5/17/2022 12:19 PM, Mickaël Salaün пишет:
On 16/05/2022 17:20, Konstantin Meskhidze wrote:This commit adds network demo. It's possible to allow a sandoxer to bind/connect to a list of particular ports restricting networks actions to the rest of ports. Signed-off-by: Konstantin Meskhidze <konstantin.meskhidze@xxxxxxxxxx> --- Changes since v4: * Adds ENV_TCP_BIND_NAME "LL_TCP_BIND" and ENV_TCP_CONNECT_NAME "LL_TCP_CONNECT" variables to insert TCP ports. * Renames populate_ruleset() to populate_ruleset_fs(). * Adds populate_ruleset_net() and parse_port_num() helpers. * Refactoring main() to support network sandboxing. --- samples/landlock/sandboxer.c | 105 +++++++++++++++++++++++++++++++---- security/landlock/ruleset.h | 4 +- 2 files changed, 95 insertions(+), 14 deletions(-) diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c index 3e404e51ec64..4006c42eec1c 100644 --- a/samples/landlock/sandboxer.c +++ b/samples/landlock/sandboxer.c@@ -51,6 +51,8 @@ static inline int landlock_restrict_self(const int ruleset_fd,#define ENV_FS_RO_NAME "LL_FS_RO" #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_PATH_TOKEN ":" static int parse_path(char *env_path, const char ***const path_list)@@ -71,6 +73,20 @@ static int parse_path(char *env_path, const char ***const path_list)return num_paths; } +static int parse_port_num(char *env_port) +{ + int i, num_ports = 0; + + if (env_port) { + num_ports++; + for (i = 0; env_port[i]; i++) { + if (env_port[i] == ENV_PATH_TOKEN[0]) + num_ports++; + } + } + return num_ports; +} + /* clang-format off */ #define ACCESS_FILE ( \@@ -80,7 +96,7 @@ static int parse_path(char *env_path, const char ***const path_list)/* clang-format on */-static int populate_ruleset(const char *const env_var, const int ruleset_fd, +static int populate_ruleset_fs(const char *const env_var, const int ruleset_fd,const __u64 allowed_access) { int num_paths, i, ret = 1;@@ -142,6 +158,49 @@ static int populate_ruleset(const char *const env_var, const int ruleset_fd,return ret; } +static int populate_ruleset_net(const char *const env_var, + const int ruleset_fd, + const __u64 allowed_access) +{ + int num_ports, i, ret = 1; + char *env_port_name; + struct landlock_net_service_attr net_service = { + .allowed_access = 0, + .port = 0, + }; + + env_port_name = getenv(env_var); + if (!env_port_name) { + /* Prevents users to forget a setting. */ + fprintf(stderr, "Missing environment variable %s\n", env_var); + return 1;I think network ports should be optional to be able to test without that (and not break compatibility). You can pass &ruleset_attr as argument to update it accordingly:- without environment variable: no network restriction; - with empty environment variable: all connect (or bind) denied; - otherwise: only allow the listed ports.
Great. That makes sense. Cause anyway fs restrictions are major ones.
+ } + env_port_name = strdup(env_port_name); + unsetenv(env_var); + num_ports = parse_port_num(env_port_name); ++ if (num_ports == 1 && (strtok(env_port_name, ENV_PATH_TOKEN) == NULL)) {+ ret = 0; + goto out_free_name; + } + + for (i = 0; i < num_ports; i++) { + net_service.allowed_access = allowed_access; + net_service.port = atoi(strsep(&env_port_name, ENV_PATH_TOKEN)); + if (landlock_add_rule(ruleset_fd, LANDLOCK_RULE_NET_SERVICE, + &net_service, 0)) {+ fprintf(stderr, "Failed to update the ruleset with port \"%d\": %s\n",+ net_service.port, strerror(errno)); + goto out_free_name; + } + } + ret = 0; + +out_free_name: + free(env_port_name); + return ret; +} + /* clang-format off */ #define ACCESS_FS_ROUGHLY_READ ( \@@ -173,19 +232,24 @@ int main(const int argc, char *const argv[], char *const *const envp)char *const *cmd_argv; int ruleset_fd, abi; __u64 access_fs_ro = ACCESS_FS_ROUGHLY_READ,- access_fs_rw = ACCESS_FS_ROUGHLY_READ | ACCESS_FS_ROUGHLY_WRITE; + access_fs_rw = ACCESS_FS_ROUGHLY_READ | ACCESS_FS_ROUGHLY_WRITE,+ access_net_tcp = LANDLOCK_ACCESS_NET_BIND_TCP | + LANDLOCK_ACCESS_NET_CONNECT_TCP; struct landlock_ruleset_attr ruleset_attr = { .handled_access_fs = access_fs_rw, + .handled_access_net = access_net_tcp, }; if (argc < 2) { fprintf(stderr, - "usage: %s=\"...\" %s=\"...\" %s <cmd> [args]...\n\n", - ENV_FS_RO_NAME, ENV_FS_RW_NAME, argv[0]); + "usage: %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]); fprintf(stderr, "Launch a command in a restricted environment.\n\n"); - fprintf(stderr, "Environment variables containing paths, " - "each separated by a colon:\n"); + fprintf(stderr, + "Environment variables containing paths and ports " + "each separated by a colon:\n"); fprintf(stderr,"* %s: list of paths allowed to be used in a read-only way.\n",ENV_FS_RO_NAME);@@ -193,11 +257,19 @@ int main(const int argc, char *const argv[], char *const *const envp) "* %s: list of paths allowed to be used in a read-write way.\n",ENV_FS_RW_NAME); fprintf(stderr, - "\nexample:\n" + "* %s: list of ports allowed to bind (server).\n", + ENV_TCP_BIND_NAME); + fprintf(stderr, + "* %s: list of ports allowed to connect (client).\n", + ENV_TCP_CONNECT_NAME);This is good and will be better with clang-format. ;)
Yep. I will fix it. Thanks.
+ fprintf(stderr, "\nexample:\n" "%s=\"/bin:/lib:/usr:/proc:/etc:/dev/urandom\" " "%s=\"/dev/null:/dev/full:/dev/zero:/dev/pts:/tmp\" " + "%s=\"15000:16000\" "Bind ports example should reference unprivileged ports such as "9418" (git, not well-known but OK).
Ok. I will change it
+ "%s=\"10000:12000\" "Connect ports example should reference well-known ports such as "80:443".
Ditto.
"%s bash -i\n", - ENV_FS_RO_NAME, ENV_FS_RW_NAME, argv[0]); + ENV_FS_RO_NAME, ENV_FS_RW_NAME, ENV_TCP_BIND_NAME, + ENV_TCP_CONNECT_NAME, argv[0]); return 1; }@@ -234,16 +306,25 @@ int main(const int argc, char *const argv[], char *const *const envp)ruleset_fd =landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);+Why?
Oh. Sorry. My mistake. I will fix it as it was.
if (ruleset_fd < 0) { perror("Failed to create a ruleset"); return 1; } - if (populate_ruleset(ENV_FS_RO_NAME, ruleset_fd, access_fs_ro)) { + if (populate_ruleset_fs(ENV_FS_RO_NAME, ruleset_fd, access_fs_ro)) goto err_close_ruleset; - }Why? I know that checkpatch.pl prints a warning for that but I delibirately chooe to use curly braces even for "if" statements with one line because it is safer. This code may be copied/pasted and I'd like others to avoid introducing goto-fail-like issues.
It was done just to reduce the number of checkpatch.pl warnings. If you want it to be formated in your way I will fix it.
- if (populate_ruleset(ENV_FS_RW_NAME, ruleset_fd, access_fs_rw)) { + + if (populate_ruleset_fs(ENV_FS_RW_NAME, ruleset_fd, access_fs_rw)) goto err_close_ruleset; - } + + if (populate_ruleset_net(ENV_TCP_BIND_NAME, ruleset_fd, + LANDLOCK_ACCESS_NET_BIND_TCP))So please use curly braces here too.
Ok. No problems.
+ goto err_close_ruleset; + + if (populate_ruleset_net(ENV_TCP_CONNECT_NAME, ruleset_fd, + LANDLOCK_ACCESS_NET_CONNECT_TCP)) + goto err_close_ruleset; + if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) { perror("Failed to restrict privileges"); goto err_close_ruleset; diff --git a/security/landlock/ruleset.h b/security/landlock/ruleset.h index 916b30b31c06..e1ff40f238a6 100644 --- a/security/landlock/ruleset.h +++ b/security/landlock/ruleset.h @@ -19,7 +19,7 @@ #include "limits.h" #include "object.h" -typedef u16 access_mask_t; +typedef u32 access_mask_t;What‽
You are right. I will move this changes to another commit, related the kernel updates. I might have forgotten to rebase this change and left it in sandboxer patch. Thank you..
/* Makes sure all filesystem access rights can be stored. */ static_assert(BITS_PER_TYPE(access_mask_t) >= LANDLOCK_NUM_ACCESS_FS); @@ -157,7 +157,7 @@ struct landlock_ruleset { * layers are set once and never changed for the * lifetime of the ruleset. */ - u32 access_masks[]; + access_mask_t access_masks[]; }; }; }; -- 2.25.1.
