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postgres_fdw: SCRAM authentication pass-through

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This enables SCRAM authentication for postgres_fdw when connecting to
a foreign server without having to store a plain-text password on user
mapping options.

This is done by saving the SCRAM ClientKey and ServeryKey from the
client authentication and using those instead of the plain-text
password for the server-side SCRAM exchange.  The new foreign-server
or user-mapping option "use_scram_passthrough" enables this.

Co-authored-by: Matheus Alcantara <mths.dev@pm.me>
Co-authored-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://www.postgresql.org/message-id/flat/27b29a35-9b96-46a9-bc1a-914140869dac@gmail.com
This commit is contained in:
Peter Eisentraut
2025-01-15 17:55:18 +01:00
parent b6463ea6ef
commit 761c79508e
14 changed files with 450 additions and 42 deletions
Download Patch File Download Diff File Expand all files Collapse all files

81
src/interfaces/libpq/fe-auth-scram.c
View File

@@ -119,25 +119,28 @@ scram_init(PGconn *conn,
return NULL;
}
/* Normalize the password with SASLprep, if possible */
rc = pg_saslprep(password, &prep_password);
if (rc == SASLPREP_OOM)
if (password)
{
free(state->sasl_mechanism);
free(state);
return NULL;
}
if (rc != SASLPREP_SUCCESS)
{
prep_password = strdup(password);
if (!prep_password)
/* Normalize the password with SASLprep, if possible */
rc = pg_saslprep(password, &prep_password);
if (rc == SASLPREP_OOM)
{
free(state->sasl_mechanism);
free(state);
return NULL;
}
if (rc != SASLPREP_SUCCESS)
{
prep_password = strdup(password);
if (!prep_password)
{
free(state->sasl_mechanism);
free(state);
return NULL;
}
}
state->password = prep_password;
}
state->password = prep_password;
return state;
}
@@ -775,20 +778,31 @@ calculate_client_proof(fe_scram_state *state,
return false;
}
/*
* Calculate SaltedPassword, and store it in 'state' so that we can reuse
* it later in verify_server_signature.
*/
if (scram_SaltedPassword(state->password, state->hash_type,
state->key_length, state->salt, state->saltlen,
state->iterations, state->SaltedPassword,
errstr) < 0 ||
scram_ClientKey(state->SaltedPassword, state->hash_type,
state->key_length, ClientKey, errstr) < 0 ||
scram_H(ClientKey, state->hash_type, state->key_length,
StoredKey, errstr) < 0)
if (state->conn->scram_client_key_binary)
{
memcpy(ClientKey, state->conn->scram_client_key_binary, SCRAM_MAX_KEY_LEN);
}
else
{
/*
* Calculate SaltedPassword, and store it in 'state' so that we can
* reuse it later in verify_server_signature.
*/
if (scram_SaltedPassword(state->password, state->hash_type,
state->key_length, state->salt, state->saltlen,
state->iterations, state->SaltedPassword,
errstr) < 0 ||
scram_ClientKey(state->SaltedPassword, state->hash_type,
state->key_length, ClientKey, errstr) < 0)
{
/* errstr is already filled here */
pg_hmac_free(ctx);
return false;
}
}
if (scram_H(ClientKey, state->hash_type, state->key_length, StoredKey, errstr) < 0)
{
/* errstr is already filled here */
pg_hmac_free(ctx);
return false;
}
@@ -841,12 +855,19 @@ verify_server_signature(fe_scram_state *state, bool *match,
return false;
}
if (scram_ServerKey(state->SaltedPassword, state->hash_type,
state->key_length, ServerKey, errstr) < 0)
if (state->conn->scram_server_key_binary)
{
/* errstr is filled already */
pg_hmac_free(ctx);
return false;
memcpy(ServerKey, state->conn->scram_server_key_binary, SCRAM_MAX_KEY_LEN);
}
else
{
if (scram_ServerKey(state->SaltedPassword, state->hash_type,
state->key_length, ServerKey, errstr) < 0)
{
/* errstr is filled already */
pg_hmac_free(ctx);
return false;
}
}
/* calculate ServerSignature */

2
src/interfaces/libpq/fe-auth.c
View File

@@ -559,7 +559,7 @@ pg_SASL_init(PGconn *conn, int payloadlen)
* First, select the password to use for the exchange, complaining if
* there isn't one and the selected SASL mechanism needs it.
*/
if (conn->password_needed)
if (conn->password_needed && !conn->scram_client_key_binary)
{
password = conn->connhost[conn->whichhost].password;
if (password == NULL)

47
src/interfaces/libpq/fe-connect.c
View File

@@ -22,6 +22,7 @@
#include <time.h>
#include <unistd.h>
#include "common/base64.h"
#include "common/ip.h"
#include "common/link-canary.h"
#include "common/scram-common.h"
@@ -366,6 +367,12 @@ static const internalPQconninfoOption PQconninfoOptions[] = {
"Load-Balance-Hosts", "", 8, /* sizeof("disable") = 8 */
offsetof(struct pg_conn, load_balance_hosts)},
{"scram_client_key", NULL, NULL, NULL, "SCRAM-Client-Key", "D", SCRAM_MAX_KEY_LEN * 2,
offsetof(struct pg_conn, scram_client_key)},
{"scram_server_key", NULL, NULL, NULL, "SCRAM-Server-Key", "D", SCRAM_MAX_KEY_LEN * 2,
offsetof(struct pg_conn, scram_server_key)},
/* Terminating entry --- MUST BE LAST */
{NULL, NULL, NULL, NULL,
NULL, NULL, 0}
@@ -1793,6 +1800,44 @@ pqConnectOptions2(PGconn *conn)
else
conn->target_server_type = SERVER_TYPE_ANY;
if (conn->scram_client_key)
{
int len;
len = pg_b64_dec_len(strlen(conn->scram_client_key));
/* Consider the zero-terminator */
if (len != SCRAM_MAX_KEY_LEN + 1)
{
libpq_append_conn_error(conn, "invalid SCRAM client key length: %d", len);
return false;
}
conn->scram_client_key_len = len;
conn->scram_client_key_binary = malloc(len);
if (!conn->scram_client_key_binary)
goto oom_error;
pg_b64_decode(conn->scram_client_key, strlen(conn->scram_client_key),
conn->scram_client_key_binary, len);
}
if (conn->scram_server_key)
{
int len;
len = pg_b64_dec_len(strlen(conn->scram_server_key));
/* Consider the zero-terminator */
if (len != SCRAM_MAX_KEY_LEN + 1)
{
libpq_append_conn_error(conn, "invalid SCRAM server key length: %d", len);
return false;
}
conn->scram_server_key_len = len;
conn->scram_server_key_binary = malloc(len);
if (!conn->scram_server_key_binary)
goto oom_error;
pg_b64_decode(conn->scram_server_key, strlen(conn->scram_server_key),
conn->scram_server_key_binary, len);
}
/*
* validate load_balance_hosts option, and set load_balance_type
*/
@@ -4704,6 +4749,8 @@ freePGconn(PGconn *conn)
free(conn->rowBuf);
free(conn->target_session_attrs);
free(conn->load_balance_hosts);
free(conn->scram_client_key);
free(conn->scram_server_key);
termPQExpBuffer(&conn->errorMessage);
termPQExpBuffer(&conn->workBuffer);

6
src/interfaces/libpq/libpq-int.h
View File

@@ -428,6 +428,8 @@ struct pg_conn
char *target_session_attrs; /* desired session properties */
char *require_auth; /* name of the expected auth method */
char *load_balance_hosts; /* load balance over hosts */
char *scram_client_key; /* base64-encoded SCRAM client key */
char *scram_server_key; /* base64-encoded SCRAM server key */
bool cancelRequest; /* true if this connection is used to send a
* cancel request, instead of being a normal
@@ -518,6 +520,10 @@ struct pg_conn
AddrInfo *addr; /* the array of addresses for the currently
* tried host */
bool send_appname; /* okay to send application_name? */
size_t scram_client_key_len;
void *scram_client_key_binary; /* binary SCRAM client key */
size_t scram_server_key_len;
void *scram_server_key_binary; /* binary SCRAM server key */
/* Miscellaneous stuff */
int be_pid; /* PID of backend --- needed for cancels */