diff options
Diffstat (limited to 'g10/seskey.c')
| -rw-r--r-- | g10/seskey.c | 47 |
1 files changed, 44 insertions, 3 deletions
diff --git a/g10/seskey.c b/g10/seskey.c index 317623ec8..5e944760d 100644 --- a/g10/seskey.c +++ b/g10/seskey.c @@ -26,6 +26,7 @@ #include "util.h" #include "cipher.h" #include "mpi.h" +#include "main.h" @@ -73,7 +74,7 @@ encode_session_key( DEK *dek, unsigned nbits ) * 0 2 RND(n bytes) 0 A DEK(k bytes) CSUM(2 bytes) * * RND are non-zero random bytes. - * A is the cipher algorithm ( 42 for Blowfish ) + * A is the cipher algorithm * DEK is the encryption key (session key) length k depends on the * cipher algorithm (20 is used with blowfish). * CSUM is the 16 bit checksum over the DEK @@ -106,7 +107,7 @@ encode_session_key( DEK *dek, unsigned nbits ) MPI encode_rmd160_value( byte *md, unsigned len, unsigned nbits ) { - static byte asn[18] = /* stored reverse FIXME: need other values*/ + static byte asn[18] = /* FIXME: need other values*/ { 0x30, 0x20, 0x30, 0x0c, 0x06, 0x08, 0x2a, 0x86,0x48, 0x86, 0xf7, 0x0d, 0x02, 0x05, 0x05, 0x00, 0x04, 0x10 }; int nframe = (nbits+7) / 8; @@ -119,7 +120,7 @@ encode_rmd160_value( byte *md, unsigned len, unsigned nbits ) /* We encode the MD in this way: * - * 0 42 PAD(n bytes) 0 ASN(18 bytes) MD(20 bytes) + * 0 A PAD(n bytes) 0 ASN(18 bytes) MD(20 bytes) * * PAD consists of FF bytes. */ @@ -138,3 +139,43 @@ encode_rmd160_value( byte *md, unsigned len, unsigned nbits ) return frame; } + +/**************** + * Encode a md5 message digest of LEN bytes into NBITS. + * returns: A mpi with the session key (caller must free) + */ +MPI +encode_md5_value( byte *md, unsigned len, unsigned nbits ) +{ + static byte asn[18] = + { 0x30, 0x20, 0x30, 0x0c, 0x06, 0x08, 0x2a, 0x86,0x48, + 0x86, 0xf7, 0x0d, 0x02, 0x05, 0x05, 0x00, 0x04, 0x10 }; + int nframe = (nbits+7) / 8; + byte *p; + MPI frame; + int i,n,c; + + if( (nbits % BITS_PER_MPI_LIMB) || nframe < 38 || len != 16 ) + log_bug("can't encode a %d bit MD into a %d bits frame\n",len*8, nbits); + + /* We encode the MD in this way: + * + * 0 A PAD(n bytes) 0 ASN(18 bytes) MD(16 bytes) + * + * PAD consists of FF bytes. + */ + frame = mpi_alloc_secure( nframe / BYTES_PER_MPI_LIMB ); + n = 0; + for(i=16-1; i >= 0; i--, n++ ) + mpi_putbyte(frame, n, md[i] ); + for( i=18-1; i >= 0; i--, n++ ) + mpi_putbyte(frame, n, asn[i] ); + mpi_putbyte(frame, n++, 0 ); + while( n < nframe-2 ) + mpi_putbyte(frame, n++, 0xff ); + mpi_putbyte(frame, n++, DIGEST_ALGO_MD5 ); + mpi_putbyte(frame, n++, 0 ); + assert( n == nframe ); + return frame; +} + |