Extend key -read and -write functions

README.md

@@ -115,6 +115,15 @@ To export the public key use:
 openssl ec -engine tpm2tss -inform engine -in mykey -pubout -outform pem -out mykey.pub
 ```
 
+## The TPM Key
+The TPM key may be provided as file name, like "mykey" in the examples above.
+Additionally, the special file name "-" is supported to read the key from stdin
+and write it to stdout after generation.
+Providing the key itself instead of the filename is also supported for reading.
+
+This allows engine-users to avoid the use of temporary files with all its
+issues and disadvantages (cleanup on error, mktemp()).
+
 ## Self Signed certificate generate operation 
 The following sequence of commands creates self signed certificate using TPM
 key. Openssl command sets tpm2tss as engine and generates a self signed

src/tpm2-tss-engine-common.c

@@ -138,7 +138,13 @@ tpm2tss_tpm2data_write(const TPM2_DATA *tpm2Data, const char *filename)
     uint8_t pubbuf[sizeof(tpm2Data->pub)];
     size_t privbuf_len = 0, pubbuf_len = 0;
 
-    if ((bio = BIO_new_file(filename, "w")) == NULL) {
+    if (filename[0] == '-' && filename[1] == 0) {
+        bio = BIO_new_fp(stdout, BIO_NOCLOSE);
+    } else {
+        bio = BIO_new_file(filename, "w");
+    }
+
+    if (bio == NULL) {
         ERR(tpm2tss_tpm2data_write, TPM2TSS_R_FILE_WRITE);
         goto error;
     }
@@ -349,7 +355,18 @@ tpm2tss_tpm2data_read(const char *filename, TPM2_DATA **tpm2Datap)
     char type_oid[64];
     BIGNUM *bn_parent;
 
-    if ((bio = BIO_new_file(filename, "r")) == NULL) {
+    if (filename[0] == '-' && filename[1] == 0) {
+        bio = BIO_new_fp(stdin, BIO_NOCLOSE);
+    } else {
+        bio = BIO_new_file(filename, "r");
+        if (bio == NULL) {
+            const char *dashes = strstr(filename, "-----BEGIN");
+            if (dashes)
+                bio = BIO_new_mem_buf(dashes, strlen(dashes));
+        }
+    }
+
+    if (bio == NULL) {
         ERR(tpm2tss_tpm2data_read, TPM2TSS_R_FILE_READ);
         goto error;
     }