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session, su: Split password-collecting logic into a separate function

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apio 2022-10-29 10:01:44 +02:00
parent 3e052c72a0
commit 8375701bf6
2 changed files with 48 additions and 18 deletions
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29
apps/src/session.c
View File

@ -39,6 +39,24 @@ static void strip_newline(char* str)
if (str[len - 1] == '\n') str[len - 1] = 0; if (str[len - 1] == '\n') str[len - 1] = 0;
} }
static char* collect_password()
{
static char buf[BUFSIZ];
printf("Password: ");
fgets(buf, BUFSIZ, stdin);
strip_newline(buf);
putchar('\n');
char* copy = strdup(
buf); // The password only stays in a caller-controlled heap-allocated buffer, where it can be freed at will.
memset(buf, 0, BUFSIZ);
return copy;
}
static void login_as(struct passwd* user) static void login_as(struct passwd* user)
{ {
pid_t child = fork(); pid_t child = fork();
@ -74,18 +92,19 @@ static int login()
printf("Unknown user %s\n", username); printf("Unknown user %s\n", username);
return 0; return 0;
} }
printf("Password: "); char* password = collect_password();
char password[BUFSIZ]; putchar('\n');
fgets(password, BUFSIZ, stdin);
strip_newline(password);
puts("\n");
if (strcmp(user->pw_passwd, password) == 0) if (strcmp(user->pw_passwd, password) == 0)
{ {
free(password);
login_as(user); login_as(user);
puts("logout\n"); puts("logout\n");
} }
else else
{
free(password);
puts("Invalid password.\n"); puts("Invalid password.\n");
}
return 0; return 0;
} }

37
apps/src/su.c
View File

@ -19,13 +19,26 @@ void strip_newline(char* str)
if (str[len - 1] == '\n') str[len - 1] = 0; if (str[len - 1] == '\n') str[len - 1] = 0;
} }
static const char* collect_password()
{
static char buf[BUFSIZ];
printf("Password: ");
fgets(buf, BUFSIZ, stdin);
strip_newline(buf);
putchar('\n');
return buf;
}
int main(int argc, char** argv) int main(int argc, char** argv)
{ {
if (argc == 1) const char* username;
{
fprintf(stderr, "Usage: %s [username] [command | login shell]\n", argv[0]); if (argc == 1) username = "root";
return EXIT_FAILURE; else
} username = argv[1];
if (getuid() != 0) if (getuid() != 0)
{ {
@ -33,24 +46,22 @@ int main(int argc, char** argv)
return EXIT_FAILURE; return EXIT_FAILURE;
} }
struct passwd* user = getpwnam(argv[1]); struct passwd* user = getpwnam(username);
endpwent();
if (!user) if (!user)
{ {
if (errno) perror("getpwnam"); if (errno) perror("getpwnam");
else else
fprintf(stderr, "Unknown user %s\n", argv[1]); fprintf(stderr, "Unknown user %s\n", username);
return EXIT_FAILURE; return EXIT_FAILURE;
} }
if (getuid() != geteuid()) // we were started from a non-root user if (getuid() != geteuid()) // we were started from a non-root user
{ {
printf("Password: "); const char* pw = collect_password();
char buf[BUFSIZ]; if (strcmp(pw, user->pw_passwd) != 0)
fgets(buf, BUFSIZ, stdin);
strip_newline(buf);
putchar('\n');
if (strcmp(buf, user->pw_passwd) != 0)
{ {
fprintf(stderr, "Invalid password\n"); fprintf(stderr, "Invalid password\n");
return EXIT_FAILURE; return EXIT_FAILURE;