I had a few (3 maybe?) system calls where I got the error checking backwards,
so I fixed those. I also realized I forgot to format the code with the 80
character thing, so I shortened a bunch of lines.
The command works fine except for when I request a shell of 15+ characters
(such as /usr/bin/xonsh), in which case it segfaults. I'm still working on
this, but I think the string is too long for the passwd struct (which wouldn't
explain why `update_passwd("/etc/passwd", user, NULL)` is failing).
Sent with [ProtonMail](https://protonmail.com) Secure Email.From 9e1aeb00748a4b99667b2aca8a0690ed343b94af Mon Sep 17 00:00:00 2001
From: Michael Christensen <[email protected]>
Date: Fri, 26 Mar 2021 16:50:01 -0600
Subject: [PATCH] Fix some system calls and clean up
---
toys/lsb/chsh.c | 73 ++++++++++++++++++++++++++++++++-----------------
1 file changed, 48 insertions(+), 25 deletions(-)
diff --git a/toys/lsb/chsh.c b/toys/lsb/chsh.c
index 1895755c..bea35e59 100644
--- a/toys/lsb/chsh.c
+++ b/toys/lsb/chsh.c
@@ -16,10 +16,9 @@ config CHSH
-s login_shell Use specified shell rather than interactive prompt
- The shell must be an absolute path to an executable file. An unpriviliged
- user can only change his/her own shell to one listed in /etc/shells, and only if
- he/she is not restricted (implementation-defined).
-*/
+ The shell must be an absolute path to an executable file. An unpriviliged
+ user can only change his/her own shell to one listed in /etc/shells, and
+ only if he/she is not restricted (implementation-defined). */
#define FOR_chsh
#include "toys.h"
@@ -40,35 +39,52 @@ void chsh_main()
// Use max login name size for buffer size
if (-1 == (buf_size = sysconf(_SC_LOGIN_NAME_MAX))) buf_size = 256;
- if (!(user = malloc(buf_size * sizeof(user)))) perror_exit("Failed to allocate memory");
- if (!(shell = malloc(buf_size * sizeof(shell)))) perror_exit("Failed to allocate memory");
- if (!(line = malloc(buf_size * sizeof(line)))) perror_exit("Failed to allocate memory");
- if (MAP_FAILED == (password = mmap(NULL, buf_size, PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS | MAP_LOCKED | MAP_NORESERVE, -1, 0))) perror_exit("Failed to get memory map");
+ if (!(user = malloc(buf_size * sizeof(user))))
+ perror_exit("Failed to allocate memory");
+ if (!(shell = malloc(buf_size * sizeof(shell))))
+ perror_exit("Failed to allocate memory");
+ if (!(line = malloc(buf_size * sizeof(line))))
+ perror_exit("Failed to allocate memory");
+ if (MAP_FAILED == (password = mmap(NULL, buf_size, PROT_WRITE | PROT_READ,
+ MAP_PRIVATE | MAP_ANONYMOUS | MAP_LOCKED | MAP_NORESERVE,
+ -1, 0))) perror_exit("Failed to get memory map");
// Get uid user information, may be discarded later
- if (!(passwd_info = getpwuid(getuid()))) perror_exit("Failed to get passwd record");
+ if (!(passwd_info = getpwuid(getuid())))
+ perror_exit("Failed to get passwd record");
if ((user = *toys.optargs)) {
errno = 0;
- if (!(passwd_info = getpwnam(user)) && !errno) error_exit("Failed to get user info");
+ if (!(passwd_info = getpwnam(user)) && !errno)
+ error_exit("Failed to get user info");
// Are we either root or changing our own shell?
- if (getuid() && strcmp(passwd_info->pw_name, user)) error_exit("Permission denied\n");
+ if (getuid() && strcmp(passwd_info->pw_name, user))
+ error_exit("Permission denied\n");
} else user = passwd_info->pw_name;
// Get a password, encrypt it, wipe it, and check it
- if (!(shadow_info = getspnam(passwd_info->pw_name))) perror_exit("Failed to get shadow record");
- if (!read_password(password, buf_size, "Password: ")) error_exit("Failed to read password\n");
- if (!(encrypted = crypt(password, shadow_info->sp_pwdp))) perror_exit("Failed to encrypt password");
+ if (!(shadow_info = getspnam(passwd_info->pw_name)))
+ perror_exit("Failed to get shadow record");
+ if (read_password(password, buf_size, "Password: "))
+ error_exit("Failed to read password\n");
+ if (!(encrypted = crypt(password, shadow_info->sp_pwdp)))
+ perror_exit("Failed to encrypt password");
memset(password, 0, buf_size);
- if (!munmap(password, buf_size)) perror_exit("Failed to unmap memory");
- if (strcmp(encrypted, shadow_info->sp_pwdp)) perror_exit("Incorrect password");
+ if (munmap(password, buf_size)) perror_exit("Failed to unmap memory");
+ if (strcmp(encrypted, shadow_info->sp_pwdp))
+ perror_exit("Incorrect password");
// Get new shell (either -s or interactive)
- if (!(file = fopen("/etc/shells", "r"))) perror_exit("Failed to open /etc/shells");
+ if (!(file = fopen("/etc/shells", "r")))
+ perror_exit("Failed to open /etc/shells");
if (toys.optflags) shell = TT.s;
else {
- xprintf("Changing the login shell for %s\nEnter the new value, or press ENTER for default\n Login shell [%s]: ", user, passwd_info->pw_shell);
+ xprintf(
+"Changing the login shell for %s\n\
+Enter the new value, or press ENTER for default\n\
+ Login shell [%s]: ",
+ user, passwd_info->pw_shell);
errno = 0; size = 0;
while (EOF != (i = fgetc(stdin))) {
@@ -102,7 +118,8 @@ void chsh_main()
// Get default shell, ignoring comments and blank lines
do {
shell = NULL;
- if (-1 == getline(&shell, &size, file)) perror_exit("Failed to read from /etc/shells");
+ if (-1 == getline(&shell, &size, file))
+ perror_exit("Failed to read from /etc/shells");
} while (*shell != '/');
size = strlen(shell) - 1;
@@ -112,15 +129,21 @@ void chsh_main()
// Update shell and write passwd entry to tempfile
strncpy(passwd_info->pw_shell, shell, buf_size);
if (!(file = tmpfile())) perror_exit("Failed to create tempfile");
- if (!putpwent(passwd_info, file)) perror_exit("Failed to write to passwd entry");
+ if (putpwent(passwd_info, file))
+ perror_exit("Failed to write to passwd entry");
// Move passwd entry from file to string
- if (-1 == (i = ftell(file))) perror_exit("Failed to get tempfile offset");
- if (buf_size < i && !realloc(line, i)) perror_exit("Failed to reallocate memory");
+ if (-1 == (i = ftell(file)))
+ perror_exit("Failed to get tempfile offset");
+ if (buf_size < i && !realloc(line, i))
+ perror_exit("Failed to reallocate memory");
rewind(file);
- if (fread(line, 1, i, file) < i) perror_exit("Failed to read from tempfile");
+ if (fread(line, 1, i, file) < i)
+ perror_exit("Failed to read from tempfile");
// Update /etc/passwd using that string
- if (-1 == update_password("/etc/passwd", user, NULL)) perror_exit("Failed to remove passwd entry");
- if (-1 == update_password("/etc/passwd", user, line)) perror_exit("Failed to add passwd entry");
+ if (-1 == update_password("/etc/passwd", user, NULL))
+ perror_exit("Failed to remove passwd entry");
+ if (-1 == update_password("/etc/passwd", user, line))
+ perror_exit("Failed to add passwd entry");
}
--
2.25.1
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