hmac_openssl.c

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/*-------------------------------------------------------------------------
 *
 * hmac_openssl.c
 *    Implementation of HMAC with OpenSSL.
 *
 * This should only be used if code is compiled with OpenSSL support.
 *
 * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * IDENTIFICATION
 *    src/common/hmac_openssl.c
 *
 *-------------------------------------------------------------------------
 */
 
#ifndef FRONTEND
#include "postgres.h"
#else
#include "postgres_fe.h"
#endif
 
 
#include <openssl/err.h>
#include <openssl/hmac.h>
 
#include "common/hmac.h"
#include "common/md5.h"
#include "common/sha1.h"
#include "common/sha2.h"
#ifndef FRONTEND
#include "utils/memutils.h"
#include "utils/resowner.h"
#endif
 
/*
 * In backend, use an allocation in TopMemoryContext to count for resowner
 * cleanup handling if necessary.  In frontend, use malloc to be able to return
 * a failure status back to the caller.
 */
#ifndef FRONTEND
#define USE_RESOWNER_FOR_HMAC
#define ALLOC(size) MemoryContextAlloc(TopMemoryContext, size)
#define FREE(ptr) pfree(ptr)
#else                           /* FRONTEND */
#define ALLOC(size) malloc(size)
#define FREE(ptr) free(ptr)
#endif                          /* FRONTEND */
 
/* Set of error states */
typedef enum pg_hmac_errno
{
    PG_HMAC_ERROR_NONE = 0,
    PG_HMAC_ERROR_DEST_LEN,
    PG_HMAC_ERROR_OPENSSL,
} pg_hmac_errno;
 
/* Internal pg_hmac_ctx structure */
struct pg_hmac_ctx
{
    HMAC_CTX   *hmacctx;
    pg_cryptohash_type type;
    pg_hmac_errno error;
    const char *errreason;
 
#ifdef USE_RESOWNER_FOR_HMAC
    ResourceOwner resowner;
#endif
};
 
/* ResourceOwner callbacks to hold HMAC contexts */
#ifdef USE_RESOWNER_FOR_HMAC
static void ResOwnerReleaseHMAC(Datum res);
 
static const ResourceOwnerDesc hmac_resowner_desc =
{
    .name = "OpenSSL HMAC context",
    .release_phase = RESOURCE_RELEASE_BEFORE_LOCKS,
    .release_priority = RELEASE_PRIO_HMAC_CONTEXTS,
    .ReleaseResource = ResOwnerReleaseHMAC,
    .DebugPrint = NULL          /* the default message is fine */
};
 
/* Convenience wrappers over ResourceOwnerRemember/Forget */
static inline void
ResourceOwnerRememberHMAC(ResourceOwner owner, pg_hmac_ctx *ctx)
{
    ResourceOwnerRemember(owner, PointerGetDatum(ctx), &hmac_resowner_desc);
}
static inline void
ResourceOwnerForgetHMAC(ResourceOwner owner, pg_hmac_ctx *ctx)
{
    ResourceOwnerForget(owner, PointerGetDatum(ctx), &hmac_resowner_desc);
}
#endif
 
static const char *
SSLerrmessage(unsigned long ecode)
{
    if (ecode == 0)
        return NULL;
 
    /*
     * This may return NULL, but we would fall back to a default error path if
     * that were the case.
     */
    return ERR_reason_error_string(ecode);
}
 
/*
 * pg_hmac_create
 *
 * Allocate a hash context.  Returns NULL on failure for an OOM.  The
 * backend issues an error, without returning.
 */
pg_hmac_ctx *
pg_hmac_create(pg_cryptohash_type type)
{
    pg_hmac_ctx *ctx;
 
    ctx = ALLOC(sizeof(pg_hmac_ctx));
    if (ctx == NULL)
        return NULL;
    memset(ctx, 0, sizeof(pg_hmac_ctx));
 
    ctx->type = type;
    ctx->error = PG_HMAC_ERROR_NONE;
    ctx->errreason = NULL;
 
 
    /*
     * Initialization takes care of assigning the correct type for OpenSSL.
     * Also ensure that there aren't any unconsumed errors in the queue from
     * previous runs.
     */
    ERR_clear_error();
 
#ifdef USE_RESOWNER_FOR_HMAC
    ResourceOwnerEnlarge(CurrentResourceOwner);
#endif
 
    ctx->hmacctx = HMAC_CTX_new();
 
    if (ctx->hmacctx == NULL)
    {
        explicit_bzero(ctx, sizeof(pg_hmac_ctx));
        FREE(ctx);
#ifndef FRONTEND
        ereport(ERROR,
                (errcode(ERRCODE_OUT_OF_MEMORY),
                 errmsg("out of memory")));
#endif
        return NULL;
    }
 
 
#ifdef USE_RESOWNER_FOR_HMAC
    ctx->resowner = CurrentResourceOwner;
    ResourceOwnerRememberHMAC(CurrentResourceOwner, ctx);
#endif
 
    return ctx;
}
 
/*
 * pg_hmac_init
 *
 * Initialize a HMAC context.  Returns 0 on success, -1 on failure.
 */
int
pg_hmac_init(pg_hmac_ctx *ctx, const uint8 *key, size_t len)
{
    int         status = 0;
 
    if (ctx == NULL)
        return -1;
 
    switch (ctx->type)
    {
        case PG_MD5:
            status = HMAC_Init_ex(ctx->hmacctx, key, len, EVP_md5(), NULL);
            break;
        case PG_SHA1:
            status = HMAC_Init_ex(ctx->hmacctx, key, len, EVP_sha1(), NULL);
            break;
        case PG_SHA224:
            status = HMAC_Init_ex(ctx->hmacctx, key, len, EVP_sha224(), NULL);
            break;
        case PG_SHA256:
            status = HMAC_Init_ex(ctx->hmacctx, key, len, EVP_sha256(), NULL);
            break;
        case PG_SHA384:
            status = HMAC_Init_ex(ctx->hmacctx, key, len, EVP_sha384(), NULL);
            break;
        case PG_SHA512:
            status = HMAC_Init_ex(ctx->hmacctx, key, len, EVP_sha512(), NULL);
            break;
    }
 
    /* OpenSSL internals return 1 on success, 0 on failure */
    if (status <= 0)
    {
        ctx->errreason = SSLerrmessage(ERR_get_error());
        ctx->error = PG_HMAC_ERROR_OPENSSL;
        return -1;
    }
 
    return 0;
}
 
/*
 * pg_hmac_update
 *
 * Update a HMAC context.  Returns 0 on success, -1 on failure.
 */
int
pg_hmac_update(pg_hmac_ctx *ctx, const uint8 *data, size_t len)
{
    int         status = 0;
 
    if (ctx == NULL)
        return -1;
 
    status = HMAC_Update(ctx->hmacctx, data, len);
 
    /* OpenSSL internals return 1 on success, 0 on failure */
    if (status <= 0)
    {
        ctx->errreason = SSLerrmessage(ERR_get_error());
        ctx->error = PG_HMAC_ERROR_OPENSSL;
        return -1;
    }
    return 0;
}
 
/*
 * pg_hmac_final
 *
 * Finalize a HMAC context.  Returns 0 on success, -1 on failure.
 */
int
pg_hmac_final(pg_hmac_ctx *ctx, uint8 *dest, size_t len)
{
    int         status = 0;
    uint32      outlen;
 
    if (ctx == NULL)
        return -1;
 
    switch (ctx->type)
    {
        case PG_MD5:
            if (len < MD5_DIGEST_LENGTH)
            {
                ctx->error = PG_HMAC_ERROR_DEST_LEN;
                return -1;
            }
            break;
        case PG_SHA1:
            if (len < SHA1_DIGEST_LENGTH)
            {
                ctx->error = PG_HMAC_ERROR_DEST_LEN;
                return -1;
            }
            break;
        case PG_SHA224:
            if (len < PG_SHA224_DIGEST_LENGTH)
            {
                ctx->error = PG_HMAC_ERROR_DEST_LEN;
                return -1;
            }
            break;
        case PG_SHA256:
            if (len < PG_SHA256_DIGEST_LENGTH)
            {
                ctx->error = PG_HMAC_ERROR_DEST_LEN;
                return -1;
            }
            break;
        case PG_SHA384:
            if (len < PG_SHA384_DIGEST_LENGTH)
            {
                ctx->error = PG_HMAC_ERROR_DEST_LEN;
                return -1;
            }
            break;
        case PG_SHA512:
            if (len < PG_SHA512_DIGEST_LENGTH)
            {
                ctx->error = PG_HMAC_ERROR_DEST_LEN;
                return -1;
            }
            break;
    }
 
    status = HMAC_Final(ctx->hmacctx, dest, &outlen);
 
    /* OpenSSL internals return 1 on success, 0 on failure */
    if (status <= 0)
    {
        ctx->errreason = SSLerrmessage(ERR_get_error());
        ctx->error = PG_HMAC_ERROR_OPENSSL;
        return -1;
    }
    return 0;
}
 
/*
 * pg_hmac_free
 *
 * Free a HMAC context.
 */
void
pg_hmac_free(pg_hmac_ctx *ctx)
{
    if (ctx == NULL)
        return;
 
    HMAC_CTX_free(ctx->hmacctx);
#ifdef USE_RESOWNER_FOR_HMAC
    if (ctx->resowner)
        ResourceOwnerForgetHMAC(ctx->resowner, ctx);
#endif
 
    explicit_bzero(ctx, sizeof(pg_hmac_ctx));
    FREE(ctx);
}
 
/*
 * pg_hmac_error
 *
 * Returns a static string providing details about an error that happened
 * during a HMAC computation.
 */
const char *
pg_hmac_error(pg_hmac_ctx *ctx)
{
    if (ctx == NULL)
        return _("out of memory");
 
    /*
     * If a reason is provided, rely on it, else fallback to any error code
     * set.
     */
    if (ctx->errreason)
        return ctx->errreason;
 
    switch (ctx->error)
    {
        case PG_HMAC_ERROR_NONE:
            return _("success");
        case PG_HMAC_ERROR_DEST_LEN:
            return _("destination buffer too small");
        case PG_HMAC_ERROR_OPENSSL:
            return _("OpenSSL failure");
    }
 
    Assert(false);              /* cannot be reached */
    return _("success");
}
 
/* ResourceOwner callbacks */
 
#ifdef USE_RESOWNER_FOR_HMAC
static void
ResOwnerReleaseHMAC(Datum res)
{
    pg_hmac_ctx *ctx = (pg_hmac_ctx *) DatumGetPointer(res);
 
    ctx->resowner = NULL;
    pg_hmac_free(ctx);
}
#endif