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/*
20140214
20241208 - reformated using clang-format
Jan Mojzis
Public domain.
*/
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <unistd.h>
#include <pwd.h>
#include "str.h"
#include "open.h"
#include "dropuidgid.h"
#include "global.h"
#include "e.h"
#include "log.h"
#include "sshcrypto.h"
#include "getln.h"
#include "bug.h"
#include "limit.h"
#include "subprocess.h"
static int findnameandkey(const char *keyname, const char *key, char *x) {
if (!str_start(x, keyname)) return 0;
x += str_len(keyname);
if (*x != ' ') return 0;
x += 1;
if (!str_start(x, key)) return 0;
x += str_len(key);
if (*x == ' ') return 1;
if (*x == '\n') return 1;
if (*x == '\r') return 1;
if (*x == 0) return 1;
return 0;
}
static void check(uid_t uid, const char *d, const char *f, long long *err) {
struct stat st;
int e = 0;
if (f) {
if (stat(f, &st) == -1) {
log_w4("auth: unable to stat file: ", d, "/", f);
e = 1;
}
if (e == 0 && !S_ISREG(st.st_mode)) {
errno = EACCES;
log_w4("auth: non-regular file: ", d, "/", f);
e = 1;
}
}
else {
if (stat(d, &st) == -1) {
log_w4("auth: unable to stat directory: ", d, "/", f);
e = 1;
}
if (e == 0 && !S_ISDIR(st.st_mode)) {
errno = ENOTDIR;
log_w4("auth: unable to stat directory: ", d, "/", f);
e = 1;
}
}
if (e == 0 && (st.st_mode & 022) != 0) {
errno = EACCES;
log_w4("auth: bad mode: directory writable by group or others: ", d,
"/", f);
e = 1;
}
if (e == 0 && st.st_uid != uid && st.st_uid != 0) {
errno = EACCES;
log_w4("auth: bad owner: ", d, "/", f);
e = 1;
}
if (e)
*err = 1;
else
log_d4("auth: path: ok: ", d, "/", f);
}
int subprocess_auth_checkpath_(char *path, long long pathlen, uid_t uid) {
long long err = 0, j, i;
if (pathlen <= 16) return 0;
if (!getcwd(path, pathlen)) return 0;
for (i = 0; i < pathlen; ++i)
if (path[i] == 0) break;
if (i == pathlen) return 0;
check(uid, path, "authorized_keys", &err);
do {
check(uid, path, 0, &err);
for (j = i; j >= 0; --j) {
if (path[j] == '/') {
path[j] = 0;
i = j;
break;
}
}
} while (j > 0);
return (err == 0);
}
int subprocess_auth_authorizedkeys_(const char *keyname, const char *key,
const char *dir, char *buf,
long long bufmax) {
int fd = -1;
int r;
fd = open_read("authorized_keys");
if (fd == -1) {
log_w3("auth: unable to open file: ", dir, "/.ssh/authorized_keys");
return 0;
}
do {
r = getln(fd, buf, bufmax);
if (r == -1) {
log_w3("auth: unable to read from file ", dir,
"/.ssh/authorized_keys");
return 0;
}
if (findnameandkey(keyname, key, buf)) return 1; /* authorized */
} while (r > 0);
log_w1("auth: unable to authorize using authorized_keys: key not found");
return 0;
}
/*
The 'subprocess_auth' is used for authorization using
~/.ssh/authorized_keys file.
*/
int subprocess_auth(const char *account, const char *keyname, const char *key) {
pid_t pid;
int status;
pid = fork();
if (pid == -1) return -1;
if (pid == 0) {
#define buf global_bspace2 /* reusing global buffer */
struct passwd *pw;
if (!account || !keyname || !key) bug_inval();
if (sshcrypto_sign_BASE64PUBLICKEYMIN > str_len(key) + 1) bug_inval();
/* drop privileges */
pw = getpwnam(account);
if (!pw) {
log_w3("auth: account ", account, ": not exist");
global_die(111);
}
if (!dropuidgid(pw->pw_name, pw->pw_uid, pw->pw_gid)) {
log_w2("auth: unable to drop privileges to account ", account);
global_die(111);
}
/* change directory to ~/.ssh */
if (chdir(pw->pw_dir) == -1) {
log_w2("auth: unable to change directory to ", pw->pw_dir);
global_die(111);
}
if (chdir(".ssh") == -1) {
log_w3("auth: unable to change directory to ", pw->pw_dir, "/.ssh");
global_die(111);
}
/* authorization starts here */
if (!subprocess_auth_checkpath_((char *) buf, sizeof buf, pw->pw_uid))
global_die(111);
if (!subprocess_auth_authorizedkeys_(keyname, key, pw->pw_dir,
(char *) buf, sizeof buf))
global_die(111);
/* authorization ends here */
global_die(0);
}
while (waitpid(pid, &status, 0) != pid) {}
if (!WIFEXITED(status)) return -1;
return WEXITSTATUS(status);
}
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