Merge pull request #49 from jhunkeler/tar-some-more

Handle unpacking when running as root:

4 files changed, 58 insertions, 3 deletions

diff --git a/README.md b/README.md
index 6025d93..fb681c3 100644
--- a/README.md
+++ b/README.md
@@ -17,6 +17,7 @@ A basic userland package management system with a few humble goals:
 - make (https://www.gnu.org/software/make)
 - openssl (https://www.openssl.org)
 - bsdtar (https://www.libarchive.org)
+  - OR gnutar (https://www.gnu.org/software/tar)
 - which (https://carlowood.github.io/which)
 
 ## Runtime Requirements
@@ -27,6 +28,7 @@ A basic userland package management system with a few humble goals:
 - reloc (https://github.com/jhunkeler/reloc)
 - rsync (https://rsync.samba.org)
 - bsdtar (https://www.libarchive.org)
+  - OR gnutar (https://www.gnu.org/software/tar)
 - which (https://carlowood.github.io/which)
 
 ## Installation
diff --git a/include/conf.h b/include/conf.h
index 7952eed..0d16f08 100644
--- a/include/conf.h
+++ b/include/conf.h
@@ -39,8 +39,10 @@ typedef struct {
     char *repo_target;
     char *user_config_basedir;
     char *user_config_file;
+    char *tar_program;
     int verbose;
     int prompt_user;
+    int privileged;
     ConfigItem **config;
     struct utsname sysinfo;
     SPM_Hierarchy fs;
diff --git a/lib/archive.c b/lib/archive.c
index 6452647..33c1dcd 100644
--- a/lib/archive.c
+++ b/lib/archive.c
@@ -35,7 +35,7 @@ int tar_extract_file(const char *_archive, const char* _filename, const char *_d
     strchrdel(destination, SHELL_INVALID);
     strchrdel(filename, SHELL_INVALID);
 
-    sprintf(cmd, "bsdtar -x -f \"%s\" -C \"%s\" \"%s\" 2>&1", archive, destination, filename);
+    sprintf(cmd, "%s -x -f \"%s\" -C \"%s\" \"%s\" 2>&1", SPM_GLOBAL.tar_program, archive, destination, filename);
     if (exists(archive) != 0) {
         fprintf(stderr, "unable to find archive: %s\n", archive);
         fprintf(SYSERROR);
@@ -92,7 +92,13 @@ int tar_extract_archive(const char *_archive, const char *_destination) {
     // sanitize destination
     strchrdel(destination, SHELL_INVALID);
 
-    sprintf(cmd, "bsdtar -x -f %s -C %s 2>&1", archive, destination);
+    sprintf(cmd, "%s -x -f %s -C %s ", SPM_GLOBAL.tar_program, archive, destination);
+    if (SPM_GLOBAL.privileged) {
+        // Extract the package as if we were a regular user instead of root.
+        strcat(cmd, "--no-same-owner --no-same-permissions ");
+    }
+    strcat(cmd, "2>&1");
+
     shell(&proc, SHELL_OUTPUT, cmd);
     if (!proc) {
         fprintf(SYSERROR);
diff --git a/lib/config_global.c b/lib/config_global.c
index 0d244fc..5f7e99d 100644
--- a/lib/config_global.c
+++ b/lib/config_global.c
@@ -6,6 +6,40 @@
 // GLOBAL
 spm_vars SPM_GLOBAL;
 
+/**
+ * Is the user executing this program the system administrator?
+ * @return 0=no, 1=yes
+ */
+static int is_root() {
+#if !OS_WINDOWS
+    uid_t euid;
+    euid = geteuid();
+    if (euid == 0) {
+        return 1;
+    }
+#endif
+    return 0;
+}
+
+/**
+ * Return path to the system's tar program
+ * @return
+ */
+static char *find_tar_program() {
+    const char *programs[] = {
+        "bsdtar",
+        "tar",
+    };
+    char *program;
+
+    for (size_t i = 0; i < (sizeof(programs) / sizeof(char *)); i++) {
+        if ((program = find_executable(programs[i])) != NULL) {
+            return program;
+        }
+        program = NULL;
+    }
+    return program;
+}
 
 /**
  * Get path to user's local configuration directory
@@ -138,7 +172,6 @@ void check_runtime_environment(void) {
 #endif
             "objdump",
             "rsync",
-            "bsdtar",
             "bash",
             "reloc",
             NULL,
@@ -157,6 +190,12 @@ void check_runtime_environment(void) {
         }
         free(result);
     }
+
+    if (SPM_GLOBAL.tar_program == NULL) {
+        fprintf(stderr, "A supported tar program could not be found.\nPlease install bsdtar or gnutar.");
+        bad_rt = 1;
+    }
+
     if (bad_rt) {
         exit(1);
     }
@@ -219,6 +258,8 @@ void init_config_global(void) {
     SPM_GLOBAL.repo_target = NULL;
     SPM_GLOBAL.mirror_list = NULL;
     SPM_GLOBAL.prompt_user = 1;
+    SPM_GLOBAL.privileged = is_root();
+    SPM_GLOBAL.tar_program = find_tar_program();
 
     if (uname(&SPM_GLOBAL.sysinfo) != 0) {
         fprintf(SYSERROR);
@@ -352,6 +393,9 @@ void free_global_config(void) {
     if (SPM_GLOBAL.mirror_list) {
         mirror_list_free(SPM_GLOBAL.mirror_list);
     }
+    if (SPM_GLOBAL.tar_program) {
+        free(SPM_GLOBAL.tar_program);
+    }
 
     free(SPM_GLOBAL.fs.bindir);
     free(SPM_GLOBAL.fs.includedir);
@@ -378,6 +422,7 @@ void show_global_config(void) {
             printf("#    -> %s: %s\n", SPM_GLOBAL.config[i]->key, SPM_GLOBAL.config[i]->value);
         }
     }
+    printf("# system target: %s\n", SPM_GLOBAL.repo_target);
     printf("# package storage: %s\n", SPM_GLOBAL.package_dir);
     printf("# temp storage: %s\n", SPM_GLOBAL.tmp_dir);
     printf("# package manifest: %s\n", SPM_GLOBAL.package_manifest);