mirror of
https://github.com/git/git.git
synced 2024-11-13 20:53:02 +01:00
0cfeed2e1d
It is in general unsafe to start a program with one or more of file
descriptors 0/1/2 closed. Karl Chen for example noticed that stat_command
does this in order to rename a pipe file descriptor to 0:
dup2(from, 0);
close(from);
... but if stdin was closed (for example) from == 0, so that
dup2(0, 0);
close(0);
just ends up closing the pipe. Another extremely rare but nasty problem
would occur if an "important" file ends up in file descriptor 2, and is
corrupted by a call to die().
Fixing this in git was considered to be overkill, so this patch works
around it only for git-shell. The fix is simply to open all the "low"
descriptors to /dev/null in main.
Signed-off-by: Paolo Bonzini <bonzini@gnu.org>
Acked-by: Stephen R. van den Berg <srb@cuci.nl>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
110 lines
2.5 KiB
C
110 lines
2.5 KiB
C
#include "cache.h"
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#include "quote.h"
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#include "exec_cmd.h"
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#include "strbuf.h"
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/* Stubs for functions that make no sense for git-shell. These stubs
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* are provided here to avoid linking in external redundant modules.
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*/
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void release_pack_memory(size_t need, int fd){}
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void trace_argv_printf(const char **argv, const char *fmt, ...){}
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void trace_printf(const char *fmt, ...){}
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static int do_generic_cmd(const char *me, char *arg)
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{
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const char *my_argv[4];
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setup_path();
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if (!arg || !(arg = sq_dequote(arg)))
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die("bad argument");
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if (prefixcmp(me, "git-"))
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die("bad command");
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my_argv[0] = me + 4;
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my_argv[1] = arg;
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my_argv[2] = NULL;
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return execv_git_cmd(my_argv);
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}
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static int do_cvs_cmd(const char *me, char *arg)
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{
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const char *cvsserver_argv[3] = {
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"cvsserver", "server", NULL
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};
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if (!arg || strcmp(arg, "server"))
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die("git-cvsserver only handles server: %s", arg);
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setup_path();
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return execv_git_cmd(cvsserver_argv);
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}
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static struct commands {
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const char *name;
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int (*exec)(const char *me, char *arg);
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} cmd_list[] = {
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{ "git-receive-pack", do_generic_cmd },
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{ "git-upload-pack", do_generic_cmd },
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{ "cvs", do_cvs_cmd },
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{ NULL },
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};
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int main(int argc, char **argv)
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{
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char *prog;
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struct commands *cmd;
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int devnull_fd;
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/*
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* Always open file descriptors 0/1/2 to avoid clobbering files
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* in die(). It also avoids not messing up when the pipes are
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* dup'ed onto stdin/stdout/stderr in the child processes we spawn.
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*/
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devnull_fd = open("/dev/null", O_RDWR);
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while (devnull_fd >= 0 && devnull_fd <= 2)
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devnull_fd = dup(devnull_fd);
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if (devnull_fd == -1)
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die("opening /dev/null failed (%s)", strerror(errno));
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close (devnull_fd);
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/*
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* Special hack to pretend to be a CVS server
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*/
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if (argc == 2 && !strcmp(argv[1], "cvs server"))
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argv--;
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/*
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* We do not accept anything but "-c" followed by "cmd arg",
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* where "cmd" is a very limited subset of git commands.
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*/
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else if (argc != 3 || strcmp(argv[1], "-c"))
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die("What do you think I am? A shell?");
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prog = argv[2];
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if (!strncmp(prog, "git", 3) && isspace(prog[3]))
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/* Accept "git foo" as if the caller said "git-foo". */
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prog[3] = '-';
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for (cmd = cmd_list ; cmd->name ; cmd++) {
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int len = strlen(cmd->name);
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char *arg;
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if (strncmp(cmd->name, prog, len))
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continue;
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arg = NULL;
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switch (prog[len]) {
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case '\0':
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arg = NULL;
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break;
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case ' ':
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arg = prog + len + 1;
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break;
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default:
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continue;
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}
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exit(cmd->exec(cmd->name, arg));
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}
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die("unrecognized command '%s'", prog);
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}
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