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file: allow exec to return stdout as a file descriptor #40

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95 changes: 80 additions & 15 deletions file.c
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,8 @@
#include <string.h>
#include <limits.h>
#include <dirent.h>
#include <sys/mman.h>
#include <sys/resource.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <libubus.h>
Expand All @@ -45,6 +47,10 @@
/* limit of regular files and command output data */
#define RPC_FILE_MAX_SIZE (4096 * 64)

/* 16 MB ceiling for streamed command output; the kernel enforces it via
* RLIMIT_FSIZE and the child dies with SIGXFSZ at the limit */
#define RPC_FILE_STREAM_MAX_SIZE (4096 * 4096)

/* limit of command line length for exec acl checks */
#define RPC_CMDLINE_MAX_SIZE (1024)

Expand Down Expand Up @@ -72,6 +78,9 @@ struct rpc_file_exec_context {
struct ustream_fd epipe;
int stat;
int deferred_status;
int memfd;
bool stream;
bool child_exited;
};


Expand Down Expand Up @@ -130,6 +139,7 @@ enum {
RPC_E_CMD,
RPC_E_PARM,
RPC_E_ENV,
RPC_E_STREAM,
RPC_E_SESSION,
__RPC_E_MAX,
};
Expand All @@ -138,6 +148,7 @@ static const struct blobmsg_policy rpc_exec_policy[__RPC_E_MAX] = {
[RPC_E_CMD] = { .name = "command", .type = BLOBMSG_TYPE_STRING },
[RPC_E_PARM] = { .name = "params", .type = BLOBMSG_TYPE_ARRAY },
[RPC_E_ENV] = { .name = "env", .type = BLOBMSG_TYPE_TABLE },
[RPC_E_STREAM] = { .name = "stream", .type = BLOBMSG_TYPE_BOOL },
[RPC_E_SESSION] = { .name = "ubus_rpc_session",
.type = BLOBMSG_TYPE_STRING },
};
Expand Down Expand Up @@ -915,13 +926,23 @@ rpc_file_exec_reply(struct rpc_file_exec_context *c, int rv)
uloop_timeout_cancel(&c->timeout);
uloop_process_delete(&c->process);

if (c->stream && c->memfd >= 0) {
lseek(c->memfd, 0, SEEK_SET);
ubus_request_set_fd(c->context, &c->request, c->memfd);
c->memfd = -1; /* ubus_complete_deferred_request() closes the fd */
}

if (rv == UBUS_STATUS_OK)
{
blob_buf_init(&buf, 0);

blobmsg_add_u32(&buf, "code", WEXITSTATUS(c->stat));
blobmsg_add_u32(&buf, "code",
WIFSIGNALED(c->stat) ? 128 + WTERMSIG(c->stat)
: WEXITSTATUS(c->stat));

if (!c->stream)
rpc_ustream_to_blobmsg(&c->opipe.stream, "stdout");

rpc_ustream_to_blobmsg(&c->opipe.stream, "stdout");
rpc_ustream_to_blobmsg(&c->epipe.stream, "stderr");

ubus_send_reply(c->context, &c->request, buf.head);
Expand All @@ -930,10 +951,13 @@ rpc_file_exec_reply(struct rpc_file_exec_context *c, int rv)

ubus_complete_deferred_request(c->context, &c->request, rv);

ustream_free(&c->opipe.stream);
ustream_free(&c->epipe.stream);

close(c->opipe.fd.fd);
if (!c->stream) {
ustream_free(&c->opipe.stream);
close(c->opipe.fd.fd);
}

close(c->epipe.fd.fd);

free(c);
Expand Down Expand Up @@ -974,7 +998,15 @@ rpc_file_exec_process_cb(struct uloop_process *p, int stat)

c->stat = stat;

ustream_poll(&c->opipe.stream);
if (c->stream) {
c->child_exited = true;

if (c->epipe.stream.eof)
rpc_file_exec_schedule_reply(c, UBUS_STATUS_OK);
} else {
ustream_poll(&c->opipe.stream);
}

ustream_poll(&c->epipe.stream);
}

Expand Down Expand Up @@ -1014,7 +1046,8 @@ rpc_file_exec_epipe_state_cb(struct ustream *s)
struct rpc_file_exec_context *c =
container_of(s, struct rpc_file_exec_context, epipe.stream);

if (c->opipe.stream.eof && c->epipe.stream.eof)
if (c->epipe.stream.eof &&
(c->stream ? c->child_exited : c->opipe.stream.eof))
rpc_file_exec_schedule_reply(c, UBUS_STATUS_OK);
}

Expand All @@ -1028,13 +1061,15 @@ rpc_fdclose(int fd)
static int
rpc_file_exec_run(const char *cmd, const struct blob_attr *sid,
const struct blob_attr *arg, const struct blob_attr *env,
bool stream,
struct ubus_context *ctx, struct ubus_request_data *req)
{
pid_t pid;

int devnull;
int opipe[2];
int opipe[2] = { -1, -1 };
int epipe[2];
int outfd = -1;

int rem;
struct blob_attr *cur;
Expand Down Expand Up @@ -1087,8 +1122,16 @@ rpc_file_exec_run(const char *cmd, const struct blob_attr *sid,
if (!c)
return UBUS_STATUS_UNKNOWN_ERROR;

if (pipe(opipe))
if (stream) {
c->memfd = memfd_create("exec", MFD_CLOEXEC);
if (c->memfd < 0)
goto fail_opipe;
outfd = c->memfd;
} else if (pipe(opipe)) {
goto fail_opipe;
} else {
outfd = opipe[1];
}

if (pipe(epipe))
goto fail_epipe;
Expand All @@ -1107,12 +1150,12 @@ rpc_file_exec_run(const char *cmd, const struct blob_attr *sid,
_exit(127);

dup2(devnull, 0);
dup2(opipe[1], 1);
dup2(outfd, 1);
dup2(epipe[1], 2);

rpc_fdclose(devnull);
rpc_fdclose(outfd);
rpc_fdclose(opipe[0]);
rpc_fdclose(opipe[1]);
rpc_fdclose(epipe[0]);
rpc_fdclose(epipe[1]);

Expand Down Expand Up @@ -1164,13 +1207,27 @@ rpc_file_exec_run(const char *cmd, const struct blob_attr *sid,
}
}

if (stream) {
struct rlimit rl = {
.rlim_cur = RPC_FILE_STREAM_MAX_SIZE,
.rlim_max = RPC_FILE_STREAM_MAX_SIZE,
};
setrlimit(RLIMIT_FSIZE, &rl);
}

if (execv(executable, args))
_exit(127);

default:
memset(c, 0, sizeof(*c));

ustream_declare(c->opipe, opipe[0], exec_opipe);
c->stream = stream;
c->memfd = stream ? outfd : -1;

if (!stream) {
ustream_declare(c->opipe, opipe[0], exec_opipe);
}

ustream_declare(c->epipe, epipe[0], exec_epipe);

c->process.pid = pid;
Expand All @@ -1180,7 +1237,9 @@ rpc_file_exec_run(const char *cmd, const struct blob_attr *sid,
c->timeout.cb = rpc_file_exec_timeout_cb;
uloop_timeout_set(&c->timeout, *ops->exec_timeout);

close(opipe[1]);
if (!stream)
close(opipe[1]);

close(epipe[1]);

c->context = ctx;
Expand All @@ -1194,8 +1253,12 @@ rpc_file_exec_run(const char *cmd, const struct blob_attr *sid,
close(epipe[1]);

fail_epipe:
close(opipe[0]);
close(opipe[1]);
if (stream)
close(c->memfd);
else {
close(opipe[0]);
close(opipe[1]);
}

fail_opipe:
free(c);
Expand All @@ -1216,7 +1279,9 @@ rpc_file_exec(struct ubus_context *ctx, struct ubus_object *obj,
return UBUS_STATUS_INVALID_ARGUMENT;

return rpc_file_exec_run(blobmsg_data(tb[RPC_E_CMD]), tb[RPC_E_SESSION],
tb[RPC_E_PARM], tb[RPC_E_ENV], ctx, req);
tb[RPC_E_PARM], tb[RPC_E_ENV],
tb[RPC_E_STREAM] && blobmsg_get_bool(tb[RPC_E_STREAM]),
ctx, req);
}


Expand Down