 6 */ > + ruleset_attr.scoped &= ~LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET; > fprintf(stderr, > "Hint: You should update the running kernel " > "to leverage Landlock features " > @@ -358,6 +401,11 @@ int main(const int argc, char *const argv[], char *const *const envp) > ~LANDLOCK_ACCESS_NET_CONNECT_TCP; > } > > + if (!check_ruleset_scope(ENV_SCOPED_NAME, &ruleset_attr)) { You should use the same pattern as for TCP access rigths: if the environment variable is not set then remove the ruleset's scopes. > + perror("Unsupported IPC scoping requested"); > + return 1; > + } > + > ruleset_fd = > landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0); > if (ruleset_fd < 0) { > -- > 2.34.1 > >
On Fri, Aug 09, 2024 at 04:11:47PM +0200, Mickaël Salaün wrote: > On Thu, Aug 01, 2024 at 10:02:35PM -0600, Tahera Fahimi wrote: > > A sandboxer can receive the character "a" as input from the environment > > variable LL_SCOPE to restrict the abstract unix sockets from connecting > > to a process outside its scoped domain. > > > > Example > > ======= > > Create an abstract unix socket to listen with socat(1): > > socat abstract-listen:mysocket - > > Create a sandboxed shell and pass the character "a" to LL_SCOPED: > > LL_FS_RO=/ LL_FS_RW=. LL_SCOPED="a" ./sandboxer /bin/bash > > If the sandboxed process tries to connect to the listening socket > > with command "socat - abstract-connect:mysocket", the connection > > will fail. > > > > Signed-off-by: Tahera Fahimi <fahimitahera@gmail.com> > > > > --- > > v8: > > - Adding check_ruleset_scope function to parse the scope environment > > variable and update the landlock attribute based on the restriction > > provided by the user. > > - Adding Mickaël Salaün reviews on version 7. > > > > v7: > > - Adding IPC scoping to the sandbox demo by defining a new "LL_SCOPED" > > environment variable. "LL_SCOPED" gets value "a" to restrict abstract > > unix sockets. > > - Change LANDLOCK_ABI_LAST to 6. > > --- > > samples/landlock/sandboxer.c | 56 +++++++++++++++++++++++++++++++++--- > > 1 file changed, 52 insertions(+), 4 deletions(-) > > > > diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c > > index e8223c3e781a..98132fd823ad 100644 > > --- a/samples/landlock/sandboxer.c > > +++ b/samples/landlock/sandboxer.c > > @@ -14,6 +14,7 @@ > > #include <fcntl.h> > > #include <linux/landlock.h> > > #include <linux/prctl.h> > > +#include <linux/socket.h> > > #include <stddef.h> > > #include <stdio.h> > > #include <stdlib.h> > > @@ -22,6 +23,7 @@ > > #include <sys/stat.h> > > #include <sys/syscall.h> > > #include <unistd.h> > > +#include <stdbool.h> > > > > #ifndef landlock_create_ruleset > > static inline int > > @@ -55,6 +57,7 @@ static inline int landlock_restrict_self(const int ruleset_fd, > > #define ENV_FS_RW_NAME "LL_FS_RW" > > #define ENV_TCP_BIND_NAME "LL_TCP_BIND" > > #define ENV_TCP_CONNECT_NAME "LL_TCP_CONNECT" > > +#define ENV_SCOPED_NAME "LL_SCOPED" > > #define ENV_DELIMITER ":" > > > > static int parse_path(char *env_path, const char ***const path_list) > > @@ -184,6 +187,38 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd, > > return ret; > > } > > > > +static bool check_ruleset_scope(const char *const env_var, > > + struct landlock_ruleset_attr *ruleset_attr) > > +{ > > + bool ret = true; > > + char *env_type_scope, *env_type_scope_next, *ipc_scoping_name; > > + > > + ruleset_attr->scoped &= ~LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET; > > Why always removing the suported scope? > What happen if ABI < 6 ? Right, I will add this check before calling chek_ruleset_scope function. > > + env_type_scope = getenv(env_var); > > + /* scoping is not supported by the user */ > > + if (!env_type_scope) > > + return true; > > + env_type_scope = strdup(env_type_scope); > > + unsetenv(env_var); > > + > > + env_type_scope_next = env_type_scope; > > + while ((ipc_scoping_name = > > + strsep(&env_type_scope_next, ENV_DELIMITER))) { > > + if (strcmp("a", ipc_scoping_name) == 0) { > > + ruleset_attr->scoped |= > > + LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET; > > There are two issues here: > 1. this would not work for ABI < 6 > 2. "a" can be repeated several times, which should probably not be > allowed because we don't want to support this > unspecified/undocumented behavior. For the second note, I think even if the user provides multiple "a" (something like "a:a"), It would not have a different effect (for now). Do you suggest that I change this way of handeling this environment variable or add documents that mention this note? > > > + } else { > > + fprintf(stderr, "Unsupported scoping \"%s\"\n", > > + ipc_scoping_name); > > + ret = false; > > + goto out_free_name; > > + } > > + } > > +out_free_name: > > + free(env_type_scope); > > + return ret; > > +} > > + > > /* clang-format off */ > > > > #define ACCESS_FS_ROUGHLY_READ ( \ > > @@ -208,7 +243,7 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd, > > > > /* clang-format on */ > > > > -#define LANDLOCK_ABI_LAST 5 > > +#define LANDLOCK_ABI_LAST 6 > > > > int main(const int argc, char *const argv[], char *const *const envp) > > { > > @@ -223,14 +258,15 @@ int main(const int argc, char *const argv[], char *const *const envp) > > .handled_access_fs = access_fs_rw, > > .handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP | > > LANDLOCK_ACCESS_NET_CONNECT_TCP, > > + .scoped = LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET, > > }; > > > > if (argc < 2) { > > fprintf(stderr, > > - "usage: %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\"%s " > > + "usage: %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\" %s " > > "<cmd> [args]...\n\n", > > ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME, > > - ENV_TCP_CONNECT_NAME, argv[0]); > > + ENV_TCP_CONNECT_NAME, ENV_SCOPED_NAME, argv[0]); > > fprintf(stderr, > > "Execute a command in a restricted environment.\n\n"); > > fprintf(stderr, > > @@ -251,15 +287,18 @@ int main(const int argc, char *const argv[], char *const *const envp) > > fprintf(stderr, > > "* %s: list of ports allowed to connect (client).\n", > > ENV_TCP_CONNECT_NAME); > > + fprintf(stderr, "* %s: list of restrictions on IPCs.\n", > > + ENV_SCOPED_NAME); > > fprintf(stderr, > > "\nexample:\n" > > "%s=\"${PATH}:/lib:/usr:/proc:/etc:/dev/urandom\" " > > "%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" " > > "%s=\"9418\" " > > "%s=\"80:443\" " > > + "%s=\"a\" " > > "%s bash -i\n\n", > > ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME, > > - ENV_TCP_CONNECT_NAME, argv[0]); > > + ENV_TCP_CONNECT_NAME, ENV_SCOPED_NAME, argv[0]); > > fprintf(stderr, > > "This sandboxer can use Landlock features " > > "up to ABI version %d.\n", > > @@ -327,6 +366,10 @@ int main(const int argc, char *const argv[], char *const *const envp) > > /* Removes LANDLOCK_ACCESS_FS_IOCTL_DEV for ABI < 5 */ > > ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_IOCTL_DEV; > > > > + __attribute__((fallthrough)); > > + case 5: > > + /* Removes LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET for ABI < 6 */ > > + ruleset_attr.scoped &= ~LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET; > > fprintf(stderr, > > "Hint: You should update the running kernel " > > "to leverage Landlock features " > > @@ -358,6 +401,11 @@ int main(const int argc, char *const argv[], char *const *const envp) > > ~LANDLOCK_ACCESS_NET_CONNECT_TCP; > > } > > > > + if (!check_ruleset_scope(ENV_SCOPED_NAME, &ruleset_attr)) { > > You should use the same pattern as for TCP access rigths: if the > environment variable is not set then remove the ruleset's scopes. I think this happens in check_ruleset_scope function. However, I will add a condition (abi >=6) to this "if" statement. > > + perror("Unsupported IPC scoping requested"); > > + return 1; > > + } > > + > > ruleset_fd = > > landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0); > > if (ruleset_fd < 0) { > > -- > > 2.34.1 > > > >
On Fri, Aug 09, 2024 at 12:16:37PM -0600, Tahera Fahimi wrote: > On Fri, Aug 09, 2024 at 04:11:47PM +0200, Mickaël Salaün wrote: > > On Thu, Aug 01, 2024 at 10:02:35PM -0600, Tahera Fahimi wrote: > > > A sandboxer can receive the character "a" as input from the environment > > > variable LL_SCOPE to restrict the abstract unix sockets from connecting > > > to a process outside its scoped domain. > > > > > > Example > > > ======= > > > Create an abstract unix socket to listen with socat(1): > > > socat abstract-listen:mysocket - > > > Create a sandboxed shell and pass the character "a" to LL_SCOPED: > > > LL_FS_RO=/ LL_FS_RW=. LL_SCOPED="a" ./sandboxer /bin/bash > > > If the sandboxed process tries to connect to the listening socket > > > with command "socat - abstract-connect:mysocket", the connection > > > will fail. > > > > > > Signed-off-by: Tahera Fahimi <fahimitahera@gmail.com> > > > > > > --- > > > v8: > > > - Adding check_ruleset_scope function to parse the scope environment > > > variable and update the landlock attribute based on the restriction > > > provided by the user. > > > - Adding Mickaël Salaün reviews on version 7. > > > > > > v7: > > > - Adding IPC scoping to the sandbox demo by defining a new "LL_SCOPED" > > > environment variable. "LL_SCOPED" gets value "a" to restrict abstract > > > unix sockets. > > > - Change LANDLOCK_ABI_LAST to 6. > > > --- > > > samples/landlock/sandboxer.c | 56 +++++++++++++++++++++++++++++++++--- > > > 1 file changed, 52 insertions(+), 4 deletions(-) > > > > > > diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c > > > index e8223c3e781a..98132fd823ad 100644 > > > --- a/samples/landlock/sandboxer.c > > > +++ b/samples/landlock/sandboxer.c > > > @@ -14,6 +14,7 @@ > > > #include <fcntl.h> > > > #include <linux/landlock.h> > > > #include <linux/prctl.h> > > > +#include <linux/socket.h> > > > #include <stddef.h> > > > #include <stdio.h> > > > #include <stdlib.h> > > > @@ -22,6 +23,7 @@ > > > #include <sys/stat.h> > > > #include <sys/syscall.h> > > > #include <unistd.h> > > > +#include <stdbool.h> > > > > > > #ifndef landlock_create_ruleset > > > static inline int > > > @@ -55,6 +57,7 @@ static inline int landlock_restrict_self(const int ruleset_fd, > > > #define ENV_FS_RW_NAME "LL_FS_RW" > > > #define ENV_TCP_BIND_NAME "LL_TCP_BIND" > > > #define ENV_TCP_CONNECT_NAME "LL_TCP_CONNECT" > > > +#define ENV_SCOPED_NAME "LL_SCOPED" > > > #define ENV_DELIMITER ":" > > > > > > static int parse_path(char *env_path, const char ***const path_list) > > > @@ -184,6 +187,38 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd, > > > return ret; > > > } > > > > > > +static bool check_ruleset_scope(const char *const env_var, > > > + struct landlock_ruleset_attr *ruleset_attr) > > > +{ > > > + bool ret = true; > > > + char *env_type_scope, *env_type_scope_next, *ipc_scoping_name; > > > + > > > + ruleset_attr->scoped &= ~LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET; > > > > Why always removing the suported scope? > > What happen if ABI < 6 ? > Right, I will add this check before calling chek_ruleset_scope function. > > > > + env_type_scope = getenv(env_var); > > > + /* scoping is not supported by the user */ > > > + if (!env_type_scope) > > > + return true; > > > + env_type_scope = strdup(env_type_scope); > > > + unsetenv(env_var); > > > + > > > + env_type_scope_next = env_type_scope; > > > + while ((ipc_scoping_name = > > > + strsep(&env_type_scope_next, ENV_DELIMITER))) { > > > + if (strcmp("a", ipc_scoping_name) == 0) { > > > + ruleset_attr->scoped |= > > > + LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET; > > > > There are two issues here: > > 1. this would not work for ABI < 6 > > 2. "a" can be repeated several times, which should probably not be > > allowed because we don't want to support this > > unspecified/undocumented behavior. > For the second note, I think even if the user provides multiple "a" > (something like "a:a"), It would not have a different effect (for now). > Do you suggest that I change this way of handeling this environment > variable or add documents that mention this note? We should have a stricter approach to only allow zero or one "a" letter. > > > > > + } else { > > > + fprintf(stderr, "Unsupported scoping \"%s\"\n", > > > + ipc_scoping_name); > > > + ret = false; > > > + goto out_free_name; > > > + } > > > + } > > > +out_free_name: > > > + free(env_type_scope); > > > + return ret; > > > +} > > > + > > > /* clang-format off */ > > > > > > #define ACCESS_FS_ROUGHLY_READ ( \ > > > @@ -208,7 +243,7 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd, > > > > > > /* clang-format on */ > > > > > > -#define LANDLOCK_ABI_LAST 5 > > > +#define LANDLOCK_ABI_LAST 6 > > > > > > int main(const int argc, char *const argv[], char *const *const envp) > > > { > > > @@ -223,14 +258,15 @@ int main(const int argc, char *const argv[], char *const *const envp) > > > .handled_access_fs = access_fs_rw, > > > .handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP | > > > LANDLOCK_ACCESS_NET_CONNECT_TCP, > > > + .scoped = LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET, > > > }; > > > > > > if (argc < 2) { > > > fprintf(stderr, > > > - "usage: %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\"%s " > > > + "usage: %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\" %s " > > > "<cmd> [args]...\n\n", > > > ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME, > > > - ENV_TCP_CONNECT_NAME, argv[0]); > > > + ENV_TCP_CONNECT_NAME, ENV_SCOPED_NAME, argv[0]); > > > fprintf(stderr, > > > "Execute a command in a restricted environment.\n\n"); > > > fprintf(stderr, > > > @@ -251,15 +287,18 @@ int main(const int argc, char *const argv[], char *const *const envp) > > > fprintf(stderr, > > > "* %s: list of ports allowed to connect (client).\n", > > > ENV_TCP_CONNECT_NAME); > > > + fprintf(stderr, "* %s: list of restrictions on IPCs.\n", > > > + ENV_SCOPED_NAME); > > > fprintf(stderr, > > > "\nexample:\n" > > > "%s=\"${PATH}:/lib:/usr:/proc:/etc:/dev/urandom\" " > > > "%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" " > > > "%s=\"9418\" " > > > "%s=\"80:443\" " > > > + "%s=\"a\" " > > > "%s bash -i\n\n", > > > ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME, > > > - ENV_TCP_CONNECT_NAME, argv[0]); > > > + ENV_TCP_CONNECT_NAME, ENV_SCOPED_NAME, argv[0]); > > > fprintf(stderr, > > > "This sandboxer can use Landlock features " > > > "up to ABI version %d.\n", > > > @@ -327,6 +366,10 @@ int main(const int argc, char *const argv[], char *const *const envp) > > > /* Removes LANDLOCK_ACCESS_FS_IOCTL_DEV for ABI < 5 */ > > > ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_IOCTL_DEV; > > > > > > + __attribute__((fallthrough)); > > > + case 5: > > > + /* Removes LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET for ABI < 6 */ > > > + ruleset_attr.scoped &= ~LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET; > > > fprintf(stderr, > > > "Hint: You should update the running kernel " > > > "to leverage Landlock features " > > > @@ -358,6 +401,11 @@ int main(const int argc, char *const argv[], char *const *const envp) > > > ~LANDLOCK_ACCESS_NET_CONNECT_TCP; > > > } > > > > > > + if (!check_ruleset_scope(ENV_SCOPED_NAME, &ruleset_attr)) { > > > > You should use the same pattern as for TCP access rigths: if the > > environment variable is not set then remove the ruleset's scopes. > I think this happens in check_ruleset_scope function. However, I will > add a condition (abi >=6) to this "if" statement. > > > > + perror("Unsupported IPC scoping requested"); > > > + return 1; > > > + } > > > + > > > ruleset_fd = > > > landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0); > > > if (ruleset_fd < 0) { > > > -- > > > 2.34.1 > > > > > > >
diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c index e8223c3e781a..98132fd823ad 100644 --- a/samples/landlock/sandboxer.c +++ b/samples/landlock/sandboxer.c @@ -14,6 +14,7 @@ #include <fcntl.h> #include <linux/landlock.h> #include <linux/prctl.h> +#include <linux/socket.h> #include <stddef.h> #include <stdio.h> #include <stdlib.h> @@ -22,6 +23,7 @@ #include <sys/stat.h> #include <sys/syscall.h> #include <unistd.h> +#include <stdbool.h> #ifndef landlock_create_ruleset static inline int @@ -55,6 +57,7 @@ static inline int landlock_restrict_self(const int ruleset_fd, #define ENV_FS_RW_NAME "LL_FS_RW" #define ENV_TCP_BIND_NAME "LL_TCP_BIND" #define ENV_TCP_CONNECT_NAME "LL_TCP_CONNECT" +#define ENV_SCOPED_NAME "LL_SCOPED" #define ENV_DELIMITER ":" static int parse_path(char *env_path, const char ***const path_list) @@ -184,6 +187,38 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd, return ret; } +static bool check_ruleset_scope(const char *const env_var, + struct landlock_ruleset_attr *ruleset_attr) +{ + bool ret = true; + char *env_type_scope, *env_type_scope_next, *ipc_scoping_name; + + ruleset_attr->scoped &= ~LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET; + env_type_scope = getenv(env_var); + /* scoping is not supported by the user */ + if (!env_type_scope) + return true; + env_type_scope = strdup(env_type_scope); + unsetenv(env_var); + + env_type_scope_next = env_type_scope; + while ((ipc_scoping_name = + strsep(&env_type_scope_next, ENV_DELIMITER))) { + if (strcmp("a", ipc_scoping_name) == 0) { + ruleset_attr->scoped |= + LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET; + } else { + fprintf(stderr, "Unsupported scoping \"%s\"\n", + ipc_scoping_name); + ret = false; + goto out_free_name; + } + } +out_free_name: + free(env_type_scope); + return ret; +} + /* clang-format off */ #define ACCESS_FS_ROUGHLY_READ ( \ @@ -208,7 +243,7 @@ static int populate_ruleset_net(const char *const env_var, const int ruleset_fd, /* clang-format on */ -#define LANDLOCK_ABI_LAST 5 +#define LANDLOCK_ABI_LAST 6 int main(const int argc, char *const argv[], char *const *const envp) { @@ -223,14 +258,15 @@ int main(const int argc, char *const argv[], char *const *const envp) .handled_access_fs = access_fs_rw, .handled_access_net = LANDLOCK_ACCESS_NET_BIND_TCP | LANDLOCK_ACCESS_NET_CONNECT_TCP, + .scoped = LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET, }; if (argc < 2) { fprintf(stderr, - "usage: %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\"%s " + "usage: %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\" %s=\"...\" %s " "<cmd> [args]...\n\n", ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME, - ENV_TCP_CONNECT_NAME, argv[0]); + ENV_TCP_CONNECT_NAME, ENV_SCOPED_NAME, argv[0]); fprintf(stderr, "Execute a command in a restricted environment.\n\n"); fprintf(stderr, @@ -251,15 +287,18 @@ int main(const int argc, char *const argv[], char *const *const envp) fprintf(stderr, "* %s: list of ports allowed to connect (client).\n", ENV_TCP_CONNECT_NAME); + fprintf(stderr, "* %s: list of restrictions on IPCs.\n", + ENV_SCOPED_NAME); fprintf(stderr, "\nexample:\n" "%s=\"${PATH}:/lib:/usr:/proc:/etc:/dev/urandom\" " "%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" " "%s=\"9418\" " "%s=\"80:443\" " + "%s=\"a\" " "%s bash -i\n\n", ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME, - ENV_TCP_CONNECT_NAME, argv[0]); + ENV_TCP_CONNECT_NAME, ENV_SCOPED_NAME, argv[0]); fprintf(stderr, "This sandboxer can use Landlock features " "up to ABI version %d.\n", @@ -327,6 +366,10 @@ int main(const int argc, char *const argv[], char *const *const envp) /* Removes LANDLOCK_ACCESS_FS_IOCTL_DEV for ABI < 5 */ ruleset_attr.handled_access_fs &= ~LANDLOCK_ACCESS_FS_IOCTL_DEV; + __attribute__((fallthrough)); + case 5: + /* Removes LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET for ABI < 6 */ + ruleset_attr.scoped &= ~LANDLOCK_SCOPED_ABSTRACT_UNIX_SOCKET; fprintf(stderr, "Hint: You should update the running kernel " "to leverage Landlock features " @@ -358,6 +401,11 @@ int main(const int argc, char *const argv[], char *const *const envp) ~LANDLOCK_ACCESS_NET_CONNECT_TCP; } + if (!check_ruleset_scope(ENV_SCOPED_NAME, &ruleset_attr)) { + perror("Unsupported IPC scoping requested"); + return 1; + } + ruleset_fd = landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0); if (ruleset_fd < 0) {
A sandboxer can receive the character "a" as input from the environment variable LL_SCOPE to restrict the abstract unix sockets from connecting to a process outside its scoped domain. Example ======= Create an abstract unix socket to listen with socat(1): socat abstract-listen:mysocket - Create a sandboxed shell and pass the character "a" to LL_SCOPED: LL_FS_RO=/ LL_FS_RW=. LL_SCOPED="a" ./sandboxer /bin/bash If the sandboxed process tries to connect to the listening socket with command "socat - abstract-connect:mysocket", the connection will fail. Signed-off-by: Tahera Fahimi <fahimitahera@gmail.com> --- v8: - Adding check_ruleset_scope function to parse the scope environment variable and update the landlock attribute based on the restriction provided by the user. - Adding Mickaël Salaün reviews on version 7. v7: - Adding IPC scoping to the sandbox demo by defining a new "LL_SCOPED" environment variable. "LL_SCOPED" gets value "a" to restrict abstract unix sockets. - Change LANDLOCK_ABI_LAST to 6. --- samples/landlock/sandboxer.c | 56 +++++++++++++++++++++++++++++++++--- 1 file changed, 52 insertions(+), 4 deletions(-)