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ptrace_intercept_execve: read back the updated syscall args in test mode.

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This makes it easier to detect problems with the syscall rewrite code
when testing with test_ptrace.
This commit is contained in:
Todd C. Miller
2022-05-12 08:32:31 -06:00
parent 4ecada04a4
commit ea2bf7f1f2
1 changed files with 86 additions and 4 deletions
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90
src/exec_ptrace.c
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@@ -661,7 +661,7 @@ get_execve_info(pid_t pid, struct sudo_ptrace_regs *regs, char **pathname_out,
strtab += len;
bufsize -= len;
sudo_debug_execve(SUDO_DEBUG_INFO, pathname, argv, envp);
sudo_debug_execve(SUDO_DEBUG_DIAG, pathname, argv, envp);
*pathname_out = pathname;
*argc_out = argc;
@@ -803,7 +803,7 @@ set_exec_filter(void)
nitems(exec_filter),
exec_filter
};
debug_decl(set_exec_filter, SUDO_DEBUG_UTIL);
debug_decl(set_exec_filter, SUDO_DEBUG_EXEC);
/* We must set SECCOMP_MODE_FILTER before dropping privileges. */
if (prctl(PR_SET_SECCOMP, SECCOMP_MODE_FILTER, &exec_fprog) == -1) {
@@ -825,7 +825,7 @@ exec_ptrace_seize(pid_t child)
PTRACE_O_TRACEFORK|PTRACE_O_TRACEVFORK;
int ret = -1;
int status;
debug_decl(exec_ptrace_seize, SUDO_DEBUG_UTIL);
debug_decl(exec_ptrace_seize, SUDO_DEBUG_EXEC);
/* Seize control of the child process. */
if (ptrace(PTRACE_SEIZE, child, NULL, ptrace_opts) == -1) {
@@ -878,6 +878,75 @@ done:
debug_return_int(ret);
}
/*
* Verify that the execve(2) argument we wrote match the contents of closure.
* Returns true if they match, else false.
*/
static bool
verify_execve_info(pid_t pid, struct sudo_ptrace_regs *regs,
struct intercept_closure *closure)
{
char *pathname, **argv, **envp, *buf;
int argc, envc, i;
bool ret = true;
debug_decl(verify_execve_info, SUDO_DEBUG_EXEC);
buf = get_execve_info(pid, regs, &pathname, &argc, &argv,
&envc, &envp);
if (buf == NULL)
debug_return_bool(false);
if (pathname == NULL || strcmp(pathname, closure->command) != 0) {
sudo_warn(
U_("pathname mismatch, expected \"%s\", got \"%s\""),
closure->command, pathname ? pathname : "(NULL)");
ret = false;
}
for (i = 0; i < argc; i++) {
if (closure->run_argv[i] == NULL) {
ret = false;
sudo_warn(
U_("%s[%d] mismatch, expected \"%s\", got \"%s\""),
"argv", i, "(NULL)", argv[i] ? argv[i] : "(NULL)");
break;
} else if (argv[i] == NULL) {
ret = false;
sudo_warn(
U_("%s[%d] mismatch, expected \"%s\", got \"%s\""),
"argv", i, closure->run_argv[i], "(NULL)");
break;
} else if (strcmp(argv[i], closure->run_argv[i]) != 0) {
ret = false;
sudo_warn(
U_("%s[%d] mismatch, expected \"%s\", got \"%s\""),
"argv", i, closure->run_argv[i], argv[i]);
}
}
for (i = 0; i < envc; i++) {
if (closure->run_envp[i] == NULL) {
ret = false;
sudo_warn(
U_("%s[%d] mismatch, expected \"%s\", got \"%s\""),
"envp", i, "(NULL)", envp[i] ? envp[i] : "(NULL)");
break;
} else if (envp[i] == NULL) {
ret = false;
sudo_warn(
U_("%s[%d] mismatch, expected \"%s\", got \"%s\""),
"envp", i, closure->run_envp[i], "(NULL)");
break;
} else if (strcmp(envp[i], closure->run_envp[i]) != 0) {
ret = false;
sudo_warn(
U_("%s[%d] mismatch, expected \"%s\", got \"%s\""),
"envp", i, closure->run_envp[i], envp[i]);
}
}
free(buf);
debug_return_bool(ret);
}
/*
* Intercept execve(2) and perform a policy check.
* Reads current registers and execve(2) arguments.
@@ -898,7 +967,7 @@ ptrace_intercept_execve(pid_t pid, struct intercept_closure *closure)
bool ret = false;
struct stat sb;
int i;
debug_decl(ptrace_intercept_execve, SUDO_DEBUG_UTIL);
debug_decl(ptrace_intercept_execve, SUDO_DEBUG_EXEC);
/* Do not check the policy if we are executing the initial command. */
if (closure->initial_command != 0) {
@@ -1000,6 +1069,8 @@ ptrace_intercept_execve(pid_t pid, struct intercept_closure *closure)
closure->command = pathname;
if (closure->run_argv == NULL)
closure->run_argv = argv;
if (closure->run_envp == NULL)
closure->run_envp = envp;
FALLTHROUGH;
case POLICY_ACCEPT:
/*
@@ -1026,6 +1097,9 @@ ptrace_intercept_execve(pid_t pid, struct intercept_closure *closure)
unsigned long strtab;
size_t len, space = 0;
sudo_debug_execve(SUDO_DEBUG_DIAG, closure->command,
closure->run_argv, envp);
/*
* Calculate the amount of space required for pointers + strings.
* Since ptrace(2) always writes in sizeof(long) increments we
@@ -1088,6 +1162,14 @@ ptrace_intercept_execve(pid_t pid, struct intercept_closure *closure)
(int)pid);
goto done;
}
if (closure->state == POLICY_TEST) {
/* Verify the contents of what we just wrote. */
if (!verify_execve_info(pid, &regs, closure)) {
sudo_debug_printf(SUDO_DEBUG_ERROR,
"%s: new execve args don't match closure", __func__);
}
}
}
break;
default: