tar: optional support for --to-command

function                                             old     new   delta
data_extract_to_command                                -     430    +430
dec2env                                                -      44     +44
tar_main                                             778     819     +41
str2env                                                -      37     +37
tar_var                                                -      32     +32
xputenv                                                -      22     +22
tar_longopts                                         257     270     +13
------------------------------------------------------------------------------
(add/remove: 6/0 grow/shrink: 2/0 up/down: 619/0)             Total: 619 bytes

Signed-off-by: Ladislav Michl <Ladislav.Michl@seznam.cz>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

5 files changed, 163 insertions, 0 deletions

diff --git a/archival/Config.src b/archival/Config.src
index 3dbd3aea1..f64b3347b 100644
--- a/archival/Config.src
+++ b/archival/Config.src
@@ -280,6 +280,15 @@ config FEATURE_TAR_LONG_OPTIONS
         help
           Enable use of long options, increases size by about 400 Bytes
 
+config FEATURE_TAR_TO_COMMAND
+        bool "Support for writing to an external program"
+        default y
+        depends on TAR && FEATURE_TAR_LONG_OPTIONS
+        help
+          If you enable this option you'll be able to instruct tar to send
+          the contents of each extracted file to the standard input of an
+          external program.
+
 config FEATURE_TAR_UNAME_GNAME
         bool "Enable use of user and group names"
         default y
diff --git a/archival/libunarchive/Kbuild.src b/archival/libunarchive/Kbuild.src
index 81854558b..6ad1d7a65 100644
--- a/archival/libunarchive/Kbuild.src
+++ b/archival/libunarchive/Kbuild.src
@@ -53,6 +53,7 @@ lib-$(CONFIG_FEATURE_SEAMLESS_BZ2)      += open_transformer.o decompress_bunzip2
 lib-$(CONFIG_FEATURE_SEAMLESS_LZMA)     += open_transformer.o decompress_unlzma.o get_header_tar_lzma.o
 lib-$(CONFIG_FEATURE_SEAMLESS_XZ)       += open_transformer.o decompress_unxz.o
 lib-$(CONFIG_FEATURE_COMPRESS_USAGE)    += decompress_bunzip2.o
+lib-$(CONFIG_FEATURE_TAR_TO_COMMAND)    += data_extract_to_command.o
 
 ifneq ($(lib-y),)
 lib-y += $(COMMON_FILES)
diff --git a/archival/libunarchive/data_extract_to_command.c b/archival/libunarchive/data_extract_to_command.c
new file mode 100644
index 000000000..983c5301d
--- /dev/null
+++ b/archival/libunarchive/data_extract_to_command.c
@@ -0,0 +1,137 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+ */
+
+#include "libbb.h"
+#include "unarchive.h"
+
+enum {
+        //TAR_FILETYPE,
+        TAR_MODE,
+        TAR_FILENAME,
+        TAR_REALNAME,
+#if ENABLE_FEATURE_TAR_UNAME_GNAME
+        TAR_UNAME,
+        TAR_GNAME,
+#endif
+        TAR_SIZE,
+        TAR_UID,
+        TAR_GID,
+        TAR_MAX,
+};
+
+static const char *const tar_var[] = {
+        // "FILETYPE",
+        "MODE",
+        "FILENAME",
+        "REALNAME",
+#if ENABLE_FEATURE_TAR_UNAME_GNAME
+        "UNAME",
+        "GNAME",
+#endif
+        "SIZE",
+        "UID",
+        "GID",
+};
+
+static void xputenv(char *str)
+{
+        if (putenv(str))
+                bb_error_msg_and_die(bb_msg_memory_exhausted);
+}
+
+static void str2env(char *env[], int idx, const char *str)
+{
+        env[idx] = xasprintf("TAR_%s=%s", tar_var[idx], str);
+        xputenv(env[idx]);
+}
+
+static void dec2env(char *env[], int idx, unsigned long long val)
+{
+        env[idx] = xasprintf("TAR_%s=%llu", tar_var[idx], val);
+        xputenv(env[idx]);
+}
+
+static void oct2env(char *env[], int idx, unsigned long val)
+{
+        env[idx] = xasprintf("TAR_%s=%lo", tar_var[idx], val);
+        xputenv(env[idx]);
+}
+
+void FAST_FUNC data_extract_to_command(archive_handle_t *archive_handle)
+{
+        file_header_t *file_header = archive_handle->file_header;
+
+#if 0 /* do we need this? ENABLE_FEATURE_TAR_SELINUX */
+        char *sctx = archive_handle->tar__next_file_sctx;
+        if (!sctx)
+                sctx = archive_handle->tar__global_sctx;
+        if (sctx) { /* setfscreatecon is 4 syscalls, avoid if possible */
+                setfscreatecon(sctx);
+                free(archive_handle->tar__next_file_sctx);
+                archive_handle->tar__next_file_sctx = NULL;
+        }
+#endif
+
+        if ((file_header->mode & S_IFMT) == S_IFREG) {
+                pid_t pid;
+                int p[2], status;
+                char *tar_env[TAR_MAX];
+
+                memset(tar_env, 0, sizeof(tar_env));
+
+                xpipe(p);
+                pid = BB_MMU ? fork() : vfork();
+                switch (pid) {
+                case -1:
+                        bb_perror_msg_and_die(BB_MMU ? "fork" : "vfork");
+                case 0:
+                        /* Child */
+                        /* str2env(tar_env, TAR_FILETYPE, "f"); - parent should do it once */
+                        oct2env(tar_env, TAR_MODE, file_header->mode);
+                        str2env(tar_env, TAR_FILENAME, file_header->name);
+                        str2env(tar_env, TAR_REALNAME, file_header->name);
+#if ENABLE_FEATURE_TAR_UNAME_GNAME
+                        str2env(tar_env, TAR_UNAME, file_header->tar__uname);
+                        str2env(tar_env, TAR_GNAME, file_header->tar__gname);
+#endif
+                        dec2env(tar_env, TAR_SIZE, file_header->size);
+                        dec2env(tar_env, TAR_UID, file_header->uid);
+                        dec2env(tar_env, TAR_GID, file_header->gid);
+                        close(p[1]);
+                        xdup2(p[0], STDIN_FILENO);
+                        signal(SIGPIPE, SIG_DFL);
+                        execl("/bin/sh", "/bin/sh" + 5, "-c", archive_handle->tar__to_command, NULL);
+                        bb_perror_msg_and_die("can't execute '%s'", "/bin/sh");
+                }
+                close(p[0]);
+                /* Our caller is expected to do signal(SIGPIPE, SIG_IGN)
+                 * so that we don't die if child don't read all the input: */
+                bb_copyfd_exact_size(archive_handle->src_fd, p[1], file_header->size);
+                close(p[1]);
+
+                if (safe_waitpid(pid, &status, 0) == -1)
+                        bb_perror_msg_and_die("waitpid");
+                if (WIFEXITED(status) && WEXITSTATUS(status))
+                        bb_error_msg_and_die("'%s' returned status %d",
+                                archive_handle->tar__to_command, WEXITSTATUS(status));
+                if (WIFSIGNALED(status))
+                        bb_error_msg_and_die("'%s' terminated on signal %d",
+                                archive_handle->tar__to_command, WTERMSIG(status));
+
+                if (!BB_MMU) {
+                        int i;
+                        for (i = 0; i < TAR_MAX; i++) {
+                                if (tar_env[i])
+                                        bb_unsetenv_and_free(tar_env[i]);
+                        }
+                }
+        }
+
+#if 0 /* ENABLE_FEATURE_TAR_SELINUX */
+        if (sctx)
+                /* reset the context after creating an entry */
+                setfscreatecon(NULL);
+#endif
+}
diff --git a/archival/tar.c b/archival/tar.c
index 3a940128b..344c9dea4 100644
--- a/archival/tar.c
+++ b/archival/tar.c
@@ -750,6 +750,7 @@ enum {
         IF_FEATURE_SEAMLESS_Z(   OPTBIT_COMPRESS    ,) // 16th bit
         IF_FEATURE_TAR_NOPRESERVE_TIME(OPTBIT_NOPRESERVE_TIME,)
 #if ENABLE_FEATURE_TAR_LONG_OPTIONS
+        IF_FEATURE_TAR_TO_COMMAND(OPTBIT_2COMMAND   ,)
         OPTBIT_NUMERIC_OWNER,
         OPTBIT_NOPRESERVE_PERM,
         OPTBIT_OVERWRITE,
@@ -772,6 +773,7 @@ enum {
         OPT_GZIP         = IF_FEATURE_SEAMLESS_GZ(  (1 << OPTBIT_GZIP        )) + 0, // z
         OPT_COMPRESS     = IF_FEATURE_SEAMLESS_Z(   (1 << OPTBIT_COMPRESS    )) + 0, // Z
         OPT_NOPRESERVE_TIME = IF_FEATURE_TAR_NOPRESERVE_TIME((1 << OPTBIT_NOPRESERVE_TIME)) + 0, // m
+        OPT_2COMMAND        = IF_FEATURE_TAR_TO_COMMAND(  (1 << OPTBIT_2COMMAND       )) + 0, // to-command
         OPT_NUMERIC_OWNER   = IF_FEATURE_TAR_LONG_OPTIONS((1 << OPTBIT_NUMERIC_OWNER  )) + 0, // numeric-owner
         OPT_NOPRESERVE_PERM = IF_FEATURE_TAR_LONG_OPTIONS((1 << OPTBIT_NOPRESERVE_PERM)) + 0, // no-same-permissions
         OPT_OVERWRITE       = IF_FEATURE_TAR_LONG_OPTIONS((1 << OPTBIT_OVERWRITE      )) + 0, // overwrite
@@ -813,6 +815,9 @@ static const char tar_longopts[] ALIGN1 =
 # if ENABLE_FEATURE_TAR_NOPRESERVE_TIME
         "touch\0"               No_argument       "m"
 # endif
+# if ENABLE_FEATURE_TAR_TO_COMMAND
+        "to-command\0"          Required_argument "\xfb"
+# endif
         /* use numeric uid/gid from tar header, not textual */
         "numeric-owner\0"       No_argument       "\xfc"
         /* do not restore mode */
@@ -904,6 +909,7 @@ int tar_main(int argc UNUSED_PARAM, char **argv)
                 , &tar_filename // -f filename
                 IF_FEATURE_TAR_FROM(, &(tar_handle->accept)) // T
                 IF_FEATURE_TAR_FROM(, &(tar_handle->reject)) // X
+                IF_FEATURE_TAR_TO_COMMAND(, &(tar_handle->tar__to_command)) // --to-command
 #if ENABLE_FEATURE_TAR_LONG_OPTIONS && ENABLE_FEATURE_TAR_FROM
                 , &excludes // --exclude
 #endif
@@ -922,6 +928,12 @@ int tar_main(int argc UNUSED_PARAM, char **argv)
         if (opt & OPT_2STDOUT)
                 tar_handle->action_data = data_extract_to_stdout;
 
+        if (opt & OPT_2COMMAND) {
+                putenv((char*)"TAR_FILETYPE=f");
+                signal(SIGPIPE, SIG_IGN);
+                tar_handle->action_data = data_extract_to_command;
+        }
+
         if (opt & OPT_KEEP_OLD)
                 tar_handle->ah_flags &= ~ARCHIVE_UNLINK_OLD;
 
diff --git a/include/unarchive.h b/include/unarchive.h
index 8009de282..f3aa05d09 100644
--- a/include/unarchive.h
+++ b/include/unarchive.h
@@ -75,6 +75,9 @@ typedef struct archive_handle_t {
         char* tar__longname;
         char* tar__linkname;
 # endif
+#if ENABLE_FEATURE_TAR_TO_COMMAND
+        char* tar__to_command;
+#endif
 # if ENABLE_FEATURE_TAR_SELINUX
         char* tar__global_sctx;
         char* tar__next_file_sctx;
@@ -128,6 +131,7 @@ extern void unpack_ar_archive(archive_handle_t *ar_archive) FAST_FUNC;
 extern void data_skip(archive_handle_t *archive_handle) FAST_FUNC;
 extern void data_extract_all(archive_handle_t *archive_handle) FAST_FUNC;
 extern void data_extract_to_stdout(archive_handle_t *archive_handle) FAST_FUNC;
+extern void data_extract_to_command(archive_handle_t *archive_handle) FAST_FUNC;
 
 extern void header_skip(const file_header_t *file_header) FAST_FUNC;
 extern void header_list(const file_header_t *file_header) FAST_FUNC;