From 27cd7fc28c020044e7394fe8274ffb853e12082c Mon Sep 17 00:00:00 2001 From: simon Date: Fri, 25 Oct 2002 13:08:01 +0000 Subject: [PATCH] Diffie-Hellman key exchange now uses a dynamically allocated context. git-svn-id: svn://svn.tartarus.org/sgt/putty@2135 cda61777-01e9-0310-a592-d414129be87e --- ssh.c | 11 +++++---- ssh.h | 14 ++++++------ sshbn.c | 6 ++--- sshdh.c | 81 ++++++++++++++++++++++++++++++++++++++--------------------------- 4 files changed, 63 insertions(+), 49 deletions(-) diff --git a/ssh.c b/ssh.c index 677ff870..c9360604 100644 --- a/ssh.c +++ b/ssh.c @@ -569,6 +569,7 @@ struct ssh_tag { const struct ssh_kex *kex; const struct ssh_signkey *hostkey; unsigned char v2_session_id[20]; + void *kex_ctx; char *savedhost; int savedport; @@ -3953,12 +3954,12 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen, int ispkt) } s->p = ssh2_pkt_getmp(ssh); s->g = ssh2_pkt_getmp(ssh); - dh_setup_group(s->p, s->g); + ssh->kex_ctx = dh_setup_group(s->p, s->g); s->kex_init_value = SSH2_MSG_KEX_DH_GEX_INIT; s->kex_reply_value = SSH2_MSG_KEX_DH_GEX_REPLY; } else { ssh->pkt_ctx |= SSH2_PKTCTX_DHGROUP1; - dh_setup_group1(); + ssh->kex_ctx = dh_setup_group1(); s->kex_init_value = SSH2_MSG_KEXDH_INIT; s->kex_reply_value = SSH2_MSG_KEXDH_REPLY; } @@ -3967,7 +3968,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen, int ispkt) /* * Now generate and send e for Diffie-Hellman. */ - s->e = dh_create_e(s->nbits * 2); + s->e = dh_create_e(ssh->kex_ctx, s->nbits * 2); ssh2_pkt_init(ssh, s->kex_init_value); ssh2_pkt_addmp(ssh, s->e); ssh2_pkt_send(ssh); @@ -3981,7 +3982,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen, int ispkt) s->f = ssh2_pkt_getmp(ssh); ssh2_pkt_getstring(ssh, &s->sigdata, &s->siglen); - s->K = dh_find_K(s->f); + s->K = dh_find_K(ssh->kex_ctx, s->f); sha_string(&ssh->exhash, s->hostkeydata, s->hostkeylen); if (ssh->kex == &ssh_diffiehellman_gex) { @@ -3994,7 +3995,7 @@ static int do_ssh2_transport(Ssh ssh, unsigned char *in, int inlen, int ispkt) sha_mpint(&ssh->exhash, s->K); SHA_Final(&ssh->exhash, s->exchange_hash); - dh_cleanup(); + dh_cleanup(ssh->kex_ctx); #if 0 debug(("Exchange hash is:\n")); diff --git a/ssh.h b/ssh.h index bf57b8fa..9f9f1e6e 100644 --- a/ssh.h +++ b/ssh.h @@ -261,8 +261,8 @@ Bignum modpow(Bignum base, Bignum exp, Bignum mod); Bignum modmul(Bignum a, Bignum b, Bignum mod); void decbn(Bignum n); extern Bignum Zero, One; -Bignum bignum_from_bytes(unsigned char *data, int nbytes); -int ssh1_read_bignum(unsigned char *data, Bignum * result); +Bignum bignum_from_bytes(const unsigned char *data, int nbytes); +int ssh1_read_bignum(const unsigned char *data, Bignum * result); int bignum_bitcount(Bignum bn); int ssh1_bignum_length(Bignum bn); int ssh2_bignum_length(Bignum bn); @@ -283,11 +283,11 @@ Bignum bignum_rshift(Bignum number, int shift); int bignum_cmp(Bignum a, Bignum b); char *bignum_decimal(Bignum x); -void dh_setup_group1(void); -void dh_setup_group(Bignum pval, Bignum gval); -void dh_cleanup(void); -Bignum dh_create_e(int nbits); -Bignum dh_find_K(Bignum f); +void *dh_setup_group1(void); +void *dh_setup_group(Bignum pval, Bignum gval); +void dh_cleanup(void *); +Bignum dh_create_e(void *, int nbits); +Bignum dh_find_K(void *, Bignum f); int loadrsakey(char *filename, struct RSAKey *key, char *passphrase); int rsakey_encrypted(char *filename, char **comment); diff --git a/sshbn.c b/sshbn.c index 40f9560f..8246e25d 100644 --- a/sshbn.c +++ b/sshbn.c @@ -482,7 +482,7 @@ void decbn(Bignum bn) bn[i]--; } -Bignum bignum_from_bytes(unsigned char *data, int nbytes) +Bignum bignum_from_bytes(const unsigned char *data, int nbytes) { Bignum result; int w, i; @@ -509,9 +509,9 @@ Bignum bignum_from_bytes(unsigned char *data, int nbytes) * Read an ssh1-format bignum from a data buffer. Return the number * of bytes consumed. */ -int ssh1_read_bignum(unsigned char *data, Bignum * result) +int ssh1_read_bignum(const unsigned char *data, Bignum * result) { - unsigned char *p = data; + const unsigned char *p = data; int i; int w, b; diff --git a/sshdh.c b/sshdh.c index 7a1772b8..2e16bbea 100644 --- a/sshdh.c +++ b/sshdh.c @@ -11,7 +11,7 @@ const struct ssh_kex ssh_diffiehellman_gex = { /* * The prime p used in the key exchange. */ -static unsigned char P[] = { +static const unsigned char P[] = { 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xC9, 0x0F, 0xDA, 0xA2, 0x21, 0x68, 0xC2, 0x34, 0xC4, 0xC6, 0x62, 0x8B, 0x80, 0xDC, 0x1C, 0xD1, 0x29, 0x02, 0x4E, 0x08, 0x8A, 0x67, 0xCC, 0x74, 0x02, 0x0B, 0xBE, 0xA6, @@ -28,51 +28,62 @@ static unsigned char P[] = { /* * The generator g = 2. */ -static unsigned char G[] = { 2 }; +static const unsigned char G[] = { 2 }; /* * Variables. */ -static Bignum x, e, p, q, qmask, g; +struct dh_ctx { + Bignum x, e, p, q, qmask, g; +}; /* * Common DH initialisation. */ -static void dh_init(void) +static void dh_init(struct dh_ctx *ctx) { - q = bignum_rshift(p, 1); - qmask = bignum_bitmask(q); + ctx->q = bignum_rshift(ctx->p, 1); + ctx->qmask = bignum_bitmask(ctx->q); + ctx->x = ctx->e = NULL; } /* * Initialise DH for the standard group1. */ -void dh_setup_group1(void) +void *dh_setup_group1(void) { - p = bignum_from_bytes(P, sizeof(P)); - g = bignum_from_bytes(G, sizeof(G)); - dh_init(); + struct dh_ctx *ctx = smalloc(sizeof(struct dh_ctx)); + ctx->p = bignum_from_bytes(P, sizeof(P)); + ctx->g = bignum_from_bytes(G, sizeof(G)); + dh_init(ctx); + return ctx; } /* * Initialise DH for an alternative group. */ -void dh_setup_group(Bignum pval, Bignum gval) +void *dh_setup_group(Bignum pval, Bignum gval) { - p = copybn(pval); - g = copybn(gval); - dh_init(); + struct dh_ctx *ctx = smalloc(sizeof(struct dh_ctx)); + ctx->p = copybn(pval); + ctx->g = copybn(gval); + dh_init(ctx); + return ctx; } /* - * Clean up. + * Clean up and free a context. */ -void dh_cleanup(void) +void dh_cleanup(void *handle) { - freebn(p); - freebn(g); - freebn(q); - freebn(qmask); + struct dh_ctx *ctx = (struct dh_ctx *)handle; + freebn(ctx->x); + freebn(ctx->e); + freebn(ctx->p); + freebn(ctx->g); + freebn(ctx->q); + freebn(ctx->qmask); + sfree(ctx); } /* @@ -90,14 +101,15 @@ void dh_cleanup(void) * Advances in Cryptology: Proceedings of Eurocrypt '96 * Springer-Verlag, May 1996. */ -Bignum dh_create_e(int nbits) +Bignum dh_create_e(void *handle, int nbits) { + struct dh_ctx *ctx = (struct dh_ctx *)handle; int i; int nbytes; unsigned char *buf; - nbytes = ssh1_bignum_length(qmask); + nbytes = ssh1_bignum_length(ctx->qmask); buf = smalloc(nbytes); do { @@ -105,43 +117,44 @@ Bignum dh_create_e(int nbits) * Create a potential x, by ANDing a string of random bytes * with qmask. */ - if (x) - freebn(x); - if (nbits == 0 || nbits > bignum_bitcount(qmask)) { - ssh1_write_bignum(buf, qmask); + if (ctx->x) + freebn(ctx->x); + if (nbits == 0 || nbits > bignum_bitcount(ctx->qmask)) { + ssh1_write_bignum(buf, ctx->qmask); for (i = 2; i < nbytes; i++) buf[i] &= random_byte(); - ssh1_read_bignum(buf, &x); + ssh1_read_bignum(buf, &ctx->x); } else { int b, nb; - x = bn_power_2(nbits); + ctx->x = bn_power_2(nbits); b = nb = 0; for (i = 0; i < nbits; i++) { if (nb == 0) { nb = 8; b = random_byte(); } - bignum_set_bit(x, i, b & 1); + bignum_set_bit(ctx->x, i, b & 1); b >>= 1; nb--; } } - } while (bignum_cmp(x, One) <= 0 || bignum_cmp(x, q) >= 0); + } while (bignum_cmp(ctx->x, One) <= 0 || bignum_cmp(ctx->x, ctx->q) >= 0); /* * Done. Now compute e = g^x mod p. */ - e = modpow(g, x, p); + ctx->e = modpow(ctx->g, ctx->x, ctx->p); - return e; + return ctx->e; } /* * DH stage 2: given a number f, compute K = f^x mod p. */ -Bignum dh_find_K(Bignum f) +Bignum dh_find_K(void *handle, Bignum f) { + struct dh_ctx *ctx = (struct dh_ctx *)handle; Bignum ret; - ret = modpow(f, x, p); + ret = modpow(f, ctx->x, ctx->p); return ret; } -- 2.11.0