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Complete analysis of the magic ASN.1 stuff in RSASSA signatures

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[originally from svn r988]
This commit is contained in:
Simon Tatham 2001-03-09 13:30:43 +00:00
parent 630a9a628f
commit 83affa4ed9
1 changed files with 11 additions and 2 deletions
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13
sshrsa.c
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@ -373,17 +373,26 @@ static char *rsa2_fingerprint(void *key) {
/*
* This is the magic ASN.1/DER prefix that goes in the decoded
* signature, between the string of FFs and the actual SHA hash
* value. As closely as I can tell, the meaning of it is:
* value. The meaning of it is:
*
* 00 -- this marks the end of the FFs; not part of the ASN.1 bit itself
*
* 30 21 -- a constructed SEQUENCE of length 0x21
* 30 09 -- a constructed sub-SEQUENCE of length 9
* 06 05 -- an object identifier, length 5
* 2B 0E 03 02 1A --
* 2B 0E 03 02 1A -- object id { 1 3 14 3 2 26 }
* (the 1,3 comes from 0x2B = 43 = 40*1+3)
* 05 00 -- NULL
* 04 14 -- a primitive OCTET STRING of length 0x14
* [0x14 bytes of hash data follows]
*
* The object id in the middle there is listed as `id-sha1' in
* ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1d2.asn (the
* ASN module for PKCS #1) and its expanded form is as follows:
*
* id-sha1 OBJECT IDENTIFIER ::= {
* iso(1) identified-organization(3) oiw(14) secsig(3)
* algorithms(2) 26 }
*/
static unsigned char asn1_weird_stuff[] = {
0x00,0x30,0x21,0x30,0x09,0x06,0x05,0x2B,