From: Andrey Rys <rys@lynxlynx.ru>
Date: Mon, 29 Apr 2019 15:48:37 +0000 (+0700)
Subject: -c: pattern fill support.
X-Git-Url: https://jxself.org/git/?a=commitdiff_plain;h=7843812e68ebd194667b244cdd6f6cbd45beb3a5;p=tfcrypt.git

-c: pattern fill support.

The syntax is:

        -c hexc:nr[,hexc:nr,...]

As example, filling with 16 byte counter with following:

        ffffffff3333337a7a7a7a88882a0b0c

is possible with following pattern:

        -c ff:4,33:3,7a:4,88:2,2a:1,0b:1,0c:1

To fill with zeroes (or any other static byte) is simple:

        -c 0:16

Note that any bytes that tend to overflow counter space are dropped, and any
unused bytes not filled by pattern are set to zeroes.
---

diff --git a/VERSION b/VERSION
index 64bb6b7..e85087a 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-30
+31
diff --git a/tfc_error.c b/tfc_error.c
index 5729de0..7d21be6 100644
--- a/tfc_error.c
+++ b/tfc_error.c
@@ -176,6 +176,11 @@ void usage(void)
 	tfc_say("    head: when decrypting, read CTR from beginning of stream,");
 	tfc_say("    rand: generate random CTR and write it to beginning of stream,");
 	tfc_say("    zero: assume zero CTR is used, do not read from and write it to stream,");
+	tfc_say("    hexc:nr[,hexc:nr,...]: construct counter from given pattern.");
+	tfc_say("      Example: \"ff:124,08:2,80:2\" will fill counter first with 124 0xff bytes,");
+	tfc_say("      then with 2 0x08 bytes, then 2 0x80 bytes. To fill with zeroes, it is");
+	tfc_say("      simple to specify just a \"0:128\" as a pattern. Note that bytes that");
+	tfc_say("      exceed CTR space will be just dropped, and any unused bytes are set to zeroes.");
 	tfc_say("    <file>: read CTR from given file (both when encrypting/decrypting).");
 	tfc_say("      default is to derive CTR from user provided password or keyfile with");
 	tfc_say("      a single Skein function turn over derived, %u byte raw key", TFC_U(TF_KEY_SIZE));
diff --git a/tfcrypt.c b/tfcrypt.c
index 7e9ef8c..4ba1dd5 100644
--- a/tfcrypt.c
+++ b/tfcrypt.c
@@ -149,6 +149,29 @@ _baddfname:
 					counter_opt = TFC_CTR_RAND;
 				else if (!strcasecmp(optarg, "zero"))
 					counter_opt = TFC_CTR_ZERO;
+				else if (strchr(optarg, ':')) {
+					char *ss, chr;
+
+					counter_opt = TFC_CTR_SSET;
+					n = sizeof(ctr);
+
+					s = d = optarg; t = NULL;
+					while ((s = strtok_r(d, ",", &t))) {
+						if (d) d = NULL;
+
+						if (n == 0) break;
+						ss = strchr(s, ':');
+						if (!ss) continue;
+						*ss = 0; ss++;
+						chr = (char)strtoul(s, &stoi, 16);
+						if (!str_empty(stoi)) continue;
+						x = (size_t)strtoul(ss, &stoi, 10);
+						if (!str_empty(stoi)) continue;
+						if (x > n) x = n;
+						memset(ctr+(sizeof(ctr)-n), (int)chr, x);
+						n -= x;
+					}
+				}
 				else counter_file = sksum_hashlist_file = optarg;
 				break;
 			case 'C':
diff --git a/tfcrypt.h b/tfcrypt.h
index e33e858..e8bee1a 100644
--- a/tfcrypt.h
+++ b/tfcrypt.h
@@ -227,6 +227,6 @@ enum {
 	TFC_MODE_SKSUM = -2, TFC_MODE_PLAIN = -1, TFC_MODE_CTR = 1,
 	TFC_MODE_STREAM, TFC_MODE_XTS, TFC_MODE_ECB, TFC_MODE_CBC, TFC_MODE_OCB
 };
-enum { TFC_CTR_SHOW = 1, TFC_CTR_HEAD, TFC_CTR_RAND, TFC_CTR_ZERO };
+enum { TFC_CTR_SHOW = 1, TFC_CTR_HEAD, TFC_CTR_RAND, TFC_CTR_ZERO, TFC_CTR_SSET };
 
 #endif