From eb28ad92a2722fd30f8114840cf2b1ade26b80ee Mon Sep 17 00:00:00 2001
From: Limeng <Meng.Li@windriver.com>
Date: Fri, 23 Jun 2017 11:39:04 +0800
Subject: [PATCH] tpm:openssl-tpm-engine:parse an encrypted tpm SRK password 
 from env

Before, we support reading SRK password from env TPM_SRK_PW,
but it is a plain password and not secure.
So, we improve it and support to get an encrypted (AES algorithm)
SRK password from env, and then parse it. The default decrypting
AES password and salt is set in bb file.
When we initialize TPM, and set a SRK pw, and then we need to
encrypt it with the same AES password and salt by AES algorithm.
At last, we set a env as below:
export TPM_SRK_ENC_PW=xxxxxxxx
"xxxxxxxx" is the encrypted SRK password for libtpm.so.

Signed-off-by: Meng Li <Meng.Li@windriver.com>
---
 e_tpm.c     | 157 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 e_tpm.h     |   4 ++
 e_tpm_err.c |   4 ++
 3 files changed, 164 insertions(+), 1 deletion(-)

diff --git a/e_tpm.c b/e_tpm.c
index 7dcb75a..11bf74b 100644
--- a/e_tpm.c
+++ b/e_tpm.c
@@ -245,6 +245,118 @@ void ENGINE_load_tpm(void)
 	ERR_clear_error();
 }
 
+static int tpm_decode_base64(unsigned char *indata,
+				int in_len,
+				unsigned char *outdata,
+				int *out_len)
+{
+	int total_len, len, ret;
+	EVP_ENCODE_CTX dctx;
+
+	EVP_DecodeInit(&dctx);
+
+	total_len = 0;
+	ret = EVP_DecodeUpdate(&dctx, outdata, &len, indata, in_len);
+	if (ret < 0) {
+		TSSerr(TPM_F_TPM_DECODE_BASE64, TPM_R_DECODE_BASE64_FAILED);
+		return 1;
+	}
+
+	total_len += len;
+	ret = EVP_DecodeFinal(&dctx, outdata, &len);
+	if (ret < 0) {
+		TSSerr(TPM_F_TPM_DECODE_BASE64, TPM_R_DECODE_BASE64_FAILED);
+		return 1;
+	}
+	total_len += len;
+
+	*out_len = total_len;
+
+	return 0;
+}
+
+static int tpm_decrypt_srk_pw(unsigned char *indata, int in_len,
+				unsigned char *outdata,
+				int *out_len)
+{
+	int dec_data_len, dec_data_lenfinal;
+	unsigned char dec_data[256];
+	unsigned char *aes_pw;
+	unsigned char aes_salt[PKCS5_SALT_LEN];
+	unsigned char key[EVP_MAX_KEY_LENGTH], iv[EVP_MAX_IV_LENGTH];
+	const EVP_CIPHER *cipher = NULL;
+	const EVP_MD *dgst = NULL;
+	EVP_CIPHER_CTX *ctx = NULL;
+
+	if (sizeof(SRK_DEC_SALT) - 1 > PKCS5_SALT_LEN) {
+		TSSerr(TPM_F_TPM_DECRYPT_SRK_PW, TPM_R_DECRYPT_SRK_PW_FAILED);
+		return 1;
+	}
+
+	aes_pw = malloc(sizeof(SRK_DEC_PW) - 1);
+	if (aes_pw == NULL) {
+		TSSerr(TPM_F_TPM_DECRYPT_SRK_PW, TPM_R_DECRYPT_SRK_PW_FAILED);
+		return 1;
+	}
+
+	memset(aes_salt, 0x00, sizeof(aes_salt));
+	memcpy(aes_pw, SRK_DEC_PW, sizeof(SRK_DEC_PW) - 1);
+	memcpy(aes_salt, SRK_DEC_SALT, sizeof(SRK_DEC_SALT) - 1);
+
+	cipher = EVP_get_cipherbyname("aes-128-cbc");
+	if (cipher == NULL) {
+		TSSerr(TPM_F_TPM_DECRYPT_SRK_PW, TPM_R_DECRYPT_SRK_PW_FAILED);
+		free(aes_pw);
+		return 1;
+	}
+	dgst = EVP_sha256();
+
+	EVP_BytesToKey(cipher, dgst, aes_salt, (unsigned char *)aes_pw, sizeof(SRK_DEC_PW) - 1, 1, key, iv);
+
+	ctx = EVP_CIPHER_CTX_new();
+	/* Don't set key or IV right away; we want to check lengths */
+	if (!EVP_CipherInit_ex(ctx, cipher, NULL, NULL, NULL, 0)) {
+		TSSerr(TPM_F_TPM_DECRYPT_SRK_PW, TPM_R_DECRYPT_SRK_PW_FAILED);
+		free(aes_pw);
+		return 1;
+	}
+
+	OPENSSL_assert(EVP_CIPHER_CTX_key_length(ctx) == 16);
+	OPENSSL_assert(EVP_CIPHER_CTX_iv_length(ctx) == 16);
+
+	if (!EVP_CipherInit_ex(ctx, NULL, NULL, key, iv, 0)) {
+		TSSerr(TPM_F_TPM_DECRYPT_SRK_PW, TPM_R_DECRYPT_SRK_PW_FAILED);
+		free(aes_pw);
+		return 1;
+	}
+
+	if (!EVP_CipherUpdate(ctx, dec_data, &dec_data_len, indata, in_len)) {
+		/* Error */
+		TSSerr(TPM_F_TPM_DECRYPT_SRK_PW, TPM_R_DECRYPT_SRK_PW_FAILED);
+		free(aes_pw);
+		EVP_CIPHER_CTX_free(ctx);
+		return 1;
+	}
+
+	if (!EVP_CipherFinal_ex(ctx, dec_data + dec_data_len, &dec_data_lenfinal)) {
+		/* Error */
+		TSSerr(TPM_F_TPM_DECRYPT_SRK_PW, TPM_R_DECRYPT_SRK_PW_FAILED);
+		free(aes_pw);
+		EVP_CIPHER_CTX_free(ctx);
+		return 1;
+	}
+
+	dec_data_len = dec_data_len + dec_data_lenfinal;
+
+	memcpy(outdata, dec_data, dec_data_len);
+	*out_len = dec_data_len;
+
+	free(aes_pw);
+	EVP_CIPHER_CTX_free(ctx);
+
+	return 0;
+}
+
 int tpm_load_srk(UI_METHOD *ui, void *cb_data)
 {
 	TSS_RESULT result;
@@ -305,8 +417,50 @@ int tpm_load_srk(UI_METHOD *ui, void *cb_data)
 		return 0;
 	}
 
-	srkPasswd = getenv("TPM_SRK_PW");
+	srkPasswd = getenv("TPM_SRK_ENC_PW");
 	if (NULL != srkPasswd) {
+		int in_len = strlen(srkPasswd);
+		int out_len;
+		unsigned char *out_buf;
+
+		if (!in_len || in_len % 4) {
+			Tspi_Context_CloseObject(hContext, hSRK);
+			free(auth);
+			TSSerr(TPM_F_TPM_LOAD_SRK, TPM_R_REQUEST_FAILED);
+			return 0;
+		}
+
+		out_len = in_len * 3 / 4;
+		out_buf = malloc(out_len);
+		if (NULL == out_buf) {
+			Tspi_Context_CloseObject(hContext, hSRK);
+			free(auth);
+			TSSerr(TPM_F_TPM_LOAD_SRK, TPM_R_REQUEST_FAILED);
+			return 0;
+		}
+
+		if (tpm_decode_base64(srkPasswd, strlen(srkPasswd),
+					out_buf, &out_len)) {
+			Tspi_Context_CloseObject(hContext, hSRK);
+			free(auth);
+			free(out_buf);
+			TSSerr(TPM_F_TPM_LOAD_SRK, TPM_R_REQUEST_FAILED);
+			return 0;
+		}
+
+		if (tpm_decrypt_srk_pw(out_buf, out_len,
+							auth, &authlen)) {
+			Tspi_Context_CloseObject(hContext, hSRK);
+			free(auth);
+			free(out_buf);
+			TSSerr(TPM_F_TPM_LOAD_SRK, TPM_R_REQUEST_FAILED);
+			return 0;
+		}
+		secretMode = TSS_SECRET_MODE_PLAIN;
+		free(out_buf);
+	}
+#ifdef TPM_SRK_PLAIN_PW
+	else if (NULL != (srkPasswd = getenv("TPM_SRK_PW")) {
 		if (0 == strcmp(srkPasswd, "#WELLKNOWN#")) {
 			memset(auth, 0, TPM_WELL_KNOWN_KEY_LEN);
 			secretMode = TSS_SECRET_MODE_SHA1;
@@ -319,6 +473,7 @@ int tpm_load_srk(UI_METHOD *ui, void *cb_data)
 			authlen = strlen(auth);
 		}
 	}
+#endif
 	else {
 		if (!tpm_engine_get_auth(ui, (char *)auth, 128,
 				"SRK authorization: ", cb_data)) {
diff --git a/e_tpm.h b/e_tpm.h
index 6316e0b..56ff202 100644
--- a/e_tpm.h
+++ b/e_tpm.h
@@ -66,6 +66,8 @@ void ERR_TSS_error(int function, int reason, char *file, int line);
 #define TPM_F_TPM_FILL_RSA_OBJECT		116
 #define TPM_F_TPM_ENGINE_GET_AUTH		117
 #define TPM_F_TPM_CREATE_SRK_POLICY		118
+#define TPM_F_TPM_DECODE_BASE64			119
+#define TPM_F_TPM_DECRYPT_SRK_PW		120
 
 /* Reason codes. */
 #define TPM_R_ALREADY_LOADED			100
@@ -96,6 +98,8 @@ void ERR_TSS_error(int function, int reason, char *file, int line);
 #define TPM_R_ID_INVALID			125
 #define TPM_R_UI_METHOD_FAILED			126
 #define TPM_R_UNKNOWN_SECRET_MODE		127
+#define TPM_R_DECODE_BASE64_FAILED		128
+#define TPM_R_DECRYPT_SRK_PW_FAILED		129
 
 /* structure pointed to by the RSA object's app_data pointer */
 struct rsa_app_data
diff --git a/e_tpm_err.c b/e_tpm_err.c
index 25a5d0f..439e267 100644
--- a/e_tpm_err.c
+++ b/e_tpm_err.c
@@ -235,6 +235,8 @@ static ERR_STRING_DATA TPM_str_functs[] = {
 	{ERR_PACK(0, TPM_F_TPM_BIND_FN, 0), "TPM_BIND_FN"},
 	{ERR_PACK(0, TPM_F_TPM_FILL_RSA_OBJECT, 0), "TPM_FILL_RSA_OBJECT"},
 	{ERR_PACK(0, TPM_F_TPM_ENGINE_GET_AUTH, 0), "TPM_ENGINE_GET_AUTH"},
+	{ERR_PACK(0, TPM_F_TPM_DECODE_BASE64, 0), "TPM_DECODE_BASE64"},
+	{ERR_PACK(0, TPM_F_TPM_DECRYPT_SRK_PW, 0), "TPM_DECRYPT_SRK_PW"},
 	{0, NULL}
 };
 
@@ -265,6 +267,8 @@ static ERR_STRING_DATA TPM_str_reasons[] = {
 	{TPM_R_FILE_READ_FAILED, "failed reading the key file"},
 	{TPM_R_ID_INVALID, "engine id doesn't match"},
 	{TPM_R_UI_METHOD_FAILED, "ui function failed"},
+	{TPM_R_DECODE_BASE64_FAILED, "decode base64 failed"},
+	{TPM_R_DECRYPT_SRK_PW_FAILED, "decrypt srk password failed"},
 	{0, NULL}
 };
 
-- 
2.9.3