implement a way for programs in the mount namespace (with glibc binaries) to launch processes in the original namespace (with musl binaries)

1 files changed, 154 insertions, 0 deletions

diff --git a/utils.c b/utils.c
new file mode 100644
index 0000000..233a6e5
--- /dev/null
+++ b/utils.c
@@ -0,0 +1,154 @@
+#include <string.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <assert.h>
+#include <unistd.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include "macros.h"
+#include "utils.h"
+
+bool isdir(const char *s)
+{
+    struct stat st;
+    int result = stat(s, &st);
+    if (result == -1)
+        ERROR("stat(%s): %s\n", s, strerror(errno));
+    return result == 0 && S_ISDIR(st.st_mode);
+}
+
+bool isexe(const char *s)
+{
+    struct stat st;
+    int result = stat(s, &st);
+    if (result == -1)
+        ERROR("stat(%s): %s\n", s, strerror(errno));
+    return result == 0 && !S_ISDIR(st.st_mode) && st.st_mode & S_IXUSR;
+}
+
+bool exists(const char *s)
+{
+    struct stat st;
+    return stat(s, &st) == 0;
+}
+
+bool mkfile(const char *s)
+{
+    int fd;
+    if ((fd = creat(s, 0700)) == -1)
+        return false;
+    close(fd);
+    return true;
+}
+
+int send_fd(int sock, int fd)
+{
+    struct msghdr msg = {0};
+    struct iovec iov[1];
+    struct cmsghdr *cmsg = NULL;
+    char ctrl_buf[CMSG_SPACE(sizeof(int))];
+    char data[1];
+
+    memset(ctrl_buf, 0, CMSG_SPACE(sizeof(int)));
+
+    data[0] = ' ';
+    iov[0].iov_base = data;
+    iov[0].iov_len = sizeof(data);
+
+    msg.msg_name = NULL;
+    msg.msg_namelen = 0;
+    msg.msg_iov = iov;
+    msg.msg_iovlen = 1;
+    msg.msg_controllen =  CMSG_SPACE(sizeof(int));
+    msg.msg_control = ctrl_buf;
+
+    cmsg = CMSG_FIRSTHDR(&msg);
+    cmsg->cmsg_level = SOL_SOCKET;
+    cmsg->cmsg_type = SCM_RIGHTS;
+    cmsg->cmsg_len = CMSG_LEN(sizeof(int));
+
+    *((int *)CMSG_DATA(cmsg)) = fd;
+
+    return sendmsg(sock, &msg, 0);
+}
+
+int recv_fd(int sock)
+{
+    struct msghdr msg = {0};
+    struct iovec iov[1];
+    struct cmsghdr *cmsg = NULL;
+    char ctrl_buf[CMSG_SPACE(sizeof(int))];
+    char data[1];
+
+    memset(ctrl_buf, 0, CMSG_SPACE(sizeof(int)));
+
+    iov[0].iov_base = data;
+    iov[0].iov_len = sizeof(data);
+
+    msg.msg_name = NULL;
+    msg.msg_namelen = 0;
+    msg.msg_control = ctrl_buf;
+    msg.msg_controllen = CMSG_SPACE(sizeof(int));
+    msg.msg_iov = iov;
+    msg.msg_iovlen = 1;
+
+    recvmsg(sock, &msg, 0);
+
+    cmsg = CMSG_FIRSTHDR(&msg);
+
+    return *((int *) CMSG_DATA(cmsg));
+}
+
+bool isxbpscommand(const char *s)
+{
+    const char *commands[] = {
+        "/xbps-install",
+        "/xbps-remove",
+        "/xbps-reconfigure"
+    };
+    for (size_t i = 0; i < ARRAY_SIZE(commands); i++) {
+        const char *command = commands[i];
+        if (!strcmp(s, command+1))
+            return true;
+        char *slash = strrchr(s, '/');
+        if (slash && !strcmp(slash, command))
+            return true;
+    }
+    return false;
+}
+
+bool strarray_append(struct strarray *a, char *s)
+{
+    if (a->end == a->size - 1)
+        return false;
+    else
+        a->list[a->end++] = s;
+    return true;
+}
+
+bool intarray_append(struct intarray *a, int i)
+{
+    if (a->end == a->size - 1)
+        return false;
+    else
+        a->list[a->end++] = i;
+    return true;
+}
+
+void strarray_alloc(struct strarray *a, size_t size)
+{
+    a->end = 0;
+    a->size = size;
+    a->list = malloc(sizeof(char *) * size);
+    assert(a->list != NULL);
+}
+
+void intarray_alloc(struct intarray *i, size_t size)
+{
+    i->end = 0;
+    i->size = size;
+    i->list = malloc(sizeof(int) * size);
+    assert(i->list != NULL);
+}
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