diff options
-rw-r--r-- | usr.bin/login/login.c | 166 |
1 files changed, 145 insertions, 21 deletions
diff --git a/usr.bin/login/login.c b/usr.bin/login/login.c index 11cb668..c5af6c0 100644 --- a/usr.bin/login/login.c +++ b/usr.bin/login/login.c @@ -27,32 +27,77 @@ * POSSIBILITY OF SUCH DAMAGE. */ +#include <sys/spawn.h> #include <sys/types.h> #include <sys/errno.h> #include <stdio.h> +#include <stdlib.h> #include <string.h> -#define USERNAME "root" - /* Row indices for /etc/passwd */ #define ROW_USERNAME 0 +#define ROW_HASH 1 #define ROW_USERID 2 #define ROW_GRPID 3 #define ROW_GECOS 4 #define ROW_HOME 5 #define ROW_SHELL 6 +#define is_ascii(C) ((C) >= 0 && (C) <= 128) +#define is_digit(C) ((C >= '0' && C <= '9')) + +#define USERNAME "root" +#define DEFAULT_SHELL "/usr/bin/osh" + +static char buf[64]; +static uint8_t buf_i; + +/* + * Verify a UID is valid + * + * Returns 0 on success + */ +static int +check_uid(const char *uid) +{ + size_t len; + + len = strlen(uid); + + /* Must not be greater than 4 chars */ + if (len > 4) { + return -1; + } + + for (int i = 0; i < len; ++i) { + if (!is_digit(uid[i])) { + return -1; + } + } + + return 0; +} + /* * Check an /etc/passwd entry against an alias * (username) * + * @alias: Alias to lookup + * @entry: /etc/passwd entry + * + * Returns -1 on failure * Returns 0 if the entry matches */ static int check_user(char *alias, char *entry) { - const char *p; + const char *p, *shell; + char *shell_argv[] = { DEFAULT_SHELL, NULL }; + char *envp[] = { NULL }; size_t row = 0; + short retval = -1; + size_t line = 1; + uid_t uid = -1; if (alias == NULL || entry == NULL) { return -EINVAL; @@ -69,39 +114,112 @@ check_user(char *alias, char *entry) while (p != NULL) { switch (row) { case ROW_USERNAME: - printf("username: %s\n", p); + if (strcmp(p, alias) == 0) { + retval = 0; + } break; /* UNREACHABLE */ case ROW_USERID: - printf("UID: %s\n", p); - break; - case ROW_GRPID: - printf("GID: %s\n", p); - break; - case ROW_GECOS: - printf("GECOS: %s\n", p); - break; - case ROW_HOME: - printf("HOME: %s\n", p); + if (check_uid(p) != 0) { + printf("bad uid @ line %d\n", line); + return -1; + } + + uid = atoi(p); break; case ROW_SHELL: - printf("SHELL: %s\n", p); + /* TODO */ break; - defaukt: } p = strtok(NULL, ":"); ++row; + ++line; } - return 0; + if (uid < 0) { + printf("failed to set uid\n"); + return -1; + } + if (shell == NULL) { + printf("failed to read shell path\n"); + return -1; + } + + if (retval == 0) { + setuid(uid); + spawn(shell_argv[0], shell_argv, envp, SPAWN_WAIT); + } + return retval; +} + +static char * +getstr(void) +{ + char c; + int input; + + buf_i = 0; + + + for (;;) { + if ((input = getchar()) < 0) { + continue; + } + + c = (char)input; + if (c == '\t') { + continue; + } + + /* return on newline */ + if (c == '\n') { + buf[buf_i] = '\0'; + putchar('\n'); + return buf; + } + + /* handle backspaces and DEL */ + if (c == '\b' || c == 127) { + if (buf_i > 0) { + fputs("\b \b", stdout); + buf[--buf_i] = '\0'; + } + } else if (is_ascii(c) && buf_i < sizeof(buf) - 1) { + /* write to fd and add to buffer */ + buf[buf_i++] = c; + putchar(c); + } + } +} + +static int +getuser(FILE *fp) +{ + char *alias; + char entry[256]; + int retval; + + printf("username: "); + alias = getstr(); + while (fgets(entry, sizeof(entry), fp) != NULL) { + retval = check_user(alias, entry); + if (retval == 0) { + printf("login: successful\n"); + return 0; + } + } + + printf("bad username \"%s\"\n", alias); + fseek(fp, 0, SEEK_SET); + memset(buf, 0, sizeof(buf)); + buf_i = 0; + return -1; } int main(void) { FILE *fp; - char *alias, *p; - char entry[256]; fp = fopen("/etc/passwd", "r"); if (fp == NULL) { @@ -109,8 +227,14 @@ main(void) return -1; } - while (fgets(entry, sizeof(entry), fp) != NULL) { - check_user(USERNAME, entry); + printf("- Please authenticate yourself -\n"); + printf("Default user 'root'\n"); + for (;;) { + if (getuser(fp) == 0) { + break; + } } + + fclose(fp); return 0; } |