From 268126a3b159fbd488eb56ebbd19c7384f1aa8a5 Mon Sep 17 00:00:00 2001 From: Daniel Golle Date: Thu, 16 Jul 2020 23:00:35 +0100 Subject: [PATCH] jail: add support for maskedPaths and readonlyPaths Parse maskedPaths and readonlyPaths string arrays if defined in OCI container linux section. readonlyPaths are implemented by adding a recursive read-only bind-mount on the path, maskedPaths are done by mounting a zero-sized tmpfs with mode 000 for directories and mount- binding an empty file having mode 000 for non-directories. Mounts of both, maskedPaths and readonlyPaths, may fail silently if the path doesn't exist. Signed-off-by: Daniel Golle --- jail/fs.c | 73 +++++++++++++++++++++++++++++++++++++++++------------ jail/jail.c | 17 ++++++++++++- 2 files changed, 73 insertions(+), 17 deletions(-) diff --git a/jail/fs.c b/jail/fs.c index 352fa0d..abe12d4 100644 --- a/jail/fs.c +++ b/jail/fs.c @@ -37,6 +37,8 @@ #include "jail.h" #include "log.h" +#define UJAIL_NOAFILE "/tmp/.ujailnoafile" + struct mount { struct avl_node avl; const char *source; @@ -81,18 +83,40 @@ static int do_mount(const char *root, const char *source, const char *target, co char new[PATH_MAX]; int fd; bool is_bind = (orig_mountflags & MS_BIND); + bool is_mask = (source == (void *)(-1)); unsigned long mountflags = orig_mountflags; - if (is_bind && stat(source, &s)) { + if (source && is_bind && stat(source, &s)) { ERROR("stat(%s) failed: %m\n", source); return error; } snprintf(new, sizeof(new), "%s%s", root, target?target:source); - if (!is_bind || S_ISDIR(s.st_mode)) { + if (is_mask) { + if (stat(new, &s)) + return 0; /* doesn't exists, nothing to mask */ + + if (S_ISDIR(s.st_mode)) {/* use empty 0-sized tmpfs for directories */ + if (mount(NULL, new, "tmpfs", MS_RDONLY | MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_NOATIME, "size=0,mode=000")) + return error; + } else { + /* mount-bind 0-sized file having mode 000 */ + if (mount(UJAIL_NOAFILE, new, NULL, MS_BIND, NULL)) + return error; + + if (mount(UJAIL_NOAFILE, new, NULL, MS_REMOUNT | MS_BIND | MS_RDONLY | MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_NOATIME, NULL)) + return error; + } + + DEBUG("masked path %s\n", new); + return 0; + } + + + if (!is_bind || (source && S_ISDIR(s.st_mode))) { mkdir_p(new, 0755); - } else { + } else if (is_bind && source) { mkdir_p(dirname(new), 0755); snprintf(new, sizeof(new), "%s%s", root, target?target:source); fd = creat(new, 0644); @@ -103,16 +127,20 @@ static int do_mount(const char *root, const char *source, const char *target, co close(fd); } - if (mountflags & MS_BIND) { - if (mount(source, new, filesystemtype, MS_BIND | (mountflags & MS_REC), optstr)) { - ERROR("failed to mount -B %s %s: %m\n", source, new); + if (is_bind) { + if (mount(source?:new, new, filesystemtype, MS_BIND | (mountflags & MS_REC), optstr)) { + if (error) + ERROR("failed to mount -B %s %s: %m\n", source, new); + return error; } mountflags |= MS_REMOUNT; } - if (mount(source, new, filesystemtype, mountflags, optstr)) { - ERROR("failed to mount %s %s: %m\n", source, new); + if (mount(source?:(is_bind?new:NULL), new, filesystemtype, mountflags, optstr)) { + if (error) + ERROR("failed to mount %s %s: %m\n", source, new); + return error; } @@ -134,15 +162,19 @@ int add_mount(const char *source, const char *target, const char *filesystemtype m = calloc(1, sizeof(struct mount)); assert(m != NULL); m->avl.key = m->target = strdup(target); - if (source) - m->source = strdup(source); + if (source) { + if (source != (void*)(-1)) + m->source = strdup(source); + else + m->source = (void*)(-1); + } if (filesystemtype) m->filesystemtype = strdup(filesystemtype); m->mountflags = mountflags; m->error = error; avl_insert(&mounts, &m->avl); - DEBUG("adding mount %s %s bind(%d) ro(%d) err(%d)\n", m->source, m->target, + DEBUG("adding mount %s %s bind(%d) ro(%d) err(%d)\n", (m->source == (void*)(-1))?"mask":m->source, m->target, !!(m->mountflags & MS_BIND), !!(m->mountflags & MS_RDONLY), m->error != 0); return 0; @@ -158,7 +190,6 @@ int add_mount_bind(const char *path, int readonly, int error) return add_mount(path, path, NULL, mountflags, NULL, error); } - enum { OCI_MOUNT_SOURCE, OCI_MOUNT_DESTINATION, @@ -299,7 +330,7 @@ static int parseOCImountopts(struct blob_attr *msg, unsigned long *mount_flags, DEBUG("mount flags(%08lx) fsopts(\"%s\")\n", mf, *mount_data?:""); return 0; -}; +} int parseOCImount(struct blob_attr *msg) { @@ -319,19 +350,29 @@ int parseOCImount(struct blob_attr *msg) return ret; } - add_mount(tb[OCI_MOUNT_SOURCE] ? blobmsg_get_string(tb[OCI_MOUNT_SOURCE]) : NULL, + return add_mount(tb[OCI_MOUNT_SOURCE] ? blobmsg_get_string(tb[OCI_MOUNT_SOURCE]) : NULL, blobmsg_get_string(tb[OCI_MOUNT_DESTINATION]), tb[OCI_MOUNT_TYPE] ? blobmsg_get_string(tb[OCI_MOUNT_TYPE]) : NULL, mount_flags, mount_data, err); +} - return 0; -}; +static void build_noafile(void) { + int fd; + fd = creat(UJAIL_NOAFILE, 0000); + if (fd == -1) + return; + + close(fd); + return; +} int mount_all(const char *jailroot) { struct library *l; struct mount *m; + build_noafile(); + avl_for_each_element(&libraries, l, avl) add_mount_bind(l->path, 1, -1); diff --git a/jail/jail.c b/jail/jail.c index aa6288e..fdf6285 100644 --- a/jail/jail.c +++ b/jail/jail.c @@ -1233,7 +1233,6 @@ static int parseOCIlinuxns(struct blob_attr *msg) { struct blob_attr *tb[__OCI_LINUX_NAMESPACE_MAX]; - blobmsg_parse(oci_linux_namespace_policy, __OCI_LINUX_NAMESPACE_MAX, tb, blobmsg_data(msg), blobmsg_len(msg)); if (!tb[OCI_LINUX_NAMESPACE_TYPE]) @@ -1384,6 +1383,22 @@ static int parseOCIlinux(struct blob_attr *msg) return res; } + if (tb[OCI_LINUX_READONLYPATHS]) { + blobmsg_for_each_attr(cur, tb[OCI_LINUX_READONLYPATHS], rem) { + res = add_mount(NULL, blobmsg_get_string(cur), NULL, MS_BIND | MS_REC | MS_RDONLY, NULL, 0); + if (res) + return res; + } + } + + if (tb[OCI_LINUX_MASKEDPATHS]) { + blobmsg_for_each_attr(cur, tb[OCI_LINUX_MASKEDPATHS], rem) { + res = add_mount((void *)(-1), blobmsg_get_string(cur), NULL, 0, NULL, 1); + if (res) + return res; + } + } + if (tb[OCI_LINUX_SECCOMP]) { opts.ociseccomp = parseOCIlinuxseccomp(tb[OCI_LINUX_SECCOMP]); if (!opts.ociseccomp) -- 2.30.2