[v2,05/13] lib/crypt: Add helpers for operating on /etc/shadow
diff mbox series

Message ID 20181128042012.25916-6-sam@mendozajonas.com
State Accepted
Headers show
Series
  • User support and client permissions
Related show

Commit Message

Samuel Mendoza-Jonas Nov. 28, 2018, 4:20 a.m. UTC
Provides helper functions for reading, writing, and checking against
/etc/shadow. The main use case if for authenticating clients against the
"system" password, which is set as the root password.

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
---
 configure.ac      |  22 +++++
 lib/Makefile.am   |   9 ++
 lib/crypt/crypt.c | 217 ++++++++++++++++++++++++++++++++++++++++++++++
 lib/crypt/crypt.h |  49 +++++++++++
 4 files changed, 297 insertions(+)
 create mode 100644 lib/crypt/crypt.c
 create mode 100644 lib/crypt/crypt.h

Patch
diff mbox series

diff --git a/configure.ac b/configure.ac
index 2bf6e6f6..4151b002 100644
--- a/configure.ac
+++ b/configure.ac
@@ -76,6 +76,27 @@  AC_CHECK_LIB([devmapper], [dm_task_create],
 	[AC_MSG_FAILURE([The libdevmapper development library is required by petitboot.  Try installing the package libdevmapper-dev or device-mapper-devel.])]
 )
 
+AC_ARG_ENABLE(
+	[crypt],
+	[AS_HELP_STRING(
+		[--enable-crypt],
+		[Include crypt support to enable password use [default=no]]
+	)],
+	[],
+	[enable_crypt=no]
+)
+AM_CONDITIONAL([ENABLE_CRYPT], [test "x$enable_crypt" = "xyes"])
+AS_IF([test "x$enable_crypt" = "xyes"],
+      [AC_DEFINE(CRYPT_SUPPORT, 1, [Enable crypt/password support])],
+      []
+)
+AS_IF([test "x$enable_crypt" = "xyes"],
+	AC_CHECK_LIB([crypt], [crypt],
+		[CRYPT_LIBS=-lcrypt],
+		[AC_MSG_FAILURE([shadow/crypt libs required])]
+	)
+)
+
 AC_ARG_WITH([fdt],
 	AS_HELP_STRING([--without-fdt],
 		[Build without libfdt (default: no)]))
@@ -455,6 +476,7 @@  AS_IF(
  
 AC_SUBST([UDEV_LIBS])
 AC_SUBST([DEVMAPPER_LIBS])
+AC_SUBST([CRYPT_LIBS])
 AC_SUBST([FDT_LIBS])
 AC_SUBST([LIBFLASH_LIBS])
 AC_SUBST([LIBTOOL_DEPS])
diff --git a/lib/Makefile.am b/lib/Makefile.am
index 016a14dd..69a66c37 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -35,6 +35,7 @@  lib_libpbcore_la_CFLAGS = \
 
 lib_libpbcore_la_SOURCES = \
 	lib/ccan/endian/endian.h \
+	lib/crypt/crypt.h \
 	lib/file/file.h \
 	lib/file/file.c \
 	lib/fold/fold.h \
@@ -93,3 +94,11 @@  lib_libpbcore_la_SOURCES += \
 	lib/security/none.c
 endif
 endif
+
+if ENABLE_CRYPT
+lib_libpbcore_la_SOURCES += \
+	lib/crypt/crypt.c
+
+lib_libpbcore_la_LDFLAGS += \
+	$(CRYPT_LIBS)
+endif
diff --git a/lib/crypt/crypt.c b/lib/crypt/crypt.c
new file mode 100644
index 00000000..b5e183a9
--- /dev/null
+++ b/lib/crypt/crypt.c
@@ -0,0 +1,217 @@ 
+/*
+ *  Copyright (C) 2018 IBM Corporation
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; version 2 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ */
+#include <string.h>
+#include <errno.h>
+#include <stdlib.h>
+#include <shadow.h>
+#include <crypt.h>
+#include <errno.h>
+
+#include <talloc/talloc.h>
+#include <log/log.h>
+
+#include "crypt.h"
+
+int crypt_set_password_hash(void *ctx, const char *hash)
+{
+	struct spwd **shadow, *entry;
+	bool found_root;
+	int rc, i, n;
+	FILE *fp;
+
+	if (lckpwdf()) {
+		pb_log("Could not obtain access to shadow file\n");
+		return -1;
+	}
+	setspent();
+
+	found_root = false;
+	shadow = NULL;
+	n = 0;
+
+	/* Read all entries and modify the root entry */
+	errno = 0;
+	fp = fopen("/etc/shadow", "r");
+	if (!fp) {
+		pb_log("Could not open shadow file, %m\n");
+		rc = -1;
+		goto out;
+	}
+
+	entry = fgetspent(fp);
+	while (entry) {
+		shadow = talloc_realloc(ctx, shadow, struct spwd *, n + 1);
+		if (!shadow) {
+			pb_log("Failed to allocate shadow struct\n");
+			rc = -1;
+			goto out;
+		}
+
+		shadow[n] = talloc_memdup(shadow, entry, sizeof(struct spwd));
+		if (!shadow[n]) {
+			pb_log("Could not duplicate entry for %s\n",
+					entry->sp_namp);
+			rc = -1;
+			goto out;
+		}
+
+		shadow[n]->sp_namp = talloc_strdup(shadow, entry->sp_namp);
+		if (strncmp(shadow[n]->sp_namp, "root", strlen("root")) == 0) {
+			shadow[n]->sp_pwdp = talloc_strdup(shadow, hash);
+			found_root = true;
+		} else {
+			shadow[n]->sp_pwdp = talloc_strdup(shadow,
+					entry->sp_pwdp);
+		}
+
+		if (!shadow[n]->sp_namp || !shadow[n]->sp_pwdp) {
+			pb_log("Failed to allocate new fields for %s\n",
+					entry->sp_namp);
+			rc = -1;
+			goto out;
+		}
+
+		n++;
+		entry = fgetspent(fp);
+	}
+
+	if (n == 0)
+		pb_debug_fn("No entries found\n");
+
+	fclose(fp);
+
+	if (!found_root) {
+		/* Make our own */
+		pb_debug_fn("No root user found, creating entry\n");
+		shadow = talloc_realloc(ctx, shadow, struct spwd *, n + 1);
+		if (!shadow) {
+			pb_log("Failed to allocate shadow struct\n");
+			rc = -1;
+			goto out;
+		}
+
+		shadow[n] = talloc_zero(shadow, struct spwd);
+		shadow[n]->sp_namp = talloc_asprintf(shadow, "root");
+		shadow[n]->sp_pwdp = talloc_strdup(shadow, hash);
+		if (!shadow[n]->sp_namp || !shadow[n]->sp_pwdp) {
+			pb_log("Failed to allocate new fields for root entry\n");
+			rc = -1;
+			goto out;
+		}
+		n++;
+	}
+
+	errno = 0;
+	fp = fopen("/etc/shadow", "w");
+	if (!fp) {
+		pb_log("Could not open shadow file, %m\n");
+		rc = -1;
+		goto out;
+	}
+
+	/* Write each entry back to keep the same format in /etc/shadow */
+	for (i = 0; i < n; i++) {
+		rc = putspent(shadow[i], fp);
+		if (rc)
+			pb_log("Failed to write back shadow entry for %s!\n",
+					shadow[i]->sp_namp);
+	}
+
+	rc = 0;
+out:
+	if (fp)
+		fclose(fp);
+	talloc_free(shadow);
+	endspent();
+	ulckpwdf();
+	return rc;
+}
+
+static const char *crypt_hash_password(const char *password)
+{
+	struct spwd *shadow;
+	char *hash, *salt;
+	char new_salt[17];
+	int i;
+
+	shadow = getspnam("root");
+	if (!shadow) {
+		pb_log("Could not find root shadow\n");
+		return NULL;
+	}
+
+	if (shadow->sp_pwdp && strlen(shadow->sp_pwdp)) {
+		salt = shadow->sp_pwdp;
+	} else {
+		for (i = 0; i < 16; i++)
+			new_salt[i] = random() % 94 + 32;
+		new_salt[i] = '\0';
+		salt = talloc_asprintf(password, "$6$%s", new_salt);
+	}
+
+	hash = crypt(password ?: "", salt);
+	if (!hash)
+		pb_log("Could not create hash, %m\n");
+
+
+	return hash;
+}
+
+
+int crypt_set_password(void *ctx, const char *password)
+{
+	const char *hash;
+
+	if (!password || !strlen(password))
+		return crypt_set_password_hash(ctx, "");
+
+	hash = crypt_hash_password(password);
+	if (!hash)
+		return -1;
+
+	return crypt_set_password_hash(ctx, hash);
+}
+
+char *crypt_get_hash(void *ctx)
+{
+	struct spwd *shadow;
+
+	shadow = getspnam("root");
+	if (!shadow) {
+		pb_log("Could not find root shadow\n");
+		return false;
+	}
+
+	return talloc_strdup(ctx, shadow->sp_pwdp);
+}
+
+bool crypt_check_password(const char *password)
+{
+	struct spwd *shadow;
+	char *hash;
+
+	shadow = getspnam("root");
+	if (!shadow) {
+		pb_log("Could not find root shadow\n");
+		return false;
+	}
+
+	hash = crypt(password ? : "", shadow->sp_pwdp);
+	if (!hash) {
+		pb_log("Could not create hash, %m\n");
+		return false;
+	}
+
+	return strncmp(shadow->sp_pwdp, hash, strlen(shadow->sp_pwdp)) == 0;
+}
diff --git a/lib/crypt/crypt.h b/lib/crypt/crypt.h
new file mode 100644
index 00000000..4b242f0c
--- /dev/null
+++ b/lib/crypt/crypt.h
@@ -0,0 +1,49 @@ 
+/*
+ *  Copyright (C) 2018 IBM Corporation
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; version 2 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ */
+#ifndef CRYPT_H
+#define CRYPT_H
+
+#include "config.h"
+
+#ifdef CRYPT_SUPPORT
+
+char *crypt_get_hash(void *ctx);
+bool crypt_check_password(const char *password);
+int crypt_set_password(void *ctx, const char *password);
+int crypt_set_password_hash(void *ctx, const char *hash);
+
+#else
+
+static inline char *crypt_get_hash(void *ctx __attribute__((unused)))
+{
+	return NULL;
+}
+static inline bool crypt_check_password(
+		const char *password __attribute__((unused)))
+{
+	return false;
+}
+static inline int crypt_set_password(void *ctx __attribute__((unused)),
+		const char *password __attribute__((unused)))
+{
+	return -1;
+}
+static inline int crypt_set_password_hash(void *ctx __attribute__((unused)),
+		const char *hash __attribute__((unused)))
+{
+	return -1;
+}
+
+#endif
+#endif /* CRYPT_H */