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authorSamuel Mendoza-Jonas <sam@mendozajonas.com>2018-06-19 16:33:42 +1000
committerSamuel Mendoza-Jonas <sam@mendozajonas.com>2018-12-03 14:39:57 +1100
commit5d7f93f2ee09de515e1e474fd752d52590b51793 (patch)
treee125ada614a82edd27269b873d77a66d99420da0 /lib
parentcfd6bf4f7da1ee71a65f57f28912d43ab757b968 (diff)
downloadtalos-petitboot-5d7f93f2ee09de515e1e474fd752d52590b51793.zip
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lib/crypt: Add helpers for operating on /etc/shadow
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>
Diffstat (limited to 'lib')
-rw-r--r--lib/Makefile.am9
-rw-r--r--lib/crypt/crypt.c217
-rw-r--r--lib/crypt/crypt.h49
3 files changed, 275 insertions, 0 deletions
diff --git a/lib/Makefile.am b/lib/Makefile.am
index 016a14d..69a66c3 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 0000000..b5e183a
--- /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 0000000..4b242f0
--- /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 */
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