src/pam_ipmisave/pam_ipmisave.c - openbmc/pam-ipmi - Gitiles

 /*
 // Copyright (c) 2018 Intel Corporation
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //      http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 // See the License for the specific language governing permissions and
 // limitations under the License.
 */

 #include <syslog.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <stdarg.h>
 #include <string.h>
 #include <unistd.h>
 #include <sys/stat.h>
 #include <fcntl.h>

 #include <security/pam_modules.h>
 #include <security/pam_ext.h>
 #include <security/pam_modutil.h>

 #include <openssl/evp.h>
 #include <openssl/hmac.h>
 #include <openssl/rand.h>

 /*
  * This module is intended to save password of  special group user
  *
  */

 #define MAX_SPEC_GRP_PASS_LENGTH 20
 #define MAX_SPEC_GRP_USER_LENGTH 16
 #define MAX_KEY_SIZE 8
 #define DEFAULT_SPEC_PASS_FILE "/etc/ipmi_pass"
 #define META_PASSWD_SIG "=OPENBMC="

 /*
  * Meta data struct for storing the encrypted password file
  * Note: Followed by this structure, the real data of hash, iv, encrypted data
  * with pad and mac are stored.
  * Decrypted data will hold user name & password for every new line with format
  * like <user name>:<password>\n
  */
 typedef struct metapassstruct {
 	char signature[10];
 	unsigned char reseved[2];
 	size_t hashsize;
 	size_t ivsize;
 	size_t datasize;
 	size_t padsize;
 	size_t macsize;
 } metapassstruct;

 /**
  * @brief to acquire lock for atomic operation
  * Internally uses lckpwdf to acquire the lock. Tries to acquire the lock
  * using lckpwdf() in interval of 1ms, with maximum of 100 attempts.
  *
  * @return PAM_SUCCESS for success / PAM_AUTHTOK_LOCK_BUSY for failure
  */
 int lock_pwdf(void)
 {
 	int i;
 	int retval;

 	i = 0;
 	while ((retval = lckpwdf()) != 0 && i < 100) {
 		usleep(1000);
 		i++;
 	}
 	if (retval != 0) {
 		return PAM_AUTHTOK_LOCK_BUSY;
 	}
 	return PAM_SUCCESS;
 }

 /**
  * @brief unlock the acquired lock
  * Internally uses ulckpwdf to release the lock
  */
 void unlock_pwdf(void)
 {
 	ulckpwdf();
 }

 /**
  * @brief to get argument value of option
  * Function to get the value of argument options.
  *
  * @param[in] pamh - pam handle
  * @param[in] option - argument option to which value has to returned
  * @param[in] argc - argument count
  * @param[in] argv - array of arguments
  */
 static const char *get_option(const pam_handle_t *pamh, const char *option,
 			      int argc, const char **argv)
 {
 	int i;
 	size_t len;

 	len = strlen(option);

 	for (i = 0; i < argc; ++i) {
 		if (strncmp(option, argv[i], len) == 0) {
 			if (argv[i][len] == '=') {
 				return &argv[i][len + 1];
 			}
 		}
 	}
 	return NULL;
 }

 /**
  * @brief encrypt or decrypt function
  * Function which will do the encryption or decryption of the data.
  *
  * @param[in] pamh - pam handle.
  * @param[in] isencrypt - encrypt or decrypt option.
  * @param[in] cipher - EVP_CIPHER to be used
  * @param[in] key - key which has to be used in EVP_CIPHER api's.
  * @param[in] keylen - Length of the key.
  * @param[in] iv - Initialization vector data, used along with key
  * @param[in] ivlen - Length of IV.
  * @param[in] inbytes - buffer which has to be encrypted or decrypted.
  * @param[in] inbyteslen - length of input buffer.
  * @param[in] outbytes - buffer to store decrypted or encrypted data.
  * @param[in] outbyteslen - length of output buffer
  * @param[in/out] mac - checksum to cross verify. Will be verified for decrypt
  * and returns for encrypt.
  * @param[in/out] maclen - length of checksum
  * @return - 0 for success -1 for failures.
  */
 int encrypt_decrypt_data(const pam_handle_t *pamh, int isencrypt,
 			 const EVP_CIPHER *cipher, const char *key,
 			 size_t keylen, const char *iv, size_t ivlen,
 			 const char *inbytes, size_t inbyteslen, char *outbytes,
 			 size_t *outbyteslen, char *mac, size_t *maclen)
 {
 	EVP_CIPHER_CTX *ctx;
 	const EVP_MD *digest;
 	size_t outEVPlen = 0;
 	int retval = 0;
 	size_t outlen = 0;

 	if (cipher == NULL || key == NULL || iv == NULL || inbytes == NULL
 	    || outbytes == NULL || mac == NULL || inbyteslen == 0
 	    || EVP_CIPHER_key_length(cipher) > keylen
 	    || EVP_CIPHER_iv_length(cipher) > ivlen) {
 		pam_syslog(pamh, LOG_DEBUG, "Invalid inputs");
 		return -1;
 	}

 	digest = EVP_sha256();
 	if (!isencrypt) {
 		char calmac[EVP_MAX_MD_SIZE];
 		size_t calmaclen = 0;
 		// calculate MAC for the encrypted message.
 		if (NULL
 		    == HMAC(digest, key, keylen, inbytes, inbyteslen, calmac,
 			    &calmaclen)) {
 			pam_syslog(pamh, LOG_DEBUG,
 				   "Failed to verify authentication %d",
 				   retval);
 			return -1;
 		}
 		if (!((calmaclen == *maclen)
 		      && (memcmp(calmac, mac, calmaclen) == 0))) {
 			pam_syslog(pamh, LOG_DEBUG,
 				   "Authenticated message doesn't match %d, %d",
 				   calmaclen, *maclen);
 			return -1;
 		}
 	}

 	ctx = EVP_CIPHER_CTX_new();
 	EVP_CIPHER_CTX_set_padding(ctx, 1);

 	// Set key & IV
 	retval = EVP_CipherInit_ex(ctx, cipher, NULL, key, iv, isencrypt);
 	if (!retval) {
 		pam_syslog(pamh, LOG_DEBUG, "EVP_CipherInit_ex failed with %d",
 			   retval);
 		EVP_CIPHER_CTX_free(ctx);
 		return -1;
 	}
 	if ((retval = EVP_CipherUpdate(ctx, outbytes + outlen, &outEVPlen,
 				       inbytes, inbyteslen))) {
 		outlen += outEVPlen;
 		if ((retval = EVP_CipherFinal(ctx, outbytes + outlen,
 					      &outEVPlen))) {
 			outlen += outEVPlen;
 			*outbyteslen = outlen;
 		} else {
 			pam_syslog(pamh, LOG_DEBUG,
 				   "EVP_CipherFinal returns with %d", retval);
 			EVP_CIPHER_CTX_free(ctx);
 			return -1;
 		}
 	} else {
 		pam_syslog(pamh, LOG_DEBUG, "EVP_CipherUpdate returns with %d",
 			   retval);
 		EVP_CIPHER_CTX_free(ctx);
 		return -1;
 	}
 	EVP_CIPHER_CTX_free(ctx);

 	if (isencrypt) {
 		// Create MAC for the encrypted message.
 		if (NULL
 		    == HMAC(digest, key, keylen, outbytes, *outbyteslen, mac,
 			    maclen)) {
 			pam_syslog(pamh, LOG_DEBUG,
 				   "Failed to create authentication %d",
 				   retval);
 			return -1;
 		}
 	}
 	return 0;
 }


 /**
  * @brief get temporary file handle
  * Function to get the temporary file handle, created using mkstemp
  *
  * @param[in] pamh - pam handle.
  * @param[in/out] tempfilename - tempfilename, which will be used in mkstemp.
  * @return - FILE handle for success. NULL for failure
  */
 FILE *get_temp_file_handle(const pam_handle_t *pamh, char *const tempfilename)
 {
 	FILE *tempfile = NULL;
 	int fd;
 	int oldmask = umask(077);
 	fd = mkstemp(tempfilename);
 	if (fd == -1) {
 		pam_syslog(pamh, LOG_DEBUG, "Error in creating temp file");
 		umask(oldmask);
 		return NULL;
 	}
 	pam_syslog(pamh, LOG_DEBUG, "Temporary file name is %s", tempfilename);

 	tempfile = fdopen(fd, "w");
 	umask(oldmask);
 	return tempfile;
 }


 /**
  * @brief updates special password file
  * Function to update the special password file. Stores the password against
  * username in encrypted form along with meta data
  *
  * @param[in] pamh - pam handle.
  * @param[in] keyfilename - file name where key seed is stored.
  * @param[in] filename - special password file name
  * @param[in] forwho - name of the user
  * @param[in] towhat - password that has to stored in encrypted form
  * @return - PAM_SUCCESS for success or PAM_AUTHTOK_ERR for failure
  */
 int update_pass_special_file(const pam_handle_t *pamh, const char *keyfilename,
 			     const char *filename, const char *forwho,
 			     const char *towhat)
 {
 	struct stat st;
 	FILE *pwfile = NULL, *opwfile = NULL, *keyfile = NULL;
 	int err = 0, wroteentry = 0;
 	char tempfilename[1024];
 	size_t forwholen = strlen(forwho);
 	size_t towhatlen = strlen(towhat);
 	char keybuff[MAX_KEY_SIZE] = {0};
 	size_t keybuffsize = sizeof(keybuff);

 	const EVP_CIPHER *cipher = EVP_aes_128_cbc();
 	const EVP_MD *digest = EVP_sha256();

 	char *linebuff = NULL, *opwfilebuff = NULL, *opwptext = NULL;
 	size_t opwptextlen = 0, opwfilesize = 0;
 	metapassstruct *opwmp = NULL;

 	char *pwptext = NULL, *pwctext = NULL;
 	size_t pwctextlen = 0, pwptextlen = 0, maclen = 0;
 	size_t writtensize = 0, keylen = 0;
 	metapassstruct pwmp = {META_PASSWD_SIG, {0, 0}, .0, 0, 0, 0, 0};
 	char mac[EVP_MAX_MD_SIZE] = {0};
 	unsigned char key[EVP_MAX_KEY_LENGTH];
 	char iv[EVP_CIPHER_iv_length(cipher)];
 	char hash[EVP_MD_block_size(digest)];

 	// Following steps are performed in this function.
 	// Step 1: Create a temporary file - always update temporary file, and
 	// then swap it with original one, only if everything succeded at the
 	// end. Step 2: If file already exists, read the old file and decrypt it
 	// in buffer Step 3: Copy user/password pair from old buffer to new
 	// buffer, and update, if the user already exists with the new password
 	// Step 4: Encrypt the new buffer and write it to the temp file created
 	// at Step 1.
 	// Step 5. rename the temporary file name as special password file.

 	// verify the tempfilename buffer is enough to hold
 	// filename_XXXXXX (+1 for null).
 	if (strlen(filename)
 	    > (sizeof(tempfilename) - strlen("__XXXXXX") - 1)) {
 		pam_syslog(pamh, LOG_DEBUG, "Not enough buffer, bailing out");
 		return PAM_AUTHTOK_ERR;
 	}
 	// Fetch the key from key file name.
 	keyfile = fopen(keyfilename, "r");
 	if (keyfile == NULL) {
 		pam_syslog(pamh, LOG_DEBUG, "Unable to open key file %s",
 			   keyfilename);
 		return PAM_AUTHTOK_ERR;
 	}
 	if (fread(keybuff, 1, keybuffsize, keyfile) != keybuffsize) {
 		pam_syslog(pamh, LOG_DEBUG, "Key file read failed");
 		fclose(keyfile);
 		return PAM_AUTHTOK_ERR;
 	}
 	fclose(keyfile);

 	// Step 1: Try to create a temporary file, in which all the update will
 	// happen then it will be renamed to the original file. This is done to
 	// have atomic operation.
 	snprintf(tempfilename, sizeof(tempfilename), "%s__XXXXXX", filename);
 	pwfile = get_temp_file_handle(pamh, tempfilename);
 	if (pwfile == NULL) {
 		err = 1;
 		goto done;
 	}

 	// Update temporary file stat by reading the special password file
 	opwfile = fopen(filename, "r");
 	if (opwfile != NULL) {
 		if (fstat(fileno(opwfile), &st) == -1) {
 			fclose(opwfile);
 			fclose(pwfile);
 			err = 1;
 			goto done;
 		}
 	} else { // Create with this settings if file is not present.
 		memset(&st, 0, sizeof(st));
 	}
 	// Override the file permission with S_IWUSR | S_IRUSR
 	st.st_mode = S_IWUSR | S_IRUSR;
 	if ((fchown(fileno(pwfile), st.st_uid, st.st_gid) == -1)
 	    || (fchmod(fileno(pwfile), st.st_mode) == -1)) {
 		if (opwfile != NULL) {
 			fclose(opwfile);
 		}
 		fclose(pwfile);
 		err = 1;
 		goto done;
 	}
 	opwfilesize = st.st_size;

 	// Step 2: Read existing special password file and decrypt the data.
 	if (opwfilesize) {
 		opwfilebuff = malloc(opwfilesize);
 		if (opwfilebuff == NULL) {
 			fclose(opwfile);
 			fclose(pwfile);
 			err = 1;
 			goto done;
 		}

 		if (fread(opwfilebuff, 1, opwfilesize, opwfile)) {
 			opwmp = (metapassstruct *)opwfilebuff;
 			opwptext = malloc(opwmp->datasize + opwmp->padsize);
 			if (opwptext == NULL) {
 				free(opwfilebuff);
 				fclose(opwfile);
 				fclose(pwfile);
 				err = 1;
 				goto done;
 			}
 			// User & password pairs are mapped as <user
 			// name>:<password>\n. Add +3 for special chars ':',
 			// '\n' and '\0'.
 			pwptextlen = opwmp->datasize + forwholen + towhatlen + 3
 				     + EVP_CIPHER_block_size(cipher);
 			pwptext = malloc(pwptextlen);
 			if (pwptext == NULL) {
 				free(opwptext);
 				free(opwfilebuff);
 				fclose(opwfile);
 				fclose(pwfile);
 				err = 1;
 				goto done;
 			}

 			// First get the hashed key to decrypt
 			HMAC(digest, keybuff, keybuffsize,
 			     opwfilebuff + sizeof(*opwmp), opwmp->hashsize, key,
 			     &keylen);

 			// Skip decryption if there is no data
 			if (opwmp->datasize != 0) {
 				// Do the decryption
 				if (encrypt_decrypt_data(
 					    pamh, 0, cipher, key, keylen,
 					    opwfilebuff + sizeof(*opwmp)
 						    + opwmp->hashsize,
 					    opwmp->ivsize,
 					    opwfilebuff + sizeof(*opwmp)
 						    + opwmp->hashsize
 						    + opwmp->ivsize,
 					    opwmp->datasize + opwmp->padsize,
 					    opwptext, &opwptextlen,
 					    opwfilebuff + sizeof(*opwmp)
 						    + opwmp->hashsize
 						    + opwmp->ivsize
 						    + opwmp->datasize
 						    + opwmp->padsize,
 					    &opwmp->macsize)
 				    != 0) {
 					pam_syslog(pamh, LOG_DEBUG,
 						   "Decryption failed");
 					free(pwptext);
 					free(opwptext);
 					free(opwfilebuff);
 					fclose(opwfile);
 					fclose(pwfile);
 					err = 1;
 					goto done;
 				}
 			}

 			// NULL terminate it, before using it in strtok().
 			opwptext[opwmp->datasize] = '\0';

 			linebuff = strtok(opwptext, "\n");
 			// Step 3: Copy the existing user/password pair
 			// to the new buffer, and update the password if user
 			// already exists.
 			while (linebuff != NULL) {
 				if ((!strncmp(linebuff, forwho, forwholen))
 				    && (linebuff[forwholen] == ':')) {
 					writtensize += snprintf(
 						pwptext + writtensize,
 						pwptextlen - writtensize,
 						"%s:%s\n", forwho, towhat);
 					wroteentry = 1;
 				} else {
 					writtensize += snprintf(
 						pwptext + writtensize,
 						pwptextlen - writtensize,
 						"%s\n", linebuff);
 				}
 				linebuff = strtok(NULL, "\n");
 			}
 		}
 		// Clear the old password related buffers here, as we are done
 		// with it.
 		free(opwfilebuff);
 		free(opwptext);
 	} else {
 		pwptextlen = forwholen + towhatlen + 3
 			     + EVP_CIPHER_block_size(cipher);
 		pwptext = malloc(pwptextlen);
 		if (pwptext == NULL) {
 			if (opwfile != NULL) {
 				fclose(opwfile);
 			}
 			fclose(pwfile);
 			err = 1;
 			goto done;
 		}
 	}

 	if (opwfile != NULL) {
 		fclose(opwfile);
 	}

 	if (!wroteentry) {
 		// Write the new user:password pair at the end.
 		writtensize += snprintf(pwptext + writtensize,
 					pwptextlen - writtensize, "%s:%s\n",
 					forwho, towhat);
 	}
 	pwptextlen = writtensize;

 	// Step 4: Encrypt the data and write to the temporary file
 	if (RAND_bytes(hash, EVP_MD_block_size(digest)) != 1) {
 		pam_syslog(pamh, LOG_DEBUG,
 			   "Hash genertion failed, bailing out");
 		free(pwptext);
 		fclose(pwfile);
 		err = 1;
 		goto done;
 	}

 	// Generate hash key, which will be used for encryption.
 	HMAC(digest, keybuff, keybuffsize, hash, EVP_MD_block_size(digest), key,
 	     &keylen);
 	// Generate IV values
 	if (RAND_bytes(iv, EVP_CIPHER_iv_length(cipher)) != 1) {
 		pam_syslog(pamh, LOG_DEBUG,
 			   "IV generation failed, bailing out");
 		free(pwptext);
 		fclose(pwfile);
 		err = 1;
 		goto done;
 	}

 	// Buffer to store encrypted message.
 	pwctext = malloc(pwptextlen + EVP_CIPHER_block_size(cipher));
 	if (pwctext == NULL) {
 		pam_syslog(pamh, LOG_DEBUG, "Ctext buffer failed, bailing out");
 		free(pwptext);
 		fclose(pwfile);
 		err = 1;
 		goto done;
 	}

 	// Do the encryption
 	if (encrypt_decrypt_data(pamh, 1, cipher, key, keylen, iv,
 				 EVP_CIPHER_iv_length(cipher), pwptext,
 				 pwptextlen, pwctext, &pwctextlen, mac, &maclen)
 	    != 0) {
 		pam_syslog(pamh, LOG_DEBUG, "Encryption failed");
 		free(pwctext);
 		free(pwptext);
 		fclose(pwfile);
 		err = 1;
 		goto done;
 	}

 	// Update the meta password structure.
 	pwmp.hashsize = EVP_MD_block_size(digest);
 	pwmp.ivsize = EVP_CIPHER_iv_length(cipher);
 	pwmp.datasize = writtensize;
 	pwmp.padsize = pwctextlen - writtensize;
 	pwmp.macsize = maclen;

 	// Write the meta password structure, followed by hash, iv, encrypted
 	// data & mac.
 	if (fwrite(&pwmp, 1, sizeof(pwmp), pwfile) != sizeof(pwmp)) {
 		pam_syslog(pamh, LOG_DEBUG, "Error in writing meta data");
 		err = 1;
 	}
 	if (fwrite(hash, 1, pwmp.hashsize, pwfile) != pwmp.hashsize) {
 		pam_syslog(pamh, LOG_DEBUG, "Error in writing hash data");
 		err = 1;
 	}
 	if (fwrite(iv, 1, pwmp.ivsize, pwfile) != pwmp.ivsize) {
 		pam_syslog(pamh, LOG_DEBUG, "Error in writing IV data");
 		err = 1;
 	}
 	if (fwrite(pwctext, 1, pwctextlen, pwfile) != pwctextlen) {
 		pam_syslog(pamh, LOG_DEBUG, "Error in encrypted data");
 		err = 1;
 	}
 	if (fwrite(mac, 1, maclen, pwfile) != maclen) {
 		pam_syslog(pamh, LOG_DEBUG, "Error in writing MAC");
 		err = 1;
 	}

 	free(pwctext);
 	free(pwptext);

 	if (fflush(pwfile) || fsync(fileno(pwfile))) {
 		pam_syslog(
 			pamh, LOG_DEBUG,
 			"fflush or fsync error writing entries to special file: %s",
 			tempfilename);
 		err = 1;
 	}

 	if (fclose(pwfile)) {
 		pam_syslog(pamh, LOG_DEBUG,
 			   "fclose error writing entries to special file: %s",
 			   tempfilename);
 		err = 1;
 	}

 done:
 	if (!err) {
 		// Step 5: Rename the temporary file as special password file.
 		if (!rename(tempfilename, filename)) {
 			pam_syslog(pamh, LOG_DEBUG,
 				   "password changed for %s in special file",
 				   forwho);
 		} else {
 			err = 1;
 		}
 	}

 	// Clear out the key buff.
 	memset(keybuff, 0, keybuffsize);

 	if (!err) {
 		return PAM_SUCCESS;
 	} else {
 		unlink(tempfilename);
 		return PAM_AUTHTOK_ERR;
 	}
 }


 /* Password Management API's */

 /**
  * @brief pam_sm_chauthtok API
  * Function which will be called for pam_chauthtok() calls.
  *
  * @param[in] pamh - pam handle
  * @param[in] flags - pam calls related flags
  * @param[in] argc - argument counts / options
  * @param[in] argv - array of arguments / options
  * @return - PAM_SUCCESS for success, others for failure
  */
 int pam_sm_chauthtok(pam_handle_t *pamh, int flags, int argc, const char **argv)
 {
 	int retval = -1;
 	const void *item = NULL;
 	const char *user = NULL;
 	const char *pass_new = NULL, *pass_old = NULL;
 	const char *spec_grp_name =
 		get_option(pamh, "spec_grp_name", argc, argv);
 	const char *spec_pass_file =
 		get_option(pamh, "spec_pass_file", argc, argv);
 	const char *key_file = get_option(pamh, "key_file", argc, argv);


 	if (spec_grp_name == NULL || key_file == NULL) {
 		return PAM_IGNORE;
 	}
 	if (flags & PAM_PRELIM_CHECK) {
 		// send success to verify other stacked modules prelim check.
 		return PAM_SUCCESS;
 	}

 	retval = pam_get_user(pamh, &user, NULL);
 	if (retval != PAM_SUCCESS) {
 		return retval;
 	}

 	// get  already read password by the stacked pam module
 	// Note: If there are no previous stacked pam module which read
 	// the new password, then return with AUTHTOK_ERR

 	retval = pam_get_item(pamh, PAM_AUTHTOK, &item);
 	if (retval != PAM_SUCCESS || item == NULL) {
 		return PAM_AUTHTOK_ERR;
 	}
 	pass_new = item;

 	struct group *grp;
 	int spec_grp_usr = 0;
 	// Verify whether the user belongs to special group.
 	grp = pam_modutil_getgrnam(pamh, spec_grp_name);
 	if (grp != NULL) {
 		while (*(grp->gr_mem) != NULL) {
 			if (strcmp(user, *grp->gr_mem) == 0) {
 				spec_grp_usr = 1;
 				break;
 			}
 			(grp->gr_mem)++;
 		}
 	}

 	pam_syslog(pamh, LOG_DEBUG, "User belongs to special grp: %x",
 		   spec_grp_usr);

 	if (spec_grp_usr) {
 		// verify the new password is acceptable.
 		size_t pass_len = strlen(pass_new);
 		size_t user_len = strlen(user);
 		if (pass_len > MAX_SPEC_GRP_PASS_LENGTH
 		    || user_len > MAX_SPEC_GRP_USER_LENGTH) {
 			pam_syslog(
 				pamh, LOG_ERR,
 				"Password length (%zu) / User name length (%zu) is not acceptable for IPMI",
 				pass_len, user_len);
 			pass_new = pass_old = NULL;
 			return PAM_AUTHTOK_ERR;
 		}
 		if (spec_pass_file == NULL) {
 			spec_pass_file = DEFAULT_SPEC_PASS_FILE;
 			pam_syslog(
 				pamh, LOG_ERR,
 				"Using default special password file name :%s",
 				spec_pass_file);
 		}
 		if (retval = lock_pwdf()) {
 			pam_syslog(pamh, LOG_ERR,
 				   "Failed to lock the passwd file");
 			return retval;
 		}
 		retval = update_pass_special_file(
 			pamh, key_file, spec_pass_file, user, pass_new);
 		unlock_pwdf();
 		return retval;
 	}

 	return PAM_SUCCESS;
 }

 /* end of module definition */
	/*
	// Copyright (c) 2018 Intel Corporation
	//
	// Licensed under the Apache License, Version 2.0 (the "License");
	// you may not use this file except in compliance with the License.
	// You may obtain a copy of the License at
	//
	// http://www.apache.org/licenses/LICENSE-2.0
	//
	// Unless required by applicable law or agreed to in writing, software
	// distributed under the License is distributed on an "AS IS" BASIS,
	// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	// See the License for the specific language governing permissions and
	// limitations under the License.
	*/

	#include <syslog.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <stdarg.h>
	#include <string.h>
	#include <unistd.h>
	#include <sys/stat.h>
	#include <fcntl.h>

	#include <security/pam_modules.h>
	#include <security/pam_ext.h>
	#include <security/pam_modutil.h>

	#include <openssl/evp.h>
	#include <openssl/hmac.h>
	#include <openssl/rand.h>

	/*
	* This module is intended to save password of special group user
	*
	*/

	#define MAX_SPEC_GRP_PASS_LENGTH 20
	#define MAX_SPEC_GRP_USER_LENGTH 16
	#define MAX_KEY_SIZE 8
	#define DEFAULT_SPEC_PASS_FILE "/etc/ipmi_pass"
	#define META_PASSWD_SIG "=OPENBMC="

	/*
	* Meta data struct for storing the encrypted password file
	* Note: Followed by this structure, the real data of hash, iv, encrypted data
	* with pad and mac are stored.
	* Decrypted data will hold user name & password for every new line with format
	* like <user name>:<password>\n
	*/
	typedef struct metapassstruct {
	char signature[10];
	unsigned char reseved[2];
	size_t hashsize;
	size_t ivsize;
	size_t datasize;
	size_t padsize;
	size_t macsize;
	} metapassstruct;

	/**
	* @brief to acquire lock for atomic operation
	* Internally uses lckpwdf to acquire the lock. Tries to acquire the lock
	* using lckpwdf() in interval of 1ms, with maximum of 100 attempts.
	*
	* @return PAM_SUCCESS for success / PAM_AUTHTOK_LOCK_BUSY for failure
	*/
	int lock_pwdf(void)
	{
	int i;
	int retval;

	i = 0;
	while ((retval = lckpwdf()) != 0 && i < 100) {
	usleep(1000);
	i++;
	}
	if (retval != 0) {
	return PAM_AUTHTOK_LOCK_BUSY;
	}
	return PAM_SUCCESS;
	}

	/**
	* @brief unlock the acquired lock
	* Internally uses ulckpwdf to release the lock
	*/
	void unlock_pwdf(void)
	{
	ulckpwdf();
	}

	/**
	* @brief to get argument value of option
	* Function to get the value of argument options.
	*
	* @param[in] pamh - pam handle
	* @param[in] option - argument option to which value has to returned
	* @param[in] argc - argument count
	* @param[in] argv - array of arguments
	*/
	static const char get_option(const pam_handle_t pamh, const char *option,
	int argc, const char **argv)
	{
	int i;
	size_t len;

	len = strlen(option);

	for (i = 0; i < argc; ++i) {
	if (strncmp(option, argv[i], len) == 0) {
	if (argv[i][len] == '=') {
	return &argv[i][len + 1];
	}
	}
	}
	return NULL;
	}

	/**
	* @brief encrypt or decrypt function
	* Function which will do the encryption or decryption of the data.
	*
	* @param[in] pamh - pam handle.
	* @param[in] isencrypt - encrypt or decrypt option.
	* @param[in] cipher - EVP_CIPHER to be used
	* @param[in] key - key which has to be used in EVP_CIPHER api's.
	* @param[in] keylen - Length of the key.
	* @param[in] iv - Initialization vector data, used along with key
	* @param[in] ivlen - Length of IV.
	* @param[in] inbytes - buffer which has to be encrypted or decrypted.
	* @param[in] inbyteslen - length of input buffer.
	* @param[in] outbytes - buffer to store decrypted or encrypted data.
	* @param[in] outbyteslen - length of output buffer
	* @param[in/out] mac - checksum to cross verify. Will be verified for decrypt
	* and returns for encrypt.
	* @param[in/out] maclen - length of checksum
	* @return - 0 for success -1 for failures.
	*/
	int encrypt_decrypt_data(const pam_handle_t *pamh, int isencrypt,
	const EVP_CIPHER cipher, const char key,
	size_t keylen, const char *iv, size_t ivlen,
	const char inbytes, size_t inbyteslen, char outbytes,
	size_t outbyteslen, char mac, size_t *maclen)
	{
	EVP_CIPHER_CTX *ctx;
	const EVP_MD *digest;
	size_t outEVPlen = 0;
	int retval = 0;
	size_t outlen = 0;

	if (cipher == NULL \|\| key == NULL \|\| iv == NULL \|\| inbytes == NULL
	\|\| outbytes == NULL \|\| mac == NULL \|\| inbyteslen == 0
	\|\| EVP_CIPHER_key_length(cipher) > keylen
	\|\| EVP_CIPHER_iv_length(cipher) > ivlen) {
	pam_syslog(pamh, LOG_DEBUG, "Invalid inputs");
	return -1;
	}

	digest = EVP_sha256();
	if (!isencrypt) {
	char calmac[EVP_MAX_MD_SIZE];
	size_t calmaclen = 0;
	// calculate MAC for the encrypted message.
	if (NULL
	== HMAC(digest, key, keylen, inbytes, inbyteslen, calmac,
	&calmaclen)) {
	pam_syslog(pamh, LOG_DEBUG,
	"Failed to verify authentication %d",
	retval);
	return -1;
	}
	if (!((calmaclen == *maclen)
	&& (memcmp(calmac, mac, calmaclen) == 0))) {
	pam_syslog(pamh, LOG_DEBUG,
	"Authenticated message doesn't match %d, %d",
	calmaclen, *maclen);
	return -1;
	}
	}

	ctx = EVP_CIPHER_CTX_new();
	EVP_CIPHER_CTX_set_padding(ctx, 1);

	// Set key & IV
	retval = EVP_CipherInit_ex(ctx, cipher, NULL, key, iv, isencrypt);
	if (!retval) {
	pam_syslog(pamh, LOG_DEBUG, "EVP_CipherInit_ex failed with %d",
	retval);
	EVP_CIPHER_CTX_free(ctx);
	return -1;
	}
	if ((retval = EVP_CipherUpdate(ctx, outbytes + outlen, &outEVPlen,
	inbytes, inbyteslen))) {
	outlen += outEVPlen;
	if ((retval = EVP_CipherFinal(ctx, outbytes + outlen,
	&outEVPlen))) {
	outlen += outEVPlen;
	*outbyteslen = outlen;
	} else {
	pam_syslog(pamh, LOG_DEBUG,
	"EVP_CipherFinal returns with %d", retval);
	EVP_CIPHER_CTX_free(ctx);
	return -1;
	}
	} else {
	pam_syslog(pamh, LOG_DEBUG, "EVP_CipherUpdate returns with %d",
	retval);
	EVP_CIPHER_CTX_free(ctx);
	return -1;
	}
	EVP_CIPHER_CTX_free(ctx);

	if (isencrypt) {
	// Create MAC for the encrypted message.
	if (NULL
	== HMAC(digest, key, keylen, outbytes, *outbyteslen, mac,
	maclen)) {
	pam_syslog(pamh, LOG_DEBUG,
	"Failed to create authentication %d",
	retval);
	return -1;
	}
	}
	return 0;
	}


	/**
	* @brief get temporary file handle
	* Function to get the temporary file handle, created using mkstemp
	*
	* @param[in] pamh - pam handle.
	* @param[in/out] tempfilename - tempfilename, which will be used in mkstemp.
	* @return - FILE handle for success. NULL for failure
	*/
	FILE get_temp_file_handle(const pam_handle_t pamh, char *const tempfilename)
	{
	FILE *tempfile = NULL;
	int fd;
	int oldmask = umask(077);
	fd = mkstemp(tempfilename);
	if (fd == -1) {
	pam_syslog(pamh, LOG_DEBUG, "Error in creating temp file");
	umask(oldmask);
	return NULL;
	}
	pam_syslog(pamh, LOG_DEBUG, "Temporary file name is %s", tempfilename);

	tempfile = fdopen(fd, "w");
	umask(oldmask);
	return tempfile;
	}


	/**
	* @brief updates special password file
	* Function to update the special password file. Stores the password against
	* username in encrypted form along with meta data
	*
	* @param[in] pamh - pam handle.
	* @param[in] keyfilename - file name where key seed is stored.
	* @param[in] filename - special password file name
	* @param[in] forwho - name of the user
	* @param[in] towhat - password that has to stored in encrypted form
	* @return - PAM_SUCCESS for success or PAM_AUTHTOK_ERR for failure
	*/
	int update_pass_special_file(const pam_handle_t pamh, const char keyfilename,
	const char filename, const char forwho,
	const char *towhat)
	{
	struct stat st;
	FILE pwfile = NULL, opwfile = NULL, *keyfile = NULL;
	int err = 0, wroteentry = 0;
	char tempfilename[1024];
	size_t forwholen = strlen(forwho);
	size_t towhatlen = strlen(towhat);
	char keybuff[MAX_KEY_SIZE] = {0};
	size_t keybuffsize = sizeof(keybuff);

	const EVP_CIPHER *cipher = EVP_aes_128_cbc();
	const EVP_MD *digest = EVP_sha256();

	char linebuff = NULL, opwfilebuff = NULL, *opwptext = NULL;
	size_t opwptextlen = 0, opwfilesize = 0;
	metapassstruct *opwmp = NULL;

	char pwptext = NULL, pwctext = NULL;
	size_t pwctextlen = 0, pwptextlen = 0, maclen = 0;
	size_t writtensize = 0, keylen = 0;
	metapassstruct pwmp = {META_PASSWD_SIG, {0, 0}, .0, 0, 0, 0, 0};
	char mac[EVP_MAX_MD_SIZE] = {0};
	unsigned char key[EVP_MAX_KEY_LENGTH];
	char iv[EVP_CIPHER_iv_length(cipher)];
	char hash[EVP_MD_block_size(digest)];

	// Following steps are performed in this function.
	// Step 1: Create a temporary file - always update temporary file, and
	// then swap it with original one, only if everything succeded at the
	// end. Step 2: If file already exists, read the old file and decrypt it
	// in buffer Step 3: Copy user/password pair from old buffer to new
	// buffer, and update, if the user already exists with the new password
	// Step 4: Encrypt the new buffer and write it to the temp file created
	// at Step 1.
	// Step 5. rename the temporary file name as special password file.

	// verify the tempfilename buffer is enough to hold
	// filename_XXXXXX (+1 for null).
	if (strlen(filename)
	> (sizeof(tempfilename) - strlen("__XXXXXX") - 1)) {
	pam_syslog(pamh, LOG_DEBUG, "Not enough buffer, bailing out");
	return PAM_AUTHTOK_ERR;
	}
	// Fetch the key from key file name.
	keyfile = fopen(keyfilename, "r");
	if (keyfile == NULL) {
	pam_syslog(pamh, LOG_DEBUG, "Unable to open key file %s",
	keyfilename);
	return PAM_AUTHTOK_ERR;
	}
	if (fread(keybuff, 1, keybuffsize, keyfile) != keybuffsize) {
	pam_syslog(pamh, LOG_DEBUG, "Key file read failed");
	fclose(keyfile);
	return PAM_AUTHTOK_ERR;
	}
	fclose(keyfile);

	// Step 1: Try to create a temporary file, in which all the update will
	// happen then it will be renamed to the original file. This is done to
	// have atomic operation.
	snprintf(tempfilename, sizeof(tempfilename), "%s__XXXXXX", filename);
	pwfile = get_temp_file_handle(pamh, tempfilename);
	if (pwfile == NULL) {
	err = 1;
	goto done;
	}

	// Update temporary file stat by reading the special password file
	opwfile = fopen(filename, "r");
	if (opwfile != NULL) {
	if (fstat(fileno(opwfile), &st) == -1) {
	fclose(opwfile);
	fclose(pwfile);
	err = 1;
	goto done;
	}
	} else { // Create with this settings if file is not present.
	memset(&st, 0, sizeof(st));
	}
	// Override the file permission with S_IWUSR \| S_IRUSR
	st.st_mode = S_IWUSR \| S_IRUSR;
	if ((fchown(fileno(pwfile), st.st_uid, st.st_gid) == -1)
	\|\| (fchmod(fileno(pwfile), st.st_mode) == -1)) {
	if (opwfile != NULL) {
	fclose(opwfile);
	}
	fclose(pwfile);
	err = 1;
	goto done;
	}
	opwfilesize = st.st_size;

	// Step 2: Read existing special password file and decrypt the data.
	if (opwfilesize) {
	opwfilebuff = malloc(opwfilesize);
	if (opwfilebuff == NULL) {
	fclose(opwfile);
	fclose(pwfile);
	err = 1;
	goto done;
	}

	if (fread(opwfilebuff, 1, opwfilesize, opwfile)) {
	opwmp = (metapassstruct *)opwfilebuff;
	opwptext = malloc(opwmp->datasize + opwmp->padsize);
	if (opwptext == NULL) {
	free(opwfilebuff);
	fclose(opwfile);
	fclose(pwfile);
	err = 1;
	goto done;
	}
	// User & password pairs are mapped as <user
	// name>:<password>\n. Add +3 for special chars ':',
	// '\n' and '\0'.
	pwptextlen = opwmp->datasize + forwholen + towhatlen + 3
	+ EVP_CIPHER_block_size(cipher);
	pwptext = malloc(pwptextlen);
	if (pwptext == NULL) {
	free(opwptext);
	free(opwfilebuff);
	fclose(opwfile);
	fclose(pwfile);
	err = 1;
	goto done;
	}

	// First get the hashed key to decrypt
	HMAC(digest, keybuff, keybuffsize,
	opwfilebuff + sizeof(*opwmp), opwmp->hashsize, key,
	&keylen);

	// Skip decryption if there is no data
	if (opwmp->datasize != 0) {
	// Do the decryption
	if (encrypt_decrypt_data(
	pamh, 0, cipher, key, keylen,
	opwfilebuff + sizeof(*opwmp)
	+ opwmp->hashsize,
	opwmp->ivsize,
	opwfilebuff + sizeof(*opwmp)
	+ opwmp->hashsize
	+ opwmp->ivsize,
	opwmp->datasize + opwmp->padsize,
	opwptext, &opwptextlen,
	opwfilebuff + sizeof(*opwmp)
	+ opwmp->hashsize
	+ opwmp->ivsize
	+ opwmp->datasize
	+ opwmp->padsize,
	&opwmp->macsize)
	!= 0) {
	pam_syslog(pamh, LOG_DEBUG,
	"Decryption failed");
	free(pwptext);
	free(opwptext);
	free(opwfilebuff);
	fclose(opwfile);
	fclose(pwfile);
	err = 1;
	goto done;
	}
	}

	// NULL terminate it, before using it in strtok().
	opwptext[opwmp->datasize] = '\0';

	linebuff = strtok(opwptext, "\n");
	// Step 3: Copy the existing user/password pair
	// to the new buffer, and update the password if user
	// already exists.
	while (linebuff != NULL) {
	if ((!strncmp(linebuff, forwho, forwholen))
	&& (linebuff[forwholen] == ':')) {
	writtensize += snprintf(
	pwptext + writtensize,
	pwptextlen - writtensize,
	"%s:%s\n", forwho, towhat);
	wroteentry = 1;
	} else {
	writtensize += snprintf(
	pwptext + writtensize,
	pwptextlen - writtensize,
	"%s\n", linebuff);
	}
	linebuff = strtok(NULL, "\n");
	}
	}
	// Clear the old password related buffers here, as we are done
	// with it.
	free(opwfilebuff);
	free(opwptext);
	} else {
	pwptextlen = forwholen + towhatlen + 3
	+ EVP_CIPHER_block_size(cipher);
	pwptext = malloc(pwptextlen);
	if (pwptext == NULL) {
	if (opwfile != NULL) {
	fclose(opwfile);
	}
	fclose(pwfile);
	err = 1;
	goto done;
	}
	}

	if (opwfile != NULL) {
	fclose(opwfile);
	}

	if (!wroteentry) {
	// Write the new user:password pair at the end.
	writtensize += snprintf(pwptext + writtensize,
	pwptextlen - writtensize, "%s:%s\n",
	forwho, towhat);
	}
	pwptextlen = writtensize;

	// Step 4: Encrypt the data and write to the temporary file
	if (RAND_bytes(hash, EVP_MD_block_size(digest)) != 1) {
	pam_syslog(pamh, LOG_DEBUG,
	"Hash genertion failed, bailing out");
	free(pwptext);
	fclose(pwfile);
	err = 1;
	goto done;
	}

	// Generate hash key, which will be used for encryption.
	HMAC(digest, keybuff, keybuffsize, hash, EVP_MD_block_size(digest), key,
	&keylen);
	// Generate IV values
	if (RAND_bytes(iv, EVP_CIPHER_iv_length(cipher)) != 1) {
	pam_syslog(pamh, LOG_DEBUG,
	"IV generation failed, bailing out");
	free(pwptext);
	fclose(pwfile);
	err = 1;
	goto done;
	}

	// Buffer to store encrypted message.
	pwctext = malloc(pwptextlen + EVP_CIPHER_block_size(cipher));
	if (pwctext == NULL) {
	pam_syslog(pamh, LOG_DEBUG, "Ctext buffer failed, bailing out");
	free(pwptext);
	fclose(pwfile);
	err = 1;
	goto done;
	}

	// Do the encryption
	if (encrypt_decrypt_data(pamh, 1, cipher, key, keylen, iv,
	EVP_CIPHER_iv_length(cipher), pwptext,
	pwptextlen, pwctext, &pwctextlen, mac, &maclen)
	!= 0) {
	pam_syslog(pamh, LOG_DEBUG, "Encryption failed");
	free(pwctext);
	free(pwptext);
	fclose(pwfile);
	err = 1;
	goto done;
	}

	// Update the meta password structure.
	pwmp.hashsize = EVP_MD_block_size(digest);
	pwmp.ivsize = EVP_CIPHER_iv_length(cipher);
	pwmp.datasize = writtensize;
	pwmp.padsize = pwctextlen - writtensize;
	pwmp.macsize = maclen;

	// Write the meta password structure, followed by hash, iv, encrypted
	// data & mac.
	if (fwrite(&pwmp, 1, sizeof(pwmp), pwfile) != sizeof(pwmp)) {
	pam_syslog(pamh, LOG_DEBUG, "Error in writing meta data");
	err = 1;
	}
	if (fwrite(hash, 1, pwmp.hashsize, pwfile) != pwmp.hashsize) {
	pam_syslog(pamh, LOG_DEBUG, "Error in writing hash data");
	err = 1;
	}
	if (fwrite(iv, 1, pwmp.ivsize, pwfile) != pwmp.ivsize) {
	pam_syslog(pamh, LOG_DEBUG, "Error in writing IV data");
	err = 1;
	}
	if (fwrite(pwctext, 1, pwctextlen, pwfile) != pwctextlen) {
	pam_syslog(pamh, LOG_DEBUG, "Error in encrypted data");
	err = 1;
	}
	if (fwrite(mac, 1, maclen, pwfile) != maclen) {
	pam_syslog(pamh, LOG_DEBUG, "Error in writing MAC");
	err = 1;
	}

	free(pwctext);
	free(pwptext);

	if (fflush(pwfile) \|\| fsync(fileno(pwfile))) {
	pam_syslog(
	pamh, LOG_DEBUG,
	"fflush or fsync error writing entries to special file: %s",
	tempfilename);
	err = 1;
	}

	if (fclose(pwfile)) {
	pam_syslog(pamh, LOG_DEBUG,
	"fclose error writing entries to special file: %s",
	tempfilename);
	err = 1;
	}

	done:
	if (!err) {
	// Step 5: Rename the temporary file as special password file.
	if (!rename(tempfilename, filename)) {
	pam_syslog(pamh, LOG_DEBUG,
	"password changed for %s in special file",
	forwho);
	} else {
	err = 1;
	}
	}

	// Clear out the key buff.
	memset(keybuff, 0, keybuffsize);

	if (!err) {
	return PAM_SUCCESS;
	} else {
	unlink(tempfilename);
	return PAM_AUTHTOK_ERR;
	}
	}


	/* Password Management API's */

	/**
	* @brief pam_sm_chauthtok API
	* Function which will be called for pam_chauthtok() calls.
	*
	* @param[in] pamh - pam handle
	* @param[in] flags - pam calls related flags
	* @param[in] argc - argument counts / options
	* @param[in] argv - array of arguments / options
	* @return - PAM_SUCCESS for success, others for failure
	*/
	int pam_sm_chauthtok(pam_handle_t pamh, int flags, int argc, const char *argv)
	{
	int retval = -1;
	const void *item = NULL;
	const char *user = NULL;
	const char pass_new = NULL, pass_old = NULL;
	const char *spec_grp_name =
	get_option(pamh, "spec_grp_name", argc, argv);
	const char *spec_pass_file =
	get_option(pamh, "spec_pass_file", argc, argv);
	const char *key_file = get_option(pamh, "key_file", argc, argv);


	if (spec_grp_name == NULL \|\| key_file == NULL) {
	return PAM_IGNORE;
	}
	if (flags & PAM_PRELIM_CHECK) {
	// send success to verify other stacked modules prelim check.
	return PAM_SUCCESS;
	}

	retval = pam_get_user(pamh, &user, NULL);
	if (retval != PAM_SUCCESS) {
	return retval;
	}

	// get already read password by the stacked pam module
	// Note: If there are no previous stacked pam module which read
	// the new password, then return with AUTHTOK_ERR

	retval = pam_get_item(pamh, PAM_AUTHTOK, &item);
	if (retval != PAM_SUCCESS \|\| item == NULL) {
	return PAM_AUTHTOK_ERR;
	}
	pass_new = item;

	struct group *grp;
	int spec_grp_usr = 0;
	// Verify whether the user belongs to special group.
	grp = pam_modutil_getgrnam(pamh, spec_grp_name);
	if (grp != NULL) {
	while (*(grp->gr_mem) != NULL) {
	if (strcmp(user, *grp->gr_mem) == 0) {
	spec_grp_usr = 1;
	break;
	}
	(grp->gr_mem)++;
	}
	}

	pam_syslog(pamh, LOG_DEBUG, "User belongs to special grp: %x",
	spec_grp_usr);

	if (spec_grp_usr) {
	// verify the new password is acceptable.
	size_t pass_len = strlen(pass_new);
	size_t user_len = strlen(user);
	if (pass_len > MAX_SPEC_GRP_PASS_LENGTH
	\|\| user_len > MAX_SPEC_GRP_USER_LENGTH) {
	pam_syslog(
	pamh, LOG_ERR,
	"Password length (%zu) / User name length (%zu) is not acceptable for IPMI",
	pass_len, user_len);
	pass_new = pass_old = NULL;
	return PAM_AUTHTOK_ERR;
	}
	if (spec_pass_file == NULL) {
	spec_pass_file = DEFAULT_SPEC_PASS_FILE;
	pam_syslog(
	pamh, LOG_ERR,
	"Using default special password file name :%s",
	spec_pass_file);
	}
	if (retval = lock_pwdf()) {
	pam_syslog(pamh, LOG_ERR,
	"Failed to lock the passwd file");
	return retval;
	}
	retval = update_pass_special_file(
	pamh, key_file, spec_pass_file, user, pass_new);
	unlock_pwdf();
	return retval;
	}

	return PAM_SUCCESS;
	}

	/* end of module definition */