Merge pull request #4094 from d-otte/development
wrong RSA_PRV_DER_MAX_BYTES for odd MBEDTLS_MPI_MAX_SIZE
diff --git a/ChangeLog.d/issue4093.txt b/ChangeLog.d/issue4093.txt
new file mode 100644
index 0000000..f6985cf
--- /dev/null
+++ b/ChangeLog.d/issue4093.txt
@@ -0,0 +1,6 @@
+Security
+ * Fix an errorneous estimation for an internal buffer in
+ mbedtls_pk_write_key_pem(). If MBEDTLS_MPI_MAX_SIZE is set to an odd
+ value the function might fail to write a private RSA keys of the largest
+ supported size.
+ Found by Daniel Otte, reported in #4093 and fixed in #4094.
diff --git a/library/pkwrite.c b/library/pkwrite.c
index 0da3698..566153d 100644
--- a/library/pkwrite.c
+++ b/library/pkwrite.c
@@ -487,7 +487,7 @@
* publicExponent INTEGER -- e 1 + 3 + MPI_MAX + 1
* }
*/
-#define RSA_PUB_DER_MAX_BYTES 38 + 2 * MBEDTLS_MPI_MAX_SIZE
+#define RSA_PUB_DER_MAX_BYTES ( 38 + 2 * MBEDTLS_MPI_MAX_SIZE )
/*
* RSA private keys:
@@ -504,10 +504,10 @@
* otherPrimeInfos OtherPrimeInfos OPTIONAL 0 (not supported)
* }
*/
-#define MPI_MAX_SIZE_2 MBEDTLS_MPI_MAX_SIZE / 2 + \
- MBEDTLS_MPI_MAX_SIZE % 2
-#define RSA_PRV_DER_MAX_BYTES 47 + 3 * MBEDTLS_MPI_MAX_SIZE \
- + 5 * MPI_MAX_SIZE_2
+#define MPI_MAX_SIZE_2 ( MBEDTLS_MPI_MAX_SIZE / 2 + \
+ MBEDTLS_MPI_MAX_SIZE % 2 )
+#define RSA_PRV_DER_MAX_BYTES ( 47 + 3 * MBEDTLS_MPI_MAX_SIZE \
+ + 5 * MPI_MAX_SIZE_2 )
#else /* MBEDTLS_RSA_C */
@@ -528,7 +528,7 @@
* + 2 * ECP_MAX (coords) [1]
* }
*/
-#define ECP_PUB_DER_MAX_BYTES 30 + 2 * MBEDTLS_ECP_MAX_BYTES
+#define ECP_PUB_DER_MAX_BYTES ( 30 + 2 * MBEDTLS_ECP_MAX_BYTES )
/*
* EC private keys:
@@ -539,7 +539,7 @@
* publicKey [1] BIT STRING OPTIONAL 1 + 2 + [1] above
* }
*/
-#define ECP_PRV_DER_MAX_BYTES 29 + 3 * MBEDTLS_ECP_MAX_BYTES
+#define ECP_PRV_DER_MAX_BYTES ( 29 + 3 * MBEDTLS_ECP_MAX_BYTES )
#else /* MBEDTLS_ECP_C */
@@ -548,10 +548,10 @@
#endif /* MBEDTLS_ECP_C */
-#define PUB_DER_MAX_BYTES RSA_PUB_DER_MAX_BYTES > ECP_PUB_DER_MAX_BYTES ? \
- RSA_PUB_DER_MAX_BYTES : ECP_PUB_DER_MAX_BYTES
-#define PRV_DER_MAX_BYTES RSA_PRV_DER_MAX_BYTES > ECP_PRV_DER_MAX_BYTES ? \
- RSA_PRV_DER_MAX_BYTES : ECP_PRV_DER_MAX_BYTES
+#define PUB_DER_MAX_BYTES ( RSA_PUB_DER_MAX_BYTES > ECP_PUB_DER_MAX_BYTES ? \
+ RSA_PUB_DER_MAX_BYTES : ECP_PUB_DER_MAX_BYTES )
+#define PRV_DER_MAX_BYTES ( RSA_PRV_DER_MAX_BYTES > ECP_PRV_DER_MAX_BYTES ? \
+ RSA_PRV_DER_MAX_BYTES : ECP_PRV_DER_MAX_BYTES )
int mbedtls_pk_write_pubkey_pem( mbedtls_pk_context *key, unsigned char *buf, size_t size )
{
